Effect of Treating of Squid with Sodium Chloride in Combination with Oxidising Agent on Bleaching, Physical and Chemical Changes During Frozen Storage

Pink discolouration is a problem faced in the squid processing industry, and some treatments have been implemented to tackle such a problem. The study aimed to elucidate the impact of NaCl in combination with oxidising agents on the quality changes of squid during frozen storage. The effects of treatment of pink squid using 3% (w/v) NaCl solution containing oxidising agents (0.05-0.5% (w/v) H ₂O ₂ or 0-10 ppm NaOCl) on colour and chemical and physical changes of squid during frozen storage were investigated. The lowest decreases in a*, b* values, {increment}E* and {increment}C* of squid were obtained with the treatment using 3% NaCl solution containing 0. 5% H ₂O ₂. Nevertheless, NaOCl (0-10 ppm) had no impact on a* and b* values. During frozen storage at -18 °C for 10 weeks, fresh squid, pink squid samples without and with treatments with 3% NaCl solution containing 0. 5% H ₂O ₂ had no changes in a* and b* values during frozen storage. Nevertheless, thiobarbituric acid reactive substances value, disulphide bond content, thaw drip and shear force were more pronounced in treated pink squid, compared with pink squid without treatment (control) and fresh squid, respectively, during the extended storage (p < 0.05). Higher denaturation and aggregation of muscle proteins during frozen storage were observed in treated pink squid than that without treatment and fresh squid, respectively. Therefore, pink squid treated with oxidising agent was prone to protein aggregation and denaturation during the extended frozen storage, though it could lower the pink colour. Therefore, fresh squid without treatment using oxidising agent is recommended for production of frozen squid with negligible loss in quality during extended storage.