Problem statement: Extremely perishable meat provides favorable growth condition for various microorganisms. Meat is also very much susceptible to spoilage due to chemical and enzymatic activities. The breakdown of fat, protein and carbohydrates of meat results in the development of off-odors, off-flavor and slim formation which make the meat objectionable for human consumption. It is, therefore, necessary to control meat spoilage in order to increase its shelf life and maintain its nutritional value, texture and flavor. Approach: A comprehensive literature review was performed on the spoliage mechanisms of meat and meat products and preservation techniques. Results: Historical data reveals that salting, drying, smoking, fermentation and canning were the traditional methods used to prevent meat spoilage and extend its shelf life. However, in order to prevent wholesomeness, appearance, composition, tenderness, flavor, juiciness and nutritive value, new methods were developed. These included: cooling, freezing and chemical preservation. Wide range of physical and chemical reactions and actions of microorganisms or enzymes are responsible for the meat spoilage. Microbial growth, oxidation and enzymatic autolysis are three basic mechanisms responsible for spoilage of meat. Microbial growth and metabolism depends on various factors including: pre-slaughter husbandry practices, age of the animal at the time of slaughtering, handling during slaughtering, evisceration and processing, temperature controls during slaughtering, processing and distribution, preservation methods, type of packaging and handling and storage by consumer. Microbial spoilage causes pH change, slime formation, structural components degradation, off odors and appearance change. Autoxidation of lipids and the production of free radicals are natural processes which affect fatty acids and lead to oxidative deterioration of meat and off-flavour development. Lipid hydrolysis can take place enzymatically or non-enzymatically in meat. In muscle cells of slaughtered animals, enzymatic actions are taken place naturally and they act as catalysts for chemical reactions that finally end up in meat self deterioration. Softening and greenish discoloration of the meat results due to tissues degradation of the complex compounds (carbohydrates, fats and protein) in the autolysis process. Conclusion: Microbial, chemical and enzymatic activities can be controlled by low temperature storage and chemical techniques in the industry. Proper handling, pretreatment and preservation techniques can improve the quality of meat and meat products and increase their shelf life. Combination of chemical additives (TBHQ and ascorbic acid) and low temperature storage (5°C) in darkness are well recognized techniques for controlling the spoilage (microbial, enzymatic and oxidative) of meat and meat products. Understanding of the intrinsic factors and extrinsic factors at every meat processing stage (from preslaughtering to meat product development) is necessary before developing proper handling, pretreatment and preservation techniques for meat.

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Meat Spoilage Mechanisms and Preservation Techniques: A Critical Review

Human safety controversies surrounding nitrate and nitrite in the diet

Food Antimicrobials - An Introduction, P. Davidson and A. Branen Sodium Benzoate and Benzoic Acid, J. Chipley Sorbic Acid and Sorbates, J. Stopforth, J. Sofos, and F. Busta Organic Acids, S. Doores Sulfur Dioxide and Sulfites, C. Ough and L. Were Nitrite, R. Tompkin Nisin, L. Thomas and J. Delves-Broughton Natamycin, J. Delves-Broughton, L. Thomas, P. Davidson, and C. Doan Parabens, P. Davidson Dimethyl Dicarbonate and Diethyl Dicarbonate, D. Golden, R. Worobo, and C. Ough Medium-Chain Fatty Acids and Esters, J. Kabara, D. Marshall Lysozyme, E. Johnson and A. Larson Bacteriocins with Potential for Use in Foods, D. Hoover and H. Chen Naturally Occurring Compounds - Plant Sources, A. Vigil, S. Alzamora, and E. Palou Naturally Occurring Compounds - Animal Sources, J. Stopforth, P. Skandamis, P. Davidson, and J. Sofos Sanitizers: Halogens, Surface-Active Agents, and Peroxides, B. Cords, S. Burnett, J. Hilgren, and J. Magnuson Indirect and Miscellaneous Antimicrobials, L. Shelef and J Seiter Antibiotic Residues in Foods and Their Significance, S. Katz and P. Ward Hurdle Technology Approaches to Food Preservation: Current Applications, Prerequisites and Pitfalls, L. Leistner and G. Gould Mechanisms of Action, Resistance, and Stress Adaptation, A. Russell Methods for Activity Assay and Evaluation of Results, A. Vigil, E. Palou, M. Parish, and P. Davidson

