Brown discoloration in pre‐rigor cut fish fillets

Abstract

SummaryThe surface browning in pre‐rigor processed cod fillets has been shown to be caused by the formation of a denatured form of methaemo‐globin produced from fish blood contaminating the surface. Browning is less likely to occur in fillets cut in rigor or later because a pre‐rigor cut surface exudes a coagulum in which blood is trapped and from which it cannot be easily removed by washing. The observation that Ocean Perch is more liable to surface discoloration has been explained in terms of differences in blood distribution in the muscle tissue. Cod haemoglobin differs markedly from mammalian haemoglobin in that oxyhaemoglobin changes to deoxyhaemoglobin as the pH is reduced below 8. Mammalian haemoglobin is stable at all pH values between 10 and 4.It is suggested that surface browning in fish fillets can be prevented by using correct bleeding procedures before filleting, or by filleting in rigor or later.