Comparison of amino acid composition, nutritional value of sesame seed proteins in some local and imported sesame cultivars in Vietnam

JOURNAL OF SCIENCE OF HNUE Natural Sci., 2008, Vol. 53, N ◦ . 5, pp. 122-127 COMPARISON OF AMINO ACID COMPOSITION, NUTRITIONAL VALUE OF SESAME SEED PROTEINS IN SOME LOCAL AND IMPORTED SESAME CULTIVARS IN VIETNAM Tran Thi Thanh Huyen, Nguyen Nhu Khanh Nguyen Thi Lan Phuong and Hoang Thi Thu Phuong Hanoi National University of Education Abstract. Amino acid composition of 5 local and imported sesame seed cul- tivars (Sesamun indicum L.) grown in Vietnam (yellow Quang Tri sesame, yellow Thua Thien Hue sesame, white Japanese sesame, black Thua Thien Hue sesame, black Thanh Hoa - Quang Tri sesame) were analyzed by deriva- tization with ortho-phthaladehyt (OPA) for primary amino acid and 9- fluorenyl methyl chloroformat (FMOC) for secondary amino acids on HP- Amino Quant series II (Hewlett Packard). The results showed that the total amino acid contents in the seeds of these cultivars were approximately 17.25 - 21.98%. The total amino acid cotents of the Japanese sesame cultivars were higher than those of the local Vietnamese ones. Among the local Viet- namese sesame cultivars, the total amino acid contents of the black Thanh Hoa - Quang Tri sesame were the highest and approximately similar to the Japanese ones. The sesame seed proteins were characterized by high nutri- tional value with high ratios of essential amino acids in comparison with the FAO standard protein. The sesame seed proteins were rich in essential amino acids, especially lysine. No significant differences were found between 2 analyzed sesame types: yellow and black. 1. Introduction Sesame (Sesamum indicum L.) is grown for short term oil producing seeds and is of potential development for its nutritional values. Sesame is known as the queen of oil producing cultivar because the oil ratio of sesame seeds takes up 44 - 52% [5]. Sesame oil contains much vitamin E, vitamin B [3], unsaturated fatty acids (oleic and linoleic), which are able to control levels of blood cholesterol [5]. Protein in sesame seeds, approximately 26.25% [3], with high nutritional values, is used as a valuable source of plant proteins. Especially, presence of most essential amino acids 122 Comparison of amino acid composition, nutritional value of sesame seed proteins... in protein of sesame seeds has contributed to increased nutritional values of sesame seeds. The comparision of amino acids in sesame seeds and in meat indicated that amino acids in sesame seeds are nearly as high as those in meat [3]. Protein in sesame seeds is also essential to human health [1]. The use of α- globulin, isolated from sesame protein, with low levels of lysine/arginine, can sub- stantially reduce cholesterol and other harmful fats present in the blood [6]. In this experiment, we selected some local sesame cultivars, the one imported from Japan for analysis and evaluation of nutritional quality of sesame seeds. The analysis of amino acid composition in sesame seeds and ratios among essential amino acids in protein of sesame seeds is the basis to select high quality sesame cultivars that are farmed and used in our country. 2. Content 2.1. Sources and methodology 2.1.1. Sources Sesame cultivars were provided by the Department of Seed Gene Bank  Viet- nam Institute of Agriculture Science and Technology. These cultivars, which have been tested, selected and publicized, including: yellow Quang Tri sesame, yellow Thua Thien Hue sesame, white Japanese sesame, black Thua Thien Hue sesame, black Thanh Hoa - Quang Tri sesame Sesame seeds that were cleaned, dried, and kept at 4 0 C, which were used for the analysis. 2.1.2. Determination of amino acid content Amino acid composition of sesame seed was analyzed by derivatization with Ortho-phthaladehyt (OPA) for primary amino acids and 9-fluorenyl methyl chloro- format (FMOC) for secondary amino acids on HP-Amino Quant Series II (Hewlett Packard). Samples were processed by hydrolysis. 2.2. Results and discussions 2.2.1. Composition and content of amino acids in sesame seeds of stud- ied cultivars The results of amino acid composition of sesame seed analysed after the hydrol- ysis with 6N HCl solution supplemented by phenol at 110 0 C in 24 hours indicated that sesame seed proteins contain all amino (except tryptophan that was identified due to complete splitting during the hydrolysis. See Figure 1, 2 and 3). 