Buckwheat Promotion 1

BUCKWHEAT

Common buckwheat (Fagopyrum esculentum Moench) is a broad-leafed herbaceous annual. It belongs to the family Polygonaceae, which is generally referred to as the buckwheat, rhubarb or sorrel family. However, because its seed structurally and chemically resembles the cereal grains, buckwheat is usually handled and classed with the cereals. Shown to have originated in the mountainous regions of southern China, buckwheat is produced in many parts of the world and has long been an important part of the human diet. Buckwheat has been grown in Canada and the U.S. for many years.

Buckwheat has a triangular seed, which is covered by a hull (pericarp). The exact shape, size, and colour of the seed may vary depending on the species and variety. The hull may be a glossy or dull brown, black or gray. The dehulled buckwheat seed, called the groat, resembles the cereal kernel in its gross chemical composition and structure. The first layer of the groat is a one-cell thick testa layer (seed coat), which is light green in color. Under the testa is a one-cell aleurone layer, which surrounds the starchy endosperm. The inner portion of groat consists of a spermaderm and an endosperm. A large embryo and two cotyledons extending in the shape of letter AS@ are embedded in the center of the endosperm.

Buckwheat has gained an excellent reputation for its nutritious qualities in the human diet. Its renewed popularity stems from its many bioactive components, which have been shown to provide various health benefits much sought after in natural foods.

SEED COMPOSITION

Buckwheat protein content varies from 13-15 % of the groat. The main protein fraction is globulin, which represents almost half of all proteins. A characteristic feature of buckwheat proteins protein is a very low content of prolamins.

Starch is the major carbohydrate in buckwheat, and its amount in the Canadian buckwheat varieties may vary from 67 to 75 %. Starch granules in the endosperm are polygonal or round in shape with diameter ranging from 2 to 12 μm. The majority of granules are 6-8 μm in diameter. The dietary fibre content may vary from 5-11%.

In the whole buckwheat grain the total lipids range from 1.5 - 4%. The highest content is in the embryo (9.6-19.7%), the endosperm contains 2 - 3% and the hulls 0.4 - 0.7 %. Buckwheat oil contains 16-20% saturated fatty acids, 30-45% oleic acid and 31-41% of linoleic acid. Palmitic, oleic, linoleic and linolenic acids account for about 95% of buckwheat total fatty acids.

The ash content of buckwheat varies from 2 - 2.2 %, depending upon the variety. The polyphenolic compounds of buckwheat were determined at 0.7% in the hulls and 0.8% in the groats. Buckwheat flour contains various kinds of vitamins, such as B1, B2, and niacin, at relatively high levels (Pomeranz, 1983). Buckwheat Promotion 2

BIOACTIVE COMPONENTS

DIETARY FIBRE, RESISTANT STARCH AND OTHER BIOACTIVE CARBOHYDRATES

Dietary fibre

The amount of total dietary fibre (TDF) in buckwheat may be affected by both genetic and environmental factors. The major components of TDF, cellulose, non-starch polysaccharides, and lignins, are concentrated in the cell walls of starchy endosperm, aleurone, seed coat and hull. The content of TDF in groats may range from 5 to 11% (Joshi and Rana, 1995; Zheng et al, 1998; Steadman et al, 2001; Izydorczyk et al, 2002). Bran fractions obtained by milling of buckwheat are especially enriched in dietary fibre (13-16%), but buckwheat flours contain considerably lower amounts of fibre (1.7-8.5%) (Steadman et al, 2001). For nutritional purposes, the TDF is classified into soluble- and insoluble dietary fibre. Insoluble dietary fibre (IDF) decreases transit time in the stomach, small intestine and colon, and increases faecal mass. It is commonly used as a bulking agent to prevent or treat constipation. Soluble dietary fibre (SDF), due to its high viscosity, slows gastric emptying, reduces adsorption of certain nutrients, and increases transit time in the small intestine. SDF contributes to slowing down of glucose absorption. SDF, and to a lesser extent IDF, are fermented by microflora in the digestive system to produce short fatty acids, implicated in serum cholesterol and colon cancer reduction. A considerable portion of buckwheat dietary fibre is soluble. However, relatively little is known about the composition and properties of SDF in buckwheat. Asano et al (1970) isolated water soluble non-starch polysaccharides from buckwheat and reported that they consisted of xylose, mannose, galactose, and glucuronic acid. It was postulated that the main chain of this polysaccharides consisted of glucuronic acid, mannose, and galactose. More recently, arabinose and glucose residues have also been identified in water-extractable buckwheat polysaccharides (Izydorczyk et al, 2002). One of the most important characteristics of buckwheat water soluble non-starch polysaccharides is their very high molecular weight; as a consequence, they can form very viscous solutions when dissolved in water.

