Viscosity and emulsifying ability of fish and chicken muscle protein

Abstract

The influence of myofibrillar and sarcoplasmic proteins on the viscosity and emulsifying properties of bonito, cod, horse mackerel and chicken muscle homogenates was studied. Variations in the emulsifying ability of the muscle homogenates and myofibrillar fractions at differing soluble protein concentrations were the same for the three fish species, which was lower than for chicken muscle. The sarcoplasmic proteins from all four species exhibited the same emulsifying properties. At low protein concentrations (5 mg/ml), the emulsifying capacity of the sarcoplasmic proteins from the fish species was higher than the emulsifying capacity of the myofibrillar proteins and the muscle homogenates; in the case of chicken muscle, however, the emulsifying capacity of the sarcoplasmic proteins was lower over the entire range of concentrations studied. A linear relationship was found for apparent viscosity (qaPp) versus protein concentration. The apparent viscosity of the chicken muscle extracts was higher than that of the fish muscle extracts. In all four species studied, the myofibrillar protein was the main factor responsible for the viscosity of the homogenates, though other factors caused it to increase. There was a linear relationship between apparent viscosity and the amount of fat emulsified per 20 ml of protein extract over a concentration range between 14 and 40 mg of protein/ml in the four species studied, so it was possible to calculate one property from the other. The lower emulsifying ability and apparent viscosity of the fish muscle extracts may be the result of greater lability of their myofibrillar proteins.