Roasting sesame seeds

Shimoda, M., Nakada, Y., Nakashima, M., and Osajima, Y. 1997. Quantitative comparison of volatile flavor compounds in deep-roasted and light-roasted sesame seed oil. J. Agric. Food Chem. 45, 3193-3196. 

Sesame Oil Sesame oil has traditionally been used in eastern Asian countries, especially China, Japan, Korea, and Taiwan. It has been prized for its nutritive and health-promoting values. Sesame oil, prepared from roasted sesame seeds, has a distinctive flavor and a long shelflife (86). Several studies have been reported on the flavor components of sesame oil (87-91). The amount of volatile flavor compounds in sesame oil is greatly affected by the roasting process. It has been reported that the ratio of the amount of volatile components in deep-roasted oils was increased by 2-7 times in deep-roasted oil as compared with that of light-roasted oils (90). 

Perhaps the most important compounds identified in the roasted sesame oils are 2-furfurylthiol and guaiacol. Using aroma extract dilution analysis method, these two compounds have been characterized by Schieberle (92) to be the most odor-active compounds in roasted sesame seeds. 2-Furfurylthiol, having an intense coffee-like odor, increased from 16 ppb in roasted oil processed at 160°C for 30 min to 158 ppb in the oil processed at 200°C for 30 min (Table 12). Guaiacol has a burnt and smoky odor with an extremely low-odor threshold of 0.02 ppt in... 

Sesame oil has a long history of human consumption. The processing of sesame seed to yield sesame oil varies from region to region. The major differences are (1) whether the seed coat is removed and (2) whether the seed is roasted. Figure 9 shows the flow diagrams of the processing of three major types of sesame oils produced worldwide, namely (1) refined sesame oil, which is produced from unroasted sesame seed either with seed coat or without seed coat (2) roasted sesame oil, which is produced from roasted sesame seed and (3) small mill sesame oil, which is produced from roasted dehulled sesame seed. 

Roasted sesame oil has a strong characteristic flavor of roasted sesame seed. It is the most popular sesame oil consumed in China, Japan, and Korea. It is also believed to be beneficial to health (40). As shown in Figure 9, sesame seeds are roasted at 140 200°C prior to oil extraction. The conditions of the roasting process... 

The extraction of sesame oil from roasted sesame seed is generally performed with pressing. Solvent extraction is not used because the desirable roasted flavor may be removed during evaporation of solvent. In commercial production, continuous screw-press or hydraulic press is employed (42). The hydraulic press can be vertical or horizontal. The continuous screw may be operated twice in order to increase the oil yield (82). Proper cooking (100°C, 7 min) and addition of water (12.5%) after roasting can also raise the oil yield (83). 

Sesame oil from roasted sesame seed has the characteristic flavor and color of the roasted sesame oil the filtered crude oil is used without further refining. Sesame oil from cold-pressed unroasted sesame seed is also used directly after filtration as a flavored oil. Crude sesame oil from unroasted sesame seeds after screw-press or hydraulic press or solvent extraction, which varies in color from yellow to dark amber, may need further refining. Refined sesame oil is usually pale yellow in color. 

Three extremely odorous pyrazines, 3-isopropyl-2-methoxypyrazine, 2-s-butyl-3-methoxypyrazine, and 2-isobutyl-3-methoxypyrazine have been shown to be present in green peas, and are likely to be of major significance in the flavor of peas (59). The volatile oil of green bell peppers has been found to contain 2-isobutyl-3-methoxypyrazine as a major component (60,61). The alkylpyrazines in potato chips (62,63) and roasted peanuts (63) have been examined. 2-Isopropyl-3-methoxypyrazine has been characterized in the vacuum steam volatile oil of potatoes (64), 2-ethyl-3-methoxypyrazine in cooked potato (65), and 3-ethyl-2,5-dimethylpyrazine and 2-ethyl-3,5-dimethylpyTazine as the components important to the aroma of baked potato (66). A variety of alkylpyrazines have been identified in roasted sesame seeds (67) and 21 pyrazines have been identified in the aroma components isolated from roasted green tea (68). 

The fatty, tallowy-smelling aroma compound 2-pentylpyridin (56), which has been identified in roasted sesame seeds [77], is formed from the reaction of a fat oxidation product, 2,4-decadienal, with ammonia from the degradation of amino acids like glutamine and asparagine [78] (cf. Fig. 3.33). 

Fukuda, Y., Nagata, M., Osawa, T. and Namiki, M. (1986b) Chemical aspects of the antioxidative activity of roasted sesame seed oil and the effects of using the oil for frying. Agric. Biol. Chem., 50,857—862. 

Studies on the volatile extract obtained from the steam distillation of roasted sesame seeds reveals that some 146 compounds are present including (346) in trace amounts <89ABC1891>. 

O Brien J., Nursten H.E., Crabbe J.C., and Ames J.M. Ed., Royal Society of Chemistry, Cambridge (1998). Manley C.H., Vallon P.P. and Erickson R.E. (1974) Some aroma components of roasted sesame seed (Sesamum indicum L.). J. Food Sci. 39, 73-6. 

Sesame seed (roasted) flavor. According to aroma extract dilution analysis, 2-furylmethanethiol, guaiacol, 2-phenylethanethiol (CgHn is, Mr 138.23), and Furaneol have the highest dilution factors in the flavor of roasted sesame seeds, besides 4-vinyl-guaiacol, 2-pentylpyridine (C,oH,5N, Mr 149.24), 2-acetyl-l-pyrroline, 2-acetylpyrazine, and 2-ethyl-3,5-dimethylpyrazine (see pyrazines). 

Kinoshita, S. Yamanishi, T. Identification of basic aroma components of roasted sesame seeds. J. Agric. Chem. Soc. Japan 1973, 47, 737—739. 

Manley, C.H. Vallon, P.P. Erikson, R.E. Some aroma components of roasted sesame seed J. Food Sci. 1974, 39, 73-76. 

A successful implementation for a commercial application was the erection of a supercritical CO2 extraction plant for roasted sesame oil. This development of a CO2 supercritical fluid extraction process for roasted sesame seeds can serve as an example for the viable production of such special oils. Sesame seeds have a relatively low tocopherol content, but contain other very effective antioxidants that stabilize the oil on the one hand and make it very tasty on the other. Roasted premium sesame oils are very popular in Asia, particularly in Korea and Japan. 

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