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Some physical properties of strawberries related to design of a selective harvester Mehra, Harsh Kumar 1971-12-31

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SOME PHYSICAL PROPERTIES OF STRAWBERRIES RELATED TO DESIGN OF "  :  ~  "  A  SELECTIVE HARVESTER  BY  HARSH KUMAR MEHRA B.E.(Agric.) Hons. U n i v e r s i t y of Udaipur, 1969  A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department o f A g r i c u l t u r a l Engineering .  We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard  ..THE UNIVERSITY OF BRITISH COLUMBIA September, 1 9 7 1 .  In  presenting  this  an a d v a n c e d  degree  the L i b r a r y  shall  I f u r t h e r agree for  scholarly  thesis  at the U n i v e r s i t y make  that permission  purposes  this  written  thesis  of B r i t i s h Columbia,  for extensive  may be g r a n t e d  of  It  i s understood  f o r f i n a n c i a l gain  AGRICULTURAL  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  September  I agree  that  30,1971.  thesis  shall  that copying o r p u b l i c a t i o n  n o t be a l l o w e d w i t h o u t my  ENGINEERING  Columbia  copying o f t h i s  by t h e Head o f my D e p a r t m e n t o r  permission.  Department  Date  f u l f i l m e n t o f the requirements f o r  i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y .  by h i s r e p r e s e n t a t i v e s . of  in p a r t i a l  ABSTRACT A fruit  s e l e c t i o n t o o l , which could  component o f  a s e l e c t i v e strawberry  designed  tested.  and  D e s i g n was  Theological properties w h i c h i s commonly Fruit  linear  bioyield  calculated  from  season. point  loading  tests.  fruit  q u a l i t y and  u s e d as  fruit  an  selection  made.  colour  surface  speed.  m e a s u r e d as  indicated that  and  fruit  2.54  the  cm.  fruit  evaluate  retention  could  be  fruit  used  as  the  selection tool.  f o r strawberry  assessment.  relative  o f the  fruit  evaluation  between r e f l e c t a n c e a t  colour,  were  at  fast  reflectance  r e f l e c t a n c e s at v a r i o u s surface  surface  spectrophotometer  f r o m the  for objective colour  that  flat  season.  q u a l i t y and  diameter surface  good c o r r e l a t i o n w i t h  of  o b j e c t i v e c o l o u r measurements were  Spectrum v a r i a b l e s o b t a i n e d  The  from  colour  therefore,  c u r v e s were u s e d  had  harvest  from a Unicam a u t o m a t i c r e c o r d i n g a  a function  curves obtained  c o l o u r was,  parameter c o n t r o l l i n g  scanning  strawberries  t a n g e n t m o d u l u s , were  R e l a t i v e r e f l e c t a n c e curves  obtained by  and  i n d i c a t o r of  Subjective  and  among q u a l i t y p a r a m e t e r s , f r u i t  surface  Fruit  was  Columbia.  i t s v a r i a t i o n o v e r the  accurate  maturity.  v a r i e t y of  T h e s e p a r a m e t e r s were u s e d t o  Correlations force, and  system,  a  Three r h e o l o g i c a l parameters,  force-deformation  plate  u s e d as  upon p h y s i c a l  Northwest  r e t e n t i o n f o r c e was  harvest  harvesting  based  grown i n B r i t i s h  time o v e r the limit,  o f the  be  the  52 5 n a n o m e t e r s and  and  maturity  wavelengths  highest percent  being surface  red  colour.  Maturity  ratio  from r e f l e c t a n c e curves reflectances represented  at the  650  nm  and to  surface  for strawberries was  525  e s t a b l i s h e d as  nm.  colour  was  and  calculated  the  ratio  Maturity  ratio  was  to  define  and  used  used  of  best fruit  ripeness. An  e l e c t r o n i c s y s t e m was  measure m a t u r i t y c o n d u c t e d on  this  ratio  and  gated.  identify  system i n the  minimum r e s p o n s e t i m e o f influence  to  designed fruit  laboratory  0.16 6 s e c o n d s p e r  o f i l l u m i n a t i o n and  to  maturity.  indicated fruit.  Tests  a  The  i t s g e o m e t r y were a l s o  investi-  -  I l l -  ACKNOWLEDGEMENTS  The for  directing  Bulley  author this  to thank  Professor  research.  Thanks  are also  for his valuable  Mr. J. Pehlke equipment  suggestions  of B r i t i s h Thanks  Agriculture  This of  research  Canada.  Staley  due to Dr. N.H.  in constructing  and  the  of A g r i c u l t u r a l  Engineering  t  Columbia.  are also  j Agassis  L.M.  and Mr. W. Gleave  for t h e i r assistance  j a l l in the Department  University  Council  wishes  extended  for providing was financed  to Canada the  Department  of  strawberries.  by the National  Research  -  iv  -  TABLE OF CONTENTS  ABSTRACT ACKNOWLEDGEMENTS TABLE OF CONTENTS L I S T OF FIGURES L I S T OF TABLES TERMINOLOGY 1.  INTRODUCTION 1.1  2.  3.  Purpose  of the  research  REVIEW OF LITERATURE 2.1  Present  harvesting  systems  2.2  A p p l i c a t i o n of c o l o r i m e t r i c  methods  2.3  Study of present  harvesters  2.4  Colorimetry  strawberry  ANALYSIS OF PHYSICAL PROPERTIES AND COLOUR MEASUREMENT 3 .1  The  strawberry  plant  3. 2  Fruit  and p l a n t  3. 3  Fruit  size  3. 4  Fruit  retention  3. 5  F/W  3. 6  Rheological  3. 7  Fruit  3. 8  Colour  3. 9.  Subjective  and  and  fruit  distribution weight force  ratio properties  quality  evaluation  evaluation colour  and m a t u r i t y o f evaluation  fruit  V  -  PAGE  ,4.  3.10  Spectral  characteristics  27  3.11  Colour c r i t e r i a  34  3.12  Maturity  35  ratio  DESIGN OF COLOUR MEASURING SYSTEM  40  4.1  Theory  of design  40  4.2  Colour  discriminator  41  4.3  Optical  requirements  44  4.3.1  The i l l u m i n a n t  44  4.3.2  The o b j e c t  45  4.3.3  The d e t e c t o r  45  4.4  Design o f o p t i c a l  4.5  The e l e c t r o n i c  4.6  apparatus  46  apparatus  47  4.5.1  The p r o b e  49  4.5.2  Amplifier  49  4.5.3  Voltage  52  4.5.4  The s o l e n o i d  Test  comparator  52  results  54  4.6.1  Speed o f r e s p o n s e  4.6.2  S u r f a c e and i l l u m i n a t i o n  4.6.3  The a n g l e o f i l l u m i n a t i o n  4.6.4  The i n s t r u m e n t  stability  54 conditions and d e t e c t i o n  57 58 58  CONCLUSIONS  59 •  SUGGESTIONS FOR FUTURE WORK  60  LITERATURE CITED  61  APPENDIX  '66  -  vi  -  L I S T OF FIGURES FIGURE  PAGE  la  A typical  strawberry  field.  8  lb  A typical  strawberry  plant.  8  2  Strawberry dense  plant  showing  b e r r i e s hidden under  10  foliage.  3  Cross-section  4  Cumulative  view o f a strawberry.  frequency  cui^ve p e r f o o t c r o p measured  fruit (30  distribution .  cm.)  about  10  of  12  strawberry  the c e n t e r of  the  row. 5  A typical.strawberry fruit.  15  6  Hand dynamometer mounted on s u r v e y o r ' s  15  t r i p o d and s t r a w b e r r y 7  Least  square  simple regression  F/W r a t i o on day o f 8  I n s t r o n l o a d i n g machine.  9  O r i e n t a t i o n of strawberry two f l a t  10  o f 2 cm. p e r square bioyield 12  Least  square tangent  o f FRF and  17  harvest. 19 compressed  T y p i c a l force-deformation curve  Least  holder.  between  19  plates.  subjected to f l a t  11  held in  for strawberry  plate loading  at  20 -  rate  minute.  simple  regression  of  FRF on  23  regression  of  FRF on  25  point. simple  modulus.  - v i i  -  FJGURE 13  PAGE Typical strawberry  sample o f v a r y i n g  surface  28  redness. 14  Unicam a u t o m a t i c r e c o r d i n g  15  Strawberry  16  "'  s u r f a c e h e l d i n sample h o l d e r .  A t y p i c a l r e l a t i v e r e f l e c t a n c e curve strawberry  surface  the  T y p i c a l s p e c t r a l r e f l e c t a n c e curves  for  totally  18  Least  green,  to pick  an a r i t h m e t i c  scale.  simple regression  on p e r c e n t  29 30  surface  (100%  31 red)  p l o t t e d on  of maturity  values  O p t i c a l apparatus  36  red.  T h e o r e t i c a l T o s s d i s t r i b u t i o n by s e l e c t i n g different  20  ready  strawberries  square  28  scale.  and o v e r - r i p e  ratio 19  for a  r e c o r d e d on  logarithmic 17  spectrophotometer.  42  of maturity c o e f f i c i e n t .  f o r c o l o u r measuring  48  system. 21  Cross  s e c t i o n a l view of the f i l t e r - p r o b e assembly  (not t o  22  C i r c u i t diagram  23  C i r c u i t diagram f o r  24  Schematic  scale).  f o r probe  diagram  48  signal  assembly.  50  amplifier.  for voltage  51  c o m p a r a t o r and  53  solenoid. 25  Schematic  diagram of e x p e r i m e n t a l arrangement  for testing  colour discriminator  equipment.  55  -  V l l l  -  FIGURE 26  • General  view o f the e x p e r i m e n t a l  for testing colour equipment.  equipment  discriminator  PAGE 56  LIST OF  Correlation of  matrix  TABLES  for physical  dimensions  strawberries  Correlation  matrix  for  rheological  properties Correlation  matrix  rheological Correlation of Results  for spectral  properties  matrix  for CIE-colour  strawberry of  the  electronic  tests  of  variables  surface conducted  on  colour-detection  performance e f f i c i e n c y variety  and  using  strawberries.  the system  for  Northwest  TERMINOLOGY Commission  Internationale  de L ' E c l a i r a g e  Day o f t h e h a r v e s t Fruit  retention  Ratio  of fruit  force retention  f o r c e t o weight o f  strawberry Current  i n amperes  Index o f v a r i a n c e Linear  limit  Maturity Sample  i n reflectance  ratio  size  Nanometer Probability  level;  ( 1 - a ) , where  a i s the l e v e l  of s i g n i f i c a n c e Simple  correlation coefficient  Reflectance Percent  factor  red colour o f the berry  Sensitivity  o f the e l e c t r o n i c instrument  Standard e r r o r o f estimate Bioyield  of y  point  A n g l e between t h e i n i t i a l force-deformation axis  surface  linear  curve  portion of the  and t h e d e f o r m a t i o n  1. Strawberries crop  i n the lower  percent  a r e about  20 percent  i s sold  to the fresh  farmers  do n o t p r o v i d e  increased This  About  annual 80  fruit  market,  (7)"*".  h a v e b e e n h a n d i c a p p e d by  e c o n o m i c c o n d i t i o n s and r e p e a t e d  during the harvesting period. costs  Columbia.  dollar  goes t o t h e p r o c e s s i n g p l a n t s and t h e  In r e c e n t y e a r s adverse  a 1 1/2 m i l l i o n  mainland o f B r i t i s h  o f the crop  remaining  INTRODUCTION  labour  High labour  forprofitable  shortages  and p r o d u c t i o n  returns.  