Comparative Analysis of Structural and in vitro Digestion Properties of Starch in Cotyledon Cells of Pinto Bean Processed by Different Methods
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Abstract:
In this paper, intact cotyledon cells isolated from pinto bean were used as a whole food model and kidney bean starch was used as the control, the effects of four heat processing methods (normal-pressure cooking/boiling, high-pressure cooking/autoclaving, high-temperature baking and deep frying with oil) on the particle morphology, crystalline structure and in vitro digestion kinetics of starch in intact pinto bean cells were studied. The results showed that after high-pressure and normal-pressure cooking, the birefringence polarization cross of pinto bean cells was significantly weakened, the crystallinity decreased by about 12%, and the gelatinization peak could not be detected. However, high-pressure and normal-pressure cooking destroyed the granular structure of pinto bean starch and caused the disappearance of the birefringence polarization cross. The deep frying and high-temperature baking did not change significantly the morphology of pinto bean cells and starch but decreased the enthalpy of gelatinization and relative crystallinity. The digestion rate of pinto bean cells with/without different heat treatments decreased in this order: high-pressure cooking (89.45%, 0.0132 min-1) > normal-pressure cooking (47.77%, 0.0033 min-1) >high-temperature baking (3.15%, 0.0001 min-1) ≈ deep frying (2.31%, 0.0003 min-1) ≈ untreated (1.80%, 0.0001 min-1). Regardless of the thermal processing methods, the apparent digestion rate and degree of digestion of pinto bean cells were much lower than those of the starch subjected to the same heat treatment, possibly due to the adsorption of digestive enzymes and physical barrier effect of substances such as cell walls and intracellular proteins. The research results indicate that low GI pinto bean products can be obtained by high-temperature baking and deep frying with oil.
