ビン長およびキハダ鮪青肉に関する研究-II

As a link in the present studies on the green meat of albacore and yellowfin tuna, a discovery was attained of that the strength in which meat specimens can react in hot water on a redox indicator pigment thereto added makes a reliable standard for the grade judgment of meats according to their inclinations to becoming green meat, while said strength was found to have any positive connection neither with reflectance spectra nor with redox potential of the corresponding raw meat.<br> Among several pigments or redox indicators thus far tested, Lauth's violet was found as most suitable to be used in said reaction in hot water. Although a higher pH in reaction medium allows the reaction to take place with the more strong impression, application of a pH greater than 6.00 should be avoided because of its often causing the decolorization degree of pigment to go out of the regularity observed in a lower range of pH of its prevalence among meat specimens of different grades, thus reducing the accuracy of judgment. It was thus found desirable that pH value of the reaction system is kept at about 5.90, for example, by the use of an aqueous acetate buffer of pH 5.65.<br> Details in practical application of the redox indicator decolorizing reaction to predicting the latent tendency to green meat development were inquired according to the following procedure, using frozen meats of albacore and yellowfin tuna as sample: Every 5g. of ground samples was brought in a test tube into a state of suspension in 20ml. of a 0.2M acetate buffer solution of pH 5.65, which contained Lauth's violet at a concentration of 2 mg%. The test tubes were then heated after loosely plugging with glass stoppers in a boiling water bath, still kept in the bath after the completion of coagulation of the meat with occasional stirring up the coagulum for additional 30-45min. and then taken out of the bath for the degrees of decolorization of redox indicator to be observed for different grades of meat. Through arranging the degrees of decolorization thus observed in accordance with the strengths of actually observed green meat development, a conclusion was drawn that meat of such a weak reactivity as unable to strongly decolorize Lauth's violet and left colored blue or bluish green (such negative decolorization is expressed in Fig. 5 as marked with-) should be classified either into a meat destined to become “green meat” or at least into a meat of low grade.<br> The correlation between the grade of cooked meat and the redox indicator decolorizing power which the same meat develops on heating was confirmed of its prevalence upon the experimental results obtained with 97 and 64 individuals of albacore and yellowfin tuna, respectively. As a measure for predicting the green meat development, reliability of said decolorizing power may be considered as compatible with that of the chromatographical, yellow spot developing property⁸⁾ of meat specimens already reported from our laboratory, though these two kinds of phenomenon stand in mutual exclusion.<br> It was confirmed that the more strongly inclined the raw meat to green meat development, the weaker is its power of decolorizing a redox indicator, while the entity of the meat constituent that weakens the decolorizing power has not been chemically identified as yet.