Monday, October 12, 2009

Food Processing, Canning, Refining and Milling

The types of food processing on food and forage have many kinds of processing like milling, canning, freezing, drying, pasteurization and sterilization.

Refining and Milling:
Sugar is obtained from its plant source (cane or beets) and converted to the common food product by various process known as refining.
Milling is the process of converting grain into flour by mechanical means. The grain is cleaned and a small amount of water is added to prevent the outer part of the kernel from pulverizing. The moistened grain is crushed slightly between two steel corrugated rolls rotating at high speed and with one roll rotating faster than the other. This exerts a shearing action and breaks the kernel into chunks. The product is sifted to remove the germ and chunk are size separated with the larger ones being recrushed and the intermediate sized ones ground between smooth rolls. The resulting flour is sieved to remove large particles.

Canning
Many types of fresh foods, such as fruit, vegetables, meats, fish, etc., are preserved for long term storage by heat treatment and sealing into air tight containers. These containers may be metal, usually tinned or un-tinned steel, which is often plastic-lined, aluminum, or special strength glass. The raw food is packed into the container, the container sealed, and the whole package is then heat treated to cook the food and sterilize both the container and the contents. The usual method of heat treating is to place the containers in a steam pressure vessel and process them at 121oC for a time dependent upon the size of the container and the nature of contents. Acid foods (pH below 4.5) require less time to process than foods with a pH between 4.5 and 7.0. the toxin produced by the microorganism clostridium botulinum is specially toxic to humans, and therefore processing must be severe enough to destroy this organism. It will not grow at a pH lower than 4.5 but it thrives between pH 4.5 and 7.0. Most vegetables, such as beams, peas, and corn, have a pH above 4.5 so that they require more heat treatment than tomatoes, fruit, barriers, and pickled products whose pH varies from 2.3 to 4.5.

Heating may degrade the odor and taste of food, and other chemical changes take place during canning. In general, short time-high temperature treatment causes less deterioration than long time low temperature process. To ensure adequate heat penetration using a short time, agitated cookers are often used. Agitation increases the rate of heat transfer from container to product by continuously changing the surface of food in contact with the can.

Heating may degrade the odor and taste of food, and other chemical changes take place during canning. In general, short time high temperature treatment causes less deterioration than long time low temperature process. To ensure adequate heat penetration using a short time treatment, agitated cookers are often used. Agitation increases the rate of heat transfer from container to product by continuously changing the surface of food in contact with the can.

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