Background Larimichthys crocea, an important economically farmed fish along China’s southeast coast, produces approximately 30% of by-products such as minced meat during processing. Most of these by-products are sold at low prices or directly discarded, which not only causes great waste of resources, but also brings significant environmental pressure. With the continuous growth of the food industry’s demand for natural umami substances, extracting umami peptides from aquatic by-products has become an important direction to realize high-value utilization. Umami peptides not only have a mellow and rich umami taste, but also have the advantages of easy absorption and high safety, showing broad application prospects in the food field.

Objective This study aims to optimize the preparation process of umami peptides from L. crocea minced meat, analyze the taste profiles of umami peptides with different molecular weights, and provide a theoretical basis for the high-value utilization of L. crocea processing by-products.

Methods Using L. crocea minced meat as raw material, suitable proteases were screened through enzyme engineering technology, and the enzymatic hydrolysis process parameters were optimized by combining single-factor method and response surface methodology. Ceramic membrane (5 mesh), ultrafiltration membranes (10, 3, 1 kDa, respectively) and nanofiltration membrane were used for fractional separation of umami peptides, and the electronic tongue system was employed to analyze the taste characteristics of components with different molecular weights.

Results The enzymatic hydrolysis effect of flavor protease was the best. The optimal process parameters were enzyme dosage of 1611 U/g, liquid-solid ratio of 10∶1, pH 8.1, enzymatic hydrolysis temperature of 48 ℃, and enzymatic hydrolysis time of 5 h. Under these conditions, the umami intensity reached 14.79±0.03, and the degree of hydrolysis was (42.61±0.36)%. Ultrafiltration separation showed that the umami peptide (UF1) with molecular weight <1 kDa had the highest umami response value and the lowest bitterness value, and its flavor quality was significantly better than that of 1−3 kDa (UF2) and >3 kDa (UF3) components (P<0.01).

Conclusion Flavor protease can efficiently prepare umami peptides from L. crocea, and small molecular peptides (<1 kDa) are the main umami-contributing substances. The study provides process references and theoretical basis for the industrial extraction of L. crocea umami peptides and the development of functional products, and is of great significance for improving the added value of the L. crocea industry and promoting the high-value utilization of aquatic by-products.