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It is common knowledge that meat will not keep for a long time unless properly preserved.
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Preservation by cold method is the simplest form of preservation, and the advent of refrigeration only accelerated the growth of the meat industry and the modern meat industry is based on effecient refrigeration .
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Low temperature preservation is referred to as refrigeration
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Refrigeration process means extraction of heat from a body and thus cooling it to a temperature below the surrounding atmosphere
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Refrigeration may be classified depending on the extent of the extraction of heat from the product, as chilling (refrigeration above the produc'ts frrezing point) or freezing (refrigeration below the product's freezing point).
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By efficient refrigeration, meat can be preserved in a condition approaching its natural state for periods adequate for commercial requirement.
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The method alters the appearance, weight and flavour of the meat to a little extent and no substance is added or extracted from it.
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The use of low temperature preserved foods is based upon the fact that, the activities of food borne microorganism can be slowed down and or stopped at the temperature just above freezing and generally stopped at sub-freezing temperature.
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At a temperature of –8°C the multiplication of all microorganisms stops and only resumes when temperature is raised later to a suitable level.
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The failure of bacteria to grow at or below freezing depends mainly on the removal of the available water as ice; about 70% is removed at 3.5°C and 94% at –10°C.
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Another factor is the inhibition of the life processes of spoilage organisms at low temperatures.
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In the case of flesh foods low temperature inhibits the action of natural autolytic enzymes.
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The reason for these is that all metabolic reactions of microorganisms are enzyme catalyzed and the rate of enzyme-catalyzed reactions is dependent on temperature. With decrease in temperature, there is an indecrease in reaction rate.
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The surface growth of mould on meat is controlled not only by the temperature but also by the relative humidity of the atmosphere.
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The organisms that grow well at low temperature are referred to as psychrophiles.
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Most psychropylic bacteria belong to the genus Pseudomonas and to a much lesser extent to the genera Achromobacter, Flovobacterium, Alcaligenes, Micrococcus and others.
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Among the moulds and yeasts, species and strains from a large number of genera are capable of growth at refrigerator temperature.
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Moulds belonging to the genera Penicillium, Mucor, Cladosporium, Torulopsis, Candida, Rbodotorula and others are known to be mesophilic.
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Moulds require high relative humidity for them to multiply, and in the absence of suitable relative humidity , they will wither away.
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For the prevention of mould the temperature and relative humidity must therefore be kept as low as possible.
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