Preservation of Fruits and Vegetables

Preservation of Fruits and Vegetables

	Preservation of Fruits and Vegetables - Fruits and vegetables are subject to contamination both when in the field as well as during harvesting and storage. If mechanical, damage occurs during transport, susceptibility to decay by microorganisms will increase. Increase in sweetness during storage may also increase the number of microorganisms. During processing, contamination occurs from the trays, pipes, tables knives, and handlers and a build up of organisms may also occur. Bacteria generally present on fruits and vegetables include species of Pseudomonas, Bacillus, Enterobacter, Sarcina, Staphlococcus, Streptococcus Lactobacillus, Leuconostoc etc.
A variety of molds and yeasts may also be present. Growth of these organisms may take place between harvesting and processing but adequate control over temperature and humidity will reduce their growth. Fruits and vegetables can be preserved by avoiding contamination between harvesting, processing, transport and storage. Washing with clean water containing borax or non ionic detergent may help in the reduction, of the microbial load.
By use of low temperature or by chilling and storage or by freezing, most vegetables can be safely stored for sometime. The method used will however, depend on die vegetable. For example, some Not crops can be preserved for some time at low temperature while sweet potatoes and onions can be stored only by chilling before storage at low temperature. Vegetables, vegetable products and fruits can be dried either by Sun drying or by artificial heat and stored.
Drying by heat may reduce the number of yeast and vegetative bacterial cells but not the number of spores. Drying is an effective way of preservation particularly for fruits, in which the acidity will add to the killing effect. Spoilage of vegetables and fruits may result from physical factors by the action of their own enzymes, microbial action or by, a combination of these factors., The common types of microbial spoilage seen in fruit and vegetables are: (i) "bacterial soft rot" caused, by Erwinia carotovora which degrades pectin giving a soft appearance and bad odour, (ii) "grey mold rot" caused by species of Botrytis (iii) "soft rot" caused by Rhizopus with cottony growth leading to softening and a variety of other rots caused by fungi, and (iv) sliminess or souring caused by saprophytic bacteria in piled, wet and heating vegetables.
	The composition of the fruits or vegetables also influences, the type of rot. For example, bacterial soft rot is widespread in non-acid vegetables and fruits while Rhizopus soft rot is common in acidic vegetables and fruits. Fruit juices are generally acidic and hence spoilage occurs mostly by fungi and yeast. Bacteria cause spoilage only in low acid fruit juices and vegetables.

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