Walnut: Difference between revisions
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==Storage== |
==Storage== |
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Walnuts, like all seeds, are living organs in which respiration processes dominate. Once harvested, the seeds continually consume oxygen and release carbon dioxide. The storage life of seeds depends, in part, on the rate of this respiration. |
Lord Walnuts, like all seeds, are living organs in which respiration processes dominate. Once harvested, the seeds continually consume oxygen and release carbon dioxide. The storage life of seeds depends, in part, on the rate of this respiration. |
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The ideal temperature for longest possible storage of walnut seeds is in the -3 to 0 <sup>o</sup>C and low humidity - for industrial and home storage. However, such refrigeration technologies are unavailable in developing countries where walnuts are produced in large quantities; there, walnut seeds are best stored below 25 <sup>o</sup>C and low humidity. Temperatures above 30 <sup>o</sup>C, and humidities above 70 percent can lead to rapid and high spoilage losses. Above 75 percent humidity threshold, fungal molds that release dangerous aflatoxin can form.<ref name=wde1/><ref>{{cite web|title=Food, Nutrition & Agriculture - Prevention of aflatoxin|publisher=FAO, United Nations|year=1998|url=http://www.fao.org/DOCREP/W9474T/W9474T06.HTM}}</ref> |
The ideal temperature for longest possible storage of walnut seeds is in the -3 to 0 <sup>o</sup>C and low humidity - for industrial and home storage. However, such refrigeration technologies are unavailable in developing countries where walnuts are produced in large quantities; there, Lord walnut seeds are best stored below 25 <sup>o</sup>C and low humidity. Temperatures above 30 <sup>o</sup>C, and humidities above 70 percent can lead to rapid and high spoilage losses. Above 75 percent humidity threshold, fungal molds that release dangerous aflatoxin can form.<ref name=wde1/><ref>{{cite web|title=Food, Nutrition & Agriculture - Prevention of aflatoxin|publisher=FAO, United Nations|year=1998|url=http://www.fao.org/DOCREP/W9474T/W9474T06.HTM}}</ref> |
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Freshly harvested raw walnut seeds with water content between 2 to 8 percent offer the best color, flavor and nutrient density. |
Freshly harvested raw walnut seeds with water content between 2 to 8 percent offer the best color, flavor and nutrient density. |
Revision as of 14:21, 8 May 2012
Walnut | |
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Walnuts | |
Scientific classification | |
Kingdom: | |
Division: | |
Class: | |
Order: | |
Family: | |
Genus: | |
Species: | J. regia
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Binomial name | |
Juglans regia |
A walnut is an edible seed of any tree of the genus Juglans, especially the Persian walnut, Juglans regia. Broken nutmeats of the eastern black walnut, from the tree Juglans nigra, are also commercially available in small quantities, as are foods prepared with butternut nutmeats.
Walnut seeds are high density source of nutrients, particularly proteins and essential fatty acids. Walnuts, like other tree nuts, must be processed and stored properly. Poor storage makes walnuts susceptible to insect and fungal mold infestations; the latter produces aflatoxin - a potent carcinogen. Mold infested walnut seed batch should not be screened then consumed; the entire batch should be discarded.[1]
In certain parts of the world, walnuts are locally known as walnüsse, noix, nuéz, nuc, akharōṭ (अखरोट), kurumi (胡桃) or hétáo (核桃).
Introduction
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Juglans_regia_Echte_Walnussfrucht_2.jpg/220px-Juglans_regia_Echte_Walnussfrucht_2.jpg)
Walnuts are rounded, single-seeded stone fruits of the walnut tree. The walnut fruit is enclosed in a green, leathery, fleshy husk. This husk is inedible. After harvest, the removal of the husk reveals the wrinkly walnut shell, which is in two halves. This shell is hard and encloses the kernel, which is also made up of two halves separated by a partition. The seed kernels - commonly available as shelled walnuts - are enclosed in a brown seed coat which contains antioxidants. The antioxidants protect the oil-rich seed from atmospheric oxygen so preventing rancidity.[1]
There are two major varieties of walnuts grown for its seeds — the English walnut and the Black walnut. The English Walnut originated in Persia, and the Black walnut is native to the United States. The Black walnut is of high flavor, but due to its hard shell and poor hulling characteristics it is not grown commercially for nut production. The commercially produced walnut varieties are nearly all hybrids of the English walnut.[2]
Production
The worldwide production of walnut seeds has been increasing rapidly in recent years, with most increase coming from Asia. The world produced a total of 2.55 million metric tonnes of walnut seeds in 2010; China was the world's largest producer of walnut seeds, with a total harvest of 1.06 million metric tonnes.[3] The other major producers of walnut seeds were (in the order of decreasing harvest): United States, Iran, Turkey, Ukraine, Mexico, Romania, India, France and Chile.