Resistant starch

The so-called resistant starch – including physically inaccessible starch, native granular starch, retrograded starch, and chemically and thermally modified starch - is another potential source of dietary fibre in buckwheat. Resistant starch is a portion of starch and starch degraded products that escapes enzymatic hydrolysis in small intestine. There are indications that metabolites formed during fermentation of resistant starch in the large intestine, contribute to the maintenance of colon health and also have beneficial effects on glucose metabolism. For most healthy adults, consumption of foods with higher amount of resistant starch is, therefore, advantageous. Starch is the major component of buckwheat. Although the majority of buckwheat starch is readily digestible, a small portion (4-7%) resists hydrolysis. Certain treatments of buckwheat starch or foods containing buckwheat, such as autoclaving/ cooling cycles, extrusion, boiling or baking, increase the amount of retrograded, nondigestible starch (Skrabanja et al, 1998; Skrabanja and Kreft, 1998). Consumption of boiled buckwheat groats or bread baked containing 50% of buckwheat flour induced significantly lower postprandial blood glucose and insulin responses compared with white wheat bread (Skrabanja et al, 2001).

Fagopyritols

Fagopyritols are specific carbohydrate compounds, first identified in buckwheat and named after the Latin name of this crop. Fagopyritols are mono-, di-, and trigalactosyl derivatives of D-chiro- Buckwheat Promotion 3 inositol that accumulate especially in the embryo and the aleurone tissues of buckwheat. Among the plant sources, buckwheat is the richest in these carbohydrates. It has been reported that the bran milling fractions may contain 2.6g of fagopyritols per 100g of dry weight, whereas dark and light buckwheat flours contain 0.7g and 0.3g/100g , respectively. Published literature indicates that D-chiro-inositol could positively affect the blood glucose level and insulin activity (Fonteles et al, 1999, 2000; Ortmeyer et al 1993). Work done at the University of Manitoba (Kawa et al, 2003) has shown that buckwheat extract could be equally efficient in lowering blood glucose level and activating insulin as synthetic D-chiro-inositol. There is also evidence that D-chiro-inositol can help to control development of polycystic ovary (Nestler et al, 1999). However, the fate of fagopyritols in the human digestive system as well as the amount necessary to consume to achieve beneficial effects remain unknown and require further investigation.

MINERALS

Buckwheat seeds are a good source of many essential minerals (Table). In comparison with other cereals such as rice, wheat flour or corn, buckwheat contains higher levels of zinc, copper, and manganese (Ikeda et al, 1998; Steadman et al, 2001). The bio-availability of zinc, copper, and potassium from buckwheat is especially high. It has been determined that 100g of buckwheat flour can provide approximately 13-89% of the recommended dietary allowance (RDA) for zinc, copper, magnesium, and manganese. The concentration of many of the minerals is higher in buckwheat bran than in the endosperm.

