Development and Utilization of Buckwheat Sprouts as a Functional Vegetables

Transcription

1 The proceeding of the 8 Ib ISB: (200l) Development and Utilization of Buckwheat Sprouts as a Functional Vegetables Sun Lim Kim, Young Koo Son, Jong Jin Hwang, Sung Kuk Kim, Han Sun Hur, and Cheol Ho Park 1 ) National Crop Experiment Station, RDA, Suwon , Korea 'tcollege of Agri. and Life Sci., Kangwon National University, Chunchon, , Korea ABSTRACT Buckwheat has been used as a traditional food and medicine in Korea and their utilization and applied products are being widely tried in recent years. The objective of this study was to develop and provide the buckwheat sprout as a functional vegetable and to increase its utility. The developed cultural procedure for buckwheat sprouts is as follows; 1) washing the buckwheat seeds to removed the dust and immatured seeds 2) germinating the buckwheat at "C under the dark condition for 3 days 3) when buckwheat sprouts are grown up to 2~ 3cm, the way of water supply must be turn-over to water spray system and supply the water for 1~ 2 minutes at every 3 hours intervals 5) after 3~4 days buckwheat sprouts are grown up to 12 ~ 15cm and 0.9~ Imm on their hypocotyl diameter. Buckwheat sprouts have light-yellow cotyledon and bright-white hypocotyl, so their appearances are very similar to those of soybean sprouts. Buckwheat sprouts provides an abundance of such nutrition as protein, amino acids, minerals (Fe, Zn, Mn, Mg, Cu, Ca), crude fiber and rutin. The free sugars in both buckwheat seed and early stages of seedling were mainly sucrose and maltose, but its composition was gradually changed as seedling days increased and glucose and fructose were detected as the main free sugars of buckwheat sprouts. Lysine contents of buckwheat sprouts were notably higher amount than buckwheat seeds and the other cereals. Rutin(vitamin P), one of a group of flavonoids and noted for its beneficial function of reducing vascular diseases and diabetes etc., is abundant in buckwheat sprouts and its contents were increased about 27 times than buckwheat seeds. Buckwheat sprouts have very soft and mild flavor and slightly crisp texture, furthermore buckwheat sprouts dose not have beany flavour as in soybean sprouts but have a very attractive fragrance. For these characteristics, buckwheat sprouts could be used as fresh vegetable, salad and various purpose including natural vegetable juice material. Key words: buckwheat sprouts, minerals, amino acids, free sugars, rutin INTRODUCTION Buckwheat (Fagopyrum esculentum Moench) is use in food and medicinal plant in some areas of the world. Buckwheat grown in Korea is milled into flour which is used largely in noodle and its pericarp is also used as pillow stuffing material (Choi et ai., 1996). The buckwheat plant provide an excellent honey source because the blossoms are rich in nectar. In other countries buckwheat is also used as in noodles, dumpling, and baking material for cakes, or pancakes. Buckwheat seed contains many kinds of nutrients such as protein, amino acids and minerals(james, 1995; Lockhart & Nesheim, 1978; Pomeranz, 1983; Pomeranz & Robbins, 1972; pomeranz et ai., 1975). Buckwheat contains a relatively high level of some

