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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 36 (1971), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: SUMMARY— A technique for determining the relative quantities of oxymyoglobin, metmyoglobin and total pigment concentration at the surface of on intact meat sample was developed. A Beck-man DK-2 spectrophotometer with reflectance attachment was used and spectra were recorded on the RA scale. The sample port of the spectrophotometer was modified so that a uniform and high intensity light beam measuring 0.5 × 0.6 cm reached the surface being evaluated. A sample holder was constructed so that known proportions of oxygenated and oxidized meat could be exposed to the light beam. A family of curves representing varying known amounts of metmyoglobin and oxymyoglobin were obtained. The height of the peak at 632 nm (ΔRA632) was directly related to the amount of metmyoglobin at the surface of the meat sample. For 100% oxymyoglobin, ΔRA632 was at a minimum and equal to RA750. For 100% metmyoglobin, ΔRA632 was at a maximum and the height of the response depended upon the amount of total pigment present. A linear relation was obtained when ΔRA362 was plotted against percent metmyoglobin or against total pigment determined by the Hornsey (1956) method. The method requires making two readings of the meat samples at a single wave length. One reading of the sample followed by one reading of the same sample after oxidation with K3 Fe(CN)6 provides a quantitative evaluation of the metmyoglobin concentration and the total heme pigment concentration. The accuracy of the method may be improved by making multiple readings.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food safety 1 (1978), S. 0 
    ISSN: 1745-4565
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The inhibitory effect of sodium nitrite upon glucose catabolism by Staphylococcus aureus was investigated using [U–1 4C] glucose, liquid chromatography, and gas-liquid chromatography.Acetate and acetoin are the end-products of glucose metabolism by S. aureus at 37°C and pH 6.3. In the presence of inhibitory levels of sodium nitrite, acetate and lactate with traces of pyruvate and acetoin are the end products. Acetate production per unit of growth is significantly lower in the sodium nitrite inhibited cultures. The decreased acetoin accumulation was not due to inhibition of diacetyl reduction. The production of acetoin was induced by the addition of acetate to the sodium nitrite containing medium.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food safety 7 (1985), S. 0 
    ISSN: 1745-4565
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A nitrite reductase was identified and purified 11 -fold from the cytoplasmic fraction of Salmonella typhimurium grown anaerobically with nitrite as the sole nitrogen source. The enzyme required NADH as a cofactor and showed maximum in vitro reductase activity at pH 8.0.S. typhimurium, grown anaerobically in glucose-limited minimal medium containing peptone and nitrite, showed shorter generation times and increased cell yields in comparison to nitrite-free cultures. The presence of nitrite had no effect on aerobic cultures. The nitrite reductase functions in a dissimilatory manner and appears to be primarily involved in physiological energy generation during anaerobic growth. The nitrite reductase may function to remove excess reducing power in the form of NADH from the cell thus increasing ATP production during the anaerobic fermentation of glucose. The formation and subsequent assimilation of ammonia from nitrite is of secondary importance to the organism.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food safety 3 (1981), S. 0 
    ISSN: 1745-4565
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A review of plasmids in Clostridium perfringens is presented. The characterization of the caseinase mediating plasmid pHB101 based upon limited DNase treatment, restriction endonuclease treatment, and agarose gel electrophoresis is described. Antibiotic profiles for the wild type strain and the cured strain were determined. The plasmid pHB101 was non self-transferable. The curing procedure resulted in a stable morphological change from rod to coccoid or bacillary-coccoid shape. A screening of C. perfringens strains showed the general presence of a 9.4 Mdal plasmid which may have been overlooked in the past due to chromosomal DNA masking effects.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 50 (1985), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The potential for growth and toxigenesis of a mixture of three strains of C. botulinum type E in model food systems at pH levels of 4.600 and 4.200 was investigated. Whole shrimp, shrimp puree, tomato puree, and tomato and shrimp puree were acidified to pH levels of 4.200 and 4.600 with acetic or citric acid. Inoculated and uninoculated control samples were tested during 8 wk incubation at 26°C. No significant C. botulinum growth or toxigenesis was detected in the food systems over the 8 wk test period and the pH of the various foods remained generally constant. This investigation affirms the safety of the generally accepted inhibitory pH level of 4.6 in the food systems studied.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 50 (1985), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: TPGY medium was acidified to pH 4.20, 4.60, 5.00 and 5.40 with acetic or citric acid. The media were inoculated with spores from three strains of C. botulinum type A, B or E. Growth, pH, and toxin production under anaerobic conditions were monitored for 8 wk. Spores of C. botulinum types A and B were incapable of outgrowth and toxin production at pH 4.60 or below when incubated at 35°C. Spores of C. botulinum type E were capable of growth and toxin production at 26°C in citric acid acidified systems at pH 4.20. Growth and toxin production were not detected below pH 5.00 when acetic acid was used.
