ABSTRACT
Imported frozen minced Alaska pollock blocks were inferior in flavor and texture when compared to minced blocks prepared from certain species of North Atlantic fish. Organoleptic scores were strongly influenced by the cooking method, that is, baked versus fried. Quality attributes assessed by objective tests (thiobarbituric acid, trimethylamine, dimethylamine, aerobic plate count) generally did not show strong correlation with sensory scores.
ABSTRACT
The rate of destruction of hemagglutinins and infectivity of Newcastle disease virus was determined over a temperature range of 37.8 to 60 C. From the calculated values of deltaH and deltaS, it was concluded that inactivation of the hemagglutinating activity and viral infectivity was due to protein denaturation.
Subject(s)
Hot Temperature , Newcastle disease virus/growth & development , Animals , Bacterial Proteins , Chick Embryo , Chickens , Erythrocytes/immunology , Hemagglutination, Viral , Hemagglutinins, Viral/analysis , Immune Sera , Newcastle disease virus/immunology , Newcastle disease virus/pathogenicity , Protein Denaturation , RabbitsABSTRACT
Newcastle disease virus was irradiated at temperatures ranging from 2.2 to 60 C. An interaction between the thermal and ionizing energy was observed in the temperature region of 49 to 60 C. At 2.2 C, the hemagglutinin was considerably more radioresistant than the infectivity property. It is believed that radiation inactivation of Newcastle disease virus infectivity at low temperatures was due to nucleic acid degradation and at higher temperatures was due to protein denaturation.
Subject(s)
Newcastle disease virus/radiation effects , Radiation Effects , Temperature , Antibodies/analysis , Bacterial Proteins , Newcastle disease virus/immunology , Newcastle disease virus/pathogenicity , Nucleic Acid Denaturation , Protein DenaturationABSTRACT
Four Salmonella serotypes which had been subjected to either 15 or 20 cycles of irradiation and subculture were examined for possible changes induced by the treatment. With three serotypes virulence remained unchanged, and with one serotype a reduction had occurred. A few minor changes in the biochemical characteristics occurred in some instances, but with all cultures the serological property was affected to some extent. Lag times and growth rates of the treated cultures were not altered, but the maximal viable population was usually less than that for untreated cultures.
Subject(s)
Radiation Effects , Salmonella/radiation effects , Animals , Chick Embryo , Mice , Microbial Sensitivity Tests , Mutation , Salmonella/growth & development , Salmonella/pathogenicity , Serotyping , VirulenceABSTRACT
Cultures of Salmonella subjected to repeated cycles of gamma-irradiation and subculture developed radiation resistance sooner at a low cycling dose ( approximately 1% survival) compared to a high cycling dose ( approximately 0.001% survival). Radioresistant cells in a population of radiosensitive cells of Salmonella newport or S. typhimurium could be selected by the double-irradiation plate method. The frequency of radioresistant cells in a population of S. newport was found to be about 1 per 8.9 million. Radio-resistant cells obtained by cyclic irradiation and subculture were larger (plumper) than the parent strain and showed a marked pleomorphism.
Subject(s)
Radiation Effects , Radiation Genetics , Salmonella/radiation effects , Methods , Microscopy, Electron , Mutation , Selection, GeneticABSTRACT
The theoretical required cooking times for inactivation of type E Clostridium botulinum toxin (5,000 ld(50) mouse units per 0.5 ml) in haddock fillets of various sizes were calculated by graphical integration of the toxin inactivation rate and heat penetration data. The results indicated that normal cooking procedures should suffice to inactivate this amount of toxin. This conclusion was substantiated by the following additional experimental observations which revealed that the original experiments had been conducted under conservative conditions. First, maximal heat stability of the toxin was found to occur at about pH 5.5, with decreasing resistance upon increasing pH. The theoretical cooking times were based on destruction of the toxin at pH 6.7. The pH of radio-pasteurized inoculated haddock, when toxin production had occurred, was on the alkaline side, at which condition the toxin is heat-labile. Second, when spoilage was discernible in radio-pasteurized inoculated haddock, the toxin titer was low, about 50 ld(50) mouse units per 0.5 ml. Third, the toxin was adequately inactivated in toxic fillets after deep-fat frying for 3 min at 375 F (190.6 C) or after pan frying for 5 min per side at 400 F (204.4 C). Fourth, in this study, residual toxin activity was assayed by intraperitoneal injection of mice. It was shown that the oral toxic dose was 50 to 100 times greater than the intraperitoneal toxic dose.
Subject(s)
Clostridium botulinum/metabolism , Cooking , Fishes , Food Microbiology , Hot Temperature , Toxins, Biological , Animals , Hydrogen-Ion Concentration , Mice , TemperatureABSTRACT
Rate of inactivation curves for the "free" toxin, prototoxin, or activated toxin in crude filtrates of Clostridium botulinum type E were nonlinear, consisting of a fast inactivating rate followed by a slow inactivating rate. Thermodynamic parameters were calculated over a temperature range of 125 to 145 F (51.7 to 62.8 C) for the two different inactivation rates. Energy of activation was low at the lower temperature and high at the higher temperature. The thermal requirement for inactivating similar concentrations of the "free" toxin, prototoxin, or activated toxin was considered to be the same.
