Proanthocyanidins from Chinese Bayberry (Myrica rubra Sieb. et Zucc.) Leaves Effectively Inhibit the Formation of Biogenic Amines in the Brewing Soy Sauce

Biogenic amines are a group of metabolites generated in the process of soy sauce brewing, which can result in severe negative impacts on human health at high concentrations. In this study, we innovatively proposed natural extracts (0.1 wt%), of proanthocyanidins, from Chinese bayberry (Myrica rubra Sieb. et Zucc.) leaves to alternate commercial additives (0.1 wt%), i.e., sodium benzoate and potassium sorbate, for lowering the harmful biogenic amine formation during the fermentation of soy sauce. HPLC results showed that natural extracts from Chinese bayberry leaves could effectively decrease the content of cadaverine, putrescine, histamine, tyramine, phenylethylamine, and agmatine (p < 0.05). In contrast to the inhibitory influence exhibited by commercial sodium benzoate and potassium sorbate, extracts from bayberry leaves can maintain spermidine, spermine, and tryptamine at certain concentrations. Furthermore, both sodium benzoate and potassium sorbate significantly reduced the production of ammonium salt and characteristic components (p < 0.05), like soluble saltless solids, total nitrogen, and amino acid nitrogen, during the 40-day fermentation of soy sauce, whereas proanthocyanidins extracted from Chinese bayberry leaves slightly inhibited the content of ammonium salt. Thus, we can conclude that, while inhibiting the biogenic amine and ammonium salt production, extracts from Chinese bayberry leaves facilitate or maintain the production of characteristic indicators compared to commercial sodium benzoate and potassium sorbate. Taken together, natural extracts from Chinese bayberry leaves can be considered a natural additive to significantly improve the quality of traditional brewing soy sauce.