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Freezing of meat involves the reduction of the internal temperature of meat below its freezing point of, -1.5 ⁰ C and further storing it at temperatures of less than its freezing point.
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Freezing of meat only has made the trans-continental trade in meat a reality and it is probably the most important contributor for the pre-eminent place that meat occupies in world trade.
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However, there exist wide differences in opinion as to the proper freezing temperature.
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In Germany the temperature is maintained at -6 ⁰ C, while in Australia it is maintained at -11 ⁰ C.
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In South America much lower temperatures are maintained and pork may be stored at -18 ⁰ C.
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During sea transport, a temperature of -9 ⁰ C to -8 ⁰ C is maintained at the holds, while the air is kept dry and in circulation.
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In the United Kingdom, it has been customary to hold meat in cold stores at temperatures of -20 ⁰ C.
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But currently, it is generally recognised that lower temperatures are more satisfactory since they reduce the deterioration of carcass meat, and temperatures no higher than -18 ⁰ C and even -30 ⁰ C are recommended.
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The reason behind the change in the recommendation is due to the realisation that the belief that very low temperatures caused excessive dehydration is actually wrong.
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The EEC regulations stipulate that:
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Beef quarters will shall be accepted for freezing at a temperature not above +7 ⁰ C and frozen within 36 hours to an internal temperature of -7 ⁰ C or below.
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The acceptance temperature for pig sides is +4 ⁰ C; they must be frozen at -30 ⁰ C and held in the freezer until all the meat is at -15 ⁰ C or below.
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Frozen storage for beef must be at a temperature of -17 ⁰ C and at -20 ⁰ C for pork.
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The meat must be wrapped in a polythene pack of at least 0.05 mm thickness and in stockinette.
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Such low temperatures can be attained by special blast freezers with temperatures around -34 ⁰ C, air speeds of about 3-5m/s and holding times of up to 25 hours.
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The form of wrapping greatly affects the freezing time; if it is loose, the pockets of air or cartons act as insulation and thereby increase freezing times.
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Wrapping in moisture proof packaging can offset water losses.
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If thoroughly chilled meat is frozen, the rate of freezing probably does not have any effect on the microbiological quality of the product.
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However, if warm meat (e.g. 21°C or higher) is frozen slowly, considerable microbial growth may develop before the temperature of the meat is brought down to the freezing point.
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Therefore, a freezer unit should never be over loaded with warm meat, particularly if the meat has been ground or comminuted which results in distribution of the microbial load throughout the product.
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The commonly held belief that frozen meat can be held indefinitely is not right.
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Freezing of any type or by any method does not destroy bacteria completely.
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The practical storage life of frozen carcass meat is furnished in the table below.
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