No description available.

No description available.

The quality of radiation-pasteurized halibut stored at 34°F was evaluated subjectively and objectively over a period of 18 weeks. Results of flavor evaluation and chemical analyses showed that the storage life of halibut irradiated at 0.50, 0.75 and 1.00 megarad was extended more than threefold. Although irradiated samples were consistently rated inferior to unirradiated reference sample by the taste panel, they remained in good condition throughout the 18-week period. No viable, aerobic microorganisms were found. Very little increase in trimethylamine nitrogen, volatile acid number and pH was observed. An increase in free amino nitrogen content was noted on the ninth week up to the twelfth week of storage after which a slight decrease was evident. Pasteurizing radiation was found to induce oxidative rancidity in ground halibut as determined by TBA number and peroxide value. Discoloration of the fish or rusting was observed in all irradiated samples except those treated with 0.005 percent of a commercial mixture of antioxidants, Tenox VI. Oxidative rancidity as measured by TBA number and peroxide value was also markedly inhibited by Tenox VI. Thiodipropionic acid used at the same concentration was found ineffective in preventing rancidity and rusting in the irradiated fish. / Graduation date: 1964

No description available.

No description available.

The over-tenderization of irradiated-sterilized meat is one of the more important adverse effects resulting from the use of irradiation for the preservation of meat. Although research has been reported on the activity and effect of the inherent proteolytic enzymes of irradiated meat, very little work has been directed toward the intimate causes of the textural problems induced by the irradiation treatment. In this study, the influence of irradiation-sterilization on some of the muscle characteristics involved in meat texture was investigated in an attempt to elucidate the over-tenderizing action of irradiation. In addition, the influence of treating the meat by several means prior to irradiation was also investigated to determine their effects upon the texture of the meat. Information relative to the above objectives was obtained by using analytical methods designed to show changes in muscle protein charges, water-holding capacity, acidic and basic groups, bound and free minerals, and disc electrophoretic analysis of the glycine soluble extracts of the treated and control samples. The results showed that the irradiation-sterilization of beef muscle at 4.5 megarads caused tenderization of the meat. Beef soaked in an equal amount of distilled water for 72 hours at 38°F prior to heat inactivation of the enzymes and irradiation was much firmer in texture than the unsoaked samples. Beef heated to an internal temperature of 160°F prior to irradiation also resulted in meat having a firm texture. However, irradiation tends to reverse the effects of both soaking and heating and/or the combination of these two treatments. When soaking, heating and irradiation are combined in one treatment, these factors tend to exert their effect individually and by different mechanisms. Soaking the meat appears to cause a partial denaturation and a net loss of anions of some of the muscle proteins resulting in a shift in the isoelectric region of such meat to a higher pH which results in a greater loss of water upon cooking and thus a firmer texture. Heating the meat to an internal temperature of 160°F results in a partial denaturation of the proteins and probably leads to the formation of stable cross linkages and a "salting-out" effect which may be responsible for a decrease in the water-holding capacity. Thus, meat would have a tighter or more "closed" structure and firmer texture. Irradiation exerts a fragmentation effect upon the beef muscle proteins. These fragments seem to be held together by hydrogen bonds and/or electrostatic forces. The fragmentary alterations of the muscle proteins, the incorporation of water within the fragments, and possibly a "salting-in" effect, appear to be the major factors responsible for effects of irradiation on beef muscle texture. The zinc cations appear to be involved with the heat-labile proteins or enzymes which are denaturated by heating to 160°F. The pH-water holding capacity curves were found to be a valuable technique for investigating some of the biochemical changes in the muscle proteins. / Graduation date: 1963

Typescript (photocopy). / Digitized by Kansas Correctional Industries

The Pectoralis major and Pectoralis minor muscles of chicken were given substerilizing doses of ɤ-irradiation at varying times post-slaughter and the pH, shear force, fragmentation, and color were evaluated. pH measurements in an iodoacetate slurry showed that doses up to 300,000 rads administered at ⅕ or 5 hours post-mortem had no effect on either rate of pH fall or final pH. Irradiation at 2, 5t or 12 hours did not change the final pH taken at 48 hours post-mortem. Excised P. major muscles cooked by boiling between aluminium plates required more shear force at the posterior portion than at the anterior. Irradiation dose levels from 30,000 to 300,000 rads on P. major increased shear resistance over unirradiated muscles. The earlier the time of application (2, 5 and 12 hours post-slaughter) the greater the increase in toughness when measured at 60 hours post-slaughter. The 300,000 rad dose at 12 hours, given after attainment of maximum inextensibility and relaxation of isometric tension, still produced a significant loss in tenderness. The irradiation generally reduced the degree of myofibrillar fragmentation after a standardized blending treatment, although the decrease was not always significant. Pasteurizing irradiation produced a pink color in raw muscle stored aerobically for 55 hours that increased with dose. Peaks typical of an oxymyoglobin-like compound emerged and the dominant wavelength was shifted toward longer wavelengths by 4 nm. After cooking there was no visible color difference between irradiated and control muscles. Correlations between these parameters on control muscles indicated that the pH decline was positively correlated to shear force, although not of high value. The fragmentation ratios were not significantly correlated with shear force. / Land and Food Systems, Faculty of / Graduate

The effect of pasteurizing dose levels of irradiation on the lipid and protein fractions of raw bovine muscle was studied by chemical amalysis and taste panel evaluation. The following storage conditions were evaluated: (a) Long term anaerobic storage at 39°F (b) Short term aerobic storage at 39°F (c) Frozen storage at -10°F (d) Cooking and short term aerobic storage at 39°F. Free fatty acid content increased with time of storage at 39°F. Irradiation with 1 Mrad of γ irradiation depressed free fatty acid development. During frozen storage the unirradiated sample was significantly higher in free fatty acids than the irradiated samples (0.1 Mrad and 0.5 Mrad). The quantity of phospholipid was reduced by both aerobic and anaerobic storage but no significant difference was evident between irradiated and unirradiated samples. The formation of free amino acids during storage was retarded by irradiation. A significant difference in flavour between control samples and those which received 0.5 Mrad of irradiation was found consistently by taste panel evaluation. The flavour difference resulted from characteristic irradiation odour. Rancid flavours were not detected by the panel. Thiobarbituric reactive substances (TBRS) increased during short term aerobic storage, however a significant difference did not exist between irradiated and unirradiated samples. During long term anaerobic storage the TBRS of irradiated samples increased faster than that of unirradiated samples, but the difference was relatively small. During frozen storage TBRS increased in direct proportion to the level of irradiation. Aerobic storage of cooked meat at 39°F resulted in a rapid increase of TBRS but the level was not affected by irradiation. / Land and Food Systems, Faculty of / Graduate

Call number: LD2668 .T4 1958 L33 / Master of Science