کتان

از ویکی‌پدیا، دانشنامهٔ آزاد
پرش به ناوبری پرش به جستجو
فارسیEnglish
کتان
Linum usitatissimum - Köhler–s Medizinal-Pflanzen-088.jpg
گیاه کتان
طبقه‌بندی علمی
فرمانرو: گیاهان
Division: گیاهان گلدار
رده: دولپه‌ای‌ها
راسته: مالپیگی‌سانان
تیره: کتانیان
سرده: کتان
گونه: لاینوم یوستیشسیمیوم
نام علمی
لاینوم یوستیشسیمیوم

گیاه کتان، بَزرَگ (با نام علمی: Linum Usitatissimum) به معنی «مفیدترین» از دسته گیاهان گلدار، رده دولپه‌ای‌ها، راسته مالپیگی‌سانان، تیره کتانیان، سرده کتان می‌باشد. کتان اصالتاً متعلق به سرزمین‌های ساحل مدیترانه شرقی تا کشور هندوستان می‌باشد و احتمالاً برای نخستین بار در منطقه هلال حاصلخیز توسط کشاورزان پرورش یافت. گیاه کتان به شکل گسترده‌ای در اتیوپی و مصر باستان کشت می‌گردید. در کشور گرجستان، در غارهایی که متعلق به دوران ماقبل تاریخ است، کتان‌های خشک شده‌ای کشف شده‌است که مربوط به ۳۰ هزار سال پیش از میلاد است. کانادا، چین، روسیه، هند، انگلستان، آمریکا، اتیوپی، قزاقستان، اوکراین و آرژانتین به ترتیب ده کشور برتر تولیدکننده کتان در جهان هستند.[۱]

مغز گردو و بذر کتان دارای بیشترین اندازه اسید چرب امگا ۳ در میان مواد غذایی گیاهی هستند.[۲][۳]

الیاف کتان[۴][ویرایش]

الیاف کتان[۵] از ساقهٔ گیاهی به همین نام (به انگلیسی فلکس)[۵] استخراج می‌شوند. کتان به عنوان یک گیاه زینتی در باغ رشد می‌کند. الیاف کتان بیشتر از پارچه کتانی کاربرد دارد. کشت این گیاه به طور سالیانه انجام می‌گیرد و حداکثر رشد طولی آن در حدود ۱۲۰ سانتی‌متر است و قطر ساقهٔ آن ۱/۸ تا ۱/۱۶ اینچ است. قسمت بالای ساقه دارای شاخه‌های متعددی است و در روی این شاخه‌ها، گل‌هایی به رنگ‌های سفید، قرمز، بنفش ولاجوردی و آبی دیده می‌شود. کیفیت الیاف به مرغوبیت زمین و شرایط جوّی بستگی دارد. این گیاه در هوای نسبتاً سرد و رطوبی و وجود باران نسبتاً زیاد بهتر به عمل می‌آید. تخم کتان در ماه‌های اردیبهشت و خرداد کاشته می‌شود و مدت رشد آن سه ماه است. پرورش عمده کتان درکشورهای کانادا، چین، روسیه، هند، انگلستان و آمریکا است. ساختمان شیمیایی الیاف کتان مانند پنبه، سلولزی است ولی با وجود شباهت زیاد بین آنها، ساختمان ملکولی کتان از سه جهت از پنبه متفاوت است:

۱-ساختمان داخلی: دیاگرام اشعه ایکس نشان می‌دهد که آرایش مولکولی در ساختمان در ساختمان داخلی الیاف به مراتب بیشتر از پنبه و افزایش کریستالینیتی در ساختمان داخلی باعث شده است که خصوصیات آن با پنبه متفاوت باشد.

۲-الیاف کتان: دارای مواد غیر سلولزی بیشتری نسبت به پنبه است و ناخالصی‌های موجود در کتان عبارت اند از همی سلولز، چربی و مواد رنگی و غیره.

۳-ساختمان فیزیکی[۶] الیاف.

۴-کامبیوم: این قسمت دیوار نازکی است که سلول‌های کورتکس را از چوب جدا کرده است.

