Ripening process of fruit

Coloration of fruits and vegetables depends on their growth maturity, concentration of carotenoid isomers, and food processing methods.

Loss of the green pigment chlorophyll to unmask yellow carotenoids is a desirable part of the ripening process in many fruits, such as peaches and yellow cultivars of apples.

Carotenoids are isoprenoid molecules that are common to all photosynthetic tissues. They are divided into the hydrocarbon carotenes, such as lycopene and β -carotene or xanthophylls, typified by lutein. Provitamin A carotenoids, most importantly beta-carotene, followed by alpha-carotene, are those which are converted into vitamin A in the body and help protecting against infection, night blindness and eye disease.

Carotenoids are localized in subcellular organelles (plastids), i.e. chloroplasts and chromoplasts. In chloroplasts, the carotenoids are chiefly associated with proteins and serve as accessory pigments in photosynthesis, whereas in chromoplasts they are deposited in crystalline form or as oily droplets.

In carotenogenic fruits and fruit vegetables, ripening is usually accompanied by enhanced carotenogenesis as chlorophylls decompose and the chloroplasts are transformed into chromoplast.
Ripening process of fruit

Grapes storage and fumigation

Grapes are highly perishable in nature. Therefore they cannot be stored for a long period or transported long distanced at ambient temperatures.

Grapes to be shipped as fresh are packed in wooden crates, then pre-cooled to about 40 ° F (4.4 °C) in railroad cars or refrigerated rooms.

The fruit can tolerate temperatures slightly lower than this, but the margin of safety above freezing the grapes becomes so narrow that for practical purposes, this temperature should he considered the minimum.

Generally, the grapes will be fumigated with sulfur dioxide prior to or during cooling to prevent mold growth. Sulfur fumigation after harvest and /or used of grapes guards have been shown to reduce postharvest losses significantly. The fungus may infect berries in vineyards, particularly when extended periods of rainy weather occur before harvest.

Sulfur dioxide is produced by burning elemental sulfur. It is lightly toxic to fungi and bacteria. The toxicity increases with the percent relative humidity.  The relative humidity of the air should be as high as practicable – 95% if possible.

Grapes that are to be stored for future shipment should be packed in crates, pre-cooled to 36-40 °F (2.2 - 4.4 °C), place in refrigerated storage 29- 32 ° F (-1.67 – 0 °F), and fumigated with sulfur dioxide and should be held in this manner until shipped.

Periodic re-fumigation with sulfur dioxide may be required to prevent spoilage by molds.
Grapes storage and fumigation 

Pest Control of Fruits and Vegetables

Pest Control of Fruits and Vegetables
Insects, rodents, plant disease, and weeds can devastate food crops, and human history is filled with famines attributable to these scourges. Large scale agricultural production tends to increase the susceptibility of crops to these hazards. Pesticides are currently an integral component of an agricultural system that produces increased yields of fresh fruits and vegetables with good visual quality. Pesticides have become a major cost of production of fruit and vegetable farmers. The use of pesticides is associated with risks of increase pest resistance, environmental contamination, exposure to farm workers, and escalating costs. With mounting regulatory pressure on pesticides it is likely that fewer compounds will be available to the farmer and that these compounds will be available for only a few crops of high economic value.

Damage to fruits and vegetables by pests is not limited to loss of visual quality. Insects and rodents can inoculate plants in the field with microorganisms that can present a health hazard, particularly if the product is not properly washed and is eaten raw. These dangers are compounded if untreated animal wastes such as manure, a potent source of human pathogens, are used for fertilization, particularly with vegetables grown close to the ground. Mold, which can be held in check by fungicide, can infect fruits and vegetables products. Mycotoxins produced by molds, such as patulin in apple products and ochratoxin in citrus fruits, present additional concern. The potential danger of these naturally occurring mycotoxins has been documented but the practical implications of decreased fungicide use are not clear.
Pest Control of Fruits and Vegetables

Damages of fruits and vegetable during storage

Damages of fruits and vegetable during storage
Certain fruits and vegetables are damaged by storage at refrigerated temperatures. These crops develop a disorder known as chilling injury. Symptoms include failure to ripen (bananas and tomatoes), development of brown sunken areas known as pitting (cucumbers, melons, and organs), increased susceptibility to decay (beans and cucumbers) and off flavor development (tomatoes). In many cases, the evidence of chilling injury does not become apparent until the susceptible item is returned to a typical room temperature.

Although the cellular mechanism for chilling injury is not clear understood, most investigators attribute it to physical changes in the membrane lipids. Prevention of chilling injury is best achieved by not storing the item at refrigerated temperatures. For example, for best quality a banana or tomato should not be stored below 12.5 degrees C, either during distribution or within the home. Such a practice, however, accelerates normal deterioration of the product. Some evidence shows of that intermittent warming or cycling the storage temperature above and below critical chilling temperature for a product will extent its shelf life.
Damages of fruits and vegetable during storage

Shelf life of a product

The perception of quality of a product also depends on its form-fresh, frozen, canned or dried. Processing of fruits and vegetables extends the season of a perishable crop. Heat preservation (canning) provides a shelf-stable product, but usually at the cost of color, flavor, and texture. 

Better sensory quality is obtained in frozen foods but at a cost if increased energy requirement to maintain them, in a frozen state. Dried fruit products such as raisins and prunes offer very different attributes than their fresh counterparts. The consumer judges canned products with a different set of criteria than frozen or fresh items of the same commodity. 

Fresh fruits and vegetables are perishable, i.e., they have limited shelf life. They are living, respiring tissue that is also senescing and dying. Certain fruits such as bananas and tomatoes will ripen after harvest, developing desirable color, texture, and flavor during handling and storage. All other fruits and vegetables such as oranges, grapes, cucumbers, and carrots will show little or no improvement in quality within the postharvest system. 

Packing and handling systems have been developed to move the product from farm to consumer expeditiously to minimize quality degradation. Techniques used to extend shelf life of fresh products include 

Lowering the temperature to slow respiration and senescence 

Maintaining an optimal relative humidity to slow water loss without accelerating decay 

Adding chemical preservatives to halt physiological and microbial losses 

Maintaining an optimal gaseous environment to slow respiration and senescence

Longer shelf life can also be obtained by selecting cultivars that are more able to withstand the rigors of the handling system and by harvesting a crop at optimal maturity for storage and handling. 

Shelf life of a product