Effects of Processing and Storage Conditions on thein vitroDigestibility and other Functional Properties of Six South Asian Starches

Abstract

White raw rice (WR), red raw rice (RR), Basmati rice (BR), sago flour (SF), ulundu flour (Vigna mungo) (UF) and kitul flour (Caryota urens) (KF) were cooked with either water or coconut milk, followed by storage for 24 h under room (25C) and refrigerated (4C) temperatures. WR, RR and BR prepared with water had increased viscosities at both storage temperatures. Resistant starch contents decreased as follows: KF > UF > RR > SF > BR > WR. The hydrolysis and predicted glycemic indices decreased as follows, regardless of the cooking conditions: BR > WR > SF > RR > UF > KF. The highest total phenolics content (TPC), water- and oil-soluble Oxygen Radical Absorbance Capacity (ORACw and ORACoil) values were observed when cooked with coconut milk. Significant differences (P < 0.05) in TPC, ORACw and ORACoil values were not observed between freshly prepared starches and their storage temperatures. Practical Applications The study serves as a platform for identifying starches which could be used for the development of therapeutic food in South Asia with a low glycemic index. The usage of an in vitro digestion model, instead of in vivo or clinical methods, is of importance given that the latter two methods are costly and time-consuming. Changes to properties such as total phenolics content and antioxidant activity are vital as well given their associated abilities of disease prevention. In addition, monitoring changes to viscosity is also of importance since it effects the sensory properties of food products. All starches studied in this paper are typically cooked using water or coconut milk. Thus, information pertaining to these two methods of cooking and the resulting changes to various physicochemical properties is of value when optimizing cooking conditions for health and wellness purposes.