Refrigeration and Air Conditioning

RUNNING COSTS FOR COLD STORAGE

The refrigeration load will comprise some or all of the following elements: • Sensible: i. e. the cooling of fluids or solids • Latent: i. e. freezing • Heat of respiration: from vegetables, fruits, etc. • Insulation: i. e. heat gain through the walls, ceiling and floor • Infiltration: air ingress through cold store doors […]

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Cold Storage

15.1 INTRODUCTION Cold storage has seen many improvements in technology during the period 1945 to the present day, resulting in better quality and performance of insula­tion and door design. The older types of insulation tend to be prone to deterio­ration, resulting in loss of efficiency and increased running costs in maintaining required temperatures. Early stores […]

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POST-STORAGE OPERATIONS

As a general principle, products leaving cold storage for ultimate consumption may be allowed to rise slightly in temperature. They should be kept as close To the storage temperature as long as possible down the chain of delivery. This requires prompt handling and the use of cooled vehicles up to the final retail outlet (see […]

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FREEZE-DRYING

Certain products cannot be kept in the liquid form for an appreciable time and must be reduced to dry powders, which can then be kept at chill or ambient temperatures. The water must be removed to make them into powders, but any heating above ambient to boil off the water would lead to rapid deterioration. […]

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CONTACT FREEZING

Modern plate cooling systems differ little in principle from the first contact freezer patented in 1929 by Clarence Birdseye. Products in regular-shaped packages, such as ice-cream in flat cartons, are pressed between horizontal, flat, refrigerated plates (see Figure 14.3). These can be opened apart slightly to admit the product and are then closed by hydraulic […]

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QUICK FREEZING

The speed of freezing is a relative matter, but ‘quick frozen’ produce is gener­ally frozen in 5-10 minutes in an air blast, and depending on the thickness this Can be somewhat quicker if immersed. Various methods have evolved, depend­ing on the available resources, the product concerned and the premium value it might earn in an […]

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FREEZING

Storage in the frozen state enables products to be kept for longer than main­taining chilled conditions. Freezing reduces bacterial degradation reactions to a very low level but causes structural change in the product due to the formation of ice crystals. The cells of animal and vegetable products contain a water solu­tion of salts and sugars. […]

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PRE-COOLING

If warm produce is taken into a cold store, moisture will evaporate from its surface and this may result in excessive humidity and condensation on the cold produce already there. This will be of no consequence with wet products such as fish and leaf vegetables. Meat and poultry is pre-cooled in a separate room under […]

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PRE-STORAGE TREATMENT

All foods must be clean on entry. Vegetables and fruits should be dirt-free and some, such as fish, leaf vegetables and some fruits, may be washed and left wet. Fish will tend to dry out and lose its fresh appearance, so it is packed wet or given a sprinkling of ice chips to keep the […]

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Food Refrigeration and Freezing

14.1 I NTRODUCTION The present-day food industry is almost totally dependent on refrigeration in one form or another, to manufacture, preserve, store and bring the product to the point of sale. Chapter 16 gives some examples for specific food products, whilst this chapter gives an overview of cooling methods. The use of low temperatures for […]

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