Effects of pre and postrigor freezing and temperature stress during frozen storage on physicochemical stability of Atlantic herring (Clupea harengus) muscle

Filleting and freezing in relation to rigor mortis, and a well-controlled cold-chain are important to maintain quality of fish. Atlantic herring (Clupea harengus) was processed and frozen pre or postrigor, and stored at either unstable modelled temperature conditions (at −25°C for 2 months, then stressed at −12°C for 1 month, followed by −25°C for up to 5 months), or at stable storage conditions (−25°C) for 5 months. Analyses on yield, physicochemical properties, lipid oxidation and hydrolysis of the light and dark muscle were performed. Prerigor freezing and stable storage conditions effectively reduced thawing loss, and inhibited lipid oxidation and hydrolysis of the light muscle. The dark muscle was more susceptible to lipid oxidation than the light; therefore, removal of the dark muscle may increase stability of the more valuable light muscle. Temperature stress must be avoided to maintain quality and extend shelf-life of industrially frozen herring fillets. Practical applications: The study emphasises the importance of maintaining a low and strictly controlled freezing temperature during logistics and transportation of fatty fish. Prerigor processing and freezing of herring proved to be beneficial to the valuable commercial light muscle with regards to retaining the quality and yield during thawing and cooking. The dark muscle should be removed by deep skinning to enhance storage stability of herring fillets.