Starch-rich pulse flours, an underutilized co-product from air classification, have limited industrial applications due to the presence of impurities such as proteins and dietary fibers. Therefore, separating starch from these impurities is essential to enable further modifications and expand its potential uses. Alkaline wet isolation is widely used to isolate pulse starches. This study aimed to optimize wet isolation conditions for producing high-purity starches from air-classified starch-rich faba bean and pea flours and to evaluate their structure, functional attributes, and in vitro digestibility in comparison with a commercial pea starch (CPS). A full factorial design with varying pH ( i.e., 8.5, 9.5, 10.5, and 11.0) and temperature ( i.e., 25°C, 30°C, 40°C, and 50°C) was employed during the wet isolation. The pulse starches isolated under the identified optimum conditions exhibited high purity with starch contents of 95.1%-97.2% and low protein (≤ 0.31%) and ash (≤ 0.07%) levels. Granular morphologies of the isolated pulse starches were generally comparable to that of CPS; however, the isolated starches contained more broken granules, particularly for pea starch extracted under harsh condition. This observation was consistent with the greatest damaged-starch content (4.94%) and lowest relative crystallinity (25.3%) of this starch. Interestingly, for both faba bean and pea, the starches isolated from mild and harsh conditions exhibited comparable amylose contents and amylopectin branch-chain-length distributions. Overall, the applied wet isolation conditions influenced the gelatinization properties, pasting viscosities, gel strength, and digestibility (in the uncooked form) of the isolated pulse starches, with more pronounced effects observed for pea starch. • Purity and yields of pulse starches were independent of isolation pH and temperature • Pulse starches obtained from optimum conditions had high purity (95.1-97.2% starch) • Isolation conditions did not induce substantial molecular degradation of starch • Pulse starches isolated from mild conditions developed higher peak viscosities • Mild conditions produced pulse starches with less digestibility in uncooked form
Cheng et al. (Fri,) studied this question.