۵-چوب: این قسمت را سلول‌های ضخیم و چوبی کوتاه تشکیل می‌دهد که از نظر مکانیکی به رشد گیاه کمک می‌کند.

۶-پیت: این قسمت دیواره نازکی است که قسمت مرکزی ساقه را احاطه می‌کند و در مرکز آن روزنه‌ای است که در سراسر طول ساقه قرار دارد و هوا در آن جریان پیدا می‌کند.

از الیاف کتان به همراه رزین‌های مختلف در تهیه کامپوزیت‌ها استفاده می‌شود که کاربرد آنها از لوازم ورزشی مانند بدنه دوچرخه‌های حرفه‌ای، راکت‌های تنیس، تخته‌های موج سواری و اسکی، تا کاربردهای صنعتی مانند صنعت خوردو سازی یا هواپیماهای بوئینگ است.

کپسول
گل

thumb|Green Flax seed

دانه‌های کتان[ویرایش]

دانه‌های کتان (ر ک مقاله اصلی تخم کتان) در دو مقوله اساسی آمده است: ۱. قهوه‌ای، و ۲. زرد یا طلایی (همچنین به عنوان تخم کتان طلایی شناخته می‌شود).[۱۸] اکثراً دارای ویژگی‌های تغذیه‌ای مشابه و تعداد مساوی از امگا ۳ اسیدهای چرب با زنجیره کوتاه هستند. دانه‌های کتان در تولید روغن نباتی شناخته شده و به عنوان روغن بذر کتان یا روغن بزرک، که یکی از قدیمی‌ترین روغن‌های تجاری است کاربرد دارد. این روغن خوراکی به دست آمده توسط expeller فشار دادن، گاهی اوقات توسط استخراج با حلال بدست می‌آید. روغن بذر کتان حلال پردازش شدهای است که قرن‌ها به عنوان یک روغن خشک در نقاشی و پوشش لاک الکل استفاده می‌شود.[۱۹] بذر کتان که گهگاه به آن تخم بزرک هم می‌گویند، منبعی سرشار از مواد مغذی همچون فیبر، منیزیوم، ویتامین B1، اسید چرب آلفا لینولنیک، و امگا ۳ است. این بذر، از درخت کتان گرفته می‌شود، درختی قدیمی که در مصر باستان و چین بار می‌آید. بذر کتان منبعی برای چربی سالم، آنتی اکسیدان، و فیبر است. تحقیقات اخیر یافته‌اند که این تخم می‌تواند در کاهش خطر ابتلا به دیابت، سرطان و بیماری‌های قلبی نیز مؤثر باشد.

دانه‌های قهوه‌ای
Inshell Green Flax seed

آشپزی[ویرایش]

جوانه بذر کتان خوراکی، با عطر و طعم کمی تنداست. مصرف بیش از حد دانه‌های کتان با آب ناکافی می‌تواند باعث انسداد روده شود. دانه‌های کتان كامل از نظر شیمیایی پایدار هستند، اما بذر کتان آسياب شده (به شكل آرد در آمده) می‌تواند در کمتر از یک هفته فاسد شود، بنابراين بايد در ظروف در بسته نگهدارى شود و در دماى مناسب قرار گيرد تااز فساد سريع آن جلوگيرى شود.

