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  • Author or Editor: Kyoung-Shim Cho x
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Fatty acid is known as a physiologically active compound, and its composition in rice may affect human health in countries where rice is the major diet. The fatty acid composition in brown rice of 120 Korean native cultivars was determined by one-step extraction/methylation method and GC. The average composition of 9 detectable fatty acids in tested rice cultivars were as followings: myristic acid; 0.6%, palmitic acid; 21.2%, stearic acid; 1.8%, oleic acid; 36.5%, linoleic acid; 36.3%, linolenic acid; 1.7%, arachidic acid; 0.5%, behenic acid; 0.4%, and lignoceric acid; 0.9%. Major fatty acids were palmitic, oleic and linoleic acid, which composed around 94%. The rice cultivar with the highest linolenic acid was cv. Jonajo (2.1%), and cvs. Pochoenjangmebye and Sandudo showed the highest composition of palmitic (23.4%) and oleic acid (44.8%), respectively. Cultivar Pochuenjangmebye exhitibed the highest composition of saturated fatty acid (28.1%), while cvs. Sandudo and Modo showed the highest mono-unsaturated (44.8%) and poly-unsaturated (42.4%) fatty acid composition, respectively. The oleic acid showed negative correlation with palmitic and linoleic acid, while positive correlation between behenic and lignoceric acids was observed.

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Red pepper, as an ingredient of Kimchi, is an important horticultural crop in Korea, and capsaicinoid content is a major factor determining the pungent quality of red pepper. To clarify the factors affecting capsaicinoid content, 122 red pepper samples of 24 varieties were collected from 21 cultivation sites in Cheongyang area, South Korea, and their nordihydrocapsaicin (NDC), capsaicin (CAP), and dihydrocapsaicin (DHC) contents were evaluated by using an HPLC. The average content of NDC, CAP, and DHC were 4.8, 74.2, and 26.5 mg/100 g, respectively, and its relative composition ratios were slightly affected by variety or cultivation places. In most cultivation places, capsaicinoid contents showed significant dependence upon variety, in that cv. WangJangKum (225.5 mg/100 g) exhibited 6.2-fold higher total capsaicinoid contents when compared to cv. ChonHaTongIl (36.2 mg/100 g). Even the same cultivar (e.g., WangDaeGum) exhibited almost 2-fold variations according to cultivation places, indicating the dependence of capsaicinoid content of red peppers upon the cultivation sites. Analysis of variance revealed significant variety–cultivation place interactions in CAP, DHC, and total capsaicinoid contents, but not in NDC. This data suggests the necessity of more-careful selection of variety and cultivation place corresponding to the expected pungency of harvested red peppers.

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Traditionally fatty acid composition used to be analysed by GC and the sample preparation consisted of lipid extraction from sample and subsequent methyl esters preparation, which are time-consuming and cumbersome. As an alternative, simultaneous extraction/methylation methods are being developed for rapid and simplified sample preparation. To optimize one-step extraction/methylation method for analysis of fatty acid composition in brown rice and adlay seeds, various factors, such as sample to reaction solution ratio, reaction time and temperature, and shaking intensity, were altered and resultant fatty acid composition data were evaluated in comparison with previous reports. The ratio of sample weight to reaction solution volume was the most critical factor in that higher sample to reaction solution ratio caused overestimation of palmitic acid and linoleic acid composition, resulting in underestimation of oleic acid. Lower reaction temperature also induced overestimation of linoleic acid and underestimation of oleic acid. Reaction duration and the intensity of shaking prior to and during the reaction, however, induced no significant changes in analysis results. In conclusion, the optimum condition for brown rice was mixing 5 grains (about 0.2 g) of brown rice with 680 μL of methylating mixture and 400 μL of heptane, followed by reaction at 80 °C for 2 hours.

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