J Sci Food Agric 1989,48, 339-345

Lipid and Fatty Acid Composition of Oat (Avena satiua) Cultivars Grown in Three Australian States

Hector Karunajeewa, Sing H Tham,

Department of Agriculture and Rural Affairs, Animal Research Institute, Werribee, Victoria 3030, Australia

Jan-Bert Brouwer

Victorian Crops Research Institute, Horsham, Victoria 3400, Australia

and

Andrew R Barr

Department of Agriculture and Fisheries, Northfield Research Laboratories, Adelaide 5001, Australia

(Received 23 March 1988; revised version received 11 July 1988; accepted 12 August 1988)

A B S T R A C T

The jkee and bound lipid content, and the fatty acid composition of these lipids, in I1 oat (Avena sativa L) cultivars grown in three Australian states were determined. There were significant differences between cultivars in both the jkee and bound lipid content and in the proportion of fatty acids in these lipids. The proportion of linolenic acid in the lipids of some oat cultivars grown in Western and South Australia was greater than that in the same cultivars grown in Victoria. There was a positive correlation between the jkee lipid content and the proportion of linoleic acid in the Swan cultivar.

Key words: Oats, free lipids, bound lipids, fatty acids, cultivars.

1 INTRODUCTION

Oats (Aoena sativa L) contain more lipids than any other cereal grain (Youngs 1978). This lipid is an excellent source of energy and unsaturated fatty acids,

339

J Sci Food Agric 0022-5142/89/$03.50 0 1989 Society of Chemical Industry, Printed in Great Britain

340 H Karunajrewu, S H Tham, J -B Brouwer, A R Burr

particularly oleic and linoleic acids (Brown et al 1966; Youngs and Puskulcu 1976; Youngs 1978). The high concentration of linoleic acid in oats enhances its nutritional value for non-ruminant animals. Karunajeewa and Tham (1987) found that oat groats were a good source of energy and linoleic acid for improving feed conversion efficiency and egg weight, respectively, in laying hens.

The fatty acid composition of oat lipids is of considerable interest to both oat breeders and animal nutritionists because of the nutritional significance of unsaturated fatty acids, particularly linoleic and linolenic acids for both humans and animals. Considerable variation in the total lipid content and the proportion of its fatty acids has been demonstrated for oat cultivars (Welch 1975; Youngs and Puskulcu 1976) elsewhere.

The geographical location of cultivation (Youngs and Puskulcu 1976) and environmental factors such as temperature (Welch 1975) and season (Brown et al 1966) have a significant influence on the fatty acid composition of oat lipids. Low environmental temperatures stimulate desaturase activity and consequently increase the linolenic acid content in oat lipids (Welch 1975). In most publications, particularly in feed composition tables (Evans 1985; Allen 1987), only the free lipid (ether extract) content of oats is reported. This may be due to the belief that the concentration of bound lipids in oats is negligible or because its determination is time consuming. However, Youngs et al (1977) have found the content of bound lipids in oat groats to be between 14 and 16 g kg-' . This indicates the need to measure and report both the free and bound forms of lipids in oats. This paper presents the results of a survey of the lipid and fatty acid composition of 11 oat cultivars grown in three states of Australia.

2 MATERIALS AND METHODS

2.1 Analysis of oat samples

Eighty-three samples of oats from 11 cultivars grown in Western Australia (WA), South Australia (SA) and Victoria (Vic) were obtained from oat breeders in these states.

The samples were ground in a laboratory mill to pass a 05-mm sieve, and 3.0 g of each milled sample was used for the determination of free and bound lipids. The free lipids were extracted in a Soxhlet extractor with diethyl ether for 16 h. The ether was driven off in a rotary evaporator, and the lipid residue was dried in an oven at 100°C to constant weight. The bound lipids were extracted from the oat residue with water-saturated butanol in a Soxhlet extractor for 5 h and the butanol was evaporated in a rotary evaporator. The residue was dissolved in chloroform, and anhydrous Na,SO, was added to the solution. It was then filtered through glass fibre paper and the residue was washed three times with chloroform. The chloroform fraction was then evaporated to dryness in a rotary evaporator and dried in the oven at 100°C to constant weight. The fatty acid composition of the neutral and bound lipids was determined by the standard AOAC method (1975).

Lipid and fatty acid composition of Australian oats 34 1

2.2 Statistical analysis

The data on lipid and fatty acid contents of the oat cultivars were subjected to a one- way analysis of variance. The relationship between lipid content and its component fatty acids was determined by linear correlation analysis.

3 RESULTS

The content and composition of the free and bound lipids in 11 oat cultivars are given in Tables 1 and 2, respectively. The free lipids (FL) content (Table 1) differed ( P <0.01) between cultivars with the mean values ranging from 61 g kg-’ in Barmah to 38 g kg-’ in Stout. The proportion of palmitic, oleic, linoleic and linolenic acids in the FL differed ( P ~ 0 0 1 ) between cultivars. There were no significant differences between cultivars in the proportion of stearic acid in the FL. The bound lipids (BL) content among the 11 oat cultivars (Table 2) ranged from 8.6 g kg- I in Cooba to 3.3 g kg-’ in Algeribee. The differences between cultivars in the BL content and the proportion of palmitic, stearic, oleic and linolenic acids therein were significant (P<O.Ol). The cultivars did not differ in the proportion of linoleic acid in the BL.