Flaxseed
مواد مغذی در هر ۱۰۰ گرم (۳٫۵ اونس)
انرژی ۲٬۲۳۴ کیلوژول (۵۳۴ کیلوکالری)
کربوهیدرات‌ها ۲۸٫۸۸ g
قندها ۱٫۵۵ g
فیبر ۲۷٫۳ g
چربی ۴۲٫۱۶ g
چربی اشباع ۳٫۶۶۳ g
چربی تک‌اشباع‌نشده ۷٫۵۲۷ g
چربی چنداشباع‌نشده ۲۸٫۷۳۰ g
امگا-۳ ۲۲٫۸ g
امگا-۶ ۵٫۹ g
پروتئین ۱۸٫۲۹ g
ویتامین ب۱ (تیامین) ۱٫۶۴۴ میلی‌گرم (۱۲۶٪)
ویتامین ب۲ (ریبوفلاوین) ۰٫۱۶۱ میلی‌گرم (۱۱٪)
ویتامین ب۳ (نیاسین) ۳٫۰۸ میلی‌گرم (۲۱٪)
پانتوتنیک اسید (ویتامین ب۵) ۰٫۹۸۵ میلی‌گرم (۲۰٪)
ویتامین ب۶ ۰٫۴۷۳ میلی‌گرم (۳۶٪)
اسید فولیک (ویتامین ب۹) ۰ میکروگرم (۰٪)
ویتامین C ۰٫۶ میلی‌گرم (۱٪)
کلسیم ۲۵۵ میلی‌گرم (۲۶٪)
آهن ۵٫۷۳ میلی‌گرم (۴۶٪)
منیزیم ۳۹۲ میلی‌گرم (۱۰۶٪)
فسفر ۶۴۲ میلی‌گرم (۹۲٪)
پتاسیم ۸۱۳ میلی‌گرم (۱۷٪)
روی ۴٫۳۴ میلی‌گرم (۴۳٪)
Link to USDA Database entry
درصدها نسبی‌اند
منبع: پایگاه اطلاعاتی مواد غذایی آمریکا

دارویی[ویرایش]

دانه‌های کتان در طب سنتی اروپایی در داخل (به طور مستقیم خیس یا به عنوان چای) و خارجی (به عنوان کمپرس یا عصاره روغن) برای درمان اختلالات دستگاه تنفسی، چشم، عفونت‌ها، سرد، آنفلوآنزا، تب، روماتیسم و نقرس استفاده می‌کردند.[۲۷]

خواص رنگرزی کتان[۴][ویرایش]

رنگرزی کتان اکثراً در حالت پارچه صورت می‌گیرد و روش رنگرزی آن کاملاً شبیه پارچه‌های پنبه‌ای است. چون پارچه‌های کتان نیز همانند پارچه‌های پنبه‌ای گران لست و لازم است برای رنگرزی آن از رنگ‌های مرغوب استفاده کرد. برای رنگرزی کتان عموماً از رنگرهای خمی که در برابر نور و شست‌وشو ثبات زیادی دارند استفاده می‌شود. برخی از رنگ‌های آزوئیک، گوگردی و تعداد محدودی از رنگ‌های مستقیم نیز در رنگرزی پارچه کتان که مصرف مبلمان و پرده‌ای دارد، به کار می‌روند. نظر به این که ساختمان مولکولی کتان متراکمتر و متبلورتر از پنبه است، نفوذ رنگ به داخل الیاف نیز مشکل تر از پنبه صورت میگیردو در نتیجه رنگرزی یکنواخت پارچهٔ کتان باید با دقت بیشتری همراه باشد.

سایر خصوصیات کتان[۴][ویرایش]

قابلیت تطویل کتان کم است، ولی اگر تحت کشش قرار گیرد و افزایش طول یابد، بع از رفع نیروی کشش میل دارد که دوباره به حالت اولیه برگردد. درجه سختی کتان بسیار زیاد است و در برابر خم شدن مقاومت می‌کند. گرچه پارچه کتانی چروک پذیر است ولی با اجرای تکمیل‌های ضد چروک می‌توان این عیب را برطرف کرد. رطوبت بازیافتهٔ کتان حدود ۱۲ درصد است. قدرت لیف کتان در حالت مرطوب ۲۰ درصد بیشتر از حالت خشک آن استو این حالت باعث می‌شود که به خوبی عملیات مکانیکی مراحل ریسندگی و عملیات تری را تحمل کند.

مقاوت کتان در مقابل حرارت زیاد است و تا ۱۲۰ درجه سانتی گراد حرارات را که در آن شروع به زرد شدن می‌کند، بدون اینکه تجزیه بشود تحمل می‌کند.

دراثر تابش نور خورشید و به مدت زیاد به تدریج از قدرتش کاسته می‌شود.

کتان در برابر محلول رقیق و سرداسیدها مقاوم است، ولی محلول اسیدهای رقیق و گرم، یا غلیظ و سرد آنرا مورد حمله قرار می‌دهد.