Most o f t h i s  cost i s incurred during the harvesting period.  popular  fruit  some m e c h a n i c a l  could  s o o n be p r i c e d  means o f c h e a p l y  out o f t h e market i f  harvesting the strawberry  are not evolved. 1.1  Purpose o f the Research I n v i e w o f t h e a b o v e p r o b l e m i t was p r o p o s e d t o  design  a selective  physical  harvesting tool.  A criteria  b a s e d on t h e  p r o p e r t i e s o r s u r f a c e c o l o u r c h a r a c t e r i s t i c s was t o  be  evolved  be  used  to decide  the quality  i n the design  Northwest  variety  grown i n B r i t i s h are l i m i t e d  of fruit  which would  o f a h a r v e s t i n g system.  Since the  o f s t r a w b e r r i e s a r e t h e most p o p u l a r Columbia, t h e r e s u l t s  to this  then  variety  discussed i n this  study  variety.  Number i n p a r e n t h e s e s literature cited.  refer  to references l i s t e d  i n the  2.  2.  vegetable increasing  REVIEW OF LITERATURE  Until  r e c e n t l y mechanical  crops  was l i m i t e d  labour shortage  t o a very  span o f t i m e .  every  2.1  Present  Because o f  crop  costs the  mechanically  in a  A number o f r e s e a r c h o r g a n i z a t i o n s have  been engaged i n v a r i o u s a s p e c t s mechanization  few t y p e s .  and i n c r e a s e d p r o d u c t i o n  emphasis has been t o h a r v e s t short  h a r v e s t i n g o f f r u i t and  of fruit  harvesting  ( 3 , 8, 22, 27, 3 7 ) . Harvesting  Present  Systems  h a r v e s t i n g s y s t e m s c a n be c l a s s i f i e d  into  t h r e e main c l a s s e s : 1.  Once-over h a r v e s t i n g systems The  crop  time. soil  under t h i s  to f a c i l i t a t e  year.  tolerated used  p r o c e s s i n g under  class  fruit  f o r h a r v e s t i n g sugar (non-regenerative  system i s e s s e n t i a l l y  controlled itself  every  and p l a n t damage c a n  to a large extent.  Once-over h a r v e s t i n g This  mature a l l a t t h e same  The p l a n t r e g e n e r a t e s  Under t h i s  widely 2.  class  plants).  The c o m p l e t e p l a n t may be removed f r o m t h e  conditions.  be  (regenerative  T h i s method i s cane and t o m a t o e s . plants)  t h e same a s t h e p r e v i o u s  one  except  and  h e n c e e x c e s s i v e p l a n t damage c a n n o t be  to  aboid  year.  adversely  affecting  The p l a n t , i n t h i s  along with widely  t h a t p l a n t s do n o t r e g e n e r a t e  used  the f r u i t :  the y i e l d  case,  year  tolerated  the f o l l o w i n g  i s not harvested  f o r processing.  f o rharvesting grain  every  T h i s method i s  crops.  3.  Selective harvesting This all  system.  s y s t e m i s u s e d where t h e f r u i t a t t h e same t i m e .  o v e r an e x t e n d e d ing  season.  suit  plant  o f time  The p l a n t s  tomatoes  fruit  may be a c h i e v e d retention ing  force.  fruit  tension,  by a p p l y i n g  c a n n o t be t o l e r a t e d . T h e s e  I n any c a s e a force  Strawberry h a r v e s t i n g  without  any c o n s i d e r a t i o n  than the f r u i t  m a c h i n e s have been  to fruit  by  apply-  designed  or plant properties of fruits,  of the f r u i t ,  criteria  separation  force or t o r s i o n a l  could  some  (3,8).  criteria,  are usually decided  t h e b a s i s by w h i c h t h e r i p e and u n r i p e This  to sever the  may be a c h i e v e d  selective harvesting  b a s e d on t h e p r o p e r t i e s  discriminated.  mushrooms ( 3 2 )  fruit  greater  o r impact  force.  as  f o r cotton,  separation  shear, i n e r t i a  For  Damage t o t h e  (37) f o r example.  system.  Fruit  crops,  may o r may n o t be  m e c h a n i c a l means a r e e m p l o y e d  from the p l a n t  the harvest-  such  the p a r t i c u l a r requirement.  and u n r i p e  Various  during  and h e n c e t h e m a c h i n e s a r e d e s i g n e d  machines have been used and  are harvested  t o d i s t i n g u i s h between r i p e and  fruit.  regenerative to  period  fruits  The m a c h i n e , h a r v e s t i n g  must be a b l e unripe  Ripe  do n o t r i p e n  fruits  be b a s e d  c a n be  upon r h e o l o g i c a l  properties, physical properties or colour o f the f r u i t . 2  •  2  Application of Colourimetric  Methods  A l t h o u g h , t h e use o f c o l o u r i m e t r i c t e c h n i q u e s design  of harvesting  machines has been v e r y  upon  in  l i m i t e d , these  techniques  have l o n g  been u s e d  for processing  and  grading  purposes. Stephenson deciding  (37)  used the  criteria, for selective harvesting  t o m a t o e s were i l l u m i n a t e d by o f the  tomato s u r f a c e  cells .  The  response current  f r o m an  out  of the  lemons  to t h e i r  528  colour  (35),  nm,  point  sample  u s e d as  (20),  and  nm  the  and  730  surface,  large.  nm  to c l a s s i f y  they the  by  get  photouniform  amount  of  a criterion (9)  the  for  according  too  small  value  They but  Dennison "Rd"  that  surface  of  "a"  that  value  redness.  i s , however, l i m i t e d  (23)  While  reflectance  variation in a tomato i s  one  classifica-  point.  used a Hunter to evaluate there  was  But  samples.  of  difference in  s t e a d i l y with  method o f c o l o u r  i n scope u n l e s s  the  colour-  colour  no  the  not  results for larger  increased  This  tomatoes.  92.98% c o r r e c t  justify  circuit  found out  the  i n surface  to  wave-  measuring  found  They o b t a i n e d  meter with  strawberries.  increase  to  used r e f l e c t a n c e at three  i n t e n s i t y about  s i z e was  "b"  reflectance  a measure o f  prunes  making r e f l e c t a n c e measurements a t  difference  tion  was  The  a l s o been u s e d as  tomatoes  H o o v e r and  the  in parallel  method t o make s e p a r a t i o n  on  significantly by  has  a l . (20)  671  the  reflectance  tion  the  The'  maturity.  w o r k i n g on a t one  tomatoes.  w a v e l e n g t h s by  shaped tomato.  circuit  the  fruit.  Heron e t lengths  o f the  of  i l l u m i n a n t and  m e a s u r e d a t two  irregularly  Surface grading  was  an  p h o t o c e l l s were a r r a n g e d  flowing  maturity  c o l o u r o f t o m a t o e s as  i t can  be  evaluarelated  to  some known r e p r o d u c i b l e design  of a harvesting Gaffney  system  and  f o r grading  Reflectance  at  as  nm  wavelength  field  IVR  as  Jahn  (19)  This  2.3  a colour  measuring  and  also  the  criteria  nm  as  reference'  the  measurements  s y s t e m was  while  w o r k i n g on  "Index o f  the  variance  develop-  in reflectance lemons:  =  R  R^  =  Reflectance  at  6780A  (678  nm)  R  =  Reflectance  at  7200A  (720  nm).  2  cumbersome  uneconomical.  f o r c o l o u r measurement o f - R  wave-  wavelengths,  IVR  [1  ?  to  classify  lemons i n t o f i v e  distinct  catagories.  Study  of  Present  Strawberry  Harvesters  A number o f o r g a n i z a t i o n s development o f  strawberry  Oregon S t a t e pelled,  of  fingers.  These the  two  crop  have been engaged  in  the  harvesters.  University  once o v e r s t r a w b e r r y  consisted  through  590  Since  a s t a t i o n a r y machine, the  operations  the  r e f l e c t a n c e a t two  m e a s u r i n g w a v e l e n g t h and  i n d e x e n a b l e s one  colour  devised  measurements made a t two  a lemon g r a d e r used  where,  in  system.  Powers et_ a l . (35) ment o f  utilized  gave good c l a s s i f i c a t i o n .  weremade by for  t o be  tomatoes u s i n g  lengths. 540  standards  (3)  developed a s e l f  harvesting  machine.  hollow p i c k i n g r e e l s with f i n g e r s s t r i p p e d a l l the  The  promachine  spring-steel  b e r r i e s as  i t moved  row.  A U n i v e r s i t y o f Arkansas group  (3)  developed  a  commercial  harvesting  t o r a i s e the could  strip  lift  the  them f r o m t h e  berries. the  using  The  g r o u n d so  (3)  the  of  and  improvement  textile  vegetables  of  forced  a i r to  accomplished  by  have a l s o been d e v e l o p e d  designs  are  different.  In  ments i s o f t e n e v e n on  The  lately  and  still  by  University units  underway.  paint  and  a recent  required.  fruit  In  l i e at the  of  industry  i s not  More-  very  problem i s  industry  one  set of  the  fruit  fruit  the  quickly adjust and  must be  vegetable separately  Successive  measuring  range.  measure-  entire  change i n c o l o u r  should  the  the  fruit  the  a second.  extremes o f  to  and  petro-  nature of  dye  that  c o l o u r o f each  in a fraction  the  innovation.  enough t o e s t a b l i s h c o l o u r o f  Hence, a p p a r a t u s  however, the  i n p a i n t , dye  a p p l i c a t i o n of c o l o r i m e t r y  i s because the  the  used  i n p e t r o l e u m and  a continuous process  changes i s not  usually  and  been w i d e l y  a p p l i c a t i o n t o the This  gradual.  has  i s comparatively  efficient.  may  was  a t r a c t o r mounted  picking fingers.  i n the  industry  industry.  over, the  and  fingers  Colorimetry  chemical and  aluminum  A l l t h e s e m a c h i n e s have been e x p e r i m e n t a l  Colorimetry the  designed  harvesting  b e r r i e s with  Illinois.  4  " a i r suction"  U n i v e r s i t y o f Iowa, U n i v e r s i t y o f T e n n e s s e e  only 2•  that  principle  Strawberry harvesters the  machine used  plant.  Rickson  harvester  stripping  The  b e r r i e s from the  Hughes and strawberry  unit.  batch  is to  large  industry, determined,  measurements  3.  ANALYSIS OF PHYSICAL PROPERTIES AND COLOUR MEASUREMENT.  This  chapter presents the physical  the r h e o l o g i c a l  characteristics  p r o p e r t i e s and  o f the strawberry  methods e m p l o y e d  t o measure i n d i v i d u a l  also  These p r o p e r t i e s a r e e s s e n t i a l  ing  discussed. the behaviour  of the f r u i t  fruit.  The  characteristics are  to the applied  f o r determin-  machine  forces.  Various  components o f t h e m a c h i n e e m p l o y e d  i n h a n d l i n g and  storage  are designed  characteristics.  3  •  The S t r a w b e r r y  1  Before designed  P l a n t and F r u i t  t h e h a r v e s t i n g system  i t i s necessary  morphological  The Fvagavia  are necessary  strawberry  y e a r , produces under.  