Amine and Formaldehyde Production in North American Squid and their Relation to Quality

Abstract

Three species of North American squid (Illex illecebrosus, Loligo pealei and Loligo opalescens) were analysed for dimethylamine (DMA) and formaldehyde (FAO) levels. DMA contents of frozen squid mantle (1.34, 0.075 and 0.020 mMole %, respectively) are generally inversely related to the quality of the cooked mantle and are sufficiently high relative to the gadoid fishes to suggest that FA accumulates to such an extent during storage that crosslinking of proteins may result in textural toughening. The rate of DMA formation was determined and this parameter was also found to be comparable to gadoid species such as red hake. Tissue homogeniza-tion resulted in an 8–9 fold increase in DMA production over whole mantle. The addition of TMAO, Fe +++, ascorbate and cysteine to the homogenate resulted in a 2–3 fold increase in DMA production when compared to a preparation with no cofactors.Crossover experiments with boiled homogenates led to the conclusion that at least some of the DMA and FA was formed ezymatically and suggested that unidentified activators and inhibitors exist in vivo. Differences between species are more likely due to variations in cofactor concentration than enzyme level. DMA was shown to be inhibitory to the reaction. Adding semicarbazide to the reaction increased measurable FA levels to those of DMA indicating equimolar production of these two compounds. When squid, frozen and held at −40°C, was stored at −5°C, both DMA and shear force increased significantly by day 14; shear then decreased so that by day 35 values lower than the original were obtained. A subsequent storage experiment performed using frozen squid held at −20°C prior to storage at −5°C showed a more rapid increase in DMA level but no change in shear value. Visual inspection of the squid and chemical analysis led to the conclusion that the toughening reaction was superceded by proteolysis which emphasizes the importance of low storage temperatures in squid quality.