Process-induced cell wall permeability modulates the in vitro starch digestion kinetics of common bean cotyledon cells

Abstract

The presence of cell walls entrapping starch granules in common bean cotyledons, prevailing after thermal processing and mechanical disintegration, has been identified as the main reason for their (s)low in vitro starch digestibility. Nevertheless, it is unknown if the role of cell walls on starch digestion changes as processing conditions (e.g. time) are modified. In this study, it was hypothesised that cell wall permeability would be differently affected depending on thermal process intensity, giving origin to distinct in vitro starch digestion kinetic profiles. Cotyledon cells were isolated from common beans by applying processing conditions normally found at the household level (95 °C and times between 30 and 180 min (palatable range)). Isolated cells were characterised and subsequently subjected to in vitro simulated digestion. Microstructural properties, the starch gelatinisation degree, and the total starch content were similar among samples. In contrast, a higher diffusion of fluorescently labelled pancreatic α-amylase inside the cells was evident as processing time increased. From the kinetic analysis of digestion products, it was determined that longer lag phases and slower reaction rate constants were present in samples with a lower degree of process-induced cell wall permeability. The qualitative analysis of the remaining pellets showed that cellular integrity was maintained throughout in vitro digestion. A mechanism for the in vitro starch digestion of isolated common bean cotyledon cells as well as an alternative kinetic model to describe this process were proposed. Overall, our work demonstrated that the in vitro starch digestion kinetics of common bean cotyledon cells can be modulated by influencing cell wall permeability through thermal processing time.