QUALITY CHARACTERISTICS OF BARLEY VARIETIES

Alicja Kawka, Aleksandra Chalcarz, Piotr Kołodziejczyk
Institute of Food Technology of Plant Origin, Poznań University of Live Sciences, Poland

ABSTRACT

The results showed that the means for spring and winter covered barley were not significantly different for 1000 kernel weight, test weight, grain uniformity as well as protein and lipid contents. Significant differences in the content of ash, proteins, lipids, total dietary fiber were noted among the eight barley samples. However the highest differences in content of total dietary fiber for "Rudzik" and "Sigma" varieties were observed. Chemical scores of spring and winter samples were similar; lysine was the first limiting amino acid. The calculated nutritional indices show good protein nutritive value of covered barley. What is more, the soluble fraction of the dietary fiber makes up about 23% of the total dietary fiber and the content of β-glucans ranges from 4.1 to 5.1%. Statistically significant differences between the means of spring and winter barleys for total, soluble and insoluble dietary fiber as well as crude fiber and pentosans were observed. On the other hand, no statistically significant differences were found in the content of β-glucans.

Key words: covered barley, chemical composition, amino acids,.

INTRODUCTION

Barley (Hordeum vulgare L.) is the world's fourth most important crop, after wheat, rice and maize. In Poland, this cereal is on the third position, after wheat and rye, with regard to the cultivation area and size of production. Spring (about 1.1 million ha) and winter (about 155 000 ha) forms of covered barley are the main types grown in our country.

Barley is utilized, primarily, as a feed for animals and for processing purposes in malt, brewery and groats industries. In Poland only a limited number of mills manufacture barley to produce barley products. The covered barley grain is first abraded to obtain hulled barley as starting material for the production pearled barley (kascha), barley flakes.

Barley, like oats, contains valuable chemical constituents and is used more and more frequently for production of human food [14,15]. Among the cereal grains, barley is rich in soluble fiber components especially β-glucans, which are effective in lowering serum cholesterol as well as in regulating blood glucose level [15,26].

Investigations conducted in domestic research centers focus, primarily, on various types of evaluations which comprise agricultural and utility properties, the assessment of product determination as well as extended evaluation of the suitability of the brewer's barley for malt production [18]. There is much information in the available domestic literature concerning barley grain of the varieties cultivated in Poland dealing with the content of, first and foremost, pentosans and β-glucans as anti-nutritional agents in animal feeding [5,6]. However, less attentions is paid to the content of chemical constituents of barley grain, in particular dietary fiber and its components determining its usefulness for the food production [4,12].

The aim of this study was to assess general quality characteristics and chemical composition of covered barley grain varieties from Poland. Perhaps this type of evaluation will make it possible to indicate a variety or varieties suitable for the production of barley products rich in β-glucans and total dietary fiber.

MATERIAL AND METHODS

Barley samples
Eight covered barleys (Hordeum vulgare L.) var. Orlik, Rudzik (brewery grains), Rodos, Start (feed grains) and var. Kroton, Gregor, Sigra (feed grains), Marinka (brewery grain), representing spring and winter forms, respectively were analyzed in this study. All the above-mentioned grains of high productivity were grown under similar soil-climate conditions in western part of Poland (Poznań region). The varieties after one-year harvest were used. Barley samples were obtained from Research Center for Cultivar Testing (Słupia Wielka, Poland).

Tests on barley samples
1000 kernel weight, test weight, grain uniformity and vitreous kernel of covered barley samples were determined according to Polish Quality Standard (PQS) methods [21]. The weight of 1000 kernels was determined by counting and weighing 1000 grains of each sample [21]. Test weight, in metric measurements, is the weight of specific volume of grain in kilograms, of a hectoliter of grain [21]. Grain uniformity of barley was determined by sieving analysis of barley samples (100 g) using hand sieves of 2.2 x 25 mm. The sieving was carried out employing a reciprocating movement for the period of 3 min (120 motions/min). The uniformity value was expressed in percent as a ratio of the mass of grains remaining on the sieve of 2.2 x 25 mm to the mass of the sieved grain [21]. The percentage of vitreous kernels was determined with farinotom [21].

