L'effet préventif de l'acide pyruvique et d'autres acides cétoniques sur la dénaturation des protéines dans le poisson congelé

Abstract

Fish muscles were treated with sodium pyruvate (by dipping or adding pyruvate solution to ground muscles to the final concentration of about 0.5%) and stored at 10°F for up to 16 weeks. By use of the extract release volume (ERV) method, the hydration capacities of the treated muscles were found to have greatly increased as compared to untreated samples or to samples which were similarly treated with sodium acetate, EDTA, chloride, citrate, phosphate, polyphosphate and glutamate. Sodium pyruvate (up to 0.9%) as well as sodium glyoxylate and α-ketoglutarate were also added to fish muscle homogenates which were then stored at 10°F for 1 week and 4 weeks, and the total salt extractable protein (TEF) in the homogenates was determined. It was found that the TEP values in homogenates containing pyruvate or α-ketoglutarate were higher, and the TEP values in homogenates containing glyoxylate were lower, than the TEP values in the homogenates which did not contain the keto acids. The anidenaturant effects of pyruvates and a-ketoglutarate were observed throughout the normal pH range of fish muscle, being stronger at pH 7.1 than at pH 6.3. The effects were also observed in the presence of KC1 (0.6M), malonaldehyde (1100ppm) formaldehyde (100ppm) and sodium linoleate (0.08%). Sodium pyruvate and sodium α-ketoglutarate appeared to prevent portein denaturation in frozen fish more effectively than sodium glutamate or polyphosphate. The anti-denaturation mechanims of keto acids could have arisen from their formation of Schiff bases with free amino groups of muscle proteins.