L. Lakritz

Effect of low dose gamma radiation on lipids in five different meats

Five types of meats were irradiated by gamma radiation up to a dose of 10 kGy. The m. longissimus dorsi from pork, lamb and beef was irradiated as well as turkey leg and turkey breast muscle. After irradiation, the lipids were extracted from the muscles to ascertain the effect of irradiation. Peroxide and iodine values along with malonaldehyde concentration were used to assess any damage made to the lipids, and to note any significant differences in these compounds due to the type of muscle tissue. Peroxide and iodine values showed that at low irradiation dose, <10 kGy, there was no significant change in any of the meat lipids. Malonaldehyde concentration changed significantly at the micromolar level due to irradiation dose, but only in turkey breast muscle.

Effects of NaCl, sucrose, and water content on the survival of Salmonella typhimurium on irradiated pork and chicken

We investigated the effects of water content, activity, sodium chloride (NaCl) and sucrose contents on the survival of Salmonella typhimurium ATCC 14028 in irradiated mechanically deboned chicken meat (MDCM) and ground pork loin. The effects of NaCl and sucrose concentration were investigated by adding various amounts to MDCM or ground pork loin, or by rehydrating freeze-dried ground pork loin with NaCl solutions with various degrees of saturation. The effects of water content were investigated by rehydrating freeze-dried ground pork loin with different quantities of water. Inoculated samples were irradiated at 5°C in vacuo to various doses up to 6.0 kGy. Highly significant effects (p < 0.01) of water content, water activity (aw) and NaCl content, but not of sucrose content, on the survival of S. typhimurium were identified. The failure of sucrose to provide the same protection for S. typhimurium in meat against radiation argues against reduced water activity being a primary mechanism of protection. The results indicate that the survival of foodborne pathogens on irradiated meats with reduced water content or increased NaCl levels may be greater than expected.

Elimination by gamma irradiation of Salmonella spp. and strains of Staphylococcus aureus inoculated in bison, ostrich, alligator, and caiman meat

There is an expanding industry for the marketing of high-value meats from animals other than the typical domesticated species, including, but not limited to, bison, ostrich, alligator, and caiman. In this study we compared the gamma radiation resistance of a mixture of salmonellae ( Salmonella dublin , S. enteritidis , S. newport , S. senftenberg , and S. typhimurium ) and a mixture of Staphylococcus aureus strains (ATCC 13565, ATCC 25923, and B124) when present on ground bison, ostrich, alligator, and caiman meats at 5°C. A minimum of five doses were used to establish the D values, and the studies were replicated three times. Because the type of meat did not significantly (P < 0.05) alter the radiation resistance of salmonellae and of S. aureus only slightly in the case of ostrich meat, all of the results for each organism were combined to obtain radiation D values of 0.53 ± 0.02 and 0.37 ± 0.01 kGy for Salmonella spp. and S. aureus , respectively. The authors conclude that both of these food-borne pathogens, if present, can be eliminated or greatly reduced in number, depending upon the level of contamination, from these meats by gamma radiation doses between 1.5 and 3.0 kGy at 5°C, the doses currently approved by the FDA and USDA for the irradiation of poultry. The authors also conclude that similar, if not identical, control of food-borne pathogens should be expected on edible meats in general, not just on those that are generically related.

Effect of ionizing radiation on unesterified tocopherols in fresh chicken breast muscle

The effect of ionizing radiation on free tocopherols in chicken was determined Raw chicken breast muscle with skin and adipose tissue removed was subjected to gamma radiation from a (137)Cs source at 1, 2·25, 5·0, and 10·0 kGy. The chicken was packaged aerobically, and irradiated at 4°C. Free tocopherols were extracted directly from the meat without a saponification step. The tocopherols were resolved using normal phase, high performance liquid chromatography by spectrophotofluorometric detection. Irradiation resulted in a significant linear decrease in alpha and gamma tocopherol with increasing dose levels. At 3 kGy, the maximum level approved by the FDA for poultry, a 15% reduction of free gamma tocopherol and a 30% reduction for free alpha tocopherol were observed.

Immediate effects of ionizing radiation on the structure of unfrozen bovine muscle tissue.

To measure the immediate changes in the ultrastrcucture of meat induced by ionizing radiation, bovine longissimus dorsi muscle was irradiated with (137) Cs 72 h after slaughter. The temperature of the samples during irradiation was maintained between 0 and 4°C to avoid cellular changes caused by freeze/thaw. Muscle was irradiated at 5, 10, 30 and 50 kGy. At low levels (up to 10 kGy) of radiation, changes in muscle structure were minimal. At levels above 30 kGy major increases in myofibril fragmentation and decreases in the tensile strength of raw and cooked muscles were noted. SDS gel electrophoresis indicated a decrease in myosin. No changes in the ultrastructure were observed using transmission electron microscopy.

