Antimicrobials are classified as traditional when they (i) have been used for many years, (ii) are approved by many countries for inclusion as antimicrobials in foods (e.g., lysozyme and lactoferrin, which are naturally occurring but regulatory-agency approved), or (iii) are produced by synthetic means (as opposed to natural extracts). Many organic acids are used as food additives, but not all have antimicrobial activity. Research suggests that the most active are acetic, lactic, propionic, sorbic, and benzoic acids. Acetic acid was the most effective antimicrobial in ground roasted beef slurries against Escherichia coli O157:H7 growth in comparison with citric or lactic acid. Sorbate is applied to foods by direct addition, dipping, spraying, dusting, or incorporation into packaging. The mechanism by which dimethyl dicarbonate (DMDC) acts is most likely related to inactivation of enzymes. A related compound, diethyl dicarbonate, reacts with imidazole groups, amines, or thiols of proteins. Lysozyme is most active against gram-positive bacteria, most likely because the peptidoglycan of the cell wall is more exposed. The primary use for sodium nitrite as an antimicrobial is to inhibit Clostridium botulinum growth and toxin production in cured meats. Sulfites may be used to inhibit acetic acid-producing bacteria, lactic acid bacteria, and spoilage bacteria in meat products. In the future, traditional food antimicrobials will continue to play an important role in food preservation.

Chemical Preservatives and Natural Antimicrobial Compounds

A selective medium was used to enumerate Clostridium botulinum growing in the presence of natural spoilage organisms in a model cured pork slurry. The growth responses of a mixed spore inoculum of six strains of Cl. botulinum type A were studied at 15 degrees, 20 degrees and 27 degrees C with 1.5, 2.5, 3.5 or 4.5% (w/v) salt added (aw range 0.961-0.990). Gompertz and logistic curves, which have a sigmoid shape, were fitted to the data and lag times, growth rates, generation times and time to maximum growth rates were derived. Variation in germination rates of the spores occasionally gave a falsely extended lag time resulting in an exceptionally high estimate for growth rate. Products containing 4.5% (w/v) NaCl would be capable of supporting growth of proteolytic strains of Cl. botulinum, even at 15 degrees C, although the lag period would be extended. In products where absence of Cl. botulinum cannot be assured additional preservative measures are essential. The information obtained provides a framework to investigate the effects of a wider range of additives or variables on the growth responses of Cl. botulinum.

The effect of sodium chloride and temperature on the rate and extent of growth of Clostridium botulinum type A in pasteurized pork slurry

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

Bacterial spores are among the most resistant of all living cells to biocides, although the response depends on the stage of sporulation. The development of resistance to some agents such as chlorhexidine occurs much earlier in sporulation than does resistance to glutaraldehyde, which is a very late event. During germination or outgrowth or both, resistance is lost and the cells become as susceptible to biocides as nonsporulating bacteria. Mechanisms of spore resistance to, and the action of, biocides are discussed, and possible means of enhancing antispore activity are considered. The clinical and other uses of sporicidal and sporostatic chemical agents are described.

Bacterial spores and chemical sporicidal agents.

Sous vide cooking: A review

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

The proteolytic activity of ginger rhizome was studied with bovine serum albumin (BSA), collagen and actomyosin as substrates. A semipurified, powdered enzyme preparation was prepared by buffer extraction of an acetone powder of ginger rhizome and subsequent acetone precipitation of the proteolytic principle from the buffer extract. With 3% BSA as substrate, a relatively high proteolytic activity occurred over a pH range of 4.5–6.0, with an optimum pH of 5.0. The optimum temperature for proteolysis of BSA was 60°C during a 10 min reaction time, with rapid denaturation of the enzyme occurring at 70° C. NaCl in cone up to 10% produced about a 20 and 50% reduction in proteolysis of collagen and BSA, respectively. The ginger protease was protected by dithiothreitol during extraction and reaction, indicating the involvement of −SH groups at the active site. The analyses of soluble peptide amino acids or terminal amino acids suggest that the proteolysis of collagen is many fold greater than that of actomyosin. The combined proteolysis of these two muscle protein fractions by the ginger protease resulted in significantly more tender meat. According to conventional nomenclature, “Zingibain” is the proper name for this proteolytically active principle in Zingiber officinale roscoe or ginger rhizome which is commonly referred to as gingerroot. For meat applications, a possible advantage of zingibain over papain and ficin is the greater proteolysis of collagen in comparison to actomyosin. When compared to reported values for bromelain, zingibain has a higher optimum activity temperature, which is desirable in some applications

Ginger rhizome: a new source of proteolytic enzyme

The effects of different meat sources (beef, pork, beef hearts) and of varying fat and textured soy protein (TSP) levels on properties of wiener-type products were studied. Beef was found to give a more stable emulsion than pork and beef hearts in high fat (30%) and TSP (25%) formulations. High levels (45%) of hydrated TSP did not adversely affect emulsion stability of formulations low in fat (10%). Toughness, caused by lowering the fat levels, was improved by inclusion of pork without causing adverse effects on emulsion stability when low levels (5%) of soy protein isolate (SPI) were used. By lowering the fat and increasing the soy level, a high-protein, low-fat wiener was produced. Shrink and moisture content of this wiener were also higher. A lean content of 40–45% was adequate for good color formation in soy-containing wieners.

Effects of lean meat source and levels of fat and soy protein on the properties of wiener‐type products

Growth and survival of a composite of various strains of Clostridium perfringens was monitored in autoclaved ground beef exposed to constantly rising temperatures increased at rates analogous to those used in beef cookery. Cooking rates from 4.1°C/hr to 12.5°C/hr were examined. Mean generation times (MGT35-52) were determined between 35° and 52°C. the temperature range at which most growth took place. The MGT35-52°C values ranged from 13 min (6.0°C/hr) to 30 min (12.5°C/hr). The most rapid growth rates (MGTmrg) at the rising temperature rates examined were essentially identical at about 8 min. At a constant temperature of 41°C, strain NCTC 8238 exhibited a generation time of 7.1 min. Data characterized growth and survival of C. perfringens during rising temperatures. These data can be used for future growth studies in particular food systems.

GROWTH AND SURVIVAL OF Clostridium perfringens DURING CONSTANTLY RISING TEMPERATURES

The effects of different soy proteins and levels of these were studied in finely comminuted wiener-type products. Lean, skeletal beef muscle, pork backfat, textured soy protein (TSP) and soy protein isolate (SPI) were the main raw ingredients. TSP, when substituted for lean meat at levels greater than 25–30%, on a hydrated (1:2) basis, resulted in emulsion instability and texture softening of product formulated at 30% fat. SPI improved emulsion stability of mixtures high in TSP and fat, but had only a slight positive effect on texture. No differences in composition, cooking losses, peelability and skin formation were found in different soy-lean combinations containing 30% fat. Flavor or treatments with high levels (more than 25%) of soy was improved by using different seasoning mixes, Forty to forty-five percent lean beef, with 30% fat, was found adequate for acceptable color intensity of the cooked product. After processing, products with increasing levels of soy in the formulation had higher residual nitrite levels.

C. E. Allen

Papers

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

Ginger rhizome: a new source of proteolytic enzyme

Effects of lean meat source and levels of fat and soy protein on the properties of wiener‐type products

GROWTH AND SURVIVAL OF Clostridium perfringens DURING CONSTANTLY RISING TEMPERATURES

Effects of soy proteins and their levels of incorporation on the properties of wiener‐type products