Effect of endogenous proteinases on histamine and honeycomb formation in mackerel

ABSTRACT Mackerel muscle homogenate treated with visceral trypsin‐like proteinme was found to contain higher free histidine and histamine than that of an untreated sample by a difference of 120ppm histamine ajier 8 days at 4°C; 5oOppm ajier 24 h at 28°C; and 205ppm ajier 4 h at 37°C. The contents of histamine and free histidine were both found to be higher in ungutted mackerel than in gutted ones. When mackerel fillets were treated with muscle alkaline proteinase and heated, it produced maximal increase in soluble peptides at 60°C. Honeycombing appeared in the cooked fillet previously treated with muscle alkaline proteinase, while no honeycombing was observed in the control. Cooked mackerel fillets previously incubated with mackerel pybric collagenase at 25°C and 55°C resulted in increases in free hydroxyproline. The release of hydroxyproline increased with prolonged incubation at 25°C but stayed constant at 55°C which was probably related to the optimal temperature of collagenase being 25°C. Honeycombing was not noticeable in the cooked jlllet previously incubated with or without collagenase at 55°C for 6 h. Extended incubation to 20h at 55°C showed honeycombing in both control and collegenase‐treated fillets. 7he possible roles of pyloric collagenase and muscle alkaline proteinase in honeycombing are discussed.