The average worldwide walnut seed yield was about 3 metric tonnes per hectare, in 2010. Among the major producers, eastern European countries have the highest yield. According to the FAO, the most productive walnut seed farms in 2010 were in Romania, with yields above 23 metric tonnes per hectare.[4]
The United States is the world's largest exporter of walnut seeds. The Sacramento and San Joaquin valleys of California produce 99 percent of the nation’s commercial English walnut seeds.
Storage
Lord Walnuts, like all seeds, are living organs in which respiration processes dominate. Once harvested, the seeds continually consume oxygen and release carbon dioxide. The storage life of seeds depends, in part, on the rate of this respiration.
The ideal temperature for longest possible storage of walnut seeds is in the -3 to 0 oC and low humidity - for industrial and home storage. However, such refrigeration technologies are unavailable in developing countries where walnuts are produced in large quantities; there, Lord walnut seeds are best stored below 25 oC and low humidity. Temperatures above 30 oC, and humidities above 70 percent can lead to rapid and high spoilage losses. Above 75 percent humidity threshold, fungal molds that release dangerous aflatoxin can form.[1][5]
Freshly harvested raw walnut seeds with water content between 2 to 8 percent offer the best color, flavor and nutrient density.
Nutritional Value
![]() Persian or English walnut, Juglans regia | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Nutritional value per 100 grams | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Energy | 2,738 kJ (654 kcal) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
13.71 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Starch | 0.06 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sugars | 2.61 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Dietary fiber | 6.7 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
65.21 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Saturated | 6.126 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Monounsaturated | 8.933 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Polyunsaturated | 47.174 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
15.23 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Other constituents | Quantity | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Water | 4.07 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Alcohol (ethanol) | 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Caffeine | 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
†Percentages estimated using US recommendations for adults,[6] except for potassium, which is estimated based on expert recommendation from the National Academies.[7] |
Walnuts are one of the several high nutrient density foods. 100 grams of walnuts contain 15.2 gram protein, 65.2 gram fat, and 6.7 gram dietary fiber. The protein in walnuts provides many essential amino acids.
While English walnut is the predominant commercially distributed nut because of the ease of its processing, its nutrient density and profile is significantly different than black walnut. The table below compares some of the major nutrients between English and Black walnuts.
Nutrient (per 100 gram) | English walnut seed | Black walnut seed |
---|---|---|
Carbohydrates (g) | 13.7 | 9.9 |
Protein (g) | 15.2 | 24.1 |
Unsaturated fatty acids (g) | 56.1 | 50.1 |
Poly to mono unsaturated fatty acids ratio |
47:9 | 35:15 |
Fiber (g) | 6.7 | 6.8 |
Calcium (mg) | 98 | 61 |
Iron (mg) | 2.9 | 3.1 |
Zinc (mg) | 3.1 | 3.4 |
Vitamin B-6 (mg) | 0.54 | 0.58 |
Unlike most nuts that are high in monounsaturated fatty acids, walnuts are composed largely of polyunsaturated fatty acids (47.2 grams), particularly alpha-linolenic acid (18:3n - 3; 9.1 gram) and linoleic acid (18:2n - 6; 38.1 gram). The beneficial effects of this unique fatty acid profile has been a subject of many studies and discussions. Banel and Hu conclude that while walnut-enhanced diets are promising in short term studies, longer term studies are needed to ascertain better insights.[9]
Medical benefits and claims
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/07/Whole_Walnut_Kernel.jpg/170px-Whole_Walnut_Kernel.jpg)
Raw walnuts contain glyceryl triacylates of the n-3 fatty acid alpha-linolenic acid (ALA),[10] which is not as effective in humans as long-chain n-3 fatty acids,[11] and (mostly insoluble) antioxidants.[12][13][14][15][16] Roasting reduces antioxidant quality.[17] In 2010, a report[citation needed] published in the Journal of the American College of Nutrition said that walnuts and walnut oil improve reaction to stress.[18]