I n many c a s e s  fruit  rows.  naturally,  Fully  (Figures l a , l b ) .  foliage  (Figure 2).  beds o r m a t t e d 1.2 M  0.6 6 M w i d e and  As t h e b e r r i e s  g e t h e a v i e r and s a g down and a r e h i d d e n  plowed  f r o m one  rows a r e s p a c e d  row i s a b o u t  them  i s made e v e r y  y e a r and i s t h e n  i s grown i n s o l i d  mature, t h e crop  0.33 M h i g h ,  and s e t t i n g  c r o p s may be p r o d u c e d  When grown i n rows, t h e c r o p  apart.  o f t h e genus  a new p l a n t i n g  the following  The s t r a w b e r r y  design.  Strawberries are propagated  form  However, two a n n u a l  planting.  they  to achieve a r a t i o n a l  i s a p e r e n n i a l herb  removing r u n n e r s , which  about  A knowledge o f t h e s e  a n d f a m i l y Rosaceae.  i n t o new f i e l d s .  o r m a c h i n e c a n be  t o have a knowledge o f p h y s i c a l and  characteristics.  characteristics  by  on t h e b a s i s o f t h e s e  mature  under t h e dense  Figure i a .  Figure  lb.  A t y p i c a l strawberry  A t y p i c a l strawberry  field  plant  9.  The  strawberry  i s a j u i c y , e d i b l e and  fruit.  Strawberry  but  the  shape changes w i t h  its  colour  berry  (seed) are  plant  system at  soft,  fluffy  attachment  and  picking.  Since  time the  picking  a l l the the  Fruit  at  x  fruit  across  at  feet  36  0.66  x  (0.33 to  find  M)  row.  M)  3).  ripe  and  pith  ripens  straw-  yellow  i s attached  The  berry  changes  to  area and  the  becomes  the  fruit  i s achieved  m a t u r e s o v e r an every  two  complete p l a n t the  by  hand  extended p e r i o d or three  days.  is stripped.  p l a n t and  h e n c e new  of When  This  plantings  e a c h o f s i x rows  A metal wire was  used to  The  fruit  o f row  at  36  (18  frame 1'  count the  foot  (0.3  months x 2'  x  3 inch  (7.6  fruits  cm)  1'  distribution  distribution  was  also  fruit  were c o n t a i n e d and  distribution  of  counted  places.  sections  plant height  M)  old)  number o f b e r r i e s were c o u n t e d between t h e  of the the  surface  fruit  harvesting  on  study.  0.33  A l l the M)  crop  places  the  The  line.  The  number o f p l a n t s were c o u n t e d p e r  (12  successive  strawberry  Plant D i s t r i b u t i o n  f o r the  (0.33  (Figure  damage t o  six different  selected  the  as. c o n i c a l  year.  and The  The  i t ripens.  The  i s scheduled  causes e x t e n s i v e  3.2  described  decreases.  machine, the  done e v e r y  as  attached. pith  be  variety.  h o l l o w when t h e  force  with  best  i n c o l o u r on  the  Almost  picked  can  from green to red  i s b r i g h t red  achenes  are  fruit  aggregate  about the within  h e n c e no  along  the  row  the  1  center foot  a t t e m p t was height  four  of the  made plant.  10.  Figure  3.  C r o s s - s e c t i o n view o f strawberry  a  11.  Results  o b t a i n e d f r o m 36 o b s e r v a t i o n s  plant distribution row was fruit  21+5.  (number o f p l a n t s )  Figure  that  across  b e r r i e s , row s l i c e s  22.5  be h a r v e s t e d . ,  Fruit  weight  on a M e t t l e r H-16  harvest  t h e 1970 + 4.15  strawberry  crop  harvested.  finger  from the  spacings  gms.  was  change  weight  Janick  (24)  was  A sample of  s e a s o n t h e mean w e i g h t  t o be 1 4 . 2 It  following  be  type chemical balance.  In  t h e 1970  the  centerline  of the i n d i v i d u a l strawberry  used to f i n d average  not  are l o c a t e d w i t h i n  t h e row  design,  b e r r i e s was  did.  figure  and  capacities. The w e i g h t  11.08  This  and s i z e a r e i m p o r t a n t  of view of a p i c k i n g r e e l  conveyor  frequency  10 0 p e r c e n t o f t h e  6 0 cm s h o u l d  the  S i z e J*nj3_J^/eJ^g_ht Strawberry  point  cm t h i c k a b o u t  that  cm) o f  and t o p i c k ' 85 p e r c e n t o f  and t o h a r v e s t  t h e e n t i r e row w i d t h o f 3. 3  (30  t h e row w i d t h .  60 p e r c e n t o f t h e b e r r i e s  15 cm o f t h e row c e n t e 3 ? l i n e  should  per foot  4 shows t h e c u m u l a t i v e  d i s t r i b u t i o n curve  indicates  showed  of  measured 172  strawberry of  fruit.  strawberry  found the average  weight  was of  gms.  found t h a t  average  weight  of r i p e  s i g n i f i c a n t l y over the harvest  season the simple r e g r e s s i o n  berries  season.  For  o f Z on X g a v e t h e  equation: Z  =  12.34  n  = 112,  r  0.22  X  = 0.258 ,  [2] Sy  =  3.914  12.  DISTANCE FIGURE 4 .  FROM  CENTER (cms.)  Cumulative frequency f r u i t d i s t r i b u t i o n curve per (30 c m . ) o f s t r a w b e r r y c r o p m e a s u r e d a b o u t t h e . c e n t e r o f the row.  foot  where  Z  =  Mean w e i g h t  X  =  Day o f  per berry  in  gms,  harvest  1 < X < 10 The a b o v e  relation indicates  dent of b e r r y weight berries  can  of the strawberry  c a n n o t be d e s c r i b e d . strawberries  From t h e d e s i g n  But most  can b e s t  is  a r e most  d i a m e t e r and h e i g h t ,  calipers.  5 shows t h e t y p i c a l  Figure  and t h e s t a t i s t i c a l  dimensions  is  given  harvest.  (Figure  and maximum important  of  a  5).  and  variables.  w e r e made w i t h shape  and  variety  conical  c o r r e l a t i o n of the  i n Table  light  not c o n s i s t e n t  be d e s c r i b e d as  strawberry  indepen-  and  of the Northwest  The m e a s u r e m e n t s ,  fruit  day o f  p o i n t of view the height  minimum d i a m e t e r o f  time i s  and e q u a l number o f h e a v y  be e x p e c t e d on t h e f i r s t  The shape  of  that ripening  hand  strawberry  physical  I.  TABLE  I  CORRELATION MATRIX FOR PHYSICAL DIMENSIONS OF STRAWBERRIES  FRF Mean  6 6 7.8  Std.Deviation  Weight. gms.  +236.7  12.3  gms.  +4.8  Height 2.260 cms. +0.404  FRF  1.0  Weight  0.286  1.0  Height  0.282  0.054  1.0  Mean D i a .  0.38 3  0.445  0.746  of  strawberry  is  2.2 6 + 0.40  2.015  cms.  +0.565  1.0  From t h e t a b l e t h e mean d i a m e t e r i s mean h e i g h t  Mean D i a .  cm.  2.02  + 0.56  cm a n d  Test  conducted  by  Janick  ( 2 4 ) on 144 s t r a w b e r r i e s  indicated  of miscellaneous v a r i e t i e s  a v a r i a t i o n i n average  strawberry  diameter from a  minimum o f 1.90 cm. t o a maximum o f 4.06 cm. 3•  Fruit  4  Retention Fruit  required  Force  retention  force  t o remove t h e f r u i t  m e a s u r e d by a C h a t t i l o n t y p e (capacity  1140 gms).  (FRF) was d e f i n e d  from t h e p e t i o l e .  the  s t e m was h e l d  of  i n a spring  was  applied  fruit dial. fruit  detachment  force  the next For  ripe tests  (FRF).  f o r c e was r e a d  vertically  detachment  The d i a l  and t e n s i o n  ring force  As t h e stem b r o k e o r t h e on t h e  t h e weight o f  force  t o get f r u i t  was t h e n r e s e t  t o zero t o  sample. t h e 1970 h a r v e s t  s e a s o n , t h e mean FRF f o r 112  b e r r i e s was 667.8 + 236.7 grams. conducted  varieties crop  was h e l d  was added t o t h e f r u i t  paper t o avoid  was s e t t o z e r o  detached, the f r u i t the f r u i t  The  i n a 1 cm s l o t t e d b r a s s  t h e screw.  Since  6)  clamp a n d t h e jaws o f  carbide  by t i g h t e n i n g  retention test  silicon  The d i a l  t r i p o d as shown.  loaded  A s t r a w b e r r y was h e l d  5 cm d i a m e t e r .  (Figure  Measurements were made w i t h t h e  clamp were c o a t e d w i t h  slipping.  The FRF was  DPP1 hand dynamometer  dynamometer mounted on a s u r v e y o r ' s fruit  as t h e f o r c e  during  (Stelemaster,  (22)  1963 and 1964 on s i x d i f f e r e n t V e r m i l l i o n , Red Glow, S p a r k l e ,  and Midway) f o u n d t h a t  t h e mean p i c k i n g  different  v a r i e t i e s o f strawberries  different  a t t h e 5% l e v e l  range o f p i c k i n g  Hoag a n d Hunt  was  Sure  force of  significantly  of significance.  F o r 1953 t h e  f o r c e was a maximum o f 1155 grams f o r  in  Figure 6.  Hand dynamometer mounted on surveyor's t r i p o d and strawberry held i n the holder  Vermillion variety  t o a minimum o f  of  7 shows  f o r r i p e o r ready  period. surface ripe  Ready t o p i c k r e d n e s s . •• The  berries  to pick berries  figure  3.5  F/W  867.3  =  n  =  112  Sy  =  215.7  r  r  0.122  2  -  32.7  =  Fruit retention  D  -  Day o f h a r v e s t  force  found  harvest:  season  progresses. i n d i c a t i n g the  [3]  force  i n gms,  for 1 < D < 1 0 .  o f c o r r e l a t i o n between t h e  and day o f h a r v e s t  fruit  gave a v a l u e o f  r a t i o i s the r a t i o o f f r u i t  f o r a sample o f 1 7 2 b e r r i e s . ranged  Mean F/W  t o be  following  mean FRF f o r t h e  - 0 . 3 4 9 .  Ratio  strawberries berries.  8 0 % o r more  D  t h e w e i g h t o f an i n d i v i d u a l b e r r y .  measured  that  o f simple regression  FRF  The F/W to  o v e r the h a r v e s t  are those having  indicates  retention  b e t w e e n t h e two v a r i a b l e s i s :  Coefficient retention  berries  d e c r e a s e s as t h e h a r v e s t  FRF  where  crop  t h e v a r i a t i o n o f mean f r u i t  The e q u a t i o n o f t h e l i n e relation  f o r t h e Sure  strawberries. Figure  force  grams  266.5  71.36  equation  from t o t a l l y  This  retention  ratio  to  r a t i o over the e n t i r e harvest +  2 4 . 2 6 .  The a n a l y s i s  f o r simple  was  The m a t u r i t y  green b e r r i e s  regression  force  of the over-ripe  period  was  o f d a t a gave t h e o f F/W  on day o f  17.  1200r  llGO  1000  80'  F  *  800  LU  g  60  600|  IJU  z o z I—  :  r = 0-122 2  UJ  at  40  Sy , 23-99  Sy = 215-7  UJ  5 a.  n :: \\2  n = 112  400  64-6 + 1-731 D  jr/W"  F RF = 867-3 - 3 2 - 7 D  r  2  r. 0-03 20  200  0  0  !  4 DAY  FIGURE 7 .  IB  OF H A R V E S T  Least square simple r e g r e s s i o n of f r u r t f o r c e a n d F/W r a t i o o n day o f h a r v e s t .  10  18.  F/W  Equations 3.6  =  64.6  n  =  112  Sy  =  23.99  r  =  0.030  2  [ 3 ] and  Rheological  v  [4]  the  D  [4]  have been i l l u s t r a t e d  demand f o r a b e t t e r end  d e l i c a t e and  soft  various  for better handling.  kinds  ment b e f o r e unit  from the  stand  the  to  processing and  product  farm.  reaches the  response  such t r e a t m e n t s  operation  can  be  b e t t e r q u a l i t y o f end  characteristics indicators  Strawberries  and  can  and  of  so t h a t designed  product.  