In the Swan cultivar the FL content was positively correlated ( r = 0.52; P < 005) with the proportion of‘ its component linoleic acid. There were no significant differences in either the FL or the BL content in the Swan, Avon and Moore cultivars when grown in,different states. There were, however, significant differences between states in the proportion of some fatty acids in the lipids of these three cultivars plus the West cultivar. The proportions of linolenic acid in the FL of West grown in WA (1.7 f 0.05 % of the total fatty acids) and SA (1.8 f 0.04 :<) were higher ( P < 001) than when grown in Vic (1.1 f 005 %). Swan grown in WA (1.8 rf- 0.08 %) and SA (1.8 k0.07 %) had a higher ( P <0.05) proportion of linolenic acid in the FL than when grown in Vic (1.4f0.08). The proportion of linoleic acid in the FL of Swan grown in WA (37.1 *0.52”/, of total fatty acids) was also higher ( P <0.01) than when grown in Vic (35.3 & 0.57 %). The proportions of linolenic acid in the FL of Avon grown in SA (1.7 f 0.07 % of total fatty acids) and in Moore grown in WA (1.9 f 008 %) were higher ( P < 0.01) than when these two cultivars were grown in WA (1.2f0.09% and 1.2fO.11 ”/, of total fatty acids, respectively).

4 DISCUSSION

The data presented in Tables 1 and 2 show that samples of oat cultivars grown in Victoria, and in Western and South Australia vary widely in FL and BL contents. This variability in lipid content is most likely due to genetic differences between cultivars. These data indicate that there is considerable potential for increasing the lipid content of Australian oat cultivars through breeding.

The total (FL+ BL) lipids content in the 11 oat cultivars studied ranged from 43 to 66 g kg- ’, and this is within the range of lipid values reported for oats grown in

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344 H Kurunujeewu, S H Tham, J-B Broirwer, A R Burr

North America (Brown et a1 1966) and the UK (Hutchinson and Martin 1955; Welch 1975). However, the BL content in these oat cultivars was considerably lower than the 2 g kg-' or more found in the cultivars Dal and Froker grown in Wisconsin, USA (Youngs et a1 1977). Furthermore, the proportion of BL in these two cultivars was over 2004 of the total lipid content whereas that in the cultivars grown in southern Australia range from 5.9 7; in Algeribee to 16.7 ;4 in the Cooba cultivar. This difference in the proportion of BL between American and Australian cultivars may be due to differences in either genetic or environmental factors.

The variation in the proportion which some fatty acids represent of the total fatty acids in both the FL and BL of the oat cultivars studied is probably due to both genetic differences and environmental influences. The proportion of linolenic acid in particular seems to be influenced by the environment in which the oats are grown. It appears that the Western and Southern Australian environments are more favourable than that of Victoria for the synthesis of linolenic acid in the West, Swan, Avon and Moore cultivars. This effect of the environment on the synthesis of unsaturated fatty acids is further substantiated by the higher proportion of linoleic acid in the lipids of the Swan cultivar grown in Western Australia. Welch (1975) found that the linolenic acid content in winter-sown wheat was greater than that in spring-sown wheat. He speculated that this might be due to the lower temperature increasing the activity of the desaturase enzyme.

Comparison ofthe fatty acid composition (Table 1) ofthe Australian oat cultivars with data for oats grown in the UK (Welch 1975) and USA (Youngs and Puskulcu 1976) show that the Australian oat cultivars tested in this study contained more oleic and less linoleic acid than in cultivars tested in England and North America. The proportions of palmitic, stearic and linolenic acids were comparable except for the lower proportion of linolenic acid in the English cultivars (Welch 1975).

Published data (Youngs and Puskulcu 1976) on the fatty acid composition of BL in oats are scarce but, when comparisons are made, the present study (Table 2) shows a similar proportion of stearic and linoleic acids whereas the proportions of palmitic acid are higher and those of oleic and linoleic acids are lower than in the North American cultivars.

The data on the fatty acid composition of lipids (Table 1 and 2) indicate considerable scope for increasing the linoleic acid content and thereby improving the nutritional value of Australian oat cultivars. Selection for a high linoleic acid content in oats may be feasible as a broad sense heritability of 95.7 % for this trait has been demonstrated elsewhere (Youngs and Puskulcu 1976).

The relationship between the FL content and its component fatty acids was similar to that reported for oat cultivars in the USA (Youngs and Puskulcu 1976) and UK (Welch 1975) except for the significant positive correlation between FL content and linoleic acid in the Swan cultivar. This unusual relationship suggests that the linoleic acid content of Swan could be increased by selecting for a higher oil content.

It is concluded that the lipid and fatty acid contents in oat cultivars grown in Victoria and in Western and South Australia vary significantly, and there is considerable scope for improving these traits through breeding.

Lipid und /;try ucid composition of Ausrrulian ours 345

ACKNOWLEDGEMENTS

Thanks are due t o M r R Bishop, Department of Agriculture, Western Australia for providing the oat samples from his state and to Ms A Hofmann for technical assistance with the lipid analyses. Financial assistance granted by the Poultry Research Council for this work is gratefully acknowledged.

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Evans M 1985 Nutrient Composition of Feedstufs for Pigs and Poultry. Queensland

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