همچنین مقاومت کتان در برابر محلول‌های قلیایی بسیار خوب است و می‌توان آن را بارها و بارهابا محلول‌های قلیایی شست‌وشو داد بدون آنکه خسارتی متوجه آن بشود.

حلالهای آلی معمولی که در خشک‌شویی‌ها به کار می‌روند، اثر مخربی روی کتان ندارد.

نگارخانه[ویرایش]

منابع[ویرایش]

  1. مشارکت‌کنندگان ویکی‌پدیا. «Flax». در دانشنامهٔ ویکی‌پدیای انگلیسی، بازبینی‌شده در ۹ ژانویه ۲۰۱۱.
  2. omega-3 fatty acids whfoods.com
  3. How can I get more omega-3 fatty acids in my daily meals? whfoods.com
  4. ۴٫۰ ۴٫۱ ۴٫۲ حاجی شریفی، محسن. خصوصیات الیاف نساجی. مرکز نشر دانشگاهی، 1388. 
  5. ۵٫۰ ۵٫۱ Flax
  6. Morphology

جستارهای وابسته[ویرایش]

Flax
Linum usitatissimum - Köhler–s Medizinal-Pflanzen-088.jpg
Scientific classification e
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Malpighiales
Family: Linaceae
Genus: Linum
Species: L. usitatissimum
Binomial name
Linum usitatissimum
L.
Synonyms[1]
  • Linum crepitans (Boenn.) Dumort.
  • Linum humile Mill.
  • Linum indehiscens (Neilr.) Vavilov & Elladi

Flax (Linum usitatissimum), also known as common flax or linseed, is a member of the genus Linum in the family Linaceae. It is a food and fiber crop cultivated in cooler regions of the world. The textiles made from flax are known in the Western countries as linen, and traditionally used for bed sheets, underclothes, and table linen. The oil is known as linseed oil. In addition to referring to the plant itself, the word "flax" may refer to the unspun fibers of the flax plant. The plant species is known only as a cultivated plant,[2] and appears to have been domesticated just once from the wild species Linum bienne, called pale flax.[3]

Description

Capsules
Flowers

Several other species in the genus Linum are similar in appearance to L. usitatissimum, cultivated flax, including some that have similar blue flowers, and others with white, yellow, or red flowers.[4] Some of these are perennial plants, unlike L. usitatissimum, which is an annual plant.

Cultivated flax plants grow to 1.2 m (3 ft 11 in) tall, with slender stems. The leaves are glaucous green, slender lanceolate, 20–40 mm long, and 3 mm broad.

The flowers are pure pale blue, 15–25 mm in diameter, with five petals. The fruit is a round, dry capsule 5–9 mm in diameter, containing several glossy brown seeds shaped like an apple pip, 4–7 mm long.

History

The earliest evidence of humans using wild flax as a textile comes from the present-day Republic of Georgia, where spun, dyed, and knotted wild flax fibers were found in Dzudzuana Cave and dated to the Upper Paleolithic, 30,000 years ago.[5][6][7] Flax was first domesticated in the Fertile Crescent region.[8] Evidence exists of a domesticated oilseed flax with increased seed size by 9,000 years ago from Tell Ramad in Syria.[8] Use of the crop steadily spread, reaching as far as Switzerland and Germany by 5,000 years ago.[9] In China and India, domesticated flax was cultivated also at least 5,000 years ago.[10]

Flax was cultivated extensively in ancient Egypt, where the temple walls had paintings of flowering flax, and mummies were entombed in linen.[11] Egyptian priests wore only linen, as flax was considered a symbol of purity.[12] Phoenicians traded Egyptian linen throughout the Mediterranean and the Romans used it for their sails.[13] As the Roman Empire declined, so did flax production, but Charlemagne revived the crop in the eighth century CE with laws designed to publicize the hygiene of linen textiles and the health of linseed oil.[14] Eventually, Flanders became the major center of the linen industry in the European Middle Ages.[14] In North America, flax was introduced by the colonists and it flourished there,[15] but by the early twentieth century, cheap cotton and rising farm wages had caused production of flax to become concentrated in northern Russia, which came to provide 90% of the world's output. Since then, flax has lost its importance as a commercial crop, due to the easy availability of more durable fibres.[16]

