The principle underlying the designing of low temperature storage is to maintain temperatures at levels which will inhibit the growth of microorganisms, thereby preserving the food.
At high temperatures, microbial activity gets accelerated because perishable foods have- a relatively high proportion of moisture, providing suitable humidity for spoilage to occur.
There are three distinct types of low temperature storages based on different temperature ranges, maintained for the storage of semi-perishable and perishable food:-
(a) Refrigerated storage:
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Is a storage space planned & maintained at a temperature between 0°C & 10°C. It can be in the form of a complete room or a cabinet which is free standing or fixed in the wall.
Such storages are necessary for maintaining the quality of perishable foods for 3-5 days only after which certain changes start taking place in the foods due to enzymatic or microbial activity.
A number of sizes of refrigerators are now available to suit the needs of every area in the establishment. Frost-free and automatic defrost models are also marketed for ease of cleaning.
It is good practice to keep foods covered in refrigerated storage to prevent them from drying. This also prevents odours from one food being picked up by another.
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The space required for refrigerated storage is determined by the volume of food produced, and the type of menus, along with the accuracy of forecasts of sales.
If the menu invoice the use of many of perishable foods, or forecasting is incorrect and plenty of food is leftover, then the space required will be greater than if the number of perishable ingredients involved are few, and all that is prepared and is sold.
Also, if the menu items involve preparation methods such as soaking, fermenting, and so on, then refrigerated space required is greater so that the degree of fermentation can be controlled over time.
For a canteen or coffee shop in which most foods are sold out each day, one 16 cubic feet refrigerator may be enough to store-fresh ingredients like milk, curds, fruits, dough’s. In small establishments, the cabinet refrigerators may generally be kept between the kitchen and service areas, for easy access from both sides. In larger establishments, there may be a separate room.
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(b) Cold Storage:
Cold storage is generally one in which the temperature is maintained between 0″ and 5° C, thereby reducing the enzyme activity to a minimum. Such storages are also called ‘chill rooms’ and can hold perishables for over a week, and in the case of fruits and vegetables, even up to a month depending on the stage of ripeness and variety.
(c) Freezer Storage:
In freezer storage the temperature ranges from -20°C to O’C. For successful freezing, it is necessary to blanch foods, cool quickly to freezing temperature and pack in airtight containers or bags in quantities which can be utilised immediately on thawing. A food removed from the freezer storage for the use never be partly or wholly kept back.
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Freezer storages may be in the form of wall or free standing cabinets, or part of cabinet in which there is refrigerated storage as well.
In the case of large central kitchens, supplying meals to schools, offices, and airlines, freezer storages may be a room designed to maintain the required temperatures. These are also referred to as walk-in freezers. Table shows the recommended temperatures for storage of various perishables.