Cold storage: Many vegetables can be stored from 14-250 days under refrigerated storage conditions. In general, tropical vegetables require slightly higher temperature of storage 42-55 0 F while vegetables grown in temperate climates or winter months in the tropics require lower temperature (32-38 0 F).
Frozen storage: Many vegetables can be stored under frozen storage conditions at 0 0F for several months. The vegetables are cut and packed in suitable containers, viz., metal foil or plastic bags and rapidly frozen to – 40 0F and stored at 0 0F.
Preservation by canning: The various steps involved in the canning of vegetables are given below. Only fresh vegetables of good quality should be used.
Washing: Washing consists of soaking followed by spray washing of the vegetables to remove adhering dirt. It also helps to remove microorganisms present on the surface.
Peeling and slicing: Some of the vegetables would have to be peeled before they are cut while some, e.g., green peas and immature legumes are used as such.
Blanching: vegetables are generally blanched in boiling water or steam to destroy enzymes causing discolouration or off-flavours. Besides, blanching causes shrinkage in the material which enables proper filling of cans. Steam blanching is better than water blanching. After blanching, the material is filled into clean sterile cans.
Brining: hot brine (2.4 per cent NaCl) is added to vegetables in the can so that they are just covered. Addition of brine improves the taste and flavour and act as a heat transfer medium. The head space in the can should be ½ cm.
Exhausting and sealing: the filled cans are then kept in boiling water for 7-20 minutes( depending on the material) until the centre of the can reaches a temperature of 175 0 F. This helps to remove the air present in the head space before sealing. After exhausting, the cans are sealed using sealers.Heat
processing and cooling: To destroy microorganisms present, the sealed cans are sterilised by steam at 240 0 F for 30-40 minutes. The cans are cooled in running cold water and stored in a cool place. The heat processing time will vary with the vegetable.
Dehydration of vegetables: Dehydration of vegetables consists of the following steps.
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