2 mineral elements, however, the nutritional properties of buckwheat minerals are still not fully clarified (Ikeda and Yamashita, 1994; Pomeranz, 1983). Rutin is the most dominant compound in buckwheat and is the substance that has pharmacological effects. Buckwheat is known as a origin plants of rutin which is a kind of flavonol glycoside compounds used in against edema, haemorrhagic diseases and stabilizing high blood pressure because it controls blood vessel (Couch et al., 1946; Havsteen, 1983). Buckwheat has been used as a food and traditional medicine(choi et al., 1996; Marshall & Pomeranz, 1983; Xiaoling et al., 1992) but their utilization and applied products are not various. The objective of this study was not only to develope the buckwheat sprout as a new functional vegetable but also to provide the information about thre nutritional and physicochemical properties of buckwheat sprouts. Wave length Column Column temperature Mobil phase MATERIALS AND METHODS Two buckwheat varieties, Yangjulmaemil and Suwon 2, developed in Korea were used in this experiment. Buckwheat sprouts were cultured in growth chamber which was specially manufactured to control the temperature and to spray the water in a regular intervals. Agronomic characteristics of buckwheat sprouts were tested according to days after seeding, and randomly selected buckwheat sprouts were immediately frozen in -70"C refrigerator and dried with freeze drier to analyse the physicochemical properties. The texture characteristics (hardness, cohesiveness, chewiness, springeness and gumness) of buckwheat sprouts were tested by two-cycle compression method (T.P.A) with texture analyzer(tx-xt2, England). Moisture content was determined by 105 "C drying method and crude ash contents of buckwheat sprouts were weighted the remnants after burning at 600"C furnace. Freeze dried buckwheat sprouts were finely grounded and wet-ashed with sulfuric acid and hydrogen peroxide to determine the crude protein with automatic nitrogen analyser (Foss, Swiss) and minerals such as Ca, Cu, Fe, K, Mg, Mn, Na and Zn with atomic absorption spectrophotometer (Hitachi, Japan). Amino acid contents were determined by Pico-Tag method (White et ai, 1986). 6N-HCl was added to the freeze dried sprout sample and hydrolyzed for 1 hour at 150 "C with Pico-Tag workstation and filtered with Sep-Pak CIM cartidge, and then PITC derivated samples were diluted and injected 20pl on HPLC. Table 1 shows the instruments and operating condition for amino acid analysis. Table 1. Instrument and operating conditions for amino acids analysis Instrument Shimadzu SPD-7AV UV detector Shimadzu LC-7A pump 2 system Shimadzu SCL-6B system controller Shimadzu C-R6A integrator 254nm Waters Pico-Tag column (3.9 x l50mm, 411m) 36"C A - HPLC grade water containing sodium acetate trihydrate TEA and mixed with CH3CN B -60%CH3CN Free sugar contents were determined with Supelco LC-NH2 column. 20ml of distilled water was added to the freeze dried sprout sample and shaken for 20 minutes at 35"C waterbath,

3 centrifuged at 15,000 rpm and collected supernants were filtered with Sep-Pak NH2 cartidge, then 20p[ was injected on HPLC. Rutin were extracted with methanol and determined with,ubondapak Cis column. Table 2 and 3 shows the instruments and operating condition for free sugar and rutin analysis, respectively. Table 2. Instrument and operating conditions for free sugar analysis Instrument Waters 510 Pump Detector Waters 410 R.I. Detector Sensitivity 8 Attenuation 32 Column Supelcosil LC-NH2(4mm X 25cm) Column temperature 35 C Detector temperature 38 C Mobile phase Acetonitrile: Water (75:25, VIV) Flow rate 1.5 ml/min Table 3. Instrument and operating conditions for rutin analysis Instrument Shimadzu SPD-7AV UV Detector Wave length 345nm Column,uBondapak Cts Column temperature 30 "c Mobile phase Acetic acid (2.4%) : Methanol: Acetonitrile (35: 5: 10, VIV) Flow rate 1.0ml I min RESULTS AND DISCUSSION Buckwheat sprouts Buckwheat plants are ha been used as a green vegetables at their early seedling stage, but most of buckwheat grown in Korea is used as grains and milled into flour which is used largely in Maggugsu, Naengmyeon and Mug which are a kind of Korea traditional noodles and curds, respectively. For Maggugsu and Naengmyeon buckwheat flour is usually blended with wheat flours at various mixture ratio. However the utilization and applied products of buckwheat are not various. For these reason the objective of this study was to develope and provide the buckwheat sprout as a functional vegetable. Buckwheat sprouts(fig. 1) are a kind of buckwheat vegetables which have a long and white hypocotyl so their appearance are very similar to those of soybean sprouts. The developed cultural procedure for buckwheat sprouts is as follows ; I) washing the buckwheat seeds to removed the dust and immatured seeds etc. 2) seeding about I ~ I.Scm amount of washed buckwheat seed on the cotten net and covered with paper towel, then spray the water throughly to moisturize the paper towel and seed bed. 3) germinating the buckwheat at C under the dark condition for 3 days. 4) when buckwheat sprouts are grown up to 2 ~3cm and formed the root mat(combined and entangled state of roots). 5) After 3~4 days seeding, removed the paper towel and supply the water for 1~2 minutes at every 3 hours intervals. 6) Harvest the buckwheat sprouts from the 6 days after seedling. Table 4. shows the general characteristics of buckwheat sprouts

