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Power Engineering and Retigeratin 521 Retigeration & Air conditioning, Usual temperatures for the storage of food products are as follows, ‘Sr.No. Commodity ‘Temperature in °C Storage period, , 1 | Bacon =2 month, , 2._| Beef chilled =a 2 to 3 weeks, 3._| Beef frozen =10 6 to 8& months, 4. | Butter fresh 0 A weeks, , 5.__| Butter frozen =10 6 months, , 6 | Eggs 0 6 months, , 7.__| Fish frozen = 20 12 months, , 8.__| Mutton chilled =1 10 days, , 9___| Mutton frozen =10 6 months, , 10.__| Pork chilled =1 to 2 weeks, 1. | Pork frozen =10 6 months, , 12.__| Poultry fresh o 1 to 2 weeks, , , , , , , , , , , , 2. Relative Humidity and Air Motion :, , A high humidity favours the growth of bacteria, yeast and molds on the food i.e. loss of moisture causing, reduction in size, weight and discolouration are the common problems faced while storing and handling foodstuffs, in cold storage. A relative humidity of 80% is suitable for meat, 85% for eggs and about 88% for most of the, vegetables., , The various problems encountered in handling and storing of foodstuff are, , 1. Loss of moisture : Loss of moisture is known as desiccation. A certain amount of desiccation always takes, place during cold storage of food products. The moisture from the product can be minimized by maintaining, proper relative humidity and most suitable temperature, , 2. Physical breakdown of tissues., , 3. Chemical change : Chemical change as hydrolysis of fats, oxidation of certain matters in products and, changes in food proteins., , 4, Respiration changes : The living coil of the product, they take oxygen and give up carbon dioxide., , 5. Bacterial yeast and mold growth : This growth is very rapid at normal temperature but decreases with, decrease in temperature., , Types of Cold Storages :, , (@) Short term storage or temporary storage., , (b) Long term storage., , (0 Frozen storage,, , These are explained as below, , (a) Short term storage : In this system, the product is chilled and stored above its freezing point. The short, term storage is normally associated with retail establishment, where rapid turn over is expected for short, term storage. Depending on the product, the storage period of the product may be from one day to fifteen, days. Household refrigerant, display cases and commercial refrigerant belong to this type., , (b) Long term storage : Long term storage is usually carried out by wholesaler and is so called cold storage of, warehouse type. The storage period depends upon the type of product to be stored and condition of, product eg. 4 to 6 weeks for ripe tomatoes. 6 to 8 months for onion. The storage period can be further, increased by frozen storage method, , (©) Frozen storage : The purpose of frozen storage is also preserve the food, but for longer duration. It differs, from short term and long term storage in two respects ie. size and storage temperature. The size of frozen, storage is considerably smaller as compared with short and long term storage and the storage temperature, of products is maintained less than freezing temperature.