Chemical analysis
Before the analysis, a representative sample (100 g) of each barley type was ground in a laboratory mill (Falling Number type 3100) to pass through a 0.5 mm screen. The performed barley analyses, included: moisture (No. 110/1), ash (No. 104/1), crude protein (N x 6.25) (No. 105/2) content, using Kjeltec system (Tecator, Sweden), lipids (No. 136), crude fiber (No. 113), β-glucan (No. 166) were assessed according to the ICC standard methods [11]. Dietary fiber content was determined according to Asp et al. [2] method using Fibertec System E apparatus (Tecator, Sweden). Total pentosans were determined by the Hashimoto et al. [8] method. Carbohydrates content was calculated from the difference using the following formula:

[100 – (content of: ash + proteins + lipids + total non-ash dietary fiber)].

In order to determine the amino acid composition, samples were hydrolyzed under nitrogen with 6 mol L^-1 HCl at 105°C for 23 h. The amino acids were determined using an automatic amino acid analyzer AAA 339 produced by Microtechna (Prague, the Czech Republic) [16]. The content of sulphur amino acids was determined separately after performic acid oxidation [24]. Tryptophan was not determined. D-Norleucine was used as an internal standard. The contents of different amino acids recovered were expressed as g per 100 g protein and were compared with the FAO reference pattern [23].

The nutritive value of protein of spring and winter barleys was calculated using the chemical score (CS) and the essential amino acid index (EAAI). The score of essential amino acids (EAAs) was determined by employing the following formula:

EAAs score = [g of EAAs in 100 g test protein/g of EAAs in 100 g FAO/WHO(1991) reference pattern]*100.

EAAI was calculated as the geometric mean of the ratios of the essential amino acids in a protein to those of the FAO/WHO reference pattern [23].

All analyses were performed either in duplicate or triplicate and the results are reported on a dry matter basis.

Statistical analysis
All determinations were made at least in duplicate or triplicate and mean values ± standard deviation (SD) are presented. The data were subjected to a one-way analysis of variance and Tukey's multiple range tests.

RESULTS AND DISCUSSION

The utilization of barley grain in processing, as in the case of other cereals, makes it necessary to recognize its physical properties, technological value and chemical composition. Ranges and means of physical features and some chemical components of covered barley for spring and winter varieties are summarized in Table 1. The kernels from winter samples were heavier (1000 kernel weight – 59.4 g) and contained about 21% more vitreous kernels than the kernels from spring barleys (1000 kernel weight – 54.0 g). The winter barleys also contained slightly more protein and ash than the spring barleys. The means for spring and winter barleys were not significantly different for 1000 kernel weight, test weight, grain uniformity as well as protein and lipid contents. Statistically significant differences between forms were found for vitreousness and ash.

Table 1. Ranges and means of physical and chemical characteristics of covered barley samples

Factors	Spring varieties		Winter varieties
	range	mean	range	mean
	Physical factors
1000 Kernel weight (g)	48.9–59.1	54.01±6.1 a2	55.7–63.2	59.4±4.5 a
Test weight (kg/hl)	66.2–67.3	66.7±0.7 a	62.6–67.2	64.9±0.7 a
Grain uniformity (%)	91.6–94.4	93.0±1.7 a	91.6–97.2	94.4±3.3 a
Vitreous kernels (%)	24.5–37.2	30.9±2.6 a	49.5–54.0	51.8±2.7 b
	Chemical factors [% of dry matter]
Ash	2.24–2.36	2.30±0.7 a	2.37–2.60	2.48±0.1 b
Protein (N x 6.25)	12.1–13.1	12.6±0.6 a	12.0–13.9	13.0±1.0 a
Lipids	2.34–2.87	2.61±0.3 a	2.48–2.90	2.69±0.3 a

1 Means of three trials followed by ± standard deviation. 2 Tukey test. Values in the same lines followed by the same letter are not significantly different at the level α = 0.05.

