Improvement of phenolic compounds extraction from high-starch lotus (Nelumbo nucifera G.) seed kernels using glycerol: New insights to amylose/amylopectin - Phenolic relationships

Lotus seed kernel (LSK) has high starch content and possesses many bioactivities, which are mainly attributed to its phenolics. In the present study, LSK phenolics were extracted using aqueous glycerol, and the obtained phenolics and its starch properties were observed for their correlations. Response surface methodology indicated significant quadratic effect of temperature and significant linear effect of glycerol on LSK phenolics (p < 0.05). Temperature also had a significant effect on LSK starch solubility and swelling power and % leaching amylose (p < 0.05). Leaching amylose in the presence of glycerol and swelling power showed positive correlations with LSK phenolics in a linear relationship (r = 0.825, p < 0.01) below 50 degrees C and a monotonic relationship (r(s) = 0.933, p < 0.01) above 60 degrees C, respectively. A building block backbone model was adopted to illustrate the interaction between amylose/amylopectin-glycerol, and most importantly, their relationship to LSK phenolics.