Protein Oxidation and Formation Mechanism of Semicarbazide in Tenebrio molitor under Different Heating Temperatures

In this study, we investigated the degree of protein oxidation and the potential generation mechanism of semicarbazide (SEM) in Tenebrio molitor under different heating temperatures, and we analyzed differential metabolites and metabolic pathways by non-targeted metabolomics. Based on the correlation between the contents of SEM and amino acids, we speculate on possible precursors of SEM, which were verified by standardized experiments. The results showed that the carbonyl content increased from 0.04 to 0.63 nmol/mg, the total sulfhydryl content decreased to 0.08 μmol/g, the dityrosine content increased by approximately 96.60% to 1192.23, the endogenous fluorescence intensity decreased, and the surface hydrophobicity and the free amino group content first rose and then decreased with increasing heating temperature. Metabolomics analysis revealed that increased temperature significantly affected the tyrosine metabolism, arginine biosynthesis and phenylalanine metabolism pathways in T. molitor. The correlation analysis indicated that SEM was positively correlated with tyrosine (r = 0.904) and negatively correlated with arginine (r = −0.781). The validation experiments demonstrated that SEM content was significantly enhanced in the tyrosine and phenylalanine groups but significantly reduced in the arginine group (P < 0.05). In summary, increased temperature aggravates protein oxidation in T. molitor and tyrosine and arginine are likely precursors of SEM.