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  • 7
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Toxin production by C. botulinum type E was studied in cod, whiting, and flounder filets packaged in air-permeable film, vacuum packages and packages flushed with N2 or CO2 during storage at 8°, 12° or 26°C. Cod and whiting filets were flushed with CO2 and stored continuously at 4°C or cycled between 4° or 8° and 26°C. Cod and whiting fillets were flushed with gas mixtures and stored at 8°C or 26°C. Flounder deteriorated rapidly and was rejected by sensory evaluation prior to toxin detection during vacuum or modified atmosphere storage at 12°C and 8°C but after toxin detection at 26°C. Toxin was present either prior to or simultaneously with sensory rejection of cod and whiting fillets for all vacuum or modified atmosphere treatments and temperature regimens.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 46 (1981), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A constant source of exponential phase cells of Clostridium perfringens ATCC 3624 could reduce the time required to carry out the protein quality evaluation test of Solberg et al. (1979) to 4 hr. Clostridium perfringens ATCC 3624 was grown in an anaerobic chemostat using the chemically defined medium, R&S, with glucose as the growth limiting nutrient. The dilution rate was set at 0.06 hr−1, the pH at 7.2, and the temperature at 43°C. In the transition from a batch culture to a continuous culture an initial oscillatory cell density response was observed. In the steady state, which was continued for as long as 50 days, the cells were typical Gram positive rods, occurring singly or in chains as long as 15 rods, which were occasionally without septa. The fermentative and biochemical responses of the cells did not change. No sporulation occurred when the cells were growing in the chemostat, but spores were observed in the glucose free culture effluent after incubation at 37°C for 24 hr. When cells produced in the chemostat, were cultured in complex media they demonstrated a growth response similar to cells which had been grown in a batch culture. In defined medium the generation time for the chemostat cultured cells was decreased approximately 17%. The chemostat cultured cells can be used as inoculum for the C. perfringens protein quality assay.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 46 (1981), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Growth of C. perfringens strain 3624 on a defined medium containing ANRC Reference Casein as the nitrogen source was investigated. Gas production, monitored manometrically as an index of growth, indicated a depressed growth response of the organism in the casein-containing medium. Increased growth response resulting from pepsin treatment of the casein was largely due to the enzyme serving as a nitrogen source. Chelation of iron by casein was not responsible for the growth inhibition. Casein suspended in complete medium was not inhibitory to the organism. Growth studies indicated that native casein was not available as a nitrogen source to the organism. Acid hydrolyzed casein and commercial casein hydrolysate served as suitable nitrogen sources for growth of the organism, however exoprotease production was repressed in both media as well as in medium containing native casein as the sole nitrogen source. C. perfringens strain 3624 produced exoprotease in the completely defined medium containing synthetic amino acids, indicating the possible presence of an amino acid or a metabolite, not produced in the casein-containing medium which functioned to derepress the enzyme synthesizing mechanism.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 45 (1980), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mutagenicity of a Maillard browned egg albumin/glucose mixture was evaluated using the Salmonella-mammalian microsome plate assay. Three parts of egg albumin were mixed with two parts glucose and the moisture content adjusted to 15%. The mixture was browned by storage at 37°C and 68% relative humidity for 0, 20, or 40 days. The samples were fractionated into lipid-soluble and water-soluble components and each fraction was tested for mutagenicity. No mutagenic response was observed in any of the samples tested.
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