PROTEIN

The protein content in buckwheat flour is the second highest after oat flour, and it is significantly higher than in rice, wheat, millet, sorghum, and maize. Compared to other cereals, the amino acids in buckwheat proteins are well balanced and rich in lysine, which is generally recognized as the first limiting amino acid in wheat and barley. The high-quality buckwheat proteins can complement cereal and vegetable proteins because of the high levels of lysine as well as arginine (Table 2). The protein of buckwheat flour has the amino acid score of 100, which is one of the highest amino acid scores among plant sources. Buckwheat protein consists of 18.2% albumin, 43.3% globulin, 0.8% prolamin, 22.7% glutelin, and 5.0% other nitrogen residue (Javornik and Kreft, 1984; Ikeda et al, 199l; Ikeda and Asami, 2000). In the absence of gluten type proteins, buckwheat flour can be an important ingredient in gluten-free diet for people suffering from the celiac disease. Buckwheat groat and flour can also be an excellent ingredient in bread and cereal formulations. Despite the balanced amino acid composition, the buckwheat protein digestibility in humans and in animals is relatively low (Farrell, 1978; Javornik et al, 1981), because of anti-nutritional factors present in common buckwheat, including protease inhibitors (such as trypsin inhibitors) and tannins (Ikeda et al 1986, 1991). Trypsin inhibitors in buckwheat seeds are resistant to thermal processing at elevated temperatures and to acidic conditions (Ikeda et al, 1986, 199l). Germination of buckwheat seeds significantly reduces the activity of proteases inhibitors, so seedlings and young buckwheat plants as a food source show improved digestibility and utilization of proteins (Kreft, 1983). The low protein digestibility may not be beneficial for growing children and persons with digestive track problems, since the consumption of insufficiently cooked buckwheat products can lead to diarrhea. On the other hand, given that obesity is one of the major health problems in North America, the low buckwheat protein digestibility may not necessary be a negative property. It has been suggested that soybean trypsin inhibitor can have beneficial effect for people with diabetes by stimulation of pancreas activity (Ookubo, 1992). In addition, current evidence suggests that polyphenols in plant foods, especially in red wine, have a beneficial effect on coronary heart disease (Renaud and de Lorgeril, 1992). "Resistant proteins" such as those in buckwheat have also beneficial effect on cholesterol level in blood (Kayashita et al, 1996; Iwami, 1998; Tomotake et Buckwheat Promotion 4 al, 2000). Carroll et al (1975) reported that ratios of Lys/Arg and Met/Gly are the main factors determining the cholestrol lowering properties of proteins. In buckwheat, the ratios of Lys/Arg and Met/Gly are lower than in the other plant proteins, and nutritional studies have shown that buckwheat proteins have the highest cholestrol lowering properties among the plant proteins.(Huff and Carroll, 1975). These amino acids help to regulate the hepatic LDL receptors, and thereby lowering the serum cholesterol, and indirectly helping to prevent formation of arteriosclerosis. Moreover, the high content of methionine in the diet negatively affects cholesterol level in serum, because methionine is the part of homocysteine catabolism which affects the homocysine transferase. As a consequence the amount of PC (phosphatidylcholine) and PE (phosphatidylethanolamine), two phosphatides important in cholesterol catabolism as well as in the clearance of cholesterol in tissues, is affected. Kayashita et al (1997) reported that the isolate of buckwheat protein (IBP) was more efficient in cholesterol lowering than soybean protein isolate. The authors also showed that weight gain of IBP-fed rats was not negatively affected when compared to the casein-fed rats, suggesting that buckwheat proteins were sufficiently digested and absorbed to provide adequate amount of amino acids for growing organisms. The IBP was shown to be more effective in lowering “bad cholesterol”, LDL and VLDL, than other plant and animal proteins (Saeki et al, 1990). Buckwheat protein isolate can also be used as a functional food ingredient to treat hypertension, obesity, as well as constipation. In Japan, a patent describing production of a specific buckwheat protein has been recently registered. This protein lowers activity of angiotensin converting enzyme (ACE) and directly controlling hypertension. Rat feeding experiments showed that high-fat diets and overeating did not affect the body weight of the animals when buckwheat protein hydrolyzate was included in diet. This protective effect was much weaker for soybean protein hydrolyzates. Mitsunaga et al (1986) reported a presence of thiamine-binding protein (TBP) in buckwheat seeds. After ingestion, this complex is digested by proteases, and thiamine is released and absorbed. The protein moiety in the TBP complex improves the stability of thiamine during storage and processing, and enhances its bioavailability. It is also has been found that buckwheat protein, together with dietary fibre, can ameliorate constipation (Kayashita et al, 1995). Several epidemiological studies have shown that buckwheat proteins, like dietary fibre, can suppress the development of colon cancer (Lipkin et al 1999; Cassidy et al 1994). Hard to digest proteins interact with resistant starch and are the main source of short chain fatty acids (SCFA), known to positively affect tissues and physiology of colon (Morita et al 1998; Scheppach et al 1992). Liu et al (2001) utilized buckwheat proteins extract, containing about 73% buckwheat proteins, to assess its effect on induced colon tumor in rats. It was shown that dietary buckwheat protein reduced incidence of colonic adenocarcinomas by 47%. Buckwheat protein also reduced carcinoma cell proliferation and expression in colonic epithelium. The results clearly suggest that buckwheat proteins have a protective effect against colon carcinogenesis.

