FACTORS INFLUENCING LIQUID-HOLDING CAPACITY AND STRUCTURAL-CHANGES DURING HEATING OF COMMINUTED COD (GADUS-MORHUA L) MUSCLE

The loss of liquid in cod muscle finely comminuted with salt was studi ed as a function of heating temperature from 5 to 70 degrees C. Three different groups of raw material were tested: wild and farmed maturing cod and wild post-spawn cod. The effects of ionic strength, pH and he ating temperature upon liquid-holding capacity were examined either in dividually or simultaneously by using a general linear statistical mod el. The liquid-holding capacity was measured by a low-speed centrifuga tion net rest. The microscopic changes of the comminuted samples were evaluated by light microscopy. The intact muscle, used as raw material , was investigated with light and transmission electron microscopy. Th e liquid loss was very low and almost constant between 5 and 30 degree s C, and increased rapidly thereafter at elevated temperatures NaCl co ncentration, pH, heating temperature and interactions among these fact ors influenced the liquid released according to a first-order interact ion linear model. Upon comminution with salt, most of the fibre struct ure is lost and a homogeneous phase Is formed from the depolymerized m yofibrils. Pores and gaps appeared in the protein matrix upon heating, enhancing the liquid loss. Melted collagen was seen either as a thin film ol as an aggregated network structure, depending on the temperatu re, in the aqueous phase filling the pores and gaps Wild, maturing cod possessed better liquid-holding capacity at higher heating temperatur es than did both fanned and post-spawn fish, owing to different fibre structure. Post-spawn fish underwent a mole severe degradation than di d the maturing fish during ice-storage. (C) 1996 Academic Press Limite d