Basic chemical composition of the covered barley varied (Table 2). The ash content was higher in "Gregor", "Marinka", "Sigra" (2.45–2.64%) than in the remaining varieties (2.24–2.38%). Smaller amounts of carbohydrates were found in winter varieties (55.5–57.5%) in comparison with the spring samples (59.0–59.9%). The protein and lipid contents in the examined samples were found in the range of 11.7–14.8% and 2.18–2.90%, respectively. The highest contents of protein and lipids were noted for "Marinka" and "Rudzik" varieties and the lowest – for the "Start" variety. Protein, lipids and ash contents are in agreement with those previously reported for European [28] and Swedish varieties [1]. From the point of view of the nutritive value of cereals, the protein content is important, but even more important is the composition of amino acids. Amino acid values for the examined covered barley are given in Table 3. In all samples, there are consistent and almost identical patterns of amino acid composition.

Table 2. Chemical composition of covered barley samples (% of dry matter)

Sample	Ash	Protein (N x 6.25)	Lipids	Dietary fiber1	Carbo- hydrate2
Spring varieties
Orlik	2.253 ± 0.044 ab	12.8±0.1 c	2.56±0.23 b	22.8±0.6 b	59.6
Rudzik	2.24±0.01 a	13.2±0.2 d	2.95±0.14 d	21.7±0.6 a	59.9
Rodos	2.35±0.01 cd	12.7±0.1 c	2.74±0.07 c	23.1±0.4 b	59.1
Start	2.38±0.01 d	11.7±0.1 a	2.18±0.12 a	24.7±0.3 c	59.0
	Winter varieties
Kroton	2.30±0.01 bc	12.8±0.0 c	2.82±0.21 c	24.6±0.1 c	57.5
Gregor	2.45±0.01 e	12.1±0.1 b	2.69±0.11 c	25.6±0.3 d	57.2
Marinka	2.54±0.03 f	14.8±0.0 e	2.90±0.11 c	23.1±0.2 b	56.7
Sigra	2.64±0.04 g	12.2±0.0 b	2.34±0.12 a	27.3±0.1 e	55.5

1 Total non-ash dietary fiber. 2 Calculated by differences. 3 Means of three trials followed by ± standard deviation. 4 Tukey test. Values in the same columns followed by the same letter are not significantly different at the level α = 0.05.

Table 3. Amino acid composition of grain proteins covered barley samples1 (g amino acid/100 g of protein)

Amino acid	Spring varieties					Winter varieties
	Orlik	Rudzik	Rodos	Start	Mean (n = 4)	Kroton	Gregor	Marinka	Sigra	Mean (n = 4)
Alanine	3.97	3.92	3.83	4.00	3.93	3.70	3.62	3.69	3.65	3.66
Glicine	3.88	3.48	3.54	3.48	3.60	3.60	3.91	3.38	3.84	3.68
Proline	11.39	11.67	12.16	11.25	11.62	11.77	11.79	12.25	11.64	11.86
Serine	3.87	3.84	3.76	3.96	3.86	3.94	4.00	3.97	4.14	4.01
Glutamic acid	26.24	27.38	27.47	27.22	27.08	27.19	27.42	28.11	27.93	27.66
Aspartic acid	5.90	5.53	5.63	5.67	5.68	5.52	5.70	5.32	5.65	5.55
Lysine	3.47	3.23	3.29	3.45	3.36	3.36	3.47	3.22	3.33	3.35
Leucine	6.72	6.59	6.70	6.74	6.69	6.62	6.64	6.67	6.58	6.63
Isoleucine	3.59	3.51	3.54	3.51	3.54	3.31	3.26	3.30	3.23	3.28
Threonine	3.28	3.30	3.15	3.30	3.26	3.28	3.39	3.21	3.49	3.34
Tryptophan	ND2	ND	ND	ND	ND	ND	ND	ND	ND	ND
Valine	4.95	4.75	4.93	4.88	4.88	4.52	4.64	4.57	4.54	4.57
Methionine	1.43	1.56	1.41	1.32	1.43	1.71	1.24	1.33	1.27	1.39
Cystine	1.32	1.36	1.24	1.30	1.31	1.50	1.32	1.43	1.27	1.38
Phenylalanine	5.22	5.39	5.25	5.01	5.22	5.29	5.04	5.23	5.03	5.15
Tyrosine	2.43	2.52	2.30	2.60	2.46	2.76	2.55	2.64	2.49	2.61
Histidine	2.82	2.63	2.67	2.86	2.75	2.39	2.81	2.47	2.93	2.65
Arginine	4.53	4.33	4.13	4.46	4.36	4.53	4.20	4.22	4.02	4.24
Protein content (% dry matter)	12.8	13.2	12.7	11.7	12.6	12.8	12.1	14.8	12.2	13.0