FLAVONOIDS

Buckwheat contains many flavonoid compounds, known for their effectiveness in reducing the blood cholesterol, keeping capillaries and arteries strong and flexible, and assisting in prevention of high blood pressure (Santos et al, 1999). Rutin, the main buckwheat flavonoid, is a flavonol glucoside (Fig XX). The flavonoids content and composition in buckwheat seeds is affected by species, growing phase and growing conditions. Flavonoids content in seeds of the wild buckwheat (Fagopyrum tataricum) is about 40 mg/g, while in the common buckwwheat (Fagopyrum esculentum) around 10 mg/g. In flowers, leaves and stems of Fagopyrum tataricum the content of these compounds can exceed 10% of wet plant weight. Many different flavonoids have been isolated and identified in buckwheat grain. Rutin, orientin, vitexin, quercetin, isovitexin, quercetrin and isoorientin are all present in the hull, while groats contain only rutin and small amounts of Buckwheat Promotion 5 isovotexin. It has been established that rutin can affect the activity of enzyme, angiotensin I, involved in controlling blood pressure (Kawakami et al, 1995). Flavonoids can, therefore, be used as effective drugs to treat some cardiovascular diseases such as arterioscleroses. These compounds also act as strong antioxidants and can prevent oxidation of DNA and lipoproteins such as LDL, VLDL. In- terestingly, flavonoids are transferred from mother to baby across placenta, and further into foetus brain. These facts suggest that flavonoids are important and essential components for brain development and for maintenance of the nervous system.

LIGNANS

Lignans are compounds with a dibenzylbutane skeleton, which have been found in many higher plants (Setchell, 1995). These plant components act in mammalians as hormone-like phytoestrogens. Although flaxseed is the richest source of plant lignans, containing 75 – 800 times more that other oilseeds, cereals, legumes, fruits and vegetables, buckwheat also contains a considerable amount of these compounds (Thompson et al 1991). Secoisolariciresinol diglycoside (SDG) and matairesinol (MAT) are the main buckwheat lignans. Mammalian lignans are formed by intestinal microorganisms from plant precursors (Fig X). The concentration of plant lignans acting as precursors of mammalian lignans is measured by subjecting a particular food ingredient to fermentation by intestinal microorganism and by measuring the amounts of enterodiol (ED) and enterolactone (EL) released (Setchell, 1995). In animals, the excretion of ED and EL is measured in the urine (Rickard and Thompson, 2000). Fig Y shows urinary excretion of ED and EL when different plant components were included in the diet. Buckwheat provided the third highest amount of excreted lignans among many cereals. Lignans have been shown to reduce mammary tumor size by more than 50% and tumor number by 37% in carcinogen treated rats (Rickard and Thompson, 2000; Setchell, 1995). Furthermore, it has been suggested that lignans have antimiotic, antiestrogenic, antiviral, antibacterial, antifungal, and antioxidant properties (Rickard &Thompson, 2000; Thompson et al, 1996; Thompson et al, 1995; Setchell et al, 1995).

FOOD USES

Buckwheat grain is milled into flour or dehulled to produce groats. Two types of milling are used to produce flour. One is similar to wheat milling in which the grain is milled into flour. The nutritive components, rheological properties and volatile components of the flour produced by this method have been reported by (Kusano and Miyshita 1973). The second type of milling involves milling the dehulled buckwheat groat. Buckwheat grain is first hydrothermally treated and then dehulled. Different conditions and equipment are used for groat production, and the effects of these treatments on the final products have been reported by Pomeranz (1983). Buckwheat flour and groats are used for a wide variety of dishes. The flour is mixed with wheat flour for the production of buckwheat noodles called ‘soba noodles’ in Japan. The buckwheat flour content ranges from 50 to 80% depending on the type of noodle produced.