4 Fig. 1. Buckwheat sprouts Table 4. General characteristics of buckwheat sprouts Days after Hypocotyl Hypocotyl Fresh Weight seeding 1ength(cm) thickness(mm) (glloog seed) Seed Pericarp sheding(%) o oo Evaluation good excellent good Buckwheat sprouts could harvest about 900~ looog from loog seed. Buckwheat sprouts have the 12~ 15cm hypocotyllength and the O.9~ lmm hypocotyl diameter. Buckwheat sprouts have light-yellow colored cotyledon and bright-white colored hypocotyl, so their appearances are very similar to those of soybean sprouts. Pericarp shedding rate is one of the important quality related characteristics of buckwheat sprout because pericarp attached buckwheat sprouts make it difficult to eat directly as a fresh vegetable. Pericarp shedding is started at 5 days after seeding and their shedding rate was showed about 85% at 8 days after seeding. For this reason sprayinge water supply system is more available than any other methods in order to accelerate the shedding of buckwheat pericarp during germination. But it is considered that more effective pericarp shedding cultral method is demanded to develope. Table 5. Texture analysis of buckwheat sprouts Test position Hardness(g/3.14mm 2 ) Cotyledon Hypocotyl I Upper 86.1 [ Middle 93.9 Bottom Springness Gumminess Cohessiveness Chewiness

5 Texture properties and chemical composition of buckwheat sprouts Table 5 shows the texture properties of buckwheat sprouts. Not only the hardness of cotyledon is higher than any parts of hypocotyl, but also springness, gumminess, cohessiveness and chewiness of cotyledon are higher than those of hypocotyl in buckwhat sprouts. Hardness, springeness and chewiness considered as the important properties that affected the tenderness of buckwheat sprouts. Buckwheat sprouts have very soft and mild flavor and slightly crisp texture, furthermore buckwheat sprouts dose not have beany flavour as in soybean sprouts but have a very attractive fragrance. For these characteristics, buckwheat sprouts could be used as fresh vegetable, salad and various purpose including natural vegetable juice material. Table 6. Moisture content and chemical composition of buckwheat sprouts Days Moisture Protein Crude after content fiber Ash Ca Cu Fe K Mg Mn Na Zn Total seeding (%) (%, DB) (mg/loog, DB) Seed 11.2 ] ] (100) (283) ] (377) ] (448) Table 6 shows the moisture content and chemical composition of buckwheat sprouts. Buckwheat sprouts contains a relatively higher level of protein, crude fiber and ash than buckwheat seed, and their contents were increased as seeding days were increased. Ikeda et al.(1995) reported that buckwheat flour contains a relatively high level of zinc, copper, manganese and magnesium; and a relatively low level of calcium, and there were variations in the contents of five mineral elements among the buckwheat flour samples examined: a higher variation was found with manganese and zinc; whereas a lower variation was found with copper. Although an exact reason responsible for the observed variations in the contents of the mineral elements among buckwheat samples is still obscure, the contents of mineral elements in buckwheat flours, may be generally influenced by some factors such as genetic factors, environmental conditions and processing conditions. The mineral contents of buckwheat sprouts were drastically increased compared to seed, and their contents were increased as seeding days were increased. Recommended dietary allowances (RDA) for these minerals have been established in several countries. Ikeda et al.( 1995) estimated buckwheat flour (on a fresh weight basis) as a dietary source of zinc, copper, manganese, magnesium and calcium. For this reason, buckwheat sprouts were evaluated as a very good dietary source of these minerals in the point of the RDA for minerals. Rutin and free sugar contents of buckwheat sprouts Rutin is the main compound in buckwheat and is also the substance that is most dominant for its pharmacological effects. Buckwheat is known as a origin plants of rutin which is a kind of flavonol glycoside compounds used in against edema, haemorrhagic diseases and stabilizing high blood pressure because it controls blood vessel. The rutin content in the buckwheat plant depends on the stage of development and the plant organs. Rutin is more concentrated in the younger leaves than in the older ones and also buckwheat cultivars such as Fagopyrum esculentum and Fagopyrum tataricum may differ in their rutin content. Hagels et al. (1995) reported that high amounts of rutin (5-7%) were found during the first blossoming phase and

