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UBC Theses and Dissertations

Understanding the swelling behavior of individual starch granules by ParCS Mo, Lanxin


Starch is a widely used ingredient in food products, acting as a thickening, clouding, and gelling agent. Starch gelatinization is an important process that can influence the texture of food products, therefore, it has been studied extensively by many researchers. A Particle Cohort Study (ParCS) apparatus was used to observe the gelatinization process of individual starch granules from four types of legume starch: yellow pea, red bean, chickpea, and green lentil. This new method allows us to capture and understand the variability between individual granules during the swelling that occurs due to gelatinization. The size as a function of time was measured for a large number of individual granules in order to quantify the intra-sample variability for each type of starch, as this information is not available from the standard techniques for characterizing gelatinization: starch pasting and differential scanning calorimetry (DSC). The swelling of individual starch granules under non-isothermal conditions was recorded and subjected to image analysis for quantifying their sizes. For each type of legume starch, around 180 granules were collected for data analysis. The cumulative size distribution measurements using image analysis were similar to that obtained from the laser diffraction method, except for red bean starch, which showed a smaller size by image analysis. We demonstrate that an empirical model, the Gompertz function, is highly effective at describing the size vs. time data. Using the Gompertz function, the data from image analysis are fitted to obtain and extract two new parameters related to gelatinization that we define for the first time in this manuscript: granule-swelling temperature and granule-swelling time scale. The accuracy of these new parameters is demonstrated by comparison with standard techniques. After proposing an alternative method for interpreting starch pasting data we show a very good correlation between all three techniques. The results indicate that these legume starches have a remarkably low variability in gelatinization properties. This new method of characterization is expected to enable optimization of starch gelatinization properties during large-scale processing of food products.

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