Effect of Reductant Level in Skeletal Muscle and Liver on the Rate of Loss of Thiamin Due to γ-radiation

A study was made of thiamin content of the skeletal muscles and livers of pork, chicken and beef after gamma-irradiation. gamma-Radiation from a 137Cs source was used to irradiate the samples with doses of 0, 1.5, 3, 6 and 10 kGy at 2 degrees C. Samples were also titrated with dichlorophenol-indophenol to determine the reducing capacity of the tissues. The rate of loss of thiamin upon irradiation was found to be about three time as as fast in skeletal muscle as it was in liver, and to be a function of the reducing capacity of the tissues, the loss decreasing with increasing reductant titer. For the same amount of thiamin loss, liver could be irradiated to three times the dose as could muscle.

Effect of gamma radiation on total tocopherols in fresh chicken breast muscle.

Chicken breasts were irradiated in air with a (137)Cs source at 0.0., 1.0, 3.0, 5.6 and 10.0 kGy at 0-2°C. The fresh muscle tissue was saponified and the total tocopherols were isolated and quantitated using normal phase high performance liquid chromatography with a fluorescence detector. Gamma irradiation of the chicken resulted in a decrease in alpha tocopherol with increasing dose. At 3 kGy and 2°C, the radiation level approved by the FDA to process poultry, there was a 6% reduction in the alpha tocopherol level. No significant changes were observed for gamma tocopherol.

Survey of human milk for volatile N-nitrosamines and the influence of diet on their formation

Human milk was analysed for volatile N-nitrosamines and the influence of diet on their possible presence and formation was assessed. 175 samples were obtained from 16 different nursing women. Analysis of samples collected at random, to ascertain baseline levels, indicated that 76.5% of the human milk samples contained less than 0.2 ppb N-nitrosodimethylamine (minimum level of reliable measurement). No other volatile nitrosamines were detected. Expressed milk was collected from volunteers over a 6-hr period after eating meals which included bacon (a source of performed nitrosamines) and at times a vegetable high in nitrate. Eating a meal containing bacon did not result in increased nitrosamine levels in milk. In certain individuals, eating a meal of bacon and a vegetable high in nitrate occasionally resulted in higher levels of N-nitrosodimethylamine in their milk.

Enzyme levels in raw meat after low dose ionizing radiation and extended refrigerated storage

Bovine semimembranosus muscle samples obtained aseptically 24 h after slaughter were irradiated at 1, 5 and 10 kGy between 0 and 4°C and stored at 2°C to determine effects of low level ionizing radiation on tissue-free enzyme levels. Samples were analyzed after 1, 7, 14 and 28 days of storage. Nonspecific proteolysis was measured using (14)C-hemoglobin as the substrate. For determination of possible effect by irradiation on lysosomal enzymes, acid phosphatase and β-glucuronidase were measured. Assays for acid phosphatase and hemoglobin proteolysis indicated negative relationship between increasing dose and enzymatic activity. At 10 kGy mean reductions in enzymatic activity were 8% and 42%, respectively, β-Glucuronidase was not affected at this or at the lower levels of radiation. Correlation between dosage and storage time with enzymatic activity was not significant.

Formation of oxo- and hydroxyfatty acids in irradiated chickens

Finely ground chicken skin and subcutaneous fat exposed to gamma radiation from (137)Cs at 0-2°C for up to 10 kGy generated oxofatty acids (OFA) and hydroxyfatty acids (HFA) in the glycerides. Both classes were determined as colored derivatives; OFA as 2,4-dinitrophenylhydrazones, and HFA as esters of pyruvic acid 2,6-dinitrophenylhydrazone. The concentration of OFA increased with increasing irradiation dose but not always linearly. Variations in the concentration of both classes were noted and some chicken lipids failed to form both classes. In the samples where OFA were generated in significant quantities, the absorption maximum of the derivatives shifted toward a higher wavelength with increasing dose due ostensibly to the formation of double bond(s) in conjugation with the oxo group. This shift in absorption maximum was initially considered to be a means for detecting irradiation as well as indicating the dose received with fair accuracy. However, in several instances irradiation of a chicken sample did not result in the formation of significant increases in OFA and therefore this method cannot be used as a definitive test.