a l s o be  utilized  obtain  from t o t a l l y  the  were p l a c e d and  critical i n an  compressed  2 centimeters curve  obtained  treat-  processing  therefore, to  strawberries  undergo  under-  when  a machine h a n d l i n g f o r maximum  and  efficiency  Moreover, r h e o l o g i c a l as  apparent  maturity  quality evaluations.  force-deformation  maturity  must  electrical  A t a b l e model I n s t r o n t e s t e r ( F i g u r e obtain  together  physical  consumer o r  It i s essential,  b e h a v i o u r and  subjected  7.  strawberries  significant  of mechanical, o p t i c a l  the  product  skin structure of  demand a b e t t e r k n o w l e d g e o f t h e i r properties  in Figure  Properties  Increasing with  + 1.73  curves  green  values  upright  between two per  minute.  from t h e s e  used t o _  f o r strawberries, ranging  to over r i p e of  8) was  strawberries.  in  To  r h e o l o g i c a l parameters, b e r r i e s  p o s i t i o n , as flat  shown i n F i g u r e  9,  p l a t e s at a l o a d i n g r a t e  A typical  force-deformation  t e s t s i s shown i n F i g u r e  10.  of  Figure  9.  Orientation between two  of strawberry flat plates.  compressed  20.  250  .Bioyield p o i n f ( y )  £ 200 O  tu  u . cm.  150  O  100  50 0-*arT (e) 1  .0  10 DEFORMATION  15 IN  MM.  FIGURE 10. T y p i c a l f o r c e - d e f o r m a t i o n curve f o r strawberry s u b j e c t e d t o l o a d i n g between two f l a t p l a t e s a t a r a t e o f 2 cm. p e r m i n u t e .  20  From t h e s e minimum  o r remains constant with  tangent  and  correlation  F/W  (LL) o r the  c u r v e becomes n o n - l i n e a r ,  increase i n deformation,  characteristics  Correlation  between r h e o l o g i c a l  were c a l c u l a t e d  correlation  force  modulus ( 0 ) , o r t h e s l o p e o f t h e f o r c e - d e f o r m a -  c u r v e , were m e a s u r e d .  linear  limit  p o i n t (Y) o r maximum l o a d b e y o n d w h i c h  decreases  tion  the values o f l i n e a r  l o a d when l o a d - d e f o r m a t i o n  bioyield  and  curves  to find  on f r u i t  coefficients  coefficients of parameters  significance  retention  force  among t h e s e  and FRF  of rheological  and F/W  variables  ratio.  The  a r e shown i n  Table I I . TABLE I I CORRELATION  MATRIX FOR RHEOLOGICAL  FRF 667.8  Mean Std.Deviation  +236.70  F/W  Lin.Lmt  71. 36  49 .97  +24.26  +26.10  PROPERTIES  BYP. 116. 6  F/W  0.41  1.00  Lin.Lmt.  0.26  0. 00  1.00  BYP.  0.42  0.25  0.47  1.00  Tan.Mod.  0. 41  0.26  0.28  0.75  of  had t h e h i g h e s t  0.42 3 w i t h b i o y i e l d  Least from  square simple  0.65 -—  1.0 0  FRF  1. 622  + 47.70  FRF  The  Tan,Mod  coefficient  1.00  of correlation  po i n t ( Y ) , ( s i g n i f i c a n t a t P < 0.05).  r e g r e s s i o n o f FRF  a.sample o f 118 s t r a w b e r r i e s i s :  on b i o y i e l d  resulting  2.2.  where  FRF  =  504.8 + 2.0  n  =  118  Sy  =  208.6  r  =•  0.178  2  FRF  =  Fruit  Y  =  Bioyield  The above r e s u l t derived point  i s c o n s i s t a n t with  berries  on t h e f i r s t  the l a s t  value  gms.  day  the harvest  may  Fruit  than  was  I t c a n be  12 6.1  i s a marked  gms,  straw-  whereas  the value decrease  was i n the  s t r a w b e r r i e s as t h e h a r v e s t  the f r u i t  those  retention  f o r 30 r i p e  season,  harvested  harvested  a l s o be d e r i v e d . f r o m  on t h e l a s t mechanical  on p r e v i o u s  the r e s u l t s  of f r u i t  day  days.  i n the  retention force to .  (^) i s n o t b e t t e r t h a n FRF i n i n d i c a t i n g  parameters  as m i g h t h a v e f i r s t  been  expected.  Quality Evaluation  The q u a l i t y surface  point  day o f h a r v e s t  Hence  11.  s e a s o n i s more s u s c e p t i b l e t o  weight o f the berry  3•7  of bioyield  t a b l e t h a t the r a t i o  rheological  i n Figure  the i n c r e a s e i n f r u i t  point of ripe  damage and b r u i s i n g It  i n gms.  t h a t an i n c r e a s e i n b i o y i e l d  I t shows t h a t t h e r e  of b i o y i e l d  previous  point  (tenth) of harvest  season p r o g r e s s e s . of  r e t e n t i o n f o r c e i n gms  f r o m t h e above r e s u l t s  The mean v a l u e  78.1  [5]  is illustrated  force.  on  Y  colour, size  quality, i s evaluated between t h e f i n g e r s . .  o f s t r a w b e r r i e s c a n be e v a l u a t e d or firmness.  In the p r o c e s s i n g u n i t s  m a n u a l l y by f e e l i n g In o r d e r  by  the b e r r i e s i n  to commercialize  the  process  900 E cn UJ  V  800  ca.  O uZ O  700  (—  z LU *-  £  u.  FRF - 504-8+ 2-03 Y  600  n - 118  Syr 208 6 500 r  0  20  40  60 BIOYIELD POINT  FIGURE  11. Least force  2  =  0178  100  80  lio*  (gms.)  square simple r e g r e s s i o n on b i o y i e l d p o i n t .  of fruit  retention  t h e 'mechanical and to  or electronic  the rheology  o f the f r u i t  s o r t e r h a s t o make t h e d e c i s i o n s ; provides  the obvious  r e p l a c e t h e manual o p e r a t i o n .  Since  w h i c h i s t h e p o i n t when t h e s k i n  starts  destructive Therefore,  test,  force also  until  behaviour  the i n i t i a l  a non-destructive  criteria  test.  m e a s u r e d by m a n u a l l y  between t h e f i n g e r s . as  on t a n g e n t  where  rupture  compressing  quality.  =  644.7 + 59.6 9  n  =  118  Sy  =  2 26.8  r  =  0.410  FRF  =  Fruit  0  =  Tangent  mechanical  i n the f r u i t , i s i s probably the  the strawberry modulus c a n be u s e d  The s i m p l e  regression of  modulus.  requires  knowledge o f t h e b e h a v i o u r  loading,  vibration,  heat  force-deformation data.  is a  r e t e n t i o n f o r c e gms,  complete design  tial  modulus  modulus i s :  Although  the  occurs  Moreover, t h i s  FRF  2  evaluation.  to applied  Hence, t h e t a n g e n t  an i n d i c a t o r o f f r u i t  FRF  rupturing, i s a  Tangent modulus, which  i n response  cell  point,  o f s t r a w b e r r i e s , tangent  seems t o be a b e t t e r p a r a m e t e r . measure o f f r u i t  the b i o y i e l d  i t i s not d e s i r a b l e f o r q u a l i t y  to define quality  solution  o f h a r v e s t i n g and h a n d l i n g  equipment  o f s t r a w b e r r i e s t o shock  and many o t h e r  characteristics  types  provide  The a n a l y s i s o f f o r c e - d e f o r m a t i o n  of  treatments,  most o f t h e e s s e n characteristics,  900  -800 E CD  FRF  700  - 644  59-64©  u D i  o Z  6001  o z  n  I—  =H8  S = 226-8 y  £500] LU  r =-. 0-168 2  D i  z> 400| D i  300 h  200  JL  !  0 0  TANGENT FIGURE 1 2 .  1-0  0-5  Least square Modulus,  1-5  MODULUS  simple  r e g r e s s i o n o f FRF on T a n g e n t  2-0  apart  from the  above t h r e e m e a s u r e d p a r a m e t e r s ,  knowledge o f p a r a m e t e r s w h i c h strawberry storage  stripping  and  can  be  used  provide  i n the  mechanisms, c o n v e y i n g  even f u r t h e r treatments  i n the  Eva1uation  of  design  systems,  of  hopper  processing  operations. ^•  Colour  8  Normally surface  redness,  and  fruit  and  Maturity  ripeness  p i c k i n g and  Fruit  i s judged sorting  on  the  basis  i s carried  out  of by  t visual  colour  mechanically, tion,  or processed  design  Therefore,  a continuous  criteria  to f i n d  spectrum of the  Subjective  Colour  Subjective  value  percent  zero  strawberry,  100  strawberry  the  colour  Appropriate  berry  and  ripeness  criteria system,  s u r f a c e was  o v e r a 10  of  for  the  the  analyzed.  r e d was  given  percent  to p a r t i a l l y  red  coloured  strawberries  o f Northwest  red  and  colour  surface  red  strawberries. variety  are  (Figure  a  period.  A  green ready  t o t h a t w h i c h was  in surface  of percent  harvest  to a t o t a l l y  and  120  were made on  day  to a completely  values  opera  f o r quick  i n d i c a t e s the  percent  b e c o m i n g deep r e d  processing  i s needed  colour determinations  strawberries  of  picked  Evaluations  sample o f 118  and  t o be  of a s u i t a b l e s e l e c t i v e h a r v e s t i n g  reflectance  pick  on  c o l o u r e v a l u a t i o n which  berry.  3.9  I f b e r r i e s are  some s u i t a b l e c o l o u r  accurate the  judgement.  to  over-ripe 13).  c o l o u r were A typical  given  sample  shown i n F i g u r e  13.  o  3.10  Spectral The  visual or subjective  compared w i t h surface.  Characteristics  the s p e c t r a l c h a r a c t e r i s t i c s of the strawberry  T h e s e r e s u l t s were t h e n u s e d  electronic  colour  used t o o b t a i n  strawberry  spectrum r e c o r d e r  the r e l a t i v e  surface.  lower p o r t i o n  A 2.54  reflectance  o f e a c h s t r a w b e r r y was h e l d  15), covered with  saran  visible  spectrum  t o 700 nm)  Unicam.  percent 5  (400 nm*  0.97).  1  curves of the from the  i n a metal  on t h e f a s t  analyses  s a m p l e s o v e r t h e 1970 h a r v e s t  holder  speed o f  c a l i b r a t e d f o r 100  on a magnesium o x i d e s u r f a c e  Spectral  (reflectance  were c a r r i e d o u t on  season.  The r e l a t i v e  into  normal curves  Figure totally  green,  .to c o l o u r single  16).  T h e s e c u r v e s were  and p l o t t e d on an a r i t h m e t i c  17 shows t y p i c a l  The  any  (Figure  ready  simplest  relative  to pick way  converted scale.  and o v e r - r i p e  strawberries.  strawberries  measurement o f r e f l e c t a n c e .  I t may  be assumed  one p e c u l i a r i t y i n t h e r e f l e c t a n c e p r o p e r t i e s  1 n a n o m e t e r (nm) Is the r a t i o  = 1 x 10  as  i t s r e f l e c t a n c e c u r v e by a  meters.  of reflected light  to incident  that  o f straw-  _c  *  on a  r e f l e c t a n c e curves f o r  to discriminate  i s to characterize  118  reflec-  t a n c e c u r v e s p l o t t e d by t h e i n s t r u m e n t were r e c o r d e d logarithmic scale  14)  wrap, and s c a n n e d o v e r t h e  The s p e c t r o p h o t o m e t e r was  reflectance  factor '"  o f an  (Figure  cm d i a m e t e r s u r f a c e  (Figure  the  i n the design  detector.  A Unicam a u t o m a t i c was  c o l o u r measurements were  light.  Figure 14.  