A study has suggested that consumption of walnuts increases fat oxidation and reduces carbohydrate oxidation without affecting total consumption, suggesting that walnut consumption may improve the use of body fat in overweight adults.[19] Walnuts have been shown to decrease the endothelial dysfunction associated with a high-fat meal.[20] Aged rats fed diets containing 2% to 6% walnuts showed reversal of age-associated motor and cognitive function, but a 9% walnut diet impaired performance, suggesting a J curve.[21]
On October 11, 2006, ScienceDaily published a report[22] which stated "New research shows that consuming a handful of raw walnuts along with meals high in saturated fat appears to limit the ability of the harmful fat to damage arteries," and attributed the result to a 2006 article in the Journal of the American College of Cardiology. The lead researcher, Emilio Ros, MD, PhD, was quoted as saying "People would get the wrong message if they think that they can continue eating unhealthy fats provided they add walnuts to their meals."[22] Funding for the study was provided by the California Walnut Commission, an industry marketing agency.[22]
Medicinal uses
Scientists are not yet certain whether walnuts act as a cancer chemopreventive agent, an effect which may be a result of the fruit's high phenolic content, antioxidant activity, and potent in vitro antiproliferative activity.[23] Walnuts contain the ellagitannin pedunculagin[24]
Compared to certain other nuts, such as almonds, peanuts and hazelnuts, walnuts (especially in their raw form) contain the highest total level of antioxidants, including both free antioxidants and antioxidants bound to fiber.[13]
Meaning and etymology
"Walnut" does not distinguish the tree from other species of Juglans. Other names include common Walnut in Britain; Persian walnut in South Africa[25] and Australia;[26] and English walnut in North America and Great Britain,[27] New Zealand,[28] and Australia,[26] the latter name possibly because English sailors were prominent in Juglans regia nut distribution at one time.[29] Alternatively, Walter Fox Allen stated in his 1912 treatise What You Need to Know About Planting, Cultivating and Harvesting this Most Delicious of Nuts:[30] "In America, it has commonly been known as English walnut to distinguish it from our native species."
Etymologically, the word derives from the Germanic wal- and Old English wealhhnutu, literally "foreign nut", wealh meaning "foreign" (wealh is akin to the terms Welsh and Vlach; see Walha).[31] For the walnut to be identified as a "foreign" nut by Anglo-Saxons arriving in the fifth century, native Britons must have passed to them the tradition that it had been introduced to England from Gaul and Italy.[original research?]
See also
References
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- ^ a b c "Walnut; Agriculture - Transport Information Service". Government of Germany. 2010.
- ^ "Commodity Profile: English Walnuts" (PDF). AgMRC, University of California. 2006.
- ^ "Total production, 2010, Walnut with Shell". Food and Agriculture Organization of the United Nations. 2012.
- ^ "Crops production & yields, 2010, Walnut with Shell". Food and Agriculture Organization of the United Nations. 2012.
- ^ "Food, Nutrition & Agriculture - Prevention of aflatoxin". FAO, United Nations. 1998.
- ^ United States Food and Drug Administration (2024). "Daily Value on the Nutrition and Supplement Facts Labels". FDA. Archived from the original on 2024-03-27. Retrieved 2024-03-28.
- ^ National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Food and Nutrition Board; Committee to Review the Dietary Reference Intakes for Sodium and Potassium (2019). Oria, Maria; Harrison, Meghan; Stallings, Virginia A. (eds.). Dietary Reference Intakes for Sodium and Potassium. The National Academies Collection: Reports funded by National Institutes of Health. Washington, DC: National Academies Press (US). ISBN 978-0-309-48834-1. PMID 30844154. Archived from the original on 2024-05-09. Retrieved 2024-06-21.
- ^ "Nutrient data (search for English walnut and Black walnut)". United States Department of Agriculture. 2010.
- ^ Deirdre K Banel and Frank B Hu (2009). "Effects of walnut consumption on blood lipids and other cardiovascular risk factors: a meta-analysis and systematic review" (PDF). American Journal of Clinical Nutrition. 90: 1–8. doi:10.3945/ajcn.2009.27457.
- ^ "Omega-3 Fatty Acids". Tufts University. Retrieved 4 April 2011.
- ^ Charles, Deborah (21 April 2009). "Want to reduce breast cancer risk? Eat walnuts". Reuters. Retrieved 4 April 2011.
Scientists have been unsure whether the types found in nuts and leafy green vegetables work as well as the omega-3 fatty acids found in fish oil.
