M.S. Candidate in BSE
Modeling the Softening of Six Grain-Based Food Products during Simulated Gastric Digestion
Knowledge of the disintegration kinetics of foods during gastrointestinal digestion is important to understand the differences in physiological responses between foods of varying chemical and structural design. A longer food softening rate may imply a slower rate of breakdown, which may decrease the nutrient release rate and promote prolonged satiety and prolonged energy stability. The objectives of this study were to examine the differences in mechanical responses (initial hardness and softening rate) of six grain-based foods (brown rice, white rice, quinoa, couscous, orzo, pretzel) under three different compression tests (single compression by 50% strain, bulk compression by 33% and 67% strain), fit the food softening data to the uni-modal Weibull distribution model, and determine which compression test may be more suitable for use in the Food Breakdown Classification System methodology.
To achieve this goal, the six foods underwent in vitro oral digestion (0.2 mL/g simulated saliva, 30 sec) followed by in vitro gastric digestion in a shaking water bath (6 mL/g simulated gastric juice, 100 rpm, 37°C) for up to 240 minutes. Triplicate digestions were completed. Hardness was quantified as the peak force during compression using a TA-XT2 Texture Analyzer (Texture Technologies Corporation). Changes in hardness, normalized against the initial hardness, were fit to the Weibull model.
Food initial hardness was significantly affected by carbohydrate matrix and compression test (p < 0.05). Under each compression test, foods tended to soften to statistically similar values after increased digestion time (p < 0.05). Food moisture content significantly increased for all foods over the 240 minute digestion period (p < 0.05). Larger moisture absorption was associated with a faster softening rate (pretzels) under all three compression tests. Pretzels and white rice were the only two foods which had significant solids loss by 240 minutes of gastric digestion (p < 0.05).
Food softening curves from all compression tests were successfully fit to the Weibull model, however the best results were obtained for single compression tests. For all compression tests, no significant difference was observed for softening half time or the Weibull parameters k and b under each compression test. The Weibull model was additionally fit to shorter time ranges of softening data (1 hour, 2 hour, 3 hour, 4 hour) and no statistical differences were observed in Weibull model parameters and softening half time under each endpoint time model fit, suggesting that the 4 hour test period may not be necessary for grain derived foods.
From this study it is suggested that the single compression method should be considered for future FBCS texture measurements and the 2 hour digestion time period be used for grain derived foods. In order to utilize food structure to target certain physiological responses and enhance functional food development efforts, it is necessary to build a fundamental understanding of the influence of food structure on the ability and rate of nutrient absorption.
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