Unicam a u t o m a t i c r e c o r d i n g spectrophotomet e r  29.  Figure  15.  Strawberry holder  surface  held  i n sample  :"T.i  ;.».:f'.':.»:i:.'  i L'-I:M.'(V  8 +->  10 4H  I I  •10  C  6 0  2 0  7 0 0  WAVELENGTH MILLIMICRONS A L I G N WITH INDEX  CONCENTRATION  SAMPLE A N D F O R M U L A  C N THE RECORDER  FIGURE 16.  READY  TQ P I C K  STRAWBERRY  A typical relative on t h e l o g a r i t h m i c  reflectance scale.  ::ENCE  I'ATII L E N G T H  curve  (SCAN  MgO. R. F. 0.  97AIE  SPEC!)  FAS I  .  SI O v /  :  J u n e 1 9 , 1970  M M | OPERATOR  f o r a strawberry  surface  recorded  0 0  PERCENT  © f— O 1  o  T "  O  RELATIVE CO  o  REFLECTANCE  ,'v O  O  O O  3  berries  is characteristic  c o l o u r measurements o f more n a r r o w r e g i o n s known t o o c c u r . be  made i n t h e  o f a l l the  fruit  o f the  can  of  the  that  this  respect  particular 520  nm  the  and  difference  in relative  between t h e r a n g e and  berry  could  different  650  the  nm  value at  of  525  f o u n d by  surface  red  regression percent  (green  -0.740 a t  equation:  region  colour  are  of  range o f above,  520  to  berry  the  insignificant  nm  525  nm  of the  increases  redness  represents  difference  to  650  the  nm  visual the  at  judgements.  colour  these evalua-  highest c o r r e l a t i o n  wavelength.  The  indicates that  negative  reflectance  spectrum) decreases berry  525  on  nm  surface  r e f l e c t a n c e s at  o r the  f o r 118  the  reflectances  the,visual colour  of r e f l e c t a n c e at  surface  should  greatest.  i s a sharp  c o r r e l a t i n g the  correlation coefficient  nm  are  ripeness.  analysis indicates that was  or  r e f l e c t a n c e up  r e f l e c t a n c e s over the  w a v e l e n g t h s were c o r r e l a t e d w i t h  coefficient  is  17  over the  However, t h e r e  wavelengths with  The  classes  w a v e l e n g t h and  E i g h t w a v e l e n g t h s were s e l e c t e d and  tions.  measurement  relative  wavelength which b e s t be  t o one  anamolies  r e f l e c t a n c e i s once a g a i n  ripeness.  relative  The colour  f r o m the  berry  colour  change s i g n i f i c a n t l y  ripeness;  o v e r the  this  r e s u l t s shown i n F i g u r e  significance since  does n o t  only  Hence,  s p e c t r u m where change i n  r e f l e c t a n c e between c o n s e c u t i v e In  confined  s p e c t r u m where s u c h  I t i s evident region  be  strawberries.  matures.  visual  as  the  The  evaluation  s a m p l e s gave t h e  simple of  following  R  =:  17.16 17.16  n  ==  118  Sy  ::  27.33  = =  0.551  525  c o c  :  2 r where  R  525  IR The  highest  Percent  :=  Percent  c o r r e l a t i o n of  of  reflectance  at  630  nm  =  :  P  i n the  measure t h e  measuring system, the restricted 525  to  nm.  to  magnitude  [7]  visual colour region  of  the  reflectance  fruit  can  a n a r r o w band o f  A portion  photocell. tional  red  R  evaluation  with' t h a t  s p e c t r u m was  0.562  wavelength. To  of  -- 0.17  The the  of  is also  of  influenced  wavelengths  These  functional  nm  f o r the with  i n the  current  berry. factors  The  vicinity  is  by  a  propor-  current  o t h e r than  relationships  colour  light  reflected is intercepted  the by  525  illuminated  resulting photoelectric  reflectance  reflectance.  light  be  at  can  strawberry  be  expressed  by:  where  The  I  =  SR  [8]  I  i s the  photoelectric  R  i s the  percent  S  i s the  sensitivity  component S c o m p r i s e s  sensitivity,  i n t e n s i t y of  location  orientation  and  current,  strawberry of  the  reflectance, system.  such q u a n t i t i e s  as  i l l u m i n a t i o n , berry of berry  with  respect  photocell shape and to  size,  illuminant  34.  and  photocell,  surface  Although reflectance reasonably  of berries  a t t h i s w a v e l e n g t h would  good e v a l u a t i o n  of berry  many e r r o r s  ripeness,  caused  by S, and v a r i a t i o n i n i n s t r u m e n t  reflectances. tances  and w e t n e s s .  t h e e l e c t r o n i c measurement o f  however, i n c o r p o r a t e ted  roughness, g l o s s ,  Therefore,  surface give  a  i t would,  by v a r i a b l e s  represen-  response a t d i f f e r e n t  i f measurements o f s u r f a c e  a r e made a t one w a v e l e n g t h , i n a c c u r a c i e s  measurements w o u l d be i n c o n s i s t e n t  reflec-  c a u s e d by  fordifferent levels of  reflectances. This variation berries the  method m i g h t , n e v e r t h e l e s s ,  i n R between c o n s e c u t i v e  were v e r y  factors  great  represented  hetrogeneous mixture berries  f o rdiscriminating  of  i f the various  to the v a r i a t i o n i n  And, a g a i n , because o f  o f g r e e n and r e d c o l o u r  e v e n o f t h e same l e v e l  impractical  reflectances  i n comparison by S.  be u s e f u l  f o rdifferent  o f m a t u r i t y , t h i s method i s berries  according  to their  colour. 3.11  Colour  Criteria  Another quantity is  the r a t i o of reflectance  This  -  sensitivity  has l o n g  ratio of reflectances  reflectance of  a t two s e l e c t e d  c o l o u r c r i t e r i o n whose m e a s u r e d v a l u e  instrument The  p r o p o s e d as a c r i t e r i o n  .,  possible  r a t i o , was  . .  , .  been used  1  wavelengths.  i s independent o f i n colorimetry.  a t two w a v e l e n g t h s , c a l l e d t h e  computed  combinations,  o f colour  f o r each b e r r y  600  e . g . gTjrjs  640  650  j f ^ o ' "530"  f o r a number  .  etc.  Out  of  a l l the  reflectance colour.  r e f l e c t a n c e . r a t i o s f o r each b e r r y ,  ratio  T h i s was  reflectance The  gave t h e  highest  required  to represent  d e t e r m i n e d by  ratios  colour.  best  was  represent  correlation  the  statistically  f o r each b e r r y w i t h  reflectance ratio  surface  the  coefficient and  surface  comparing a l l  each b e r r y ' s  f o r a l l the  colour  one  b e r r i e s which  was  was  surface  considered  called  the  to  maturity  ratio. 3.12  Maturity The  Ratio maturity  of r e f l e c t a n c e s at of strawberry maturity used t o  ripeness  of the define  the  relation  increase  and  two  525  nm.  can  be  In  the  present  i n d i c a t e d that in surface  The  simple  the  and  the  ratio  I t i s a good i n d i c a t o r  used e f f e c t i v e l y  redness.  ratio  study  to  define  i t would  be  purposes. maturity Figure  percent  ratio 18  increases  shows  surface  regression indicating  the  redness the  relation  values i s :  . Mr  =  -1.7 6 + 0.11  n  =  118  Sy  =  29.05  r  =  0.493  Mr  =  Maturity  Rp  =  Percent  2  b e e n e s t a b l i s h e d as  and  between m a t u r i t y  between t h e  has  quality for harvesting  of strawberries.  where  nm  fruit.  Analysis with  650  ratio  Rp  [9]  ratio, surface  redness.  FIGURE  18.  Least ratio  square simple r e g r e s s i o n of on p e r c e n t s u r f a c e r e d .  maturity  37.  It the  fruit  Almost  o f maturity  ratios  ranging  between  ratio  as t h e m a t u r i t y  among m a t u r i t y BYP a r e g i v e n  0 t o 10.  increases, have  Negative  correla-  and r e f l e c t a n c e a t 52 5 nm waveg r e e n c o l o u r on t h e s u r f a c e  ratio  ratio,  ratio  t h a t as  from green t o o v e r - r i p e  i n d i c a t e s the percent  decreases  and  the value  between m a t u r i t y  length  tion  ripens  f r o m t h e above r e l a t i o n  a l l the strawberries  maturity tion  c a n be d e r i v e d  increases.  FRF, F/W,  Simple  percent  correla-  surface  redness  i n Table I I I . TABLE I I I '  CORRELATION MATRIX RHEOLOGICAL  Lin.Lmt.  BYP.  525  FOR SPECTRAL AND PROPERTIES  . nm 650 nm r r  n  Lin.Lmt.  1.0  BYP.  0.47  1.0  nm-5 25  0.14  0. 54  1.0  nm-6 5 0  0. 20  0.00  -0,06  1.0  Matu.. rity Ratio  Maturity Ratio  -0.18  -0.47  -0.76  0.24  Tan.Mod.  0.28  0.76  0.57  -0.06  -0.44  Tan. Mod.  Percent Red  1.0 1.0  Percent Red  -0.19  -0 . 57 -0.74  -0.05  0.70  -0.51  1.0  Day  -0.27  -0.27  -0.44  -0.21  -0.05  -0.01  The correlation decreases  0..14  bioyield point  w i t h rnaturi ty as t h e m a t u r i t y  and  ratio. ratio  tangent The  Day  modulus h a v e p o o r  value of tangent  increases  1.0  further  modulus  confirming  t h e f a c t t h a t t h e b e r r y becomes  s o f t e r as i t r i p e n s .  decreased value of b i o y i e l d point with i n c r e a s i n g (increased value of maturity r a t i o ) becomes  increasingly In  is  usually  L'Eclairage)  quality control operations e v a l u a t e d i n CIE variables.  cated spectrophotometers a r e made on l e s s  of high prices of  equipment  variables  can, however,  f o r comparison. samples  A study  show ( T a b l e I V )  products de  sophisti-  in colour  s u c h as  D i f f e r e n c e Meter or H i t a c h i P e r k i n - E l m e r These  damage.  Internationale  t h e measurements  expensive  berry  the c o l o u r of  (Commission  Because  ripeness  shows t h a t t h e  s u s c e p t i b l e to mechanical  The  variables  a Hunter  Colour  Spectrophotometer.  be c o n v e r t e d i n t o CIE  standards  c a r r i e d o u t on a l i m i t e d number t h a t CIE  '>", y and ss v a l u e s h a v e  c o r r e l a t i o n with the surface redness TABLE  value of a  of good  strawberry.  IV  CORRELATION MATRIX FOR CIE COLOUR VARIA3LES OF STRAWBERRY SURFACE  PercentSurface . Red Percent  Surface  Red  CIE-x  CIE-y  1.00  Y-value  0. 893  CIE-x  0. 8 74  CIE-y  0. 870  Studies  Y-value  1.00  c a r r i e d o u t by H o o v e r  1.00 1.0 0  and D e n n i s o n  a H u n t e r C o l o u r D i f f e r e n c e M e t e r w i t h an ' R d ' 1  circuit  (23) to  cn  measure  the c o l o u r of  strawberries,  between s u r f a c e redness  and  They  value which i s  suggested that  'a'  pigment  i n the  quality  control.  berries  by a method s u c h as  it  strawberries  'a'  showed t h a t  v a l u e was  significantly  i n d i c a t i v e of  But any e v a l u a t i o n o f c o l o u r o f  t h e CIE  Meter v a r i a b l e s partially  values  are not  above  is  is  not  red  straw-  l i m i t e d i n scope  unles  standards.  