Effects of electrolyzed water pretreatment on quality changes of large yellow croaker (Larimichthys crocea) during chilled storage

The annual output of large yellow croaker (Larimichthys crocea) in Fujian Province always exceeds 80% of the annual output in China. At present, L. crocea is mainly sold all over the country in the form of chilled storage. Therefore, it is important to prolong the shelf life of chilled L. crocea by taking the suitable pretreatment. Electrolyzed water has a high-efficiency and broad-spectrum bactericidal action, and its application in fish refrigeration preservation has been widely concerned. However, the effect of electrolyzed water pretreatment on the freshness, taste and odor of chilled L. crocea has not been reported. In order to investigate the effect of electrolyzed water pretreatment on quality changes of L. crocea during chilled storage, the total viable counts, total volatile basic nitrogen (TVB-N), ATP-related compounds contents, pH, hardness, color, taste and volatile odor of L. crocea pretreated by soaking in electrolyzed water with different available chlorine concentrations (50, 100, and 200 mg/L) and 1% NaCl solution were measured during storage at 4 °C. The results show that, the initial total viable counts of L. crocea decreased from 2.30 to 1.83 lg(CFU/g), when the available chlorine concentration of electrolyzed water was 200 mg/L. After 16 day storage at 4 °C, the TVB-N values of L. crocea muscle pretreated by electrolyzed water with the available chlorine concentration of 100 and 200 mg/L were 24.38 and 23.63 mg/100 g respectively, which were significantly lower than the control group (28.92 mg/100 g). The increases of HxR, Hx and K values in the fish muscle were retarded by electrolyzed water pretreatment, and the inhibitory effect was increased with the increase of available chorine concentration. No significant differences were observed in the pH and hardness of fish muscle with and without electrolyzed water pretreatment. The yellowness b^* value of fish muscle was increased with the increase of available chorine concentration under the same condition for 16 day storage. The bitterness, aftertaste-B and richness of fish muscle increased gradually with increasing storage time, while the umami, saltiness and sweetness decreased. The taste values of aftertaste-B and saltiness in fish muscle pretreated with electrolyzed water were higher than those in the control group. The volatile odors in fish muscle pretreated by electrolyzed water with the available chlorine concentration of 200 mg/L were decreased during 4-10 day storage, but were higher than those in the control group after 16 day storage at 4 °C. In conclusion, electrolyzed water pretreatment can be effective in inhibiting the microbial growth and freshness decline of L. crocea during chilled storage. The inhibition effect of electrolyzed water was related to its available chlorine concentration. However, after being pretreated by the electrolyzed water with high available chlorine concentration, L. crocea is easy to turn yellow and produce volatile odors during chilled storage. The results of present study provide a theoretical reference for the selection of electrolyzed water with suitable available chlorine concentration in the preservation of chilled L. crocea.