Uses

Brown flaxseeds
Golden flaxseeds
Golden flaxseed meal

Flax is grown for its oil, used as a nutritional supplement, and as an ingredient in many wood-finishing products. Flax is also grown as an ornamental plant in gardens. Flax fibers are used to make linen. The Latin species name usitatissimum means "most useful".[17]

Flax fibers are taken from the stem of the plant, and are two to three times as strong as those of cotton. Additionally, flax fibers are naturally smooth and straight. Europe and North America depended on flax for vegetable-based cloth until the nineteenth century, when cotton overtook flax as the most common plant used for making rag-based paper. Flax is grown on the Canadian prairies for linseed oil, which is used as a drying oil in paints and varnishes and in products such as linoleum and printing inks. In India, flax seed oil also is known as alsi in Hindi and javas in Marathi. It is mainly used in Savji curries, such as mutton curries.

Linseed meal, the by-product obtained after oil production from flax seeds, is used to feed livestock. It is a protein-rich feed for ruminants, rabbits and fish.[18]

Flaxseeds

Green flaxseeds

Flaxseeds occur in two basic varieties: brown, and yellow or golden (also known as golden linseeds).[19] Most types have similar nutritional characteristics and equal numbers of short-chain omega-3 fatty acids. The exception is a type of yellow flax called solin (trade name Linola), which has a completely different oil profile and is very low in omega-3 FAs. Flaxseeds produce a vegetable oil known as flaxseed oil or linseed oil, which is one of the oldest commercial oils. It is an edible oil obtained by expeller pressing, sometimes followed by solvent extraction. Solvent-processed flaxseed oil has been used for many centuries as a drying oil in painting and varnishing.[20]

Although brown flax may be consumed as readily as yellow, and has been for thousands of years, its better-known uses are in paints, for fiber, and for cattle feed.

Culinary

A 100-gram portion of ground flaxseed supplies about 534 calories (2,230 kJ), 41 g of fat, 28 g of fiber, and 20 g of protein.[21]

Flaxseed sprouts are edible, with a slightly spicy flavor. Excessive consumption of flaxseeds with inadequate amounts of water may cause bowel obstruction.[22] In northern India, flaxseed, called tisi or alsi, traditionally is roasted, powdered, and eaten with boiled rice, a little water, and a little salt.[23]

Whole flaxseeds are chemically stable, but ground flaxseed may go rancid when left exposed to air at room temperature in as little as one week because of oxidation.[24] Refrigeration and storage in sealed containers will keep ground flax from becoming rancid for a longer period. Under conditions similar to those found in commercial bakeries, trained sensory panelists could not detect differences between bread made with freshly ground flax and bread made with milled flax that had been stored for four months at room temperature.[25] If packed immediately without exposure to air and light, milled flax is stable against excessive oxidation when stored for nine months at room temperature [26] and under warehouse conditions, for twenty months at ambient temperatures.

Three natural phenolic glucosides, secoisolariciresinol diglucoside, p-coumaric acid glucoside, and ferulic acid glucoside, can be found in commercial breads containing flaxseed.[27]

Flax fibers

A heckling shop used to prepare flax fibers

Flax fiber is extracted from the bast beneath the surface of the stem of the flax plant. Flax fiber is soft, lustrous, and flexible; bundles of fiber have the appearance of blonde hair, hence the description "flaxen" hair. It is stronger than cotton fiber, but less elastic. The best grades are used for linen fabrics such as damasks, lace, and sheeting. Coarser grades are used for the manufacturing of twine and rope, and historically, for canvas and webbing equipment. Flax fiber is a raw material used in the high-quality paper industry for the use of printed banknotes, laboratory paper(Blotting and Filter), rolling paper for cigarettes, and tea bags.

