Proteolysis patterns and biogenic amines content in bovine mozzarella manufactured from fresh milk or stored curd

The use of stored curd in mozzarella manufacturing offers technological and economic advantages, including easier processing, flexibility during milk shortages, and reduced liquid waste. However, this practice is not specifically regulated by EU legislation, raising concerns about consumer protection and product safety, particularly regarding the impact of curd storage on the formation of undesired compounds. Proteolysis during curd storage leads to the release of free amino acids that can act as precursors for biogenic amines (BAs), which may pose health risks. This study evaluated proteolysis, microbial populations, and BA accumulation in mozzarella produced from fresh curds, stored curds, and their mixtures. Chemical and microbiological results on curds showed slight differences for moisture, fat, and pH values; whereas among spoilage bacteria presumptive staphylococci were found at higher amounts in stored curd. Concerning mozzarella, those obtained from stored curds underwent more intense primary and secondary proteolysis, resulting in higher BA concentrations compared with those made from fresh curds. Nevertheless, total and individual BA levels were below the thresholds suggested in scientific literature, indicating that mozzarella from stored curds does not represent a significant health risk. From a microbiological point of view, Presumptive Pseudomonas spp. were detected only in mozzarella samples that included stored curd. Further investigation is needed, especially for longer storage times, which may enhance BA accumulation. This lack of information is both a weakness and a strength, because whilst on the one hand we have no information on the matter, on the other hand we find ourselves in the most realistic scenario possible. Finally, combining proteolysis and biogenic amine data enabled the development of an experimental chemometric index capable of discriminating between mozzarella produced from fresh and stored curds, providing a potential tool—requiring further validation on a broader dataset—for authenticity assessment.