Improved solubility of proteins from white and red clover – inhibition of redox enzymes

Abstract New alternative protein sources are needed. Clover grasses as white clover (WC) and red clover (RC) may provide a novel protein source to achieve high‐quality food protein. To prevent protein oxidation, endogenous oxidative enzymes as polyphenol oxidase (PPO) and peroxidases were inhibited with sulphite. RC showed higher PPO activity than WC. Low sulphite inhibited the PPO activity in both species, but browning still occurred in RC. Sulphite did not affect the polyphenol (PP) content in WC, rather suggesting peroxidase than PPO activity. In RC juice, the PP content increased in a dose‐dependent manner with increasing sulphite. High sulphite impaired browning and increased the content of soluble rubisco in RC, mainly by increasing the content of native rubisco. In vitro digestibility of RC protein increased with increasing sulphite. In conclusion, sulphite inhibited oxidative enzymes and increased the quality of protein extracted from WC and RC.