1 Duplicate samples were run for the amino acid composition. 2Not determined

The essential amino acid profile of seed proteins compared well with the FAO/WHO reference pattern (Table 4). With the exception of lysine and threonine, the essential amino acids of seed proteins from spring and winter barley samples registered higher values than the FAO/WHO [23] recommended pattern. The chemical score (CS) and essential amino acid index (EAAI) of barley varieties were calculated (Table 4). The essential amino acid score ranged between 57.9 (lysine) and 139.4 (valine) in spring barley seeds, while in winter barley seeds, it fluctuated from 57.7 (lysine) to 130.5 (valine). The CS which indicates the limiting amino acids: the lower the value, the more limiting amino acid. Thus in the spring and winter samples, lysine was the first nutritionally limiting the amino acid; the next – threonine. EAAI of spring samples was slightly higher than in the winter varieties. The nutritional values (CS, EAAI) of the proteins of examined barleys showed the good quality of a protein for human use.

Table 4. Means of essential amino acids (EAAs) 1 (g amino acid/100 g of protein) EAAs score, limiting amino acids and EAAs index of proteins of barley samples

EAAs	Spring varieties		Winter varieties			FAO/WHO ref. Pattern (1991)
	EAAs means	EAAs score		EAAs means	EAAs score
Lysine	3.36	57.9		3.35	57.7	5.8
Leucine	6.69	101.3		6.63	100.4	6.6
Isoleucine	3.54	126.3		3.28	117.0	2.8
Threonine	3.26	95.8		3.34	98.3	3.4
Tryptophan	ND2	ND		ND	ND	1,1
Valine	4.88	139.4		4.57	130.5	3.5
Methionine + Cystine	2.74	109.4		2.77	110.7	2.5
Phenylalanine + Tyrosine	7.68	121.9		7.76	123.1	6.3
Σ EAAs3	32.15			31.70
Chemical score  (vs. FAO Pattern) Limiting amino acids		57.9 Lys			57.8 Lys
EAAI4	74.4			73.1

Duplicate samples were run for the amino acid composition. 2 Not determined. 3 Total essential amino acids. 4 Essential amino acid index. Indices were calculated without Tryptophan.

The amino acid content of cereals is largely determined by the proportion of the Osborne protein fractions. Albumins and globulins are rich in lysine, whereas hordein is lysine poor. The content of lysine in glutenin is intermediate between the albumin, globulin and hordein fractions. Pomeranz et al. [22] showed that the increase in protein content is associated, mainly, with the increase in nonessential amino acids: glutamic acid and proline, major components of barley hordeins and glutelin. The increase in protein is accompanied by decreases in practically all essential amino acids. Shewry [25] suggested that nutritional quality of the grain decreases with increasing grain protein contents as an increasing proportion of the nitrogen is incorporated into prolamin storage proteins. In our study, the content of total essential amino acids in kernel protein of spring and winter barleys was similar. However, these values were higher than in the proteins of wheat, but lower in comparison with the amounts found in rye and oat proteins [7,29]. Covered barley contains higher concentrations of limiting essential amino acids – lysine and threonine – than hull-less barley or wheat [4,6,12].

