Enzyme release of phenolics from muscadine grape (Vitis rotundifolia Michx.) skins and seeds

• This study comprehensively studied the enzymatic method of extracting muscadine grape skin and seed phenolics.
• Combinations of solvent and enzyme, and treatment order greatly affected the release of grape phenolics.
• Both enzymes and substrates should be considered to achieve an effective enzymatic hydrolysis for phenolics.
• Enzymatic hydrolysis could modify the grape polyphenol profiles and release more potent antioxidant activity phenolics.

Enzyme degradation of plant cell wall polysaccharides can potentially enhance the release of bioactive phenolics. The aim of this study was to evaluate various combinations of solvent and enzyme, enzyme type (cellulase, pectinase, ß-glucosidase), and hydrolysis time (1, 4, 8, 24 h) on the release of muscadine grape skin and seed phenolics, and their antioxidant activities. Results showed that pre-treated muscadine skins and seeds with enzymes decreased total phenolic yield compared with solvent (50% ethanol) alone. Enzyme release of phenolics from skins of different muscadine varieties was significantly different while release from seeds was similar. Enzyme hydrolysis was found to shorten extraction time. Most importantly, enzyme hydrolysis modified the galloylated form of polyphenols to low molecular weight phenolics, releasing phenolic acids (especially gallic acid), and enhancing antioxidant activity.