UBC Theses and Dissertations
Preparation and characterization of acid-solubilized wheat flour for use as a dairy substitute base Fung, Chi-Pun
A main problem in preparing dairy substitute bases from wheat flour is the insolubility of wheat gluten and starch. In this study, wheat flour was solubilized by acid hydrolysis. More than 90 percent of the dry weight of wheat flour solids were solubilized by autoclaving a 10 percent flour suspension in 0.1N hydrochloric acid at 121°C for 15 minutes. The dried hydrolysate was similar in colour to the original flour and had excellent solubility. The apparent viscosity at 4°C of a 5 percent wheat flour hydrolysate was 4.9 centipoises as compared to 5.7 centipoises for pasteurized skimmilk. Proximate analysis of the dried hydrolysate showed the total carbohydrate and protein contents similar to those of the original flour. Gel filtration of the wheat proteins eluted with AUC (an aqueous mixture of acetic acid, urea and cetyltrimethyl-ammonium bromide) revealed an extensive degradation of most of the glutenin and the high molecular weight gliadin into a protein fraction of 24,000 daltons during hydrolysis. The chloranil test did not indicate a significant increase in amino acids or in small molecular weight peptides. According to a Kjeldahl analysis subsequent to dialysis, ammonia cations accounted for 22% of the total nitrogen, indicating almost complete deamidation during acid hydrolysis. Other nonprotein nitrogen was not detacted in the hydrolysate. SDS-polyacrylamide gel electrophoresis showed disappearance of the typical wheat protein bands and appearance of 3 diffused bands of molecular weights 53,500, 30,000 and 11,700 upon hydrolysis. The 24,000 daltons fraction from Sephadex G-150 column appeared as 2 diffused bands of molecular weights 30,000 and 11,700. A high temperature gel filtration chromatography on Biogel P-2 exhibited the following saccharide composition: 18.7 percent glucose, 11.3 percent maltose, 37 percent oligosaccharides (3-7 glucose units) and 33 percent higher saccharide (more than 7 glucose units). A gel filtration chromatography on Sephadex G-50 indicated only a trace amount of polysaccharides with more than 20 glucose units. No significant destruction of essential amino acids during hydrolysis was observed. Using 0.5 percent protein solutions, the foamability of the hydrolysed wheat flour was found to be slightly better than that of casein, although the foam stability was inferior. A strong wheaty off-flavour appeared after hydrolysis. The most effective method for decreasing this off-flavour was a treatment with granular activated carbon at 90°C. A milk-like beverage made by adding butter was acceptable in taste, appearance and stability. The protein to carbohydrate ratio of the product was lower than that of cow's milk. Addition of other proteins or decreasing wheat starch by a selective washing of wheat flour was suggested to improve the ratio.
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