and t h e H u n t e r C o l o u r  Difference  j u s t i f i e d for colour evaluation  r i p e o r even r i p e b e r r i e s  the strawberry  hig  c o u l d be u s e d e f f e c t i v e l y f o r  c a n be r e l a t e d t o some known r e p r o d u c i b l e  Moreover,  correlation  because  the colour  uniform over the e n t i r e berry  of of  surface  no.  4.  DESIGN OF COLOUR MEASURING SYSTEM  This detection  system.  siderations electronic also 4  been  •  chapter  discusses the design  The o p t i c a l  which a f f e c t circuitry  of a colour  and o p e r a t i o n a l d e s i g n  con-  the performance o f t h e system, the  and i n s t r u m e n t a t i o n  o f t h e s y s t e m have  discussed.  .Theory o f D e s i g n It  h a s been e s t a b l i s h e d t h a t m a t u r i t y  measure o f f r u i t ripe  and u n r i p e  of maturity  s t r a w b e r r i e s c a n be made b a s e d on t h e v a l u e  ratio.  .In o r d e r  to d i v i d e the strawberries (ready  (not  of maturity  selected.  to pick),  one v a l u e  t o p i c k ) and immature ratio  T h i s v a l u e w h i c h marks t h e d i v i d i n g  m a t u r e and Immature b e r r i e s  was c a l l e d  The  by c o m p a r i n g  s e p a r a t i o n was a c h i e v e d  colour  isa  r i p e n e s s and any d i s c r i m i n a t i o n b e t w e e n t h e  b e t w e e n two c a t e g o r i e s , mature ready  ratio  determinations  value o f maturity  obtained  line  maturity  between  coefficient.  the s u b j e c t i v e  made on t h e s t r a w b e r r y  ratio  h a s t o be  c o l o u r and  from r e l a t i v e r e f l e c t a n c e  curves. The  m a t u r e b e r r i e s were e s t a b l i s h e d a s t h o s e  berries  having  berries  were s e p a r a t e d  maturity  ratio  80 p e r c e n t  o r more s u r f a c e r e d n e s s .  allowing different, values  t o be t h e m a t u r i t y  t h e m a t u r e and immature b e r r i e s . ratio and  higher  than  berries with  coefficient compared  the maturity the maturity  to the visual  of the  coefficient  and s e p a r a t i n g  The b e r r i e s  with  coefficient ratio  a r e t o be r e j e c t e d .  The  a r e t o be p i c k e d  lower than  These r e s u l t s  c o l o u r judgement  a maturity  the maturity were  then  and t h e m a t u r i t y  41.  coefficient found.  t h a t would g i v e  The l o s t b e r r i e s  t h e minimum l o s s o f b e r r i e s  was  i n c l u d e d the immature b e r r i e s  having  a v a l u e o f m a t u r i t y r a t i o more t h a n t h e m a t u r i t y c o e f f i c i e n t , and t h e m a t u r e b e r r i e s h a v i n g  a value of maturity r a t i o  than the maturity c o e f f i c i e n t . berries  lost  by c o n s i d e r i n g  coefficients.  The p e r c e n t  s e l e c t i o n of  increasing  the value  reaches  4.5.  berries.  A sample o f  Figure  d i f f e r e n t values lost  berries  650 nm and  values  118 b e r r i e s  give  525 nm w a v e l e n g t h s  ready  to  pick. The p u r p o s e  g a v e a minimum l o s s o f  of  10  4.5.  of strawberries  would  thus  measurements  and where t h e r e f l e c t a n c e  than 4.5,  o f the system  is  reflectance  c o e f f i c i e n t and t o o b t a i n a  mechanical  response.  the b e r r y  t o measure  is  ripe  a valu©  and  of  corresponding  Discriminator  The a c c u r a c y  o f manual p i c k i n g  commercial purposes.  even a s m a l l  investment  increased precision. reducing  increasing  s y s t e m by m a k i n g r e f l e c t a n c e  equal t o , or greater  for  with  loss  is  Colour  decreases  Higher  ratio  4.2  maturity  until  The s e l e c t i v e s e p a r a t i o n  at  of  percent-  value of maturity c o e f f i c i e n t  percent at a maturity c o e f f i c i e n t of  be a c h i e v e d i n t h i s  19 shows t h e  less  costs  approximately  It  is  is  adequate  questionable,  then,  w o u l d be j u s t i f i e d s o l e l y  The p r o b l e m , t h e r e f o r e , i s  while maintaining a t t h e same l e v e l  accuracy  of  enough whether  for one  of  picking  as t h a t o f h a n d  picking.  FIGURE  19. Showing t h e t h e o r e t i c a l l o s s d i s t r i b u t i o n by s e l e c t i n g d i f f e r e n t values of m a t u r i t y c o e f f i c i e n t .  In  a h a r v e s t i n g machine, d e t e c t i o n of  o f t h e many o p e r a t i o n s  colour is  i n a sequence which i n c l u d e s ,  picking,  orientation,  detecting, harvesting,  hauling.  any o p e r a t i o n s h o u l d i n t e r r u p t f o r a s h o r t  If  o f t i m e , a l l o f them m u s t is  thus  of great  stop.  conveying,  storing  The c o n t i n u i t y o f  though  o f 144 b e r r i e s p e r f o o t  i t m i g h t be p o s s i b l e  advisable.  row  ( 0 . 3 3 M).  a colour sensor  It  Even to  questionable w o u l d be b e t t e r t o  t h e f l o w among two o r more s e n s o r s mounted on t h e  same m a c h i n e not  to design  f l o w o f b e r r i e s , i t w o u l d be  whether such a machine i s divide  period  importance.  a total  handle f u l l  and  operation  The d i s t r i b u t i o n o f s t r a w b e r r i e s o v e r t h e indicates  one  so t h a t t e m p o r a r y f a i l u r e o f one s e n s o r  i n t e r r u p t the whole  does  operation.  The c o l o u r o f s t r a w b e r r i e s  is  f a r from u n i f o r m .  E v e n t h e r i p e r f r u i t s a r e b l o t c h y and m i g h t have p a t c h e s green c o l o u r .  Although, to view the e n t i r e b e r r y  of  surface  c o l o u r w o u l d be u n e c o n o m i c a l , t h e e s s e n t i a l c r i t e r i o n f o r efficient  c o l o u r d e t e c t i n g s y s t e m w o u l d be t o v i e w as  s u r f a c e a r e a as i s alignment  economically possible.  of photodiodes,  • photodiode  an  much  The g e o m e t r y  of  a n g l e o f v i e w i n g and d i s t a n c e  of  f r o m t h e b e r r y s u r f a c e w o u l d be i m p o r t a n t i n  this  context. In  commercial operations  w e t , c o v e r e d w i t h mud, t o o l i t t l e sunshine.  It  is  t h e s t r a w b e r r i e s may be o r t o o much i l l u m i n a t i o n o r  d e s i r a b l e t h e r e f o r e , t h a t the system  is  •capable  o f adjustment All  kinds  expected  during  not  that  it  only  the  the  for operation  of adverse  The  m a c h i n e be  some o f t h e  simulate  and  The  be  requirements  compact b u t  accurately during  call  also  actual  an  that  operation.  e l e c t r o n i c system  c r i t e r i a have t o be The  d e t e c t o r are  considered  c o m p o n e n t s , namely  illumi-  essential considerations  in  any  operation.  r e f l e c t a n c e of a surface  incident  light  requires  that there  reflected  by  performance.  Although, too  cause  in  a shift The  i t .  The  i s the  not  light  adversely  intense  an  same c o l o u r t e m p e r a t u r e o v e r an  affect  time are  like  provide  not  small  the  i l l u m i n a t i o n of  o r mercury  the  operation.  c h a n g e s due  suitable for colour  to  measurement.  lamps a r e  also  operations.  i l l u m i n a t i o n provided  becomes a l l t h e  that  extended p e r i o d o f  fluorescent light  s u i t a b l e f o r such The  system  i l l u m i n a t i o n might  i l l u m i n a n t whose s p e c t r a l d i s t r i b u t i o n  Illuminants  so  of a  of  hue.  i l l u m i n a n t should  operation  percentage  efficiency  i s enough r e f l e c t e d  c h a n g e s i n i l l u m i n a t i o n do  not  can  Illuminant The  long  The  r u g g e d and  measuring r e f l e c t a n c e .  c o l o u r measuring  The  conditions  manual s o r t i n g by  basic optical  nant, object  4.3.1  and  conditions.  O p t i c a l Requirements To  while  field  machine o p e r a t i o n .  perform e f f i c i e n t l y  ^•3  under these  more i m p o r t a n t  must be  i n the  uniform.  case, o f  This  strawberries  because o f t h e i r non-uniformity illuminant berries.  light  devices  with  colour.  i l l u m i n a t e the e n t i r e surface  The  of the straw-  I t i s p r e f e r a b l e , but not e s s e n t i a l t h a t the  incident day  should  i n surface  should  this  be s t r a i g h t  and p a r a l l e l .  i s not d i f f i c u l t .  With  An i l l u m i n a n t  f o c u s s i n g l e n s w o u l d be r e a s o n a b l y  present  equipped  sufficient  f o r the  purpose. The the  object  tance.  o r i e n t a t i o n o f the illuminant with  has c o n s i d e r a b l e  effect  While measuring d i f f u s e  illuminated  f r o m an a n g l e  respect to  on t h e m e a s u r e d  reflec-  r e f l e c t a n c e the object i s  o f 4 5°  to the surface  o f the  object. 4.3.2  The  Object  The  surface  smooth w h i l e  of the object  measuring d i f f u s e  a condition i s ideal, sacrificed.  be l e v e l and  reflectance.  Although  the q u a l i t y of strawberries  Moreover, the purpose here  specification all  should  but evaluation  the colour evaluations  of berry  such  c a n n o t be  i s not colour  quality.  w o u l d be c o m p a r a t i v e  Therefore, and n o t  absolute. Since  continuity of operation  berry  must move p a s t  field  of the detector,  of detector 4  ' • 3  3  The Of  the f i e l d  i s important,  o f i l l u m i n a n t and t h e v i e w i n g  a n d must be w i t h i n  f o r the time d u r i n g  each  the viewing  range  w h i c h measurements a r e made.  Detector a l l the three  components i n c o l o u r  detection,  the c o l o u r d e t e c t o r i s operation requires  most  important.  The u n i f o r m i t y  t h a t d e t e c t o r response  be  consistent,  at l e a s t , over the range of spectrum i n which the ments  are  measure-  made. The economy  of o p e r a t i o n r e q u i r e s  s h o u l d have the l e a s t p o s s i b l e  response  that the detector  time.  A slow  d e t e c t o r c o u l d s l o w down t h e o p e r a t i o n o f t h e e n t i r e thereby s e r i o u s l y  s m a l l and r u g g e d .  equipment  a t the d e t e c t i o n head o f t h e machine. to operate i n adverse  field  the  Because  conditions  congestion  the  i t is  machine  essential  t o h a v e a d e t e c t o r w h i c h w o u l d n o t be a f f e c t e d by s h o c k s other mechanical  a wide angle o f view  t h a t t h e e n t i r e o b j e c t c a n be v i e w e d .  To measure  surface o f the o b j e c t .  the  The d e t e c t o r must a l s o be a c c u r a t e  s i n c e even a s m a l l v a r i a t i o n i n performance c o u l d  4.4  so  diffuse  r e f l e c t a n c e t h e d e t e c t o r must be a l i g n e d a t 90° t o  loss  and  hindrances.  