PROTEIN DENATURATION IN FROZEN STORED HAKE (MERLUCCIUS-MERLUCCIUS L) MUSCLE - THE ROLE OF FORMALDEHYDE

Protein solubility of whole and minced muscle of hake (Merluccius merl uccius L.) was evaluated at different temperatures of storage: -5 degr ees, -12 degrees and -20 degrees C. Proteins soluble in 1% NaCl did no t show any change at any of the temperatures of storage, while the 5% NaCl-soluble proteins decreased significantly when whole hake was stor ed at -5 degrees and -12 degrees C (p < 0.01). A correlation was found between the decrease of solubility and the production of formaldehyde at -5 degrees and -12 degrees C (p < 0.001 and p < 0.01, respectively ). Bound formaldehyde (formaldehyde not extractable) increased with st orage time at -5 degrees (p < 0.001). The addition of formaldehyde to the minced muscle brought about a decrease in both the 1% and the 5% N aCl-soluble proteins. The decrease was dependent upon the temperature, the amount of formaldehyde added and the time of storage. The role of formaldehyde in the denaturation of sarcoplasmic proteins was confirm ed by measuring trimethylamino oxide demethylase activity during the e xperiment.