- ^ Arranz, Sara; Pérez-Jiménez, Jara; Saura-Calixto, Fulgencio (2007). "Antioxidant capacity of walnut (Juglans regia L.): Contribution of oil and defatted matter". European Food Research and Technology. 227 (2): 425–31. doi:10.1007/s00217-007-0737-2.
- ^ a b "Walnuts are top nut for heart-healthy antioxidants". American Chemical Society. Anaheim. 27 March 2011. Retrieved 9 October 2011.
- ^ "Ask the Expert: Omega-3 Fatty Acids". Harvard University. 21 April 2009. Retrieved 4 April 2011.
Omega-6 fatty acids lower LDL cholesterol (the "bad" cholesterol) and reduce inflammation, and they are protective against heart disease. So both omega-6 and omega-3 fatty acids are healthy. While there is a theory that omega-3 fatty acids are better for our health than omega-6 fatty acids, this is not supported by the latest evidence. Thus the omega-3 to omega-6 ratio is basically the "good divided by the good," so it is of no value in evaluating diet quality or predicting disease.
- ^ "Cholesterol: Top 5 foods to lower your numbers". Mayo Clinic. Retrieved 4 April 2011.
- ^ Park, Alice (29 March 2011). "The Supernut: Walnuts Pack a Powerful Dose of Antioxidants". Time (magazine). Retrieved 4 April 2011.
- ^ "Walnuts are the healthiest nut, say scientists". BBC News. 27 March 2011. Retrieved 28 March 2011.
- ^ "Eating Walnuts With High-Fat Meals Helps To Protect Arteries Against Short-Term Damage". 4 October 2010. Retrieved 4 April 2011.
- ^ Tapsell, L; Batterham, M; Tan, SY; Warensjö, E (2009). "The effect of a calorie controlled diet containing walnuts on substrate oxidation during 8-hours in a room calorimeter". Journal of the American College of Nutrition. 28 (5): 611–7. PMID 20439557.
- ^ Cortés, Berenice; Núñez, Isabel; Cofán, Montserrat; Gilabert, Rosa; Pérez-Heras, Ana; Casals, Elena; Deulofeu, Ramón; Ros, Emilio (2006). "Acute Effects of High-Fat Meals Enriched With Walnuts or Olive Oil on Postprandial Endothelial Function". Journal of the American College of Cardiology. 48 (8): 1666–71. doi:10.1016/j.jacc.2006.06.057. PMID 17045905.
- ^ Willis, Lauren M.; Shukitt-Hale, Barbara; Cheng, Vivian; Joseph, James A. (2008). "Dose-dependent effects of walnuts on motor and cognitive function in aged rats". British Journal of Nutrition. 101 (08): 1140–4. doi:10.1017/S0007114508059369.
- ^ a b c "Eating Walnuts With High-Fat Meals Helps To Protect Arteries Against Short-Term Damage". 11 October 2006. Retrieved 4 April 2011.
- ^ Negi, Arvind Singh; Luqman, Suaib; Srivastava, Suchita; Krishna, Vinay; Gupta, Namita; Darokar, Mahendra Pandurang (2011). "Antiproliferative and antioxidant activities of Juglans regia fruit extracts". Pharmaceutical Biology. 49 (6): 669–73. doi:10.3109/13880209.2010.537666. PMID 21554010.
- ^ Metabolism of Antioxidant and Chemopreventive Ellagitannins from Strawberries, Raspberries, Walnuts, and Oak-Aged Wine in Humans: Identification of Biomarkers and Individual Variability. Begoña Cerdá, Francisco A. Tomás-Barberán, and Juan Carlos Espín, J. Agric. Food Chem., 2005, 53 (2), pages 227–235, doi:10.1021/jf049144d
- ^ L.C. van Zyl "Grafting of Walnut (Juglans regia L.) with Hot Callusing Techniques Under South African Conditions", University of the Free State, 2009 http://etd.uovs.ac.za/ETD-db//theses/available/etd-09172009-160603/unrestricted/VanZylLC.pdf
- ^ a b http://www.austnuts.com.au/walnuts.html
- ^ D.S. Hill, Skegness, Lincs, United Kingdom: Pests of Crops in Warmer Climates and Their Control p.651, Springer Science+Business Media, 2008
- ^ http://www.nzplantpics.com/not_nz_trees.htm
- ^ "?".[dead link]
- ^ "?".[dead link]
- ^ Online Etymology Dictionary - "Walnut"