Effect of exogenous tannic acid on reduction of biogenic amines and citrinin in monascal soybean and metabolomics analysis

Biogenic amines (BAs) are often involved in human pathologies such as hypersensitivity symptoms. This research studied the effect of exogenous tannic acid (ETA) supplementation at various concentrations (0–20 mg/mL) on BA and mycotoxin citrinin levels in monascal soybean (MSB) and conducted a metabolomics analysis to estimate the metabolites in MSB. Addition of 20 mg/mL ETA decreased BA and citrinin levels in MSB after 25 days of fermentation by > 1.76 and >2.46 fold, respectively compared to the treatment without ETA addition. After 10 days of fermentation, the number of enterococci in MSB after treatment of >10 mg/mL ETA decreased by a minimum of 1.33 log CFU/g. ETA promoted large amounts of monacolin K, Monascus pigments, and free amino acids (FAAs) in MSB. A heatmap-HCA revealed that the 20 mg/mL ETA treatment was optimal, as confirmed by the VIP score and PCA. During MSB fermentation, seven notable metabolic pathways were identified as 1. phenylalanine metabolism, 2. arginine and proline metabolism, 3. phenylalanine, tyrosine, and tryptophan biosynthesis, 4. arginine biosynthesis, 5. histidine metabolism, 6. tryptophan metabolism, and 7. tyrosine metabolism. Supplementation of ETA in soybean substrate led to reduced BA and citrinin levels in MSB. The metabolomics analysis provide a better understanding of metabolite correlations, especially FAA formation and BA biosynthesis.