The importance of oral processing of bean-based wraps with different microstructures on starch digestion: an in vivo and in vitro study

Abstract

Cellular pulse flours, containing intact cotyledon cells, can be incorporated in various food products to stimulate pulse consumption. This has been shown to slow gastric and small intestinal nutrient digestion compared to traditional, raw-milled flours. Though increasing evidence points to the considerable contribution of the oral phase in the digestion of solid starch-rich food products, this phase has been omitted from most studies. Therefore, this study applied both in vivo and in vitro oral processes to study their impact on starch digestion in innovative bean-based wraps with distinct microstructures. In vivo mastication was performed by 38 participants, who showed large differences in chewing behaviour. However, this variability did not affect bolus microstructure, with intact cells present in all boluses of wraps containing cellular flour. Incorporation of these cells significantly decreased oral starch hydrolysis from 10 to 7%, although large inter-individual differences were seen. This variation probably contributed to the absence of clear correlations between mastication parameters and starch digestibility. All tested in vitro oral phase simulations resulted in similar bolus microstructures to in vivo observations, with intact cells causing a non-significant decrease in starch digestion. In vitro amylolysis levels were within the in vivo range, while the exact extent was significantly affected by the applied amylase activity. Moreover, Bacillus sp. amylase was shown to be a suitable, cost-efficient alternative to human salivary amylase. As substantial amounts of starch were hydrolysed, this study highlights the importance of considering a relevant oral phase when evaluating the digestibility of starch-rich solid foods.