Antimicrobials in Food

Botulism control by nitrite and sorbate in cured meats: A review

Nisin at 75 ppm (75 microgram/g) was superior to 150 ppm of nitrite in inhibiting outgrowth of Clostridium sporogenes PA3679 spores in meat slurries, which had been heated to simulate the process used for cooked ham The inhibitory activity of nisin decreased as the spore load or pH of the slurries increased Unlike nitrite, inhibition by nisin was unaffected by high levels of iron either as a constituent of meats or when added as an iron salt In slurries treated with 75 ppm of nisin, refrigerated storage for 56 days resulted in depletion of nisin to a level low enough to allow outgrowth within 3 to 10 days if the slurries were subsequently abused at 35 degrees C In contrast, a combination of 40 ppm of nitrite and either 75 or 100 ppm of nisin almost completely inhibited outgrowth in these slurries The nisin-nitrite combination appeared to have a synergistic effect, and the low concentration of nitrite was sufficient to preserve the color in meats similar to that of products cured with 150 ppm of nitrite

Nisin: a possible alternative or adjunct to nitrite in the preservation of meats.

C. botulinum growth and toxin production and residual nitrite depletion were studied in a mechanically deboned chicken meat (MDCM) frankfurter-type product, during 27°C temperature abuse. A series of three trials were conducted in order to determine the effects of sodium nitrite and sorbic acid on the above parameters. Low nitrite concentrations (20 and 40 μg/g), did not influence C botulinum growth and toxin production. The addition of sorbic acid (0.2%) to these nitrite levels resulted in a significant extention of the time necessary for toxin to develop. The 0.1% sorbic acid level was ineffective. Nitrite concentrations of 156 μg/g doubled the time necessary, for botulinal toxin production, as did 0.2% sorbic acid alone. The magnitude of toxin production delay was increased five fold when 156 μg/g nitrite and 0.2% sorbic acid were combined. Nitrite depletion, was rapid during processing and 27°C incubation. Low residual nitrite concentrations were present for a longer time in nitrite-sorbic acid combination treatments, indicating that the presence of sorbic acid may delay depletion of residual nitrite. Gas production and spoilage of the product followed the same rate of development as toxin.

SODIUM NITRITE AND SORBIC ACID EFFECTS ON Clostridium botulinum TOXIN FORMATION IN CHICKEN FRANKFURTER‐TYPE EMULSIONS

The study consisted of five treatments including formulations with or without sodium nitrite (120 ppm) or potassium sorbate (0.26%) or both nitrite (40, 80 ppm) and sorbate (0.26%). Packages (300 per treatment) of commercially prepared bacon were inoculated with Clostridium botulinum spores from 10 strains (5 type A and 5 type B) and temperature abused at 27°C. Uninoculated packages (100 per treatment) were also abused. The packages were visually checked for gas production during a 60-day incubation period and tested for botulinal toxin. Spore and vegetative cell counts, aerobic total plate counts, product pH, residual nitrite depletion, and sorbate levels were also monitored. Toxic samples frequently occurred without gas, and many samples showing gas were nontoxic. Added sorbate or added nitrite extended the time to detection of first gas-containing and first toxic samples. A combination of sorbate (0.26%) with reduced nitrite levels (40, 80 ppm) extended this time further. Nitrite or sorbate used singly in the formulation also decreased the rate of toxin production. None of the uninoculated packages was toxic, while the total number of toxic inoculated packages decreased with nitrite or sorbate in the formulations. Ninety percent of the samples from the control treatment became toxic during the 60-day incubation period; 58.8% from the treatment with 0.26% sorbate; 22.0% from the treatment with 40 ppm nitrite and 0.26% sorbate; none from the treatment with 80 ppm nitrite and 0.26% sorbate; and 0.4% from the treatment with 120 ppm nitrite. Low nitrite-sorbate combinations were thus effective in delaying botulinal toxin production in temperature abused bacon.

K. Bhothipaksa

Papers

SODIUM NITRITE AND SORBIC ACID EFFECTS ON Clostridium botulinum TOXIN FORMATION IN CHICKEN FRANKFURTER‐TYPE EMULSIONS

EFFECTS OF VARIOUS CONCENTRATIONS OF SODIUM NITRITE AND POTASSIUM SORBATE ON Clostridium botulinum TOXIN PRODUCTION IN COMMERCIALLY PREPARED BACON