Lesson 16 : Vegetables- Processing and Preparation


  • Refrigerated storage: Living organisms have an optimum temperature for growth and lower temperatures greatly retard metabolism and near the freezing point, rate of respiration is reduced. If foods are stored at temperatures near 32 to 340F the storage life may be prolonged as not only respiration rate is decreased but also growth of many spoilage micro-organisms is also retarded but not totally inhibited. In this type of storage, in addition to temperature the relative humidity should be in such a way that there should not be too much moisture losses which cause wilting or too much moisture which may decay fruits and vegetables.

  • Cold storage of fruits and vegetables: Storage life of fruits and vegetables can be enhanced by storing them at temperature below 400F. The exceptions are melon, cucumber, squash, egg plant sweet potato, okra, tomato and certain tropical fruits like the banana, pine apple etc. These have to be stored at higher temperatures.

    Before any commodity is stored in cold storage its field heat or sensible heat should be removed by placing in precooling room, where the temperature is slightly higher than the optimum temperature and thereafter stored in cold rooms.

  • Waxing of fruits and vegetables: The principle of application of wax emulsion is based on partial coverage of these surface cells of the commodity thereby reducing the respiration rates and therefore extension of storage life.

    Wax coating prevents moisture loss, maintains the appearance, delays ripening and decreases the rate of decay and sprouting. This method of storage has been applied in the case of mango, banana, citrus fruits and potato.

  • Modified atmosphere packaging ( MAP): MAP is the method for extending the shelf life of perishable and semi-perishable food products by altering the relative proportions of atmospheric gases that surround the food.

    One common method is to adjust the permeability of the packaging to match the respiration of the fruits or vegetables so that oxygen and carbon dioxide inside is optimally maintained. The proportion of oxygen inside the package has to be lower than in air and of carbon dioxide higher. Such a mixture reduces the rate of respiration, inhibits the synthesis and retards microbial growth.

  • Factors that extend shelf life
    • Harvesting at optimum maturity with minimum injuries.
    • Using proper sanitation procedures.
    • Providing optimum storage condition, namely, temperature, humidity and also the storage atmosphere during all marketing steps.

  • Post-Harvest losses: The extent of post-harvest losses depends on the perishability of the commodity, e.g., vegetables like tomatoes which have moisture content favour maximum losses.
    • Environment factors such as ambient temperature and relative humidity which influence the rate of deterioration in foods.
    • The length of time between harvesting and final consumption.
    • Post-harvest handling, storage and processing practices.
    • In India, post-harvest losses of vegetables are around 10-30 per cent.
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Last modified: Sunday, 11 December 2011, 8:45 AM