Pumpkin seed coat pigments affected aqueous enzymatic extraction processing through interaction with its interfacial protein

Abstract

In this study, the oil recovery from pumpkin seed with or without the presence of pigment was evaluated during the aqueous enzymatic extraction process (AEEP). Additionally, the interaction of pumpkin seed coat pigment—protochlorophyll (Pchl) with interfacial proteins (globulin-O/W, globulin-W, and albumin-W) during the aqueous extraction process was investigated. When Pchl was removed from pumpkin seeds, the yield of free oil was significantly increased by 50.71% after the first centrifugation. And the total oil recovery increased from 68.59% to 89.91% using enzymatic demulsification. The β-sheet percentage of globulin-O/W decreased by 5.6% with the presence of Pchl based on the circular dichroism spectra analysis. The particle size of globulin-W and albumin-W significantly increased in contrast to globulin-O/W. In addition, the increase of surface hydrophobicity and surface sulfhydryl group showed a conformational change of three protein extracts. Fluorescence spectra analyses showed that Pchl quenched the intrinsic fluorescence of globulin-W, albumin-W, and globulin-O/W in a static mode. Thermodynamic analyses indicated that the main force between Pchl and proteins was hydrophobic interactions. The hydrolysis efficiency of Papain was reduced during demulsification in AEEP with the presence of Pchl. Therefore, the removal of pumpkin seed coat pigments facilitated the aqueous extraction of seed oil by getting rid of the interaction of Pchl with its interfacial protein.