The groats are utilized in many dishes in through out the world. In Asia they are consumed as noodles, dumplings and as unleavened chapattis. In Europe, Kasha is used in dishes ranging from pilafs to mixtures with meat. In North America, the main use has been in pancakes; however, utilization of buckwheat has been increasing in the form of noodles and various ethnic dishes. Buckwheat is also used in pastries and as a meat extender. Buckwheat Promotion 6

THIS MATERIAL WAS PREPARED BY:

Canadian Grains Commission Website: http://grainscanada.gc.ca

Marta Izydorczyk Program Manager, Barley Research Grain Research Laboratory Canadian Grains Commission 1404-303 Main Street Winnipeg, MB R3C 3G8 Phone: (204) 983-1300 Fax: (204) 983-0724 Email: [email protected]

University of Manitoba Website: http://umanitoba.ca

Roman Przybylski Associate Professor University of Manitoba Dept of Human Nutritional Sciences 190 Dysart Rd. Winnipeg, MB R3T 2N2 Phone: (204) 474-8657 Fax: (204) 474-7593 Email: [email protected]

Kade Research Ltd. Website: http://kaderesearch.com

Clayton Campbell 135-13 Street Morden, MB R6M 1E9 Phone: 204-822-7235 Fax: 204-822-5960 Email: [email protected] Buckwheat Promotion 7

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COMPANIES OFFERING BUCKWHEAT PRODUCTS

Minn-Dak Growers Ltd. Grand Forks, ND 5820803276

The Birkett Mills 263 Main, Penn Yan, NY 14527

Sobaya 201 Miner St., Cowansville, Quebec J2K 3H1

Port Royal Mills 240 Industrial Parkway South, Aura, ON. L4G 3V6

Arrowhead Mills 734 Franklin Ave, #444, Garden City, NY 11530

Bouchard Family Farm RR#2 Box 2690, Fort Kent, Maine 04743

Bob’s Red Mill Natural Foods 5209 SE International Way, Milwaukee, OR 97222

Brownville Mills P.O. Box 145, Brownsville, NB 68321

Purity Foods 2871 W. Jolly Road, Okemos, MI 48864

Clic Import Export 2025 Boul. Fortin, Laval, QB H7S 1P4

Mountain Peoples Warehouse 22-30th Street NE, Suite 102, Auburn WA 98002

Ontario Natural Foods Co-op 70 Fima Cresent, Etibicoke, ON, M8W 4V9

Great Eastern Sun 92 McIntosh Road, Ashville, NC Buckwheat Promotion 11

BUCKWHEAT USE IN FOOD RECIPES

BUCKWHEAT PILAF

2 Tbsp. butter or margarine 3 1/2 cups chicken stock or 1 cup uncooked, whole buckwheat 3 1/2 cups boiling water and 3 chicken 1/3cup currants Bouillon cubes 1/4 tsp. oregano 1 Tbsp. grated orange rind Salt and pepper to taste 1/3 cup finely chopped pecans, optional 2 Tbsp. chopped parsley

Melt butter in large saucepan. Add buckwheat. Stir well. Add chicken stock, cover and cook for approx. 20 minutes or until all the liquid is absorbed. Add rest of ingredients except parsley. Transfer to greased 2 1/2 quart casserole dish and bake at 350 0F for 30 to 40 minutes. Garnish with parsley. Serves 6

BUCKWHEAT PUDDING

1cup buckwheat groats 2 cups water 1 tsp. cinnamon 1cup raisins 2 cup sunflower seeds

Bring 2 cup water to a boil. Add 1cup buckwheat or millet. Bring to a boil. Stir once. Add raisins and seeds and cinnamon. Turn heat to low, cook uncovered for 20 minutes or until grain is cooked. Serve hot with yogurt and honey.

