Effect of thawing methods on processing quality of Antarctic krill

Antarctic krill (Euphausia superba) is widely distributed in Antarctic waters. The resource of Antarctic krill is rich, whose fishable amount is up to 100 million tons each year. In China, considerable amount of Antarctic krill is frozen and stored in boats before transported to the land for processing. Therefore, thawing is indispensable in Antarctic krill industry. The thawing way has great effect on the quality of fishery materials. In order to explore how thawing process influenced the quality of Antarctic krill as raw material, 3 ways including natural air thawing, static water thawing and low-temperature air thawing were designed in this study. The consumption of time, sensory evaluation and biochemical indices such as non-protein nitrogen (NPN), total volatile basic nitrogen (TVB-N) and thiobarbituric acid reactive substance (TBARS) were determined for each kind of thawing method. The results showed that the thawing time taken by natural air way, static water way and low-temperature air way was 220, 51 and 826 min respectively. The sensory score of Antarctic krill with static water thawing was the highest, followed by natural air way and low-temperature air way. The NPN values of Antarctic krill thawed by the 3 ways were 6.89, 8.55 and 12.13 mg/g respectively for static water thawing, natural air thawing and low-temperature air thawing, with the highest value of low-temperature air way, followed by natural air way and static water way in sequence. The TVB-N values of Antarctic krill thawed by the 3 ways were 9.60, 10.33 and 22.47 mg/100 g, respectively. The TVB-N value of low-temperature air way was significantly higher than the other 2 ways, but those of the static water way and natural air way had no significant difference (P>0.05). The TBARS values of Antarctic krill thawed by the 3 ways were 6.77, 4.78 and 2.17 mg/kg, respectively. The differences were significant (P<0.01), with the highest value of static water way, followed by natural air way and low-temperature air way. The proportion of polyunsaturated fatty acids of total fat from Antarctic krill was more than 30%. Low-temperature air thawing had a certain effect on the protection of polyunsaturated fatty acids. In conclusion, in the process of production, choosing the way to thaw Antarctic krill material should fully consider the type of products. The way of static water thawing is suitable for general food processing. The ways of static water thawing and natural air thawing are suitable for fishmeal production. The way of low-temperature air thawing is suitable for shrimp oil extraction. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.