Process Info: Pasteurization in vegetable production

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Pasteurization for fruits and vegetables (BAT for Food, Drink and Milk Industries, June 2005)

For fruit and vegetable products which can be microbiologically sterilized at temperatures not higher than 100°C, sterilizing, which, in this case, is generally named pasteurization, can be carried out in installations using hot water or steam at atmospheric pressure. The most traditionally used low temperature process is the open bath. These are metallic cylindrical or parallel piped baths, containing water heated by direct steam injection with a nozzle placed on the bottom. These baths are not generally equipped with automatic thermostats. The operating temperature is the boiling point water at atmospheric pressure with a continuous flow of excess steam. The packs to be sterilized are loaded into large baskets; the baskets, by means of pulleys, are immersed in the baths and treated by boiling water for the required time. Cooling does not generally take place in the sterilizing bath itself, which is thus ready to receive a new load, but in another bath containing cold running water.

Pasteurization for packaged fruits and vegetables (BAT for Food, Drink and Milk Industries, June 2005)

For products packaged in glass containers, linear tunnels are used, including the phases of feeding, preheating, heating, precooling, cooling and drying. Heating is by means of saturated dry steam or hot water coming down on the packs from the top from a series of nozzles or by simple percolation from from a perforated ceiling. The water is then recovered in recycling baths equipped with direct or indirect steam heating. Cooling is also carried out by sprinkling with water. Precooling water is partially recycled, thus keeping it at around 60°C. The drying step is indispensable for the prevention of marks on the cap and above all to enable labeling and secondary online packaging. It is carried out by means of hot or cold air blowers. To sterilize low acidity products, which require temperatures greater than 100°C, various means of heating can be used, although autoclaves are predominantly used. All high temperature sterilizers operate at pressure higher than atmospheric.

Pasteurization for fruit and vegetable juices and purees, tomato purees and desert sauces (BAT for Food, Drink and Milk Industries, June 2005)

Single-phase acid products or products with small pieces, such as fruit juices, vegetable juices and purees, tomato purees, jams, marmalades and jellies, can be hot-filled. Heat sterilization may be carried out before packaging because of the low pH and/or aw of these products. The hot product itself sterilizes the metal or glass container, so that only the caps and necks of bottles, and lids of small containers, need to be sterilized separately. Filling and hermetic closure of the container need to be carried out before the product cools down. The filling temperatures must be kept between 85-92°C. In all cases, the subsequent cooling is undertaken with sterilized chlorinated water.

Aseptic packaging for fruit and vegetable products (BAT for Food, Drink and Milk Industries, June 2005)

Aseptic packaging is a combination of sterilizing plants for the product and for the containers of various types, with an isolated system of filling and sealing. The aseptic packaging of liquid products involves the following sequence of operations: heating at pre-fixed temperatures; transfer to a holding section; cooling at a temperature of around 35°C; filling of the pre-sterilized pack, opening and kept in conditions of perfect asepsis; and closure of the pack. The type of heat exchanger is selected according to the rheological properties of the fluid. They can be tubular of the circular crown type or scraped-film exchangers for products with high Re values and tube-in-tube-in-tube exchangers or plate exchangers for products with low Re values.


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