Legomo: Malsamoj inter versioj
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Enhavo forigita Enhavo aldonita
Linio 156:
=== Afrikaj legomoj ===
* [[gombo]]
==Produktado==
{{redaktata}}
===Kultivado===
{{Ĉefartikolo|Legomĝardeno|Utilĝardeno}}
[[File:AUSAID SOUTH AFRICA (10672860713).jpg|thumb|right|Growing vegetables in South Africa]]
Vegetables have been part of the human diet from [[time immemorial]]. Some are staple foods but most are accessory foodstuffs, adding variety to meals with their unique flavors and at the same time, adding nutrients necessary for health. Some vegetables are [[Perennial plant|perennials]] but most are [[Annual plant|annuals]] and [[Biennial plant|biennials]], usually harvested within a year of sowing or planting. Whatever system is used for growing crops, cultivation follows a similar pattern; preparation of the soil by loosening it, removing or burying weeds and adding organic manures or fertilisers; sowing seeds or planting young plants; tending the crop while it grows to reduce weed competition, control pests and provide sufficient water; harvesting the crop when it is ready; sorting, storing and marketing the crop or eating it fresh from the ground.<ref name=RHS/>
Different soil types suit different crops, but in general in temperate climates, sandy soils dry out fast but warm up quickly in the spring and are suitable for early crops, while heavy clays retain moisture better and are more suitable for late season crops. The growing season can be lengthened by the use of [[Horticultural fleece|fleece]], [[Cloche (agriculture)|cloches]], [[plastic mulch]], [[polytunnel]]s and [[greenhouse]]s.<ref name=RHS>{{cite book |title=The Royal Horticultural Society Encyclopedia of Gardening |last1=Brickell |first1=Christopher (ed) |year=1992 |type=Print |publisher=Dorling Kindersley |isbn=978-0-86318-979-1 |pages=303–308}}</ref> In hotter regions, the production of vegetables is constrained by the climate, especially the pattern of rainfall, while in temperate zones, it is constrained by the temperature and day length.<ref name=Field/>
[[File:John Deere tractor between cabbage rows.jpg|thumb|right|Weeding cabbages in Colorado, US]]
On a domestic scale, the spade, fork and hoe are the tools of choice while on commercial farms a range of mechanical equipment is available. Besides tractors, these include [[plough]]s, [[Harrow (tool)|harrows]], [[drill]]s, [[transplanter]]s, [[cultivator]]s, [[irrigation]] equipment and [[Forage harvester|harvesters]]. New techniques are changing the cultivation procedures involved in growing vegetables with computer monitoring systems, [[GPS]] locators and self-steer programmes for driverless machines giving economic benefits.<ref name=Field>{{cite book|author1=Field, Harry|author2=Solie, John|title=Introduction to Agricultural Engineering Technology: A Problem Solving Approach |url=https://books.google.com/books?id=WWWc8VmdqDAC |year=2007 |publisher=Springer Science & Business Media|isbn=978-0-387-36915-0}}</ref>
===Harvesting===
[[File:Harvesting - geograph.org.uk - 290336.jpg|thumb|left|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.<ref name=Dixie>{{cite web |url=http://www.fao.org/docrep/008/a0185e/a0185e0a.htm |title=8. Post-harvest handling: Storage |author=Dixie, Grahame |year=2005 |work=Horticultural Marketing |publisher=FAO |accessdate=2015-03-21}}</ref>
===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.<ref name="PrakashGarg">{{cite book|author1=Garg & Prakash|author2=Garg, H.P. |title=Solar Energy: Fundamentals and Applications |url=https://books.google.com/books?id=-v_LfcIdĴIC&pg=PA191 |year=2000 |publisher=Tata McGraw-Hill Education |isbn=978-0-07-463631-2 |pages=191}}</ref>
[[File:Gerooide aardappels.JPG|thumb|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.<ref name=Dixie/>
Proper post-harvest storage aimed at extending and ensuring shelf life is best effected by efficient [[cold chain]] application.<ref name=pxk>Kohli, Pawanexh (2008) "Why Cold Chain for Vegetables" in [http://crosstree.info/Documents/Care%20of%20F%20n%20V.pdf ''Fruits and Vegetables Post-Harvest Care: The Basics'']. Crosstree Techno-visors</ref> 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.<ref name=Sinha>{{cite book|author1=Sinha, Nirmal |author2=Hui, Y.H. |author3= Evranuz, E. Özgül |author4=Siddiq, Muhammad |author5=Ahmed, Jasim |title=Handbook of Vegetables and Vegetable Processing |url=https://books.google.com/books?id=Fz58umYZVK8C&pg=PT192 |year=2010|publisher=John Wiley & Sons |isbn=978-0-470-95844-5 |pages=192, 352}}</ref> 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.<ref name=Thompson>{{cite book|author= Thompson, A. Keith|title=Controlled Atmosphere Storage of Fruits and Vegetables |url=https://books.google.com/books?id=9DUh8FcKQtsC&pg=PA18|year=2010 |publisher=CABI |isbn=978-1-84593-647-1 |page=18}}</ref>
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.<ref>{{cite web |url=https://www.iaea.org/sites/default/files/publications/magazines/bulletin/bull18-0/18005480406su.pdf |title=Use of nuclear energy to preserve man's food |author=de Zeeuw, Dick |publisher=International Atomic Energy Agency |accessdate=2015-03-22}}</ref>
===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 [[enzyme]]s and the spoilage caused by [[micro-organism]]s.<ref name=MAFF/> 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 [[carotenoid]]s, [[vitamin E]], [[Dietary element|minerals]] and [[dietary fiber]].<ref>{{cite journal |author=Rickman, Joy C. ; Bruhn, Christine M.; Barrett, Diane M. |year=2007 |title=Nutritional comparison of fresh, frozen, and canned fruits and vegetables II. Vitamin A and carotenoids, vitamin E, minerals and fiber |journal=Journal of the Science of Food and Agriculture |volume=87 |issue=7 |pages=1185–1196 |doi=10.1002/jsfa.2824 }}</ref>
[[File:Bean field Seabrook Farm1a33785v.jpg|thumb|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.<ref name=MAFF/>
[[Frozen food|Freezing]] vegetables and maintaining their temperature at below {{convert|-10|°C}} will prevent their spoilage for a short period, whereas a temperature of {{convert|-18|°C}} is required for longer-term storage. The enzyme action will merely be inhibited, and [[Blanching (cooking)|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.<ref>{{cite book|author1=Hui, Y. H. |author2=Ghazala, Sue|author3=Graham, Dee M. |author4=Murrell, K. D. |author5= Nip, Wai-Kit |title=Handbook of Vegetable Preservation and Processing|url=https://books.google.com/books?id=dVpQVJ46C5gC&pg=PA288 |year=2003 |publisher=CRC Press|isbn=978-0-203-91291-1|pages=286–290}}</ref>
[[File:Sun-dried tomatoes (4694706270).jpg|thumb|left|Sun-drying tomatoes in Greece]]
Traditionally, [[Drying (food)|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 power]]ed driers.<ref name="PrakashGarg"/> The dried produce must be prevented from reabsorbing moisture during storage.<ref name=MAFF/>
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.<ref name=MAFF/> [[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 [[Pickling|pickles]], [[chutney]]s and relishes.<ref name=MAFF>{{cite book |title=Home preservation of Fruit and Vegetables |year=1968 |publisher=Ministry of Agriculture, Fisheries and Food |pages=1–6 }}</ref> [[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.<ref name=Sinha/>
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