The use of flax fibers dates back tens of thousands of years; linen, a refined textile made from flax fibers, was worn widely by Sumerian priests more than 4,000 years ago.[28] Industrial-scale flax fiber processing existed in antiquity. A bronze-age factory dedicated to flax processing was discovered in Euonymeia.[29]

Flax mills for spinning flaxen yarn were invented by John Kendrew and Thomas Porthouse of Darlington, England, in 1787.[30] New methods of processing flax have led to renewed interest in the use of flax as an industrial fiber.

A flax field in bloom in North Dakota, United States

Nutrition

Flaxseed
Nutritional value per 100 g (3.5 oz)
Energy 2,234 kJ (534 kcal)
28.88 g
Sugars 1.55 g
Dietary fiber 27.3 g
42.16 g
Saturated 3.663 g
Monounsaturated 7.527 g
Polyunsaturated 28.730 g
22.8 g
5.9 g
18.29 g
Vitamins Quantity
%DV
Thiamine (B1)
143%
1.644 mg
Riboflavin (B2)
13%
0.161 mg
Niacin (B3)
21%
3.08 mg
Pantothenic acid (B5)
20%
0.985 mg
Vitamin B6
36%
0.473 mg
Folate (B9)
0%
0 μg
Vitamin C
1%
0.6 mg
Minerals Quantity
%DV
Calcium
26%
255 mg
Iron
44%
5.73 mg
Magnesium
110%
392 mg
Phosphorus
92%
642 mg
Potassium
17%
813 mg
Zinc
46%
4.34 mg

Percentages are roughly approximated using US recommendations for adults.
Source: USDA Nutrient Database

In a 100-gram serving, flaxseed contains high levels (> 19% of the Daily Value, DV) of protein, dietary fiber, several B vitamins, and dietary minerals.[31][32] Ten grams of flaxseed contains one gram of water-soluble fiber (which lowers blood cholesterol) and three grams of insoluble fiber (which helps prevent constipation).[33] Flax contains hundreds of times more lignans than other plant foods.[33] Flaxseeds are especially rich in thiamine, magnesium, potassium, and phosphorus (DVs above 90%).

As a percentage of total fat, flaxseeds contain 54% omega-3 fatty acids (mostly ALA), 18% omega-9 fatty acids (oleic acid), and 6% omega-6 fatty acids (linoleic acid); the seeds contain 9% saturated fat, including 5% as palmitic acid.[31][32] Flaxseed oil contains 53% 18:3 omega-3 fatty acids (mostly ALA) and 13% 18:2 omega-6 fatty acids.

Health effects

One study of research published between 1990 and 2008 showed that consuming flaxseed or its derivatives may reduce total and LDL-cholesterol in the blood, with greater benefits in women and those with high cholesterol.[34]

A meta-analysis has shown that consumption of more than 30 grams of flaxseed daily for more than 12 weeks reduced body weight, body mass index (BMI), and waist circumference for persons with a BMI greater than 27.[35] Another meta-analysis has shown that consumption of flaxseed for more than 12 weeks produced small reductions in systolic blood pressure and diastolic blood pressure.[36] Flaxseed supplementation showed a small reduction in c-reactive protein (a marker of inflammation) only in persons with a BMI greater than 30.[37]

Linseed oil

Toxicity

Flaxseed and its oil have repeatedly been demonstrated to be nontoxic and are generally recognized as safe for human consumption.[38] Like many common foods, flax contains small amounts of cyanogenic glycoside;[39] these are nontoxic when consumed in typical amounts, but may be toxic when consumed in large quantities of such staple foods such as cassava.[40] Typical concentrations (for example, 0.48% in a sample of defatted dehusked flaxseed meal) can be removed by special processing.[41]

Cultivation

The soils most suitable for flax, besides the alluvial kind, are deep loams containing a large proportion of organic matter. Flax is often found growing just above the waterline in cranberry bogs. Heavy clays are unsuitable, as are soils of a gravelly or dry sandy nature. Farming flax requires few fertilizers or pesticides. Within eight weeks of sowing, the plant can reach 10–15 cm (3.9–5.9 in) in height and grows several centimeters per day under its optimal growth conditions, reaching 70–80 cm (28–31 in) within 50 days.

