Post-Harvest factors

Factors affecting quality of Post harvest Quality
    POST – HARVEST FACTORS
    1. Temperature
    Optimal temperature is a major important factor in determining the PH life of the produce. Senescence accelerate at higher temperature, whereas at low
    temperature, respiration comes down and in F, V and flowers lesser amount of ethylene and the multiplication of microorganism does not take place at faster rate.
    Harvested produce is ideally transported and stored under reduced temperature likely to maximize longevity. However, the effect of reducing temperature on maintaining produce quality is not uniform over the normal temperature range i.e. 0 - 300C for non chilling sensitive produce; 7.5 - 300C for moderately chilling sensitive produce; 13 - 300C for chilling sensitive plants. Normal ripening occur at temperature range of 10-300C, but best quality fruit develops ripening at 20-230C (Fig 1 & 2).
    Response of nonchilling temperature effect of temperature on length of shelf life

    2. Light
    Potted flowering plants/cut flower, it is advisable to illuminate the plants with 2 - 3 k lux (200-300 f.c.) with fluorescent and incandescent to create illumination of red and
    blue light.

    3. Humidity
    Many horticultural produce should be kept at 80-95% RH for maintenance of freshness/turgidity. Produce start showing wilting symptoms when they have lost 10-15%
    of their fresh weight. The rate of transpiration from the produce is reduced with the increases of high RH. Care should to be taken not to maintain high RH coupled with high temperature results in faster infection by pathogen. Produce should not be stores in dry atmosphere because they become less turgid through quick transpiration.
    4. Water Quality
    Water quality relates to pH, EC values, hardness contents of phytotoxic elements and microorganism causing vascular obstruction affecting longevity of the produce
    particularly cut flowers. Saline water decreases vase life flowers. Longevity of flowers reduced when salts concentrations reaches 200 ppm (roses, chrysanthemum and carnation) and 700 ppm (gladiolus). Basic ions like Ca++ and Mg++ present in hard water are less harmful than soft water containing sodium ions. Use of de-ionised water is better than ordinary tap water in enhancing vase life and even use of boiled water containing less air then tap water is readily absorbed by stem.
    Use of Millipore filter water enhances flow rate of water through cut stem and reduction of air blockage from vessel. Acidification of alkaline water with H2So4 and HCL has been found to increase the vase life of cut flowers. At low pH, microbial population in stem of the flowers decreases. Acidification of water through citric acid is also helpful. The optimum pH for extending the vase life of flowers varies from 4.0 - 5.0.
    Wetting agents/surfactants like Tween -20®/APSA® at 0.1 -0.01%(1.0 ml - 0.1 ml L-1) decrease the surface tension of water , increase the lateral water flux which removes air bubbles and helps to maintain a continuous xylem water column in cut flowers.

    5. Plant hormones
    Use of Cytokinin(Kinetin, BA and B-9), auxin(IAA) and gibberellins (GA3) are will delay senescence of the produce and are known to be ethylene inhibitors.
    Abscisic acid – ABA accelerate the developmental process associated with aging and increase sensitivity of the tissue to the ethylene production. ABA is also involves in senescence to increase the permeability of the tonoplast leading to cell disorganization, resulting in decreased water uptake and development of water/ion stress effects.

    6. Preservatives
    In the form of tablet containing a mixture of chemicals such as sugars, germicides, salts, growth regulators, etc. is being used to extend the vase life of the flowers.
    Sugars, biocides, anti-ethylene compounds(1-MCP, Potassium permanganate) and hydrated compound are used for conditioning. All sugars used in holding solution make excellent media for the growth of micro-organism causing stem plugging. Therefore, sugars must be used in the combination with germicides in the vase solution. Metallic salts like silver nitrate, cobalt chloride, Al So4 , Zn So4, calcium nitrate and nickel chloride are used to extend the vase life of flowers. Growth regulators such as BA, IAA, NAA, 2.4.5.T, GA3, B-Nine and CCC are also used.
    7. Ventilation, Spacing & Packaging
    Provision for air circulation must be maintained to remove respiration heat. Sufficient commodity spacing should be provided so that at least
    one side remains exposed for air circulation to prevent heat generation. And only pre cooled products are allowed to be packed, but there should not be any direct contact between product and the containers (Refer chapter storage and packing).

    8. Packing and packaging of fruits, vegetables and flowers
    Preparation of produce for market may be done either in the field or at the packing house. This involves cleaning, sanitizing, and sorting according to quality and size, waxing and, where appropriate, treatment with an approved fungicide prior to packing into shipping containers. Packaging protects the produce from mechanical injury, and contamination during marketing. Corrugated fiberboard containers are commonly used for the packaging of produce, although reusable plastic containers can be used for that purpose. Packaging accessories such as trays, cups, wraps, liners, and pads may be used to help immobilize the produce within the packaging container while serving the purpose of facilitating moisture retention, chemical treatment and ethylene absorption. Either hand-packing or mechanical packing systems may be used. Packing and packaging methods can greatly influence air flow rates around the commodity, thereby affecting temperature and relative humidity management of produce while in storage or in transit.

    9. Length of Storage
    One of the most significant factors that affect the quality of fresh produce is storage. Making sure that fresh produce is stored at optimum conditions is a key to retain their quality. If it is stored in poor storage conditions such as high temperatures, it will lose its nutritional value or spoil quickly. Storing fresh produce beyond the recommended periods even at optimum temperature can still cause loss of nutritional value.

Last modified: Friday, 2 December 2011, 6:04 AM