Characteristics of grains and oils of four different oats (Avena sativa L ...

International Journal of Food Sciences and Nutrition, August/September 2006; 57(5/6): 345 352

Characteristics of grains and oils of four different oats (Avena sativa L.) cultivars growing in Turkey

¨ ZCAN1, GU ¨ ZKAN2, & ALI TOPAL3 ¨ LCAN O M. MUSA O 1

Department of Food Engineering, Faculty of Agricultural, Selc¸uk University, Konya Turkey, Department of Food Engineering, Faculty of Agricultural, Su ¨ leyman Demirel University, Isparta, Turkey, and 3Department of Crop Science, Faculty of Agricultural, Selc¸uk University, Konya, Turkey 2

Abstract Some physical and chemical properties of four oat (Avena sativa L.) varieties (BDMY-6, BDMY-7, Che-Chois and Y-2330) harvested from Konya in Turkey were investigated. The weight of the grain, moisture, crude protein, crude ash, crude fibre, crude energy, crude oil and water-soluble extract contents of all oat variety grains were analysed. Contents of aluminium, calcium, cadmium, phosphorus, magnesium, zinc, lead, potassium and manganese were also determined in the oat grains. The specific gravity, refractive index, free fatty acids, peroxide value, saponification number and unsaponifiable matter were determined in the grain oil. Tocopherol contents of these four oat grain oils were measured. Palmitic acid (15.72%), oleic acid (33.97 51.26%) and linoleic acid (22.80 35.90%) were found to be rich in protein, oil, fibre, unsaturated fatty acids and minerals, suggesting that they may be valuable for food uses. Due to high nutritive values, it is recommended to process for healthy food products.

Keywords: Oat grain, Avena sativa L., proximate composition, minerals, tocopherol, fatty acid composition

Introduction Oat (Avena sativa L.) is cultivated as an annual crop in several regions of the world. It is a member of the family Gramineae, which grows in Turkey. Food oats are used primarily in hot and ready-to-eat cereals, and some in granolas, cookies, breads and other cereal products. Oats have excellent moisture holding qualities that keep baked goods fresh. Oat varieties are being developed with improved yields, higher protein content and stronger resistance to rust, disease and insects (Anonymous 2005; McKechnie 1983). For centuries, oats have been valued for their medicinal qualities. In folk medicine, an alcoholic extraction of oats has been reported to be a deterrent for smoking. Reports that oat extract helped correct the tobacco habit were disproven by Bye et al. (1974). Among the compositional components of the oat, the protein concentration often is ranked highly in importance because of its nutritional significance (Peterson 1992). Studies have shown genotypic and environmental effects on oat protein concentration (Jenkins 1969; Forsberg et al. 1974; Saastamoinen et al. 1989). As early as 400 BC,

¨ zkan, Department of Food Engineering, Faculty of Agricultural, Su¨leyman Correspondence: Gu¨lcan O Demirel University, 32260 Isparta, Turkey. Tel: /90 246 211 1666. Fax: /90 246 237 0437. ISSN 0963-7486 print/ISSN 1465-3478 online # 2006 Informa UK Ltd DOI: 10.1080/09637480600802363

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ground oat was used on skin for drying and healing. Doehlert et al. (2001) investigated the effects of genotype and environment on grain yield and quality. The grain yield, test weight groat percentage, groat weight and groat composition (protein, oil, b-glucan, and starch concentrations) were evaluated. Oats have the highest concentration of oil, about 6%. Oat oil is rich in phospholipids and glycolipids, also called polar lipids, and is free of trans-fatty acids (Anonymous 2005; Bedford and Joslyn 1937). Oats are also used in salad dressings, sauce thickeners, ice-cream coatings and stabilizes, baby foods, beverages, baked goods and snack foods. Oat flour also stabilizes fat in ice-cream and other dairy products. No detailed study of the physical properties, chemical composition, mineral contents and fatty acid composition of the grains of A. sativa has so far been performed. The study presented here evaluates various physical and nutritional properties of A. sativa grains. Materials and methods Materials The grains of oat varieties were obtained from Konya province in Turkey in 2004. Grains were transported to the laboratory in polypropylene bags and held at room temperature. They were cleaned in an air screen cleaner to remove all foreign matter such as dust, dirt, stones and chaff, and immature and broken grains were discarded as well. Their moisture content was measured on arrival. Methods The proximate properties (moisture, crude protein, crude oil, crude fibre, crude energy, ash, refractive index, free fatty acids, special gravity, saponification number and unsaponifiable matter) were analysed according to AOAC (1990). The oil was extracted with diethyl ether (508C) in a Soxhlet apparatus (Bu¨chi Universal Extraction System B-811, Essen, Germany). The extract was evaporated in vacuum. The lipid extract was collected in a flask. The extracted lipid was weighed to determine the oil content and stored under nitrogen at 48C for further analyses. Tocopherol analysis The method of Lavedrine et al. (1997) was used for extraction. Tocopherols were analysed by high-performance liquid chromatography (Shimadzu), equipped with an auto sampler (SIL-10AD vp). The detector used was a fluorescence detector with wavelengths set at 295 nm for extinction and 330 nm for emission. Tocopherols were separated on a normal phase column (Luna, 150 cm /4.6 mm i.d., 5 mm particle size) with the mobile phase flow rate at 1.2 ml/min. The mobile phase was a mixture of heptane:tetrahydrofuran (THF) (95:5) (v/v). The system controller, pump degasser, column oven and column temperature were SCL-10Avp, LC-10Advp, DGU-14A, CTO-10Avp and 308C, respectively. The data were integrated and analysed using the Shimadzu Class-VP Chromatography Laboratory Automated Software system. Standard samples of a, b, g and d isomers of tocopherol (Sigma Chemical Co., St Louis, MO, USA) were dissolved in hexane and used for identification and quantification of peaks. The amount of tocopherols in the extracts was calculated as