The d e t e c t o r s h o u l d h a v e  significant  cost.  c a s e , s h o u l d p r e f e r a b l y be  Too b i g a d e t e c t o r w o u l d c a u s e  cause  i n performance e f f i c i e n c y .  The D e s i g n o f O p t i c a l Analysis  has  Apparatus  i n d i c a t e d that the maturity r a t i o  a function of r e f l e c t a n c e at  65 0 nm and 5 25 nm.  evident t h e r e f o r e t h a t the r e f l e c t a n c e s at these s h o u l d be m e a s u r e d  simultaneously  same s e n s i t i v i t y .  This  It  is  is  wavelengths  and w i t h e q u i p m e n t o f  was done by i l l u m i n a t i n g t h e  1  response  r e d u c i n g t h e c a p a c i t y and i n c r e a s i n g  The d e t e c t o r , i n t h i s  has  of  the  straw-  47.  b e r r i e s w i t h one i l l u m i n a n t and measuring the r e f l e c t a n c e s with two photodiodes of the same s e n s i t i v i t y .  The d e t a i l s of  photodiodes are discussed l a t e r i n the chapter. The o p t i c a l apparatus used f o r the purpose i s shown i n Figure 20.  The i l l u m i n a t i o n was provided by a 12 V  tungsten lamp, (colour temperature  2854°K).  The lamp was of  f i x e d i n t e n s i t y and could be operated on AC o r DC voltages. A focussing lens was mounted i n f r o n t to focus the l i g h t on the  object.  The r e f l e c t e d l i g h t was f i l t e r e d through two  narrow band i n t e r f e r e n c e f i l t e r s .  Since f i l t e r s of exact  s p e c i f i c a t i o n were not a v a i l a b l e , f i l t e r s with a close approximation were used.  In the prototype, two a v a i l a b l e  B a l z e r i n t e r f e r e n c e f i l t e r s with peak t r a n s m i s s i o n at 640 nm and 540 nm and with 9 nm h a l f band width were used to make measurements at these wavelengths.  The f i l t e r e d r e f l e c t a n c e s  were i n t e r c e p t e d by two Hewlett-Packard #HP 5082-4205 p i n photodiodes.  The photodiodes were p r e f e r r e d over the  t r a d i t i o n a l photo tubes because of t h e i r p o r t a b i l i t y and e f f i c i e n c y .  The photodiodes had a response  time of l e s s than one nanosecond. the  compactness-,  Other s p e c i f i c a t i o n s f o r  photodiodes are given i n Appendix A.  Because of h i g h l y  d i r e c t i o n a l s e n s i t i v i t y of the photodiodes, t h e i r axis has t o be w i t h i n + 10 degrees of the d i r e c t i o n of r e f l e c t e d light. 14  •5  The.__E_1_^.J^£?A_ A P P a r a t u s <  C  < n  c  To evaluate the s u i t a b i l i t y of the system an  48 .  inteference filter  FIGURE 20.  Optical system.  apparatus f o r colour  FIGURE 2 1 .  Cross s e c t i o n a l probe assembly.  measuring  view o f t h e f i l t e r (Not t o s c a l e ) .  49.  e x p e r i m e n t a l a p p a r a t u s was tests of  were l i m i t e d  performance,  performance  and  the e f f e c t  4.5.1  electronic  comparator, The  of and  22.  copper  and  probe  p i n photodiode filter  and  assembly The  obtained 4.5.2  solenoid.  circuitry  was  formed  diameter.  The  on  construction  i s shown i n F i g u r e  f r o m 1/16 filter  end o f t h e p r o b e .  filter  The  filter,  was  The  a plexiglass  inch  (1.5  held  in a  photodiode  mount.  21 mm)  was  Foam p a d d i n g  The  probe  circuit  from H e w l e t t - P a c k a r d a p p l i c a t i o n  notes  915  was  (21).  Amplifier  circuit  amplifier  (Figure  23) was  s u g g e s t e d by H e w l e t t - P a c k a r d  photodiodes.  The  l e a d s which  m o d i f i e d from  photodiodes, f i e l d  effect  short  to minimize  mounted on a p e r f o r a t e d  circuit  transistor,  the probe  are s e p a r a t e d from ground  i m p e d e n c e were k e p t  a  (1967) f o r use w i t h p i n  10 Meg fl r e s i s t o r were mounted w i i t h  was  primary  amplifier,  switch or  circuitry.  to cushion the photodiodes.  The  three  on  consisted of interference  the probe  casing  t u b e o f 25 mm  used  of four  sensor o r probe,  the e l e c t r o n i c  and p r o b e  probe  b e h i n d the  was  speed  parameters  apparatus c o n s i s t e d  assembly  r u b b e r h o l d e r a t one held  of different  the  Probe The  the  efficiency,  The  system.  components n a m e l y , t h e c o l o u r voltage  i n the l a b o r a t o r y .  to the o p e r a t i o n a l  o f the  The  tested  circuit.  and The  by h i g h  pickup.  b o a r d and  The  amplifier  enclosed i n a  10 M E G Q  AA/WVV  <  FEEDBACK  D <+9V  2N3457- FET 5082-4205 PIN DIODE <  SIGNAL  <-9V  C i r c u i t diagram f o r r o b e assembly P  8-4  FIGURE'23..  Circuit  8-4  V  diagram f o r s i g n a l  amplifier  v  metal  casing.  4.5.3  Voltage  Comparator  The p u r p o s e  o f t h e c o m p a r a t o r was t o g e t a  response at the solenoid corresponding measurements  made by t h e p r o b e s .  voltage  comparator i s  through  the i n d i v i d u a l probe i s  t a n c e a t ' w h i c h t h e measurements The s i g n a l v o l t a g e E probe  voltmeter.  °~ ^  signals (green  24.  e  o  i g i  r  p r o p o r t i o n a l to the  a  l  from each probe.  v  a  -l  u  s  t>y  a  10-turn  probe.  was r e a d on a one-fifth,  poteniometer.  r e f l e c t a n c e at  540  The r e s u l t i n g  signal  The  nm  compared w i t h  o f a p o t e n t i o m e t e r by o p p o s i n g  currents  was f e d i n t o a  diode which in t u r n c o n t r o l l e d the s i g n a l 4.5.4  reflec-  o b t a i n e d f r o m t h e 64 0 nm m e a s u r i n g  R  c o l o u r r e g i o n o f s p e c t r u m ) , E g , was signal  the  flowing  a r e b e i n g made by t h a t  from the probe measuring  the output  diagram f o r  T h i s v o l t a g e was r e d u c e d t o n  ratio  The c u r r e n t  (red c o l o u r r e g i o n of the spectrum)  digital ^R/5'  to the maturity  The c i r c u i t  shown i n F i g u r e  mechanics  at the  zenor  solenoid.  The_ SoJLenoid The s o l e n o i d was  t h e component  mechanical response corresponding maturity ratio.  The c u r r e n t  used t o o b t a i n  t o the measured v a l u e  flow i n the s o l e n o i d  c o n t r o l l e d by a z e n o r d i o d e i n t h e c o m p a r a t o r .  the of  was  If  the  m e a s u r e d v a l u e o f m a t u r i t y r a t i o i s more t h a n 5 ( m a t u r i t y coefficient),  t h e s o l e n o i d w o u l d come t o  but i f t h e measured  'close'  value of maturity r a t i o i s  the s o l e n o i d would remain i n  'open'  position.  position,  less  than 5  SOLENOID  TO A M P . RED SIG.  10K 10k  10 T U R N "  AAAAA  POT  TO  AMP.  GREEN  S!G  FIGURE 24.  Schematic diagram f o r v o l t a g e  c o m p a r a t o r and  solenoid  cn co  The T e s t  4.6  Results  An e x p e r i m e n t a l s e t - u p was  shown i n F i g u r e s  used t o t e s t the e l e c t r o n i c system.  p a i n t e d w i t h b l a c k m a t t e p a i n t on i t s by a v a r i a b l e s p e e d m o t o r . equispaced holes  2 5 and 2 6  A circular disc,  p e r i p h e r y , was  Strawberries  rotated  w e r e p l a c e d i n 12  along the periphery of the d i s c .  Each  b e r r y i n t h e h o l e was i l l u m i n a t e d f r o m t h e t o p by a 12V tungsten  l a m p , as  photodiodes. reflectance  i t passed  The e l e c t r o n i c s y s t e m was from a b l a c k  under' t h e p h o t o d i o d e s , photodiodes surface,  under the v i e w i n g f i e l d o f  surface.  zeroed  two  for  As t h e b e r r i e s  passed  t h e r e f l e c t a n c e was m e a s u r e d  by  a t an a n g l e b e t w e e n 4 0° - 4 5° t o t h e b e r r y  arranged  i n t h r e e d i m e n s i o n a l symmetry  about  the  strawberry. Speed o f  4.6.1  Response  The maximum s p e e d o f r e s p o n s e  was m e a s u r e d a t  s o l e n o i d by i n c r e a s i n g t h e s p e e d o f r o t a t i o n o f t h e until  t h e s o l e n o i d w o u l d no l o n g e r  change.  The maximum r e s p o n s e  components  u s e d was  respond t o the  time obtainable  0.166 s e c o n d s  signal  (electrical).  Although  such  different  transducer.  signal  This  to the maturity a response  the e c o n o m i c a l performance' of a h a r v e s t i n g c a n be i n c r e a s e d by u s i n g  disc  from the  per strawberry.  was l i m i t e d by t h e s o l e n o i d r e s p o n s e  a f a s t e r response  the  is  system,  ratio  low  for  the  solenoid  time  or  speed  >  o  DIGITAL VOLTMETER  FIGURE  25.  Schematic diagram o f e x p e r i m e n t a l arrangement c o l o u r d i s c r i m i n a t o r equipment.  for testing  56.  Figure  26.  G e n e r a l view o f the e x p e r i m e n t a l equipment f o r t e s t i n g c o l o u r d i s c r i m i n a t o r equipment.  57.  4  ,  6  ,  2  Surface  and I l l u m i n a t i o n C o n d i t i o n s .  A number o f s t r a w b e r r i e s  f r e s h l y p i c k e d from the  f i e l d were t e s t e d under t h e s y s t e m . and s u r f a c e  c o n d i t i o n s h a v e no e f f e c t on t h e  of the system. laboratory  conditions  and a l l t h e s a m p l e s  signal,  The f l u o r e s c e n t and s t r a y  giving  surface  performance under  c o u l d be i d e n t i f i e d  a 10 0 p e r c e n t  performance.  l i g h t h a d no e f f e c t on t h e  performance but d i r e c t s u n l i g h t o f measured m a t u r i t y r a t i o . was  and  The s y s t e m p e r f o r m e d s a t i s f a c t o r i l y  by t h e e l e c t r i c a l  fruit  The s h a p e  found Independent  causes a s h i f t  i n the  The s i g n a l p r o d u c e d by of the surface  each  conditions  w i t h i n the l i m i t s o f the a c c u r a c y of measurements. it  seems p r o b a b l e t h a t s u r f a c e  affect noise  the s i g n a l , level.  any c h a n g e  conditions i n output  An e f f e c t o f t h i s m a g n i t u d e  commercial operations  of t h i s  kind.  Not r e a d y t o  Total  masked by is  the  unimportant  i n Table  of  in  tests  V.  R e s u l t s o f t h e t e s t s c o n d u c t e d on t h e e l e c t r o n i c c o l o u r d e t e c t i o n system f o r performance e f f i c i e n c y using Northwest v a r i e t y of s t r a w b e r r i e s .  