15C-22 |
Development of a lysine determination method for small-quantity rice sample |
H. Y. CHUNG1, W. C. J. Ma1, and J. S. Kim2. (1) Dept. of Biology, Food and Nutritional Sