Flavor Quality of Scomberomorus niphonius

Scomberomorus niphonius, an important marine economic fish in China, is widely distributed in the Bohai, Yellow, and East China Seas. In 2022, the total catch of Scomberomorus niphonius in China was 356, 100 tons, representing 3.75% of China's overall marine fish catch. Shandong Province accounted for a significant portion, with a catch of 175, 300 tons, constituting 49.22% of the national total. The annual catch of S. niphonius in Shandong ranks first in the country. S. niphonius is rich in protein, unsaturated fatty acids, essential amino acids, minerals, and other nutrients. It has a delicious flavor and is popular with consumers. S. niphonius, during processing and storage, is susceptible to microorganisms, temperature, and other external environmental influences of corruption deterioration and loss of commodity value; therefore, its storage quality must be improved. Among various fish products, vacuum-packed ready-to-eat soft canned products are popular and widely used with high commercial value due to their short sterilization time, low nutritional loss, and easy portability. Sterilization is an important way of ensuring product quality and extending shelf-life. However, the irrationality of the sterilization process, which focuses mainly on the effect of a single sterilization temperature and time on these quality indicators, often results in a reduction in the quality of the product in terms of flavor, texture, and nutritional value.Lipids are important components of seafood and essential biomolecules. They are also involved in organismal processes essential in the nutritional value, texture, and overall organoleptic properties of seafood. For flavor modification, they act as solvents and precursors of volatile compounds. In addition, seafood contains essential nutritional lipids, including phospholipids, triglycerides, and essential fatty acids, which is an important feature distinguishing it from other species. In addition, most of the volatile flavor compounds in meat are produced by the Melad reaction and the thermal degradation of lipids (oxidation) and thiamine. Oxidative degradation of lipids is the main pathway for forming the characteristic flavor of aquatic products. S. niphonius, due to its high content of unsaturated fatty acids, releases unsaturated fatty acids from the lipids during sterilization to further oxidize them into volatile compounds such as aldehydes, ketones, and alcohols, which have a low threshold value and can significantly impact the flavor quality of the product. Currently, the processing of S. niphonius is focused on dry-cured products, and relatively few studies have been conducted on the quality changes during the processing and sterilization of its soft canning. Based on this, the present study took the S. niphonius as a research object and used conventional physicochemical tests combined with the electronic nose, gas chromatography-ion mobility spectrometry (GC-IMS), and other technical means to compare the effects of different sterilization conditions on the physicochemical indices and volatile substances of S. niphonius, to extend its shelf life while reducing the effects of sterilization on its flavor, sensory, and nutritional qualities. This will provide a reference for quality control in the processing of prepared fish dishes and enrich the basic theory of flavor formation in thermally sterilized aquatic products.The results showed that the sensory scores of texture, taste, and odor of S. niphonius changed significantly after sterilization. The total lipid, triglyceride, and phospholipid contents in the samples were significantly decreased after sterilization (P < 0.05), and the free fatty acid content was significantly increased (P < 0.05). Differences were observed in lipid composition between different sterilization groups, with the highest degree of lipid loss in Group C samples. The degree of lipid oxidation was significantly affected by sterilization conditions (P < 0.05), peroxidevalue (POV) content was significantly increased, and thiobarbituric acid reactive substances (TBARS) content was significantly decreased (P < 0.05). The results of electronic nose analysis showed that the odor characteristics of fish meat after different sterilization conditions were significantly different. Twenty-two volatile compounds were identified from the four groups of samples using GC-IMS, including seven aldehydes, five ketones, four alcohols, three esters, two acids, and one furan. Among these compounds, heptyl aldehyde, hexaldehyde, 3-hydroxybutane-2-ketone, acetic acid, and 1-octene-3-alcohol were identified as the primary volatile substances in the control group. The signal intensity of valeraldehyde, isovaleraldehyde, butyraldehyde, 3-hydroxy-butanone, and ethyl propionate significantly increased after the fish underwent various sterilization conditions. This observation suggests that sterilization promotes lipid oxidation and decomposition in fish while leading to significant variations in volatile substance profiles among different sterilization processes. Hexanal, pentanal, 2-methylbutanal, 3-pentanone, cyclohexanone, 3-hydroxybutan-2-one, and ethyl acetate were the major aroma compounds in the fish, and the highest levels were found in the samples from Group B. In conclusion, the organoleptic and flavor qualities of the samples at 115 ℃ for 14.7 min (Group B) were significantly better than those of the other sterilization conditions, and the degree of lipid oxidation was lower, which provides technical support for the fine processing of S. niphonius products.