Characteristics of grains and oils of oats

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milligrams of tocopherols in a 100 g oil sample using external calibration curves, which were obtained for each tocopherol standard (Lampi et al. 1999). Analysis of fatty acids Fatty acid composition was determined using a modified fatty acid methyl ester method as described by Marquard (1987). The methyl esters of the fatty acids (0.5 ml) were analysed in a Shimadzu 17A series gas chromatograph equipped with a flame ionizing detector, a fused silica capillary column (MN FFAP, 50 m /0.32 mm i.d.; film thickness, 0.25 mm). It was operated under the following conditions: oven temperature programme, 1208C for 1 min raised to 2408C at a rate of 68C/min and then kept at 2408C for 15 min); injector and detector temperatures, 250 and 2608C, respectively; carrier gas, helium at flow rate of 40 ml/min; and split ratio, 1/20 ml/min. The contents of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3) were determined by computing integrator. Determination of mineral contents About 0.5 g dried and ground sample was put into a burning cup and 10 ml pure HNO3 was added. The sample was incinerated in a MARS 5 Microwave Oven under 170 psi at 2008C and the solution diluted to a certain volume (25 ml) with water. Samples were filtered in filter paper, and were determined with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) (Skujins 1998). Statistical analyses Results were analysed for statistical significance by analysis of variance (Pu¨sku¨lcu¨ and Ikiz 1989). The statistical evaluation was performed using the Minitab package program (Minitab 1991). Results and discussion The physical and chemical properties of four different oat grains and oils are presented in Table I. The energy and water-soluble extract of all oat grains were determined Table I. Physical and chemical properties of oat cultivars. Cultivar Property Weight (g) Moisture (%) Crude proteina (%) Crude oil (%) Crude fibre (%) Ash (%) Energy (ca./100 g) Water-soluble extract (%) a

Nx6.25.

BDMY-6 0.0189/0.002 8.309/0.80 14.809/1.20 2.069/0.16 1.609/0.40 1.919/0.21 352.109/12.30 74.709/2.40

BDMY-7 0.0169/0.001 7.909/0.40 15.309/1.70 2.769/0.21 1.409/0.20 1.539/0.13 361.409/21.70 78.309/1.60

Che-Chois 0.0139/0.001 8.609/0.50 13.709/1.30 4.779/0.11 1.909/0.30 1.459/0.17 337.809/14.30 67.109/2.80

