Vegitable Harvest

Harvesting

Harvesting beetroot in the United Kingdom

When a vegetable is harvested, it is cut off from its source of water and nourishment. It continues to transpire and loses moisture as it does so, a process most noticeable in the wilting of green leafy crops. Harvesting root vegetables when they are fully mature improves their storage life, but alternatively, these root crops can be left in the ground and harvested over an extended period. The harvesting process should seek to minimise damage and bruising to the crop. Onions and garlic can be dried for a few days in the field and root crops such as potatoes benefit from a short maturation period in warm moist surroundings during which time wounds heal and the skin thickens up and hardens. Before marketing or storage, grading needs to be done to remove damaged goods and select produce according to its quality, size, ripeness and color.^[34]

Storage

All vegetables benefit from proper post harvest care. A large proportion of vegetables and perishable foods are lost after harvest during the storage period. These losses may be as high as thirty to fifty percent in developing countries where adequate cold storage facilities are not available. The main causes of loss include spoilage caused by moisture, moulds, micro-organisms and vermin.^[35]

Temporary storage of potatoes in the Netherlands

Storage can be short-term or long-term. Most vegetables are perishable and short-term storage for a few days provides flexibility in marketing. During storage, leafy vegetables lose moisture, and the vitamin C in them degrades rapidly. A few products such as potatoes and onions have better keeping qualities and can be sold when higher prices may be available, and by extending the marketing season, a greater total volume of crop can be sold. If refrigerated storage is not available, the priority for most crops is to store high-quality produce, to maintain a high humidity level and to keep the produce in the shade.^[34]
Proper post-harvest storage aimed at extending and ensuring shelf life is best effected by efficient cold chain application.^[36] Cold storage is particularly useful for vegetables such as cauliflower, eggplant, lettuce, radish, spinach, potatoes and tomatoes, the optimum temperature depending on the type of produce. There are temperature-controlling technologies that do not require the use of electricity such as evaporative cooling.^[6] Storage of fruit and vegetables in controlled atmospheres with high levels of carbon dioxide or high oxygen levels can inhibit microbial growth and extend storage life.^[37]
The irradiation of vegetables and other agricultural produce by ionizing radiation can be used to preserve it from both microbial infection and insect damage, as well as from physical deterioration. It can extend the storage life of food without noticeably changing its properties.^[38]

Preservation

The objective of preserving vegetables is to extend their availability for consumption or marketing purposes. The aim is to harvest the food at its maximum state of palatability and nutritional value, and preserve these qualities for an extended period. The main causes of deterioration in vegetables after they are gathered are the actions of naturally-occurring enzymes and the spoilage caused by micro-organisms.^[39] Canning and freezing are the most commonly used techniques, and vegetables preserved by these methods are generally similar in nutritional value to comparable fresh products with regards to carotenoids, vitamin E, minerals and dietary fiber.^[40]

Bean field and canning factory, New Jersey, US

Canning is a process during which the enzymes in vegetables are deactivated and the micro-organisms present killed by heat. The sealed can excludes air from the foodstuff to prevent subsequent deterioration. The lowest necessary heat and the minimum processing time are used in order to prevent the mechanical breakdown of the product and to preserve the flavor as far as is possible. The can is then able to be stored at ambient temperatures for a long period.^[39]
Freezing vegetables and maintaining their temperature at below −10 °C (14 °F) will prevent their spoilage for a short period, whereas a temperature of −18 °C (0 °F) is required for longer-term storage. The enzyme action will merely be inhibited, and blanching of suitably sized prepared vegetables before freezing mitigates this and prevents off-flavors developing. Not all micro-organisms will be killed at these temperatures and after thawing the vegetables should be used promptly because otherwise, any microbes present may proliferate.^[41]

Sun-drying tomatoes in Greece

Traditionally, sun drying has been used for some products such as tomatoes, mushrooms and beans, spreading the produce on racks and turning the crop at intervals. This method suffers from several disadvantages including lack of control over drying rates, spoilage when drying is slow, contamination by dirt, wetting by rain and attack by rodents, birds and insects. These disadvantages can be alleviated by using solar powered driers.^[35] The dried produce must be prevented from reabsorbing moisture during storage.^[39]
High levels of both sugar and salt can preserve food by preventing micro-organisms from growing. Green beans can be salted by layering the pods with salt, but this method of preservation is unsuited to most vegetables. Marrows, beetroot, carrot and some other vegetables can be boiled with sugar to create jams.^[39] Vinegar is widely used in food preservation; a sufficient concentration of acetic acid prevents the development of destructive micro-organisms, a fact made use of in the preparation of pickles, chutneys and relishes.^[39] Fermentation is another method of preserving vegetables for later use. Sauerkraut is made from chopped cabbage and relies on lactic acid bacteria which produce compounds that are inhibitory to the growth of other micro-organisms.^[6]

Top producers

Farmers' market showing vegetables for sale near the Potala Palace in Lhasa, Tibet

Vegetable shop in India

Vegetables in a supermarket in the United States

Vegetables in a supermarket in Canada

In 2010, China was the largest vegetable producing nation, with over half the world's production. India, the United States, Turkey, Iran and Egypt were the next largest producers. China had the highest area of land devoted to vegetable production, while the highest average yields were obtained in Spain and the Republic of Korea.^[42]

Country	Area cultivated thousand hectares (2,500 acres)	Yield thousand kg/ha (89 lbs/acre)	Production thousand tonnes (1,100 short tons)
China	23,458	230	539,993
India	7,256	138	100,045
United States	1,120	318	35,609
Turkey	1,090	238	25,901
Iran	767	261	19,995
Egypt	755	251	19,487
Italy	537	265	14,201
Russia	759	175	13,283
Spain	348	364	12,679
Mexico	681	184	12,515
Nigeria	1844	64	11,830
Brazil	500	225	11,233
Japan	407	264	10,746
Indonesia	1082	90	9,780
South Korea	268	364	9,757
Vietnam	818	110	8,976
Ukraine	551	162	8,911
Uzbekistan	220	342	7,529
Philippines	718	88	6,299
France	245	227	5,572
Total world	55,598	188	1,044,380

Standards

The International Organization for Standardization (ISO) sets international standards to ensure that products and services are safe, reliable and of good quality. There are a number of ISO standards regarding fruits and vegetables.^[43] ISO 1991-1:1982 lists the botanical names of sixty-one species of plants used as vegetables along with the common names of the vegetables in English, French and Russian.^[44] ISO 67.080.20 covers the storage and transport of vegetables and their derived products.^[45]