6 young fruit development, and, moreover, the level of rutin was influenced by sowing time, sowing density and nitrogen fertilization. Table 7. Rutin and free sugar contents ofbuckwheat sprouts Days after Rutin Free sugars (%) seeding (mg/loog DB) Fructose Glucose Sucrose Maltose Total Seed ] Rutin content in the buckwheat sprouts was 27 times higher than that of buckwheat seed, and its contents were gradually increased as seeding days increased. For these results, buckwheat sprouts were could be considered as a good dietary source of rutin and evaluated as a new functional vegetables. One of the interesting and characteristic properties of buckwheat sprouts is the changing pattern of free sugars. The major of free sugars in both buckwheat seed and early stages of seeding were sucrose and maltose, but their compositions were gradually changed as seedling days increased and glucose and fructose were detected as the main free sugars of buckwheat sprouts. Amino acid contents of buckwheat sprouts Buckwheat is not a cereal but is usually grouped with the cereals due to its ways of Table 8. Amino acid contents of buckwheat sprouts (Unit: mg / 100g, DB ) Amino acid Days after seeding Seed Aspartic acid Glutamic acid Serine Glycine Histidine Arginine Theronine Alanine Proline Tyrosine Valine Methionine Cysteine Isoleucine Leucine Phenylalanine Lysine Total (100) ] ,722 (130.3) ,065 (138.2) 1, ,675 (128.3) ] ].0 9,

7 cultivation and utilization. It is reported to have a protein of high quality rich in lysine and containing less glutamic acid, proline and more arginine and aspartic acid than cereal proteins. Due to the high lysine content buckwheat will be having a higher biological value than other cereal grains as lysine is the first limiting amino acid in these protein source. Table 8 shows the analysis results of 17 amino acid contents of buckwheat sprouts at 6, 7 and 8 days after seeding. Total amino acid content of buckwheat sprouts was higher about 28~38% than buckwheat seed. The 14 kinds of amino acids including aspartic acid, glutamic acid and lysine were notably increased than buckwheat seed, but arginine and cysteine (sulfur containing amino acid) were decreased than those of buckwheat seed. Utilization of buckwheat sprouts Buckwheat sprouts have very soft and mild flavor and slightly crisp texture, furthermore buckwheat sprouts dose not have beany flavour as in soybean sprouts but have a very attractive fragrance. For these characteristics, buckwheat sprouts could be used as fresh vegetable, salad, seasoned vegetables, cooking mixture and various purpose including natural vegetable juice material(fig. 2). Freezed dried buckwheat sprouts is powdered and mixed to make rice cake, bread, and snack. Dried powder of buckwheat sprouts is also mixed in media to cultivate artificially edible and medicinal mushroom. Fig. 2. Examples of cooks made ofbuckwheat sprouts

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