The content of dietary fiber and its components in eight covered barleys are presented in Table 5. Total dietary fiber (TDF) values of the samples ranged from 22.6–29.1%. The winter samples (Kroton, Gregor, Sigra) exhibited higher TDF (24.8–29.1%) and soluble dietary fiber (SDF) (6.1–6.7%) content than the spring barleys. However, the percentage of SDF constituted 22.0-23.3% of the TDF in all samples. The crude fiber, β-glucans and pentosans concentrations in the eight covered barleys fluctuated in the intervals from 4.1–5.9%, 4.1–5.1% and 5.7–8.0%, respectively. In these samples, the ratio of pentosans to β-glucans content varied and ranged from 1.4 to 1.7. Henry [9] reported that the content ratio of pentosans to β-glucans in barley, oat, rye and wheat is 1.3; 2.3; 7.1; 5.5, respectively which indicates different content levels of β-glucans and pentosans depending on the type of cereal. The observed differences in pentosans and β-glucan proportions reflect physicochemical properties and endosperm structure between different wheat varieties. Similar suggestions were also put forward in investigations on barley and rye [10,27].

Table 5. Dietary fiber and its components content of covered barley varieties

Samples	Dietary fiber			Soluble fiber in total fiber [%]	Crude fiber	β-Glucans	Pentosans	Pentosans/ β-Glucans ratio
	insoluble	soluble	total
	[% of dry matter]				[% of dry matter]
Spring varieties
Orlik	18.51±0.42 b	5.2±0.1 b	23.8±0.2 b	22.1	4.2±0.0 a	4.3±0.1 bc	6.0±0.3 a	1.4
Rudzik	17.7±0.1 a	5.0±0.1 a	22.6±0.0 a	22.0	4.1±0.0 a	4.1±0.1 a	5.7±0.2 a	1.4
Rodos	18.7±0.1 bc	5.5±0.1 c	24.2±0.1 b	22.8	4.4±0.0 b	4.6±0.0 de	6.2±0.2 b	1.4
Star	20.4±0.3 d	5.7±0.3 cd	26.0±0.4 d	21.8	4.7±0.0 d	4.7±0.1 e	7.2±0.3 c	1.5
Winter varieties
Kroton	20.6±0.4 d	6.2±0.4 e	26.8±0.2 e	23.1	5.3±0.0 e	4.2±0.1 ab	7.3±0.2 c	1.7
Gregor	21.2±0.2 e	6.1±0.2 e	27.4±0.1 f	22.4	5.9±0.1 f	4.4±0.0 cd	6.6±0.2 b	1.5
Marinka	19.0±0.1 c	5.8±0.1 d	24.8±0.3 c	23.3	4.5±0.1 c	4.7±0.1 e	6.3±0.3 b	1.4
Sigra	22.4±0.2 f	6.7±0.2 f	29.1±0.4 g	22.9	5.8±0.0 f	5.1±0.1 f	8.0±0.3 d	1.6

1 Means of three trials followed by ± standard deviation. 2 Tukey test. Values in the same columns followed by the same letter are not significantly different at the level α = 0.05.

The data in Table 6 were used to compare ranges and means of dietary fiber and its components for spring and winter varieties. There were statistically significant differences between the means of spring and winter barleys for insoluble dietary fiber (IDF), SDF, TDF, crude fiber and pentosans. On the other hand, no statistically significant differences were found in the content of β-glucans. The content of TDF, including IDF and SDF, was on average by about 15% higher, while that of crude fiber and pentosans – respectively, by 20 and 10% higher in winter varieties in comparison with the grain of spring varieties. The above-mentioned differences, though statistically significant, are nevertheless small (about 15%) and cannot be taken as a basis for indicating one particular variety or a group of spring or winter varieties which would be particularly desirable in industrial uses.