Diseases

Production

In 2014, world production of flax (linseed) was 2.65 million tonnes, led by Canada with 33% of the global total.[42] Other major producers were Kazakhstan, China, and Russia (table).

Flax (linseed) production – 2014
Country Production (tonnes)
 Canada
872,500
 Kazakhstan
419,957
 China
387,000
 Russia
365,088
 United States
161,750
 India
141,000
World
2,654,432
Source: FAOSTAT of the United Nations[42]

Harvesting

Maturation

Flax is harvested for fiber production after about 100 days, or a month after the plants flower and two weeks after the seed capsules form. The bases of the plants begin to turn yellow. If the plants are still green, the seed will not be useful, and the fiber will be underdeveloped. The fiber degrades once the plants turn brown.

Flax grown for seed is allowed to mature until the seed capsules are yellow and just starting to split; it is then harvested in various ways. A combine harvester may either cut only the heads of the plants, or the whole plant. These are then dried to extract the seed. The amount of weeds in the straw affects its marketability, and this, coupled with market prices, determines whether the farmer chooses to harvest the flax straw. If the flax straw is not harvested, typically, it is burned, since the stalks are quite tough and decompose slowly (i.e., not in a single season). Formed into windrows from the harvesting process, the straw often clogs up tillage and planting equipment. Flax straw that is not of sufficient quality for fiber uses can be baled to build shelters for farm animals, or sold as biofuel, or removed from the field in the spring.[43]

Two ways are used to harvest flax fiber, one involving mechanized equipment (combines), and a second method, more manual and targeting maximum fiber length.

Harvesting for fiber

Mechanical

Flax for fiber production is usually harvested by a specialized flax harvester. Usually built on the same machine base as a combine, but instead of the cutting head it has a flax puller. The flax plant turned over and is gripped by rubber belts roughly 20–25 cm (8-10") above ground, to avoid getting grasses and weeds in the flax. The rubber belts then pulls the whole plant out of the ground with the roots so the whole length of the plant fiber can be used. The plants then pass over the machine and is placed on the field crosswise to the harvesters direction of travel. The plants are left in the field for field retting.

The mature plant can also be cut with mowing equipment, similar to hay harvesting, and raked into windrows. When dried sufficiently, a combine then harvests the seeds similar to wheat or oat harvesting .

Manual

The plant is pulled up with the roots (not cut), so as to increase the fiber length. After this, the flax is allowed to dry, the seeds are removed, and it is then retted. Dependent upon climatic conditions, characteristics of the sown flax and fields, the flax remains on the ground between two weeks and two months for retting. As a result of alternating rain and the sun, an enzymatic action degrades the pectins which bind fibers to the straw. The farmers turn over the straw during retting to evenly rett the stalks. When the straw is retted and sufficiently dry, it is rolled up. It is then stored by farmers before extracting the fibers.

De vlasoogst (1904) ("Flax harvesting") painting by Emile Claus, Royal Museums of Fine Arts of Belgium, Brussels, Belgium

Processing

A hackle or heckle, a tool for threshing flax and preparing the fiber
Flax tissues, Tacuinum sanitatis, 14th century

Threshing is the process of removing the seeds from the rest of the plant. Separating the usable flax fibers from other components requires pulling the stems through a hackle and/or beating the plants to break them.

Flax processing is divided into two parts: the first part is generally done by the farmer, to bring the flax fiber into a fit state for general or common purposes. This can be performed by three machines: one for threshing out the seed, one for breaking and separating the straw (stem) from the fiber, and one for further separating the broken straw and matter from the fiber.

The second part of the process brings the flax into a state for the very finest purposes, such as lace, cambric, damask, and very fine linen. This second part is performed by a refining machine.


Preparation for spinning

Stem cross-section, showing locations of underlying tissues: Ep = epidermis; C = cortex; BF = bast fibers; P = phloem; X = xylem; Pi = pith
Threshing, retting, and dressing flax at the Roscheider Hof Open Air Museum (German)

Before the flax fibers can be spun into linen, they must be separated from the rest of the stalk. The first step in this process is retting, which is the process of rotting away the inner stalk, leaving the outer parts intact. At this point, straw, or coarse outer stem (cortex and epidermis), is still remaining. To remove this, the flax is "broken", the straw is broken up into small, short bits, while the actual fiber is left unharmed. Scutching scrapes the outer straw from the fiber. The stems are then pulled through "hackles", which act like combs to remove the straw and some shorter fibers out of the long fiber.

