Effects of different curing methods on physicochemical parameters and volatile flavor components of Trachinotus ovatus

Trachinotus ovatus is a marine commercial fish because of high nutritional value and special flavour, which is widely cultured in Guangdong, Fujian and other southern coastal areas in China. In recent years, as the production of T. ovatus increases, T. ovatus in the domestic market is mainly sold live or chilled, causing many problems such as short shelf life, low economic benefits and so on. Salting is one of traditional ways to preserve or to process fish. Salting is based on the penetration of salt into the fish muscles as a direct consequence of its ability not only to reduce water activity of fish muscles and inhibit the growth of microorganisms, but also improve the quality and flavour of the product. Because T. ovatus has no muscle spines, it is suitable to extend the shelf life of products and improve the added value of products by salting, air drying and other techniques. Traditional curing methods include dry salting, wet salting and mixed-salting and they have some shortcomings such as slow curing speed and uneven curing. With the development of technology, ultrasonic assisted curing and ultra-high pressure assisted curing have been developed, which has the advantages of fast curing speed and good product quality. At present, there are few reports on the comparison between the new curing methods and the traditional curing methods. In order to explore the effects of dry salting, wet salting and ultrasonic assisted curing on the physicochemical parameters and volatile flavor components of T. ovatus, the basic nutritional components, salt content, pH, thiobarbituric acid (TBA) value, fatty acid composition and volatile flavor compounds of salted fish were determined and analyzed. The results showed that after different curing processes the protein and fat content of T. ovatus increased, but the moisture content of T. ovatus decreased. The moisture contents of dry salted, wet salted and ultrasonic assisted salted fish were 53.71% ± 0.97%, 61.45% ± 0.72%, 59.29%±1.41%, respectively. Compared with fresh T. ovatus, the salt content of dry salted, ultrasonic assisted salted and wet salted fish increased, which were (3.29 ± 0.15), (2.64 ± 0.02) and (2.15 ± 0.11) g/100 g, respectively. However, the pH value of T. ovatus decreased after different curing processes. After curing processing, the lipids of fish meat underwent oxidation reaction, the TBA value increased. The TBA values of dry salted, wet salted and ultrasonic assisted cured fish were (0.80±0.07)、(0.55±0.09) and (0.73±0.08) mg MDA/kg. The fatty acid composition changed after curing processes with increase of saturated fatty acids and monounsaturated fatty acids and decrease of poly-unsaturated fatty acids. In this study, 54, 56, 62 and 57 volatile flavor compounds were detected from T. ovatus, dry salted, wet salted and ultrasonic assisted salted fish respectively. The volatile flavor compounds were mainly aldehydes, alcohols and ketones, which played an important role in flavor formation. The results showed that compared with the other two methods, the water content of dry salted fish was the lowest, but both the salt content and TBA value was the highest. The relative content of aldehydes and alcohols in the volatile flavor compounds of fish cured by ultrasonic assisted was the highest, and the pH value was the lowest. This study can provide technical and theoretical reference for curing processing and production process optimization.