Enhancing techno-functional and bioactive properties of whey proteins by conjugation with quercetin using combined treatment of redox pair and ultrasonication

Abstract

Camel whey-quercetin conjugates were fabricated via free radicals using a combination of ultrasonication treatment and a redox-pair (ascorbic acid/H2O2). Conjugation of whey with quercetin was confirmed using UV-Vis. spectroscopy, FTIR and SDS-PAGE. UV-Visible spectroscopy showed a bathochromic shift and appearance of a hump around ≈350 nm (absent in whey sample) that can be attributed to binding of quercetin with whey protein. As indicated by FTIR, the association of whey with quercetin took place via covalent (appearance of new peak at 3399 cm-1) as well as noncovalent linkages (shift-ing of peak at 3271 cm-1, 1655 cm-1 (amide I), 1534 cm-1 and 1422 cm-1 (Amide II). The appearance of new peaks in UV-Visible spectroscopy and FTIR of conjugates was resolved using a second derivative of the spectrum. Reducing SDS-PAGE revealed shifting of protein bands towards higher molecular weight due to increase in the mass of conjugates that can be attributed to covalent conjugation between whey and quercetin. A significant improvement in the functionality and bioac-tive properties was witnessed after conjugation of whey with quercetin. Ultrasonication improved the emulsifying and foaming properties while a combination of ultrasonication and redox pair method enhanced the antioxidant properties. Moreover, conjugated samples showed higher inhibition of enzymatic markers involved in diabetes (α-amylase & DPP-IV) and obesity (cholesterol esterase & lipase) with highest potential recorded for conjugates produced using ultrasonication only. Therefore, ultrasonication can be successfully used individually as well as in combination with redox-pair for produc-tion of whey-quercetin conjugates with enhanced bioactive and techno-functional properties.