Retting flax

Several methods are used for retting flax. It can be retted in a pond, stream, field, or tank. When the retting is complete, the bundles of flax feel soft and slimy, and quite a few fibers are standing out from the stalks. When wrapped around a finger, the inner woody part springs away from the fibers. Pond retting is the fastest. It consists of placing the flax in a pool of water which will not evaporate. It generally takes place in a shallow pool which will warm up dramatically in the sun; the process may take from a few days to a few weeks. Pond-retted flax is traditionally considered of lower quality, possibly because the product can become dirty, and is easily over-retted, damaging the fiber. This form of retting also produces quite an odor. Stream retting is similar to pool retting, but the flax is submerged in bundles in a stream or river. This generally takes two or three weeks longer than pond retting, but the end product is less likely to be dirty, does not smell as bad, and because the water is cooler, is less likely to be over-retted. Both pond and stream retting were traditionally used less because they pollute the waters used for the process.

In field retting, the flax is laid out in a large field, and dew is allowed to collect on it. This process normally takes a month or more, but is generally considered to provide the highest quality flax fibers,[citation needed] and it produces the least pollution.

Retting can also be done in a plastic trash can or any type of water-tight container of wood, concrete, earthenware, or plastic. Metal containers will not work, as an acid is produced when retting, and it would corrode the metal. If the water temperature is kept at 80 °F (27 °C), the retting process under these conditions takes 4 or 5 days. If the water is any colder, it takes longer. Scum collects at the top, and an odor is given off the same as in pond retting. 'Enzymatic' retting of flax has been researched as a technique to engineer fibers with specific properties.[44][45]

Dressing the flax

Dressing the flax is the process of removing the straw from the fibers. Dressing consists of three steps: breaking, scutching, and heckling. The breaking breaks up the straw. Some of the straw is scraped from the fibers in the scutching process, and finally, the fiber is pulled through heckles to remove the last bits of straw.

Breaking breaks up the straw into short segments.
Scutching removes some of the straw from the fiber.
Heckling is pulling the fiber through various sizes of heckling combs or heckles. A heckle is a bed of "nails"—sharp, long-tapered, tempered, polished steel pins driven into wooden blocks at regular spacing.

Genetically modified flax contamination

Small flax plants

In September 2009, it was reported that Canadian flax exports had been contaminated by a deregistered genetically modified cultivar called 'Triffid' that had food and feed safety approval in Canada and the U.S.,[46][47] however, Canadian growers and the Flax Council of Canada raised concerns about the marketability of this cultivar in Europe where a zero tolerance policy exists regarding unapproved genetically modified organisms.[48] Subsequently, deregistered in 2010 and never grown commercially in Canada or the U.S.,[49] 'Triffid' stores were destroyed, but future exports and further tests at the University of Saskatchewan proved that 'Triffid' persisted among flax crops, possibly affecting future crops.[49] Canadian flaxseed cultivars were reconstituted with 'Triffid'-free seed used to plant the 2014 crop.[46] Laboratories are certified to test for the presence of 'Triffid' at a level of one seed in 10,000.[47]

Symbolic images

Flax is the emblem of Northern Ireland and displayed by the Northern Ireland Assembly. In a coronet, it appeared on the reverse of the British one-pound coin to represent Northern Ireland on coins minted in 1986, 1991, and 2014. Flax also represents Northern Ireland on the badge of the Supreme Court of the United Kingdom and on various logos associated with it.

Common flax is the national flower of Belarus.

In early versions of the Sleeping Beauty tale, such as "Sun, Moon, and Talia" by Giambattista Basile, the princess pricks her finger, not on a spindle, but on a sliver of flax, which later is sucked out by her children conceived as she sleeps.

See also

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External links