Structural features and starch digestion properties of intact pulse cotyledon cells modified by heat-moisture treatment

Abstract

• Intact cell wall limits disruption of starch crystalline structure during HMT. • Cell wall hinders enzyme access to entrapped starch during in vitro digestion. • Higher moisture content during HMT alters the porosity of cell wall leading to increase in the enzyme susceptivity. Intact pinto bean cotyledon cells were isolated and hydrothermally treated at three different moisture contents (15%, 25% and 35%) at 100 °C for 8 h to investigate the effect of cell wall encapsulation on starch molecular re-arrangement during heat-moisture treatment (HMT). Compared to the intact cells, HMT had a more pronounced effect on isolated starch as deduced from damage on the surface as well as an increase in crystallinity and thermal stability, suggesting that intact cell wall structure can limit the molecular mobility of starch polymers within granules. The different digestion results between isolated starches and intact cells suggested that cellular structure may control starch digestion rate and extent. Furthermore, the diffusion experiments using the amylase-sized FITC dextran probe revealed the mechanisms behind the differential effect of HMT on isolated starches and intact cells, and findings can be useful in green processing of whole pulse foods.