Y-2330 0.0219/0.003 8.209/0.30 16.409/1.60 4.419/0.14 2.109/0.20 1.629/0.22 372.709/17.10 71.809/3.10

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between 7.9 and 8.6%, 13.7 and 16.400%, 2.06 and 77.00%, 1.40 and 2.10%, 1.53 and 1.91%, 337.00 and 372.00 cal/100 g and 67.00 and 78.00%, respectively. Crude protein, crude fibre and calorie values of Y-2330 variety were higher than in other varieties. The oil content varied between 2.06% (BDMY-6) and 4.77% (Che-Chois). Oat contains much higher oil concentrations than do other small grains (Youngs 1986). Studies have indicated that varieties and environment affect the oat oil concentration (Brown et al. 1966; Welch 1975; Saastamoinen et al. 1989; Humphreys et al. 1994). Cooler growth environments have been reported to stimulate oil accumulation in groats (Beringer 1971; Saastamoinen et al. 1989). Per 100 g, the mature oat seed is reported to contain 374.00 cal, 11.00 g moisture, 13.10 g protein, 6.10 g fat, 5.80 g fibre and 2.40 g ash (Miller 1958). Doehlert et al. (2001) reported 14.60 19.60% protein, 4.64 7.81% lipid, and 1.84 2.07% ash in the oat grain. According to these results, it can be concluded that oat grains have high crude oil, crude protein, crude fibre, crude ash and water-soluble extract. The mineral composition and variance analyses results of oat grains are presented in Table II. Mineral elements were found to vary widely depending on the different oat varieties. According to the results, calcium, phosphorus, magnesium and potassium contents were too high in all the grains. The cadmium, zinc and manganese contents of varieties were partly low. The potassium level of all varieties (except for Y-2330) of all varieties in this work was higher than those of others. The phosphorus content was high in most cases and ranged from 1375.20 ppm (BDMY6) to 4365.40 ppm (Y-2330). The magnesium content ranged from 1375.20 ppm (BDMY-6) to 1532.60 ppm (Che-Chois). The calcium content ranged from 318.30 ppm (Y-2330) to 427.10 ppm (Che-Chois). The phosphorus, magnesium and potassium contents of all varieties determined in this study were found similar with respect to the results of McKechnie (1983). But some of our results of mineral contents of oat grains show minor differences when compared with the literature (McKechnie 1983). These differences might be due to growth conditions, penetic ¨ zcan factors, geographical variations and analytical procedures (Guil et al. 1998; O 2004). This work attempts to contribute to the knowledge of the nutritional properties of these seeds. In addition, knowledge of the mineral contents, as an ingredient of various baked and other products such as salad dressing, baby foods and snack foods is of great interest. Table II. Mineral contents of oat cultivars. Cultivar Mineral (ppm) Aluminium Calcium Cadmium Potassium Manganese Magnesium Phosphorus Lead Zinc

BDMY-6 106.409/2.10 357.409/3.20 3.609/0.30 4217.109/27.30 36.609/1.60 1375.209/17.90 3879.109/21.30 136.109/6.30 17.209/0.40

BDMY-7 97.109/3.10 411.209/3.90 7.109/0.80 4675.309/43.20 41.109/1.10 1457.109/24.80 3917.209/32.60 143.409/3.70 21.309/1.30

Che-Chois

Y-2330

112.409/2.80 427.109/3.10 4.809/0.70 4787.109/17.80 34.709/2.10 1532.609/21.60 4027.409/28.50 127.409/4.20 19.109/0.90

126.309/1.70 318.309/2.30 5.309/0.40 4092.709/32.60 42.309/1.40 1397.709/28.30 4365.409/23.70 118.309/3.90 26.109/1.10


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Table III. Some characteristic properties of oat grain oils. Cultivar Property

BDMY-6

Free fatty acid (%) Peroxide value (meq/kg) Saponification number Unsaponifiable matter (%) Specific gravity (25/258C) Refractive index (258C)

