| Abstract: | A modified cell fragility method is described for estimating the deterioration which occurs during the storage of frozen fish. A sample of only 100 mg is needed and this is homogenised in a medium consisting of 2% trichloroacetic acid in 1.2% formaldehyde. The results obtained by the new modification are almost unaffected by the pH of the fish, so can give a more truthful estimate of the time-temperature history than those of the original method. Experimental points on optical density/time curves obtained by the new modification show less scatter than those by the original method. Values decrease during storage rather more rapidly than by the original method, to an asymptote which is lower. Modified cell fragility values do not correlate with the length of the fish or its water content. It appears that the escape of myofilaments from the fibrils of high-pH cod accounted for the drop in optical density (scattering) seen in the original method, while in the modified method such proteinaceous material is precipitated and contributes to the optical density of the homogenate. Good curves of optical density/storage time were obtained with other non-fatty fish species, but fatty fish were not satisfactory. Advanced bacterial spoilage of the fish before freezing reduces the optical density in both methods. |