123 Tran Thi Thanh Huyen, Nguyen Nhu Khanh, Nguyen Thi Lan Phuong and Hoang Thi Thu Phuong Figure 1. Amino acid composition of yellow Thua Thien Hue sesame Figure 2. Amino acid composition of white Japanese sesame Figure 3. Amino acid composition of black Thanh Hoa - Quang Tri sesame 124 Comparison of amino acid composition, nutritional value of sesame seed proteins... Table 1. Composition and content of amino acids in sesame seed cultivars (g of amino acid per 100 g of seed) No. Amino acid Yellow QT Yellow TTH White NB Black TTH Black TH-QT 1 Aspartic acid 1.64 1.35 1.70 1.73 1.51 2 Glutamic acid 4.03 3.17 4.88 4.97 4.48 3 Serine 0.99 0.81 1.02 1.00 1.13 4 Histidine 0.68 0.61 0.07 0.68 0.64 5 Glycine 1.19 1.00 1.25 1.24 1.22 6 Threonine 0.82 0.71 0.85 0.83 0.83 7 Alanine 1.03 0.86 1.07 1.06 1.04 8 Arginine 2.69 2.17 2.80 1.93 2.53 9 Tyrosine 0.52 0.44 0.54 0.63 0.53 10 Cysteine + Xystin 0.25 0.23 0.26 0.26 0.26 11 Valine 1.14 0.99 1.18 1.13 1.18 12 Methionine 0.44 0.49 0.50 0.44 0.67 13 Phenylalanine 1.11 0.93 1.14 1.13 1.16 14 Isoleucine 0.80 0.69 0.85 0.82 0.86 15 Leucine 1.53 1.32 1.59 1.56 1.63 16 Lysine 0.95 0.85 0.99 0.96 1.23 17 Proline 0.71 0.63 0.66 0.75 0.70 Total 20.52 17.25 21.98 21.12 21.60 The results of amino acid content of sesame seed in the Table 1 are shown as follows: Amino acid content in total in the sesame cultivars analysed ranges 17.25  21.98%. The white Japanese sesame is the highest in amino acid content of 21.98%. Meanwhile other local sesame cultivars are lower in the total amino acid content. The levels of yellow Thua Thien Hue sesame, black Thua Thien Hue sesame, yellow Quang Tri sesame, black Thanh Hoa - Quang Tri sesame are 17.25%, 21.12%, 20.52%, 21.60% respectively. Of the local sesame cultivars analysed, black Thanh Hoa - Quang Tri sesame has the highest amino acid content, which is almost equivalent to that of the im- ported white Japanese sesame. No significant differences in the total amino acid content between the white sesame and the black sesame is found. The total amino acid content in sesame seed is three times as high as it is in rice grain (approximately 7 - 8%), half of that in the soya seed (approximately 35 - 40%) and a little lower than that in mung bean seed (22 - 25%) [4]. 125 Tran Thi Thanh Huyen, Nguyen Nhu Khanh, Nguyen Thi Lan Phuong and Hoang Thi Thu Phuong As in other plant proteins, sesame protein is rich in amino acids: Glutamic acid, Aspartic acid, Arginine, etc. Lysine content in the sesame seed is as high as 0.85 - 1.25%. These factors are characterized by its preeminence [2]. No difference in the total amino acid content between the black sesame and the yellow sesame is found. 2.2.2. Nutritional values of proteins in studied sesame seeds The sesame seed proteins were characterized by high nutritional value with the high ratios of essential amino acids present in that protein. Amino acid content of proteins in sesame seeds is shown in Table 2. Table 2. Amino acid content of proteins in sesame seeds (g of amino acid per 100 g of protein) STT Amino acid Yellow QT Yellow TTH White NB Black TTH Black TH-QT FAO Standard 1 Aspartic acid 7.99 7.83 7.73 8.19 6.99 2 Glutamic acid 19.64 18.38 22.20 23.53 20.74 3 Serine 4.82 4.69 4.64 4.73 5.23 4 Histidine 3.31 3.54 3.18 3.22 2.96 5 Glycine 5.79 5.79 5.69 5.87 5.65 6 Threonine 3.99 4.12 3.87 3.93 3.84 2.80 7 Alanine 5.02 4.98 4.67 5.02 4.81 8 Arginine 13.11 12.58 12.74 9.14 11.76 9 Tyrosine 2.53 2.55 2.47 2.98 2.45 10 Cysteine + Xystin 1.22 1.33 1.18 1.23 1.20 11 Valine 5.56 5.74 5.37 5.35 5.46 4.20 12 Methionine 2.14 2.84 2.27 2.08 3.10 2.20 13 Phenylalanine 5.41 5.39 5.19 5.35 5.37 2.80 14 Isoleucine 3.89 4.00 3.87 3.88 3.98 4.20 15 Leucine 7.46 7.65 7.23 7.39 7.55 4.20 16 Lysine 4.63 4.93 4.50 4.55 5.69 4.20 17 Proline 3.46 3.65 3.00 3.55 3.24 Data in the Table 2 indicates that ratios of essential amino acids in proteins of analysed sesame seeds are similar (methionine, lysine) or higher (threonine, valine, phenylalanine, leucine) than in the FAO standard proteins [7]. No clear difference in protein quality of the black and yellow sesame cultivars is found. 126 Comparison of amino acid composition, nutritional value of sesame seed proteins... 3. Conclusion 1- The total amino acid content in the sesame cultivars studied ranges 17.25 - 21.98%. The imported Japanese cultivar has the highest content. 2- The black Thanh Hoa - Quang Tri sesame, one of the four local cultivars studied, is the highest in the total amino acid content  almost as high as it is in white Japan sesame. 3- Protein in the black sesame is high in nutritional value and in essential amino acids. 4- There is no clear difference in quality and content of amino acids in the yellow and black sesame cultivars. REFERENCES [1] Dang Thi Ly, Tu Giay, Tu Ngu, Le Thi Thai, 1997. Use of sesame powder to prepare food for babies at 12-36 months of age. Journal of Preventive Medicine, Vol. 7, N ◦ . 4, pp. 78-80, (in Vietnamese). [2] Nguyen Thi Ty, Tong Quynh Mai, Nguyen Bich Nhi, Phan Van Chi, 2003. 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