Table 6. Ranges and means of dietary fiber and its components of spring and winter covered barley varieties (% of dry matter)

Dietary fiber and its components	Spring varieties		Winter varieties
	range	mean	range	mean
Insoluble dietary fiber	18.1–19.5	18.81±1.12 a	20.0–21.6	20.8±1.3 b
Soluble dietary fiber	5.2–5.5	5.4±0.3 a	6.0–6.4	6.2±0.4 b
Total dietary fiber	23.3–25.0	24.2±1.3 a	26.0–28.0	27.0±1.6 b
Crude fiber	4.1–4.5	4.3±0.2 a	4.9–5.9	5.4±0.6 b
β-glucans	4.3–4.6	4.4±0.2 a	4.4–4.8	4.6±0.4 a
Pentosans	6.0–6.8	6.4±0.7 a	6.6–7.5	7.1±0.7 b

1 Means of three trials followed by ± standard deviation. 2 Tukey test. Values in the same lines followed by the same letter are not significantly different at the  level Α = 0.05.

Similarly, other authors reported the TDF, β-glucans, and pentosans ranging from 14–26%, 3–7%, and 4–7%, respectively in covered barley [1,3,10,14,17,20]. The higher content of TDF and ash in the covered barley samples is due to the presence of the hull. The hull usually constitutes about 10–13% of the grain dry weight and consists, mainly, of cellulose, hemicellulose, lignin, minerals and smaller quantity of protein, starch and lipids [14]. Among cereals, barley – like oats – contains greater content of TDF than rye (15–16%) or wheat (12%). The non-starch polysaccharides of barley, cellulose and hemicellulose are present largely in the hull, with β-glucans and pentosans in the endosperm. The level of β-glucans, and pentosans in barley may vary considerably, depending on cultivar, method of determination and environmental influences but most, frequently, their content falls within the interval of 4–7% [19].

CONCLUSIONS

Barley is excellent source of soluble and insoluble dietary fiber and provides important health promoting benefits. It has been reported that barley as functional ingredients can be incorporated into many food products.  In present study, general characteristic of barley grown in Poland confirming the previous studies reported in the literature. The all examined varieties represent raw material of good quality and, despite differences in their chemical composition, they can be used for the production of new, nutritionally valuable barley products. The richer in β-glucans and total dietary fiber barley products can be effectively substituted for wheat in baked products [12]. The method for a laboratory and industrial milling of barley grains to obtain above barley products has been processed in our Institute [12,13].

In Poland, analogous as in other countries, consumers are interested in high fiber food products. Barley as naturally healthy, readily available, and inexpensive, can be used to produce new barley products, rich in β-glucans, dietary fiber, which can substitute partially or totally for wheat in many baked products.

ACKNOWLEDEGMENTS

This research project was financially supported by the State Committee for Scientific Research, Warsaw, Poland. The authors wish to thank Dr. E. Klockiewicz-Kamińska from the Research Center for Cultivar Testing, Słupia Wielka, Poland for letting them have samples of covered barley grains as well as for her help in carrying out analyses.

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28. Welch RW., 1978. Genotypic variation in oil and protein in barley grain. J. Sci. Food Agric. 29, 953–958.

29. Wrigley C.W., Bietz J.A., 1987. Proteins and amino acids. pp. 159–275. In: Wheat: chemistry and technology. Pomeranz Y. (ed.) AACC, St. Paul, MN.

Accepted for print: 12.10.2009

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Alicja Kawka
Institute of Food Technology of Plant Origin,
Poznań University of Live Sciences, Poland
Wojska Polskiego 31, 60-624 Poznań, Poland
Phone: (+48 61) 848 73 03
Fax: (+48 61) 848 73 14
email: alikaw@au.poznan.pl

Aleksandra Chalcarz
Institute of Food Technology of Plant Origin,
Poznań University of Live Sciences, Poland
Wojska Polskiego 31, 60-624 Poznań, Poland
Phone: (+48 61) 848 72 74
Fax: (+48 61) 848 73 14
email: aleksandra.chalcarz@up.poznan.pl

Piotr Kołodziejczyk
Institute of Food Technology of Plant Origin,
Poznań University of Live Sciences, Poland
Wojska Polskiego 31, 60-624 Poznań, Poland
Phone: (+48 61) 848 72 68
Fax: (+48 61) 848 73 14
email: pikol@up.poznan.pl

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Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.

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