479–484. Crop Post-Harvest: Science and Technology

360 Crop Post-Harvest: Science and Technology , First Edition. Edited by Debbie Rees, Graham Farrell and John Orchard. © 2012 Blackwell Publishing Ltd. Published 2012 by Blackwell Publishing Ltd. 17 Onions, Shallots and Garlic Lesley Currah, Katherine Cools and Leon A. Terry INTRODUCTION Onions Allium cepa L., shallots A. cepa group Aggregatum and garlic A. sativum are all plants of the genus Allium which produce edible bulbs and leaves. Botanically, the family Alliaceae is related to the Liliaceae and the Amaryllidaceae within the monocotyledons. The majority of species of the large Allium genus are distingui- shed by the presence of sulphur containing compounds which give the typical onion or garlic smell and flavour for which the allium crops are prized. Other important compounds include saponins and flavonols, which also contribute to the flavour and the health benefits from eating alliums. The main storage carbohydrates in onions are complex fructans, especially abundant in pungent onions, while in sweet onions there are higher levels of simple sugars Davis et al. 2007. Onions and other bulb alliums are important vegetables in world trade since they can be shipped when dormant. Annual figures published by the FAO Food and Agriculture Organization of the United Nations show that onion world production has risen steadily in recent years, reaching a total of 64.47 million tonnes in 2007 FAOSTAT 2008. Estimates of the proportion of onions traded internationally vary from 6 to 10: for example, the volume exported in 2005 Tables 17.1 and 17.2 was nearly 5 million tonnes, representing about 7.6 of reported production. However, we should be aware that a lot of ‘informal’ trade across frontiers is not reported in the official figures from Tanzania to Kenya for example. In addition to ‘dry bulb onions’, over 500 000 tonnes of ‘green onions plus shallots’ were also exported in 2005 Tables 17.3 and 17.4. For garlic, world annual production is about 15 million tonnes and of this, over two-thirds originate in China, which is also by far the most successful exporter Table 17.5, while many different countries are substantial importers Table 17.6 FAOSTAT 2008. Major onion producing countries extend from the tropics to temperate regions and onions are produced in countries ranging from the equator to Scandinavia. Since onions are sensitive to photoperiod, a very wide range of onion cultivars has been developed, from ‘short day’ to ‘very long day’ adapted, to cover all the latitudes where onions are grown. The highest national onion yields are recorded from temperate countries with long growing seasons e.g. Ireland and Korea, mean yields 58.0 and 57.0 tha respectively in 2007, compared to an average world yield of 18.7 tha; FAOSTAT 2008. Temperate climates allow the onion to develop a large vegetative plant before bulbing starts, thereby giving it the capacity to produce a large bulb. In many tropical countries with seasonal climates, onions grow and produce well in the cool season. However, they are more difficult to grow near to the equator in very humid climates and at low altitudes: here, tropical shallots are the traditional alliums produced e.g. in Indonesia. Traditional garlic production areas are mostly located in Mediterranean climates including California, Argentina and Chile and also in India and the East Asian countries. Onions, Shallots and Garlic 361 Table 17.1 World Trade in Dry Bulb Onions: Exports, 2005. Country Quantity mt Value US million World 4 868 797 1129.0 Argentina 201 871 30.9 Australia 54 060 16.4 Austria 44 281 5.5 Belgium 88 367 23.8 Canada 58 235 24.3 Chile 54 700 15.8 China, People’s Republic of 570 669 117.8 Egypt 300 996 31.0 France 42 825 20.6 Germany 39 128 14.5 Guatemala 21 048 3.7 India 961 806 160.9 Iran 23 471 3.3 Italy 35 252 33.5 Kazakhstan 64 337 7.9 Malaysia 112 727 25.9 Myanmar 39 908 8.8 Netherlands 847 310 195.5 Niger 68 008 20.9 Pakistan 29 597 3.7 Peru 58 400 17.3 Poland 168 051 39.9 Saudi Arabia 24 495 5.0 Spain 203 826 63.0 Tajikistan 31 862 6.4 Thailand 67 713 11.8 Turkey 63 673 6.9 United States 327 904 145.4 Uzbekistan 48 626 19.0 Note: Only countries exporting 20 000 metric tonnes mt are shown. 1 mt = 1000 kg Source: Data from FAOSTAT 2008. Table 17.2 World Trade in Dry Bulb Onions: Imports, 2005. Country Quantity mt Value US million World 4 780 980 1428.4 Bangladesh 332 551 69.4 Belgium 153 547 45.7 Canada 154 504 80.3 China, People’s Republic of 39 579 16.9 Colombia 43 990 3.2 Czech Republic 31 737 5.5 France 95 223 40.2 Germany 227 456 90.4 Indonesia 22 133 6.8 Ireland 36 085 20.0 Italy 44 937 12.7 Japan 357 544 100.2 Jordan 20 697 4.6 Korea, Republic of South 39 876 5.6 Kuwait 62 909 8.5 Malaysia 420 832 100.6 Nepal 31 876 3.8 Netherlands 87 834 27.7 Oman 36 076 8.2 Philippines 40 323 8.6 Portugal 30 247 6.1 Qatar 24 806 4.9 Romania 42 493 6.3 Russian Federation 500 473 113.7 Saudi Arabia 255 157 43.5 Senegal 107 601 13.4 Singapore 42 527 13.5 Spain 27 847 8.7 Sri Lanka 122 454 21.4 Sweden 29 614 17.6 Thailand 35 870 5.1 United Arab Emirates 142 919 26.3 United Kingdom 304 265 117.7 United States 299 014 228.5 Viet Nam 42 684 5.9 Note: Only countries exporting 20 000 metric tonnes mt are shown. Denotes countries which act as important entrepôts for onion trade. Source: Data from FAOSTAT 2008. TRADE IN ONIONS, SHALLOTS AND GARLIC Both production figures and the import and export figures for dry bulb onions and garlic are recorded annually by the FAO, based on national data FAOSTAT 2008. The summary tables Tables 17.1, 17.2, 17.3, 17.4, 17.5 and 17.6 presented here aim to give an idea of the major exporters and importers of the main allium bulb crops. Some big onion producing countries do not export the bulbs e.g. Brazil, whereas smaller countries such as the Netherlands may export a large percentage of their onion crop Tables 17.1 and 17.2.