Pre-harvest factors affecting the postharvest quality of fruits and vegetables
The factors affecting the quality of fruits and vegetables can be divided into two categories.
A. Environmental factor
B. Cultivating or cultural Factors
A. Environmental factors
- Temperature – Maturity, colour, sugar, acidity, etc. High temperature reduces the quality, e.g., citrus, radish, spinach, cauliflower, etc., and increased the quality of grapes, melons tomatoes, etc. Low temperature cause chilling and freezing injury.
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2. Light – Required for the formation of anthocyanins. Lighter in weight, thinner rind, less juiciness and acid due to exposure to sunlight, and develop more TSS than shaded fruits, e.g., citrus fruits, mangoes, etc. Exposure to light potatoes causes greening (solanine formation) which has toxic properties. High sunlight intensity causes sunscald in citrus and tomatoes and reduces the pure white color of cauliflower. Leafy vegetables tend to have thin and large leaves due to low light intensity.
3. Rain – produces cracking (bursting) in grapes, dates, litchi, lemon, tomato, sweet potato, etc. It reduces the appearance and sweetness.
4. Wind – causes abrasion, scratching, and corky marks on fruits (citrus fruits) and damages leafy vegetables.
5. Humidity –High humidity reduces color and TSS and increases acidity in citrus, grapes, tomato, etc., but on the other hand it is needed for the better quality of banana, litchi, and pineapple.
B. Cultural factors
i) Mineral Nutrition
- Nitrogen– High nitrogen reduces ascorbic acid content, TSS/acid ratio, and quality but increases thiamine, riboflavin, and carotene, its deficiency reduces fruit size.
- Phosphorus – High phosphorus reduces size, weight, and vitamin C, like citrus. Due to its deficiency, the appearance of fruits is poor.
- Potassium – Increases size, weight, and vitamin C, like citrus. Its deficiency leads to uneven ripening.
- Calcium – Increases the firmness of many fruits, such as apple, mango, guava, tomato, etc.
- Magnesium – Increases size, weight, and Vitamin C, eg, citrus.
- Zinc – Increases size, weight, and Vitamin C, eg, citrus. Its deficiency causes scattered bunches in the grapes.
- Boron – Deficiency causes brownish pulp in fruits, for example, sticky discoloration of albedo in gooseberry and citrus fruits. Fruits and vegetables become tough and perishable. Cabbage, turnips, and cauliflower are sensitive to boron deficiency.
- Copper– Deficiency of this causes irregular spots on citrus fruits and their appearance becomes distorted.
ii) Growth regulator
- Auxin increases size in loquat (2, 4, 5-T), oranges (NAA), and TSS in mango (2, 4, -D).
- Gibberellic Acid – Increases the size and weight of grapes, apricots, and strawberries and produces parthenocarpic fruits in figs, guavas, grapes, tomatoes, etc. It reduces the discoloration of fruits, e.g., water spots and cork spots in citrus.
- Cytokinins – Maintains green color of leafy vegetables and produces parthenocarpic fruits in figs.
- Ethylene – Ethephon increases anthocyanins (colored grapes, plums, apples, peppers, brinjal), carotenoids (mango, guava, papaya, citrus, tomato etc.), ascorbic acid and TSS and reduces tannins (grapes, dates, etc.) and acidity (grapes, mangoes, tomatoes, etc.).
- Growth retardant – Alar (B9) Increases color in fruits, e.g., apple, cherry, apricot, etc. Maleic hydrazide (MH) inhibits germination in onion bulbs.
iii) Rootstock – Citrus Troyer and Carizzo (citrange) Rootstocks produce fruits of excellent quality in sweet oranges, mandarins, and lemons. Fruit sugar from P. pumilum rootstock and P. cujavillis in guava increase the content of ascorbic acid.
iv) Irrigation – Over irrigation leads to high acidity and lack of moisture reduces fruit size, juice content, and increases peel thickness.
v) Pruning- It affects the size, colour, acidity and sugar content of grapes, phalsa, ber, peach, apple etc.
vi) Thinning – In grapes, dates, peaches, plums, etc., increases the size, colour, acidity and sugar content of the fruit.
vii) Girdling – In grapes it increases the size, color and sugar content of the berry.
viii) Varieties – Varieties differ in size, shape, color and chemical composition. High yield, bright appearance and good shipping qualities are the most important characteristics of the varieties.
ix) Diseases and pests – Both are harmful to fruits and vegetables
x) Pesticides – Pesticide spray residues may contaminate the taste of the processed product. Excessive use of pesticides can also produce harmful metabolites and their toxicity is not necessarily destroyed during processing.
xi) Maturity- Over and under maturity of vegetables reduces the quality of fruits and shortens the shelf life of fruits
xii) Harvesting – Fruits and vegetables should not be injured or damaged under any circumstances otherwise injury, such as abrasion of the skin and tearing of tissue, will reduce the appearance and may lead to infection.