Fermentation time and ethanol/water-based solvent system impacted in vitro ACE-inhibitory activity of the extract of Mao-tofu fermented by Mucor spp

Abstract

Mao-tofu was fermented by Mucor spp. for 3-9 days. Soluble protein fractions were then extracted by three solvents with ethanol/ water ratios of 2:8, 4:6 or 6:4 (v/v), respectively, under fixed weight-volume ratio of 3:10 (w/v). Analysis results showed that the longer fermentation time of Mao-tofu, the higher extraction yield or degree of hydrolysis (DH) of the protein fractions. The solvent with higher ethanol content trended to extract less protein fractions but lead them higher DH. When Mao-tofu was fermented for five days and extracted by the solvent with ethanol/water ratio of 6:4 (v/v), the extract exhibited the highest ACE-inhibitory activity in vitro. Amino acid composition analysis showed that the extract with higher activity contained more total hydrophobic amino acids or proline. Further hydrolysis of the extract by five proteases in vitro might damage or enhance its activity, depending on the extract hydrolyzed and the protease applied. © 2012 Taylor & Francis.