0.109/0.00 0.709/0.10 181.009/4.00 3.709/0.20 0.9169/0.003 1.4719/0.001

BDMY-7

Che-Chois

0.209/0.10 1.109/0.10 176.009/3.00 4.109/0.70 0.9219/0.002 1.4699/0.002

0.309/0.10 0.609/0.10 186.009/5.00 3.909/0.40 0.9329/0.001 1.4709/0.001

Y-2330 0.209/0.00 0.909/0.20 179.009/7.00 4.309/0.30 0.9149/0.001 1.4719/0.001

The extracted oil was yellowish in colour. The physical and chemical properties (refractive index, free fatty acids, special gravity, saponification number and unsaponifiable matter) of oat grain oils are presented in Table III. The free fatty acid content of oils ranged between 0.10 meq/kg (BDMY-6) and 0.30% (Che-Chois). The refractive index varied between 1.469 (BDMY-7) and 1.471 (Y-2330 and BDMY-6). Peroxide values ranged between 0.60 meq/kg (Che-Chois) and 1.10 meq/kg (BDMY-7). Other values were partly similar in all varieties. It will be seen that, when compared with literature, there are significant variations in some chemical composition of most of these grains. The unsaponifiable matter, saponification number, specific gravity and refractive index values were found similar to those of other seed oils (e.g. corn, rice, ¨ zcan and Seven peanut, terebinth fruit and wheat germ oils) (Formo et al. 1979; O ¨ zcan 2004). Differences among the free fatty acids, refractive index, peroxide 2003; O value, saponification number, specific gravity and unsaponifiable matter values of grains are probably due to varieties and environmental conditions. The contents of tocopherols of oat varieties are presented in Table IV. The oat grain oils contained an appreciable amount of a-tocopherol (15.58 41.39 mg/g). g-Tocopherol contents of oat variety oils ranged from 0.30 mg/g (BDMY 7) to 3.57 mg/ g (Che-Chois). b-Tocopherol contents were found between 0.85 mg/g (BDMY 7) and 8.44 mg/g (Che-Chois). d-Tocopherol was not established in all samples. Tocopherols are also an important component of the unsaponifiable fraction. Corn oil tocopherols are primarily g-tocopherol. An analysis of two different commercial samplers showed the following results: a-tocopherol, 7.80 16.20 mg/100 g oil; b-tocopherol, 44.70 60.30 mg/100 g oil; g-tocopherol and d-tocopherol, 0 mg/100 g oil (Formo et al. 1979). Also, the tocopherol content of wheat germ oil is: a-tocopherol, 1179.00 mg/kg; b-tocopherol, 398.00 mg/kg; g-tocopherol, 493.00 mg/kg; and d-tocopherol, 118.00 Table IV. Tocopherol contents of oat oils. Cultivar Tocopherol (mg/g) a-Tocopherol b-Tocopherol g-Tocopherol d-Tocopherol , unidentified.

BDMY-6 13.359/0.19 3.629/0.25 1.799/0.40

BDMY-7

Che-Chois

Y-2330

5.589/0.03 0.859/0.02 0.309/0.04

41.399/0.24 8.449/0.26 3.579/0.43

28.319/0.17 2.579/0.31

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¨ zcan et al. M. M. O Table V. Fatty acid compositions of oat oils. Cultivar

Fatty acid (%)

BDMY-6

BDMY-7

Che-Chois

Y-2330

Palmitic acid Stearic acid Oleic acid Linoleic acid Linolenic acid

18.82 2.79 41.48 35.90 0.64

15.72 51.26 27.90

18.25 33.97 22.80

, unidentified.

mg/kg (Formo et al. 1979). The tocopherol results were found low compared with literature values (Formo et al. 1979). But the a-tocopherol contents were higher than ¨ zcan and Seven (2003). those reported for peanut oil (3.87 4.47 mg/kg) by O The oil fatty acid composition of oat varieties is presented in Table V. According to the results, oleic acid was the dominant fatty acid of all oat seed oils. Linoleic acid was found high in all the samples, and varied between 22.80% (Y-2330) and 35.90% (BDMY-6). The high content of linoleic acid makes it more suitable for development as a high linoleic acid crop. The proportion of oleic acid and linoleic acids determines the quality of oil and its end use (Harris et al. 1980; Green 1986; Singh et al. 1990). There is a high percentage of palmitic acid (15.72 18.82%), but stearic acid and linolenic acid were found in only the BDMY-6 sample (2.79 and 0.64%), respectively. In addition, fatty acid compositions of the Che-Chois sample were not established. From a nutritional point of view, oat seed oil is also a good source of essential fatty acids, especially linoleic acid, as compared ¨ tles¸ 1994). In general, high linolenic with the other edible oilseeds (Nergiz and O acid is unsuitable for oil-food products due to its instability and the reversion of flavour associated with autoxidation (Smouse 1979; Green 1986; Singh et al. 1990). Formo et al. (1979) found that the contents of the main fatty acids corn oil were 8.00 12.00% palmitic acid, 2.00 5.00% stearic acid, 19.00 49.00% oleic acid and 34.00 62.00% linoleic acid. In another study, the fatty acid distribution of wheat germ oil is as follows: palmitic acid, 11.00 16.00%; stearic acid, 1.00 6.00%; oleic acid, 8.00 30.00%; linoleic acid, 44.00 65.00%; and linolenic acid, 4.00 10.00% (Formo et al. 1979). The linoleic acid content was lower than that of olive and hazelnut (67.10 76.20% and 77.80 84.20, respectively) (Mannina et al. 1999). Our findings were found similar compared with results of oat seed oil reported by McKechnie (1983). The reported health benefits of oils rich in linoleic acid, such as corn or saff (lower oils), result in lowering serum cholesterol levels (Gottenbos 1988; Imaizumi et al. 2000). As a result, crops having such oil quality have considerable agriculture significance (Singh et al. 1990).

Acknowledgement ¨ .-BAP, This work was supported by Selcuk University Scientific Research Project (S.U Konya, Turkey).


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