VEGETARIAN SOBA NOODLE SUSHI

1/2 pound soba noodles - blanched al dente 1/4 cup scallions, green part only finely chopped 2 Tbsp. light soy sauce 1 Tbsp. rice wine vinegar Wasabi oil 1/4 cup pickled ginger - finely chopped Buckwheat Promotion 12

10 sheets nori 1 cucumber, peeled and finely julienned 1 red bell pepper, julienned 1 yellow bell pepper, julienned

In a large mixing bowl, combine soba noodles, spring onions (scallions), soy sauce, rice wine vinegar, wasabi oil, and pickled ginger. Taste for seasoning. On a sushi mat, place one sheet of nori, shiny side down. On the bottom third of the nori, place a thin layer of the noodle mixture. Place some cucumber and peppers on top. Roll tightly. Moisten the top edge of the nori with water to seal the sushi roll closed. Serves 8 to 10 Buckwheat Promotion 13

Table 1. Content of Minerals in Buckwheat and Milling Fractions.

Minerals Whole groats Flour Bran mg/kg mg/kg mg/kg K 5650 5003 14163

P 4900 4167 13533 Mg 2676 2530 59910

Ca 197 300 333 Fe 30.3 34.0 60.4

Zn 29.2 28.3 72.6 Mn 16.4 18.0 46.2

B 6.7 6.6 24.1 Cu 7.1 7.0 10.4

Buckwheat Promotion 14

Table 2. Comparison of Essential Amino Acid Contribution in Buckwheat, Cereals, and Egg. (g/100g protein).

Amino Acid Buckwheat Barley Wheat Corn Egg1 Lysine 5.1 3.7 2.5 2.8 6.0 Methionine 1.9 1.8 1.8 2.4 3.8 Cystine 2.2 2.3 1.8 2.2 2.4 Threonine 3.5 3.6 2.8 3.9 4.3 Valine 4.7 5.3 4.5 5.0 7.2 Isoleucine 3.5 3.7 3.4 3.8 5.9 Leucine 6.1 7.1 6.8 10.5 8.4 Phenylalanine 4.2 4.9 4.4 4.5 6.1 Histidine 2.2 2.2 2.3 2.4 2.2 Tryptophan 1.6 1.1 1.0 0.6 1.5 TD (%) 79.9 84.3 92.4 93.2 99 BV (%) 93.1 76.3 62.5 64.3 100 NPU (%) 74.4 64.3 57.8 59.9 94 UP (%) 9.1 7.3 7.3 6.0 12.2

Abbreviations: TD – True Protein Digestibility; BV – Biological Value (Based on amino acid composition); NPU – Net Protein Utilization; UP – Utilizable Protein (Protein x NPU/100); 1 – For whole egg.

Buckwheat Promotion 15

OH OH OH OH O OH

OH OH O OH O H H O OH OH O Quercetin OH OH H H H OH O OH CH2OH O OH O H O H OH H OH H O HO OH O OH H H OH H H H H O H

CH3 Rutin Quercetrin

Buckwheat flavonoids Buckwheat Promotion 16

Plant Lignans O H3CO OR H3CO O OR HO HO

OCH Secoisolariciresinol 3 OCH3 OH Matairesinol Diglycoside (SDG) OH

Bacterial Bacterial Fermentation Fermentation

O HO HO OH O OH

Bacterial Fermentation OH OH Enterodiol (ED) Enterolactone (EL) Mammalian Lignans

Formation of mammalian lignans and their plant precursors. Buckwheat Promotion 17 ) t 800 e i d

g 21 / g m 18 (

n 15 o i t e 12 r c x 9 E

y 6 r a n 3 i r

U 0 l l l il l l l a l l l i a r m n a a a l e a i a O e u r a O e e e a e O e lo e r n e M rn M F G B a M M M M t M d M t t t t t a e o n a e n y a e e e d C r a a b a le le y s e o e e e y e r O il h R x e C h h h o b a w a s W S y B M k l x W W o c F la S u F B

Fig X.Total excretion of mammalian lignans in the urine of rats after diet supplementation with various foods.