Total berries  Ready t o  Although  do t o some e x t e n t  The r e s u l t s  c o n d u c t e d i n t h e 19 71 s e a s o n a r e g i v e n TABLE V.  is  value  pick  pick  " No."of lost berries unripe accepted or ripe rejected  Percent loss  207  52  25  177  25  14.4  384  77  20  58  4  .  6  .  The A n g l e o f I l l u m i n a t i o n  3  The  output at  on t h e s t r a w b e r r y  an a n g l e between  4 0°  The I n s t r u m e n t The  the  between 10° t o 60° f r o m t h e i n c i d e n t  s i g n a l was o b t a i n e d  4.6.4  Detection  a n g l e o f v i e w i n g h a d no e f f e c t when t h e measure-  ments were c o n f i n e d illumination  and  surface.  But t h e maximum  when t h e r e f l e c t a n c e was m e a s u r e d  t o 45° f r o m t h e i n c i d e n t i l l u m i n a t i o n  Stability  s y s t e m was t e s t e d  forits stability  by c o m p a r i n g  r e s u l t s p e r f o r m e d on t h e same s a m p l e s a t two d i f f e r e n t  times.  A sample o f 24 s t r a w b e r r i e s  switching after  hours.  to justify  system i s t h e r e f o r e having  just after  on the. s y s t e m and t h e same s a m p l e s were  several  signals  were t e s t e d  t o wait  T h e r e was no a p p r e c i a b l e  tested  shift  t h e e f f e c t o f "warm up" p e r i o d . capable o f performing a c c u r a t e l y  f o r long  warm up  periods.  i n the The without  CONCLUSIONS Tests berries  p e r f o r m e d on t h e N o r t h w e s t  variety  i n d i c a t e that the f o l l o w i n g conclusions  of  straw-  c a n be  drawn: 1.  The mean f r u i t - r e t e n t i o n f o r c e o f r i p e decreases  2.  as  the harvest  season  The f r u i t - r e t e n t i o n f o r c e , d e c r e a s e s redness these  increases  as t h e b e r r y  characteristics  strawberries progresses.  and t h e  surface  ripens.  Both  of  of  berry  a r e a good measure  ripeness. 3.  The r h e o l o g i c a l p r o p e r t i e s  of the s t r a w b e r r i e s  from the f o r c e - d e f o r m a t i o n curves indicators  of f r u i t q u a l i t y .  had t h e h i g h e s t parameters fruit 4.  components  The r e l a t i v e r e f l e c t a n c e a t  ratio is  These  525 nm ( g r e e n  d e c r e a s e d and r e l a t i v e  the b e r r y  evaluations.  of  the b e r r i e s  reflec-  spectrum)  ripens.  This  criteria  in a processing  plant.  a  strawberry  c a n a l s o be u s e d  r i p e and u n r i p e b e r r i e s  ripe-  colour  c a n e f f e c t i v e l y be u s e d as  d e c i d i n g parameter f o r a s e l e c t i v e  separating  machine.  an e x c e l l e n t i n d i c a t o r o f b e r r y  It  of  coloured  n e s s and c o u l d be u s e d i n p l a c e o f v i s u a l  harvester.  point  i n the h a r v e s t i n g  640 nm ( r e d c o l o u r e d r e g i o n  i n c r e a s e d as Maturity  The b i o y i e l d  c o r r e l a t i o n w i t h FRF.  r e g i o n o f spectrum)  5.  good  c a n be e f f e c t i v e l y u s e d i n t h e d e s i g n  handling  tance at  are  obtained  or f o r  for grading  SUGGESTIONS FOR FUTURE WORK  Although the s t r a w b e r r i e s behaviour  the r e s u l t s  give  a fairly  of the t e s t s  good k n o w l e d g e  of the  t o a p p l i e d machine f o r c e s , f u r t h e r study  be c a r r i e d o u t on t h e s t r a w b e r r i e s effects  c o n d u c t e d on  of such o p e r a t i o n s  as  impact l o a d i n g ,  due t o f r i c t i o n w i t h t h e c o n v e y o r s p h y s i c a l parameters  to i n v e s t i g a t e  of various  should the  bruising  and v a r i a t i o n i n  v a r i e t i e s of  fruit  the  strawberries.  The p e r f o r m a n c e o f t h e e l e c t r o n i c s y s t e m t o differentiate  b e t w e e n t h e r i p e and u n r i p e  strawberries  s h o u l d be i n v e s t i g a t e d w i t h a p r o t o t y p e o f t h e in actual field  conditions.  Since  harvester  t h e speed of  response  o f t h e s o l e n o i d may be l o w e r f o r e c o n o m i c a l o p e r a t i o n the h a r v e s t i n g machine, d i f f e r e n t transducers t r i e d t o get optimum r e s p o n s e  speed.  should  of be  61.  LITERATURE CITED 1.  Abridged  Coloratiometery for Production Quality  Agricultural 2.  Agricultural Statistics ture,  3.  Province  Where We S t a n d  A u s t i n , M.E.,  Report;  of  British  5.  V.G.  Hort.  B i r t h , G.S.;  S h u t a k and E . P .  Sci  75 : 3 8 2 - 3 8 6 ,  and K.O.  Transmittance Maturity, 7.  British  of  Strawberries,  Christopher;  Color  Strawberry F r u i t , Proc.  A Fiber Optics  B i t t n e r , D.R.  Agricul-  C o l u m b i a , V i c t o r i a , 19 68.  Reflectance  Stephenson;  Properties  ASAE P a p e r No.  Columbia Department  Amer*,  1955.  A g r i c u l t u r a l E n g i n e e r i n g ,448-449 .6.  of  F r u i t G r o w e r , May 19 6 9 .  Changes i n H a r v e s t Soc.  California.  Department  on M e c h a n i c a l H a r v e s t i n g  American 4.  C o n t r o l Systems I n c . ,  Control,  Attachment, (8),  August  Reflectance  o f Tomatoes  of Agriculture, Crops,  and  Versus  6 8-329, June  Berry  1967.  1968. Horticulture  B r a n c h .j  Production of  Grapes  and  Filberts  t o g e t h e r w i t h an E s t i m a t e o f Farm  Values,  1969. 8.  Buchele, of  W.F.  and E . L .  Strawberries,  Denisen;  Mechanical  ASAE P a p e r No.  Harvesting  67-620,  December  1967. 9.  Burkhardt,  T.H.  and R.F.  Mrozek;  Criterion for Sorting • No.  7 1 - 3 1 3 , J u n e 19 7 1 .  Light  R e f l e c t a n c e as  Dried Prunes,  ASAE  Paper  a  62.  10.  Burr,  A.H.  and  M.J.  Duncan;  Portable  Spectroradiometer  f o r Underwater E n v i r o n m e n t s , Department Biological 11.  C a r n e , I.C; Costs,  Sciences,  Strawberry British  Abbotsford, 12.  Chen, P.,  M.O.  No. 13.  Simon F r a s e r U n i v e r s i t y ,  E n t e r p r i s e Data Sheet  CMT-200 and  F.M;  The  Measurement o f C o l o r , 16-22, J a n u a r y  C o n t r o l Systems I n c . ,  F i s c h e r , R.R.,  J.H.  and  Moore;  J.D.  Von  175-179,  and  E l b e , R.T.  Foods, P a r t  Clydesdale;  IX;  Foods, P a r t  April-May R.B.,  P.A. to  Color  Food P r o d u c t  H.D.  No.  Bruhn of  2,  Measurement  Development,  19 69,  XIII;  H.  Goehlich, Factors  Mechanically 2,  California.  Food  Color  Product  Measurement  Development,  19 69.  Adrian;  Vol.  Sheet;  Schular,  ;  Fridley,  1969.  ASAE, V o l . 12,  17.  18.  Food  Some P h y s i c a l P r o p e r t i e s  F.M.  February-March,  of  Paper  1969.  F r a n c i s , F.J. of  ASAE  1969.  Sour C h e r r i e s , Trans.  16.  Leonard;  200B C o l o r R a t i o M e t e r s , D a t a  Agricultural 15.  S.J.  means o f h a r v e s t i n g b e r r i e s ,  T e c h n o l o g y , V o l . 23, 14.  1967  B.C.  69-648, December  Clydesdale,  B.C.  Columbia Department o f A g r i c u l t u r e ,  B r i e n , F, W i n t e r and  Mechanical  of  No.  9;  L.L.  Claypool  Affecting  Harvested  Fruit,  409-411,  1964.  and  Impact Trans.  Injury ASAE  63.  19.  Gaffney,  J . J . and  Sorting  O.L.  o f Vine  Research  Jahn;  Photoelectric color  Ripened Tomatoes,  R e p o r t No.  868,  Marketing  USDA, W a s h i n g t o n ,  D.C.  1970. 20.  H e r o n , J.R.,  K.H.  Kromer and  o f Tomato R e f l e c t a n c e Evaluation, 21.  Hewlett HP  22.  Hoag, Dean L.  H o o v e r , M.W.  Proc.  Luria,  The  ASAE P a p e r No.  65-620,  A  Rapid  Objective  S c i . , 70:  Hort.  Vision,  Fruit  S c i . 76: Physics  Strawberries,  195-198, Size in  1955. Strawberry.  343-348,  Today,  1961.  34-41,  Physical Properties of Plant  University, and  Mechanical  Part  1 o f V o l . 1,  Engineering,  The  and  Department  Pennsylvania  of  State  March 19 68. A.A.  Kaftan;  Harvesting  Strawberries, 1970.  Stripping for  1966.  Agricultural  G.S.  Hort.  Measurement o f  Color  M o h s e n i n , N.N;  Nelson,  1968.  Evaluation of Color i n  Animal M a t e r i a l .  27.  1971.  Photodiodes  Mechanical  Dennison;  Amer. Soc.  March 26.  R.A.  Amer. Soc.  S.M;  Hunt;  Maturity  1965.  f o r the  Janick, J; Proc.  D.R.  Strawberries,  and  Method  25.  T e c h n i c a l Data, P i n  and  Variation  71-329, J u l y  5082-4200 S e r i e s , O c t o b e r  December  24.  Zachariah;  Properties i n  ASAE P a p e r No.  Packard;  Harvesting  23.  G.L.  Trans.  and  Development Grading  of  Equipment  ASAE-, V o l . 13,  No.  for  5 , 743-745 ,  N i c k e r s o n , D;  C o l o r Measurement and  to the Grading Miscellaneous  of Agricultural Publication  A g r i c u l t u r e , January Nimeroff,  I;  January  U.S.  and  T.L.  Mechanical 12,  Columbia, O u r e c k y , D.K. Texture  5,  Ph.D.  Standards  and  M.C. an  S c i . , 93: and  D.E.  Manual C h e r r y 36,  Powers, J.B.,  Transmittance Properties  640-643, O c t o b e r  C o u l t h a r d , Design  1958.  Parameters  Harvester, Trans,  573-576,  Engineer-  for  o f ASAE  1969.  Raspberry  Harvesting,  Thesis, University  of  British  1970.  with  B.E.  No. J.T.  Color Sorting Agricultural March  10,  Mechanical  unpublished  Vol.  Light  Raspberry  No.  N y b o r g , E.O;  Parker,  of  Commerce,  Commodities, A g r i c u l t u r a l  V o l . 39, No.  N y b o r g , E.O.  Hort.  Department  1958.  Department o f  Measuring  of A g r i c u l t u r a l  Vol.  U.S.  196 8.  K.H;  ing,  Products,  C o l o r i m e t e r y , N a t i o n a l Bureau o f  Monograph 104,  Norris,  580,  i t s Application  1953.  Bourne;  Measurement o f  I n s t r o n M a c h i n e , P r o c . Amer. 317-325, Waint;  Efficiency  100-105, F e b r u a r y  Gunn and of Fruits  Soc.  1969.  Sorting, Agricultural 1,  Strawberry  F.C. and  Jacob;  of  Visual  Engineering, 1955. Electronic  Vegetables,  E n g i n e e r i n g , V o l . 34,  No.  3,  149-154,  65.  36.  R o t h , L.O.  and J.G. P o r t e r f i e l d ;  Strawberry  Harvesting,  Mechanical  ASAE P a p e r No.  Aids to  6 0-644,  December 1960. 37.  S t e p h e n s o n , K.Q; Mechanical  Selective  Tomato H a r v e s t e r ,  Engineering, May  1964.  Fruit  V o l . 45, No.  Separation  for  Agricultural  5, 250-253,  66  APPENDIX A P I N PHOTODIODE ( S E R I E S HP 5082-4200)  SPECIFICATIONS  Dimension i n inches O  \o  ZO  50  40  J  Relative  X,  \ • V, \  directional sensitivity of D i n photodiode  O p t i c a l and e l e c t r i c a l c h a r a c t e r i s t i c s a t 2 5°C Sensitive area ... - mO - 3 cm —,2, 3a v X I 0.2 54 mm. Diameter <1 n a n o s e c o n d . Speed o f r e s p o n s e Series resistance ' 50 fi. - 3  2  

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