In vitro digestibility of starches with different crystalline polymorphs at low α-amylase activity to substrate ratio.

In this study, potato, lotus seed and wheat starch samples with different degree of gelatinization (DG) were prepared and their in vitro digestibility at low α-amylase activity evaluated by measuring the release of reducing sugar. The hydrolysis rate (k) and the final equilibrium concentration (C∞) of the three starches increased with increasing DG. Kinetic analyses showed that the Michaelis-Menten constant (Km) and the catalytic efficiency (kcat/Km) increased with increasing DG, indicative of the increasing affinity and catalytic efficiency of α-amylase with all three starch samples. Of the three starches, lotus seed starch showed a much greater increase in k and kcat/Km than potato and wheat starches as the DG of starch increased. From this study, we concluded that at low activity of α-amylase, DG is a major determinant for the binding affinity and catalytic efficiency of α-amylase to starch and in turn the digestion rate of starch.

Fabrication and characterization of whey protein isolates- lotus seedpod proanthocyanin conjugate: Its potential application in oxidizable emulsions.

Emulsified ω-3 polyunsaturated fatty acid have expanding application in different food matrix with improved water solubility while still prone to oxidation. Lotus seedpod proanthocyanidin (LSPC) was grafted to whey protein isolate (WPI) to create nature-derived antioxidant emulsifiers. 1HNMR, SDS-PAGE and multiple spectrometry showed that the structure of protein was changed after grafting. DPPH and FRAP measurements showed that WPI-LSPC conjugate (90.53 ± 1.48% of DPPH scavenging, 691.85 ± 4.54 µg/mL for FRAP assay) possessed a much better antioxidant ability than WPI (17.06 ± 3.34% of DPPH scavenging, 10.43 ± 0.26 µg/mL for FRAP assay). Ultrasonic emulsification and DSC experiments showed that WPI-LSPC conjugate were more effective at forming and stabilizing the flaxseed oil emulsions than pure WPI, with higher thermostability. Likewise, low levels of primary and secondary oxidation products were formed for the conjugate than the pure protein in O/W systems after storage, again suggesting WPI-LSPC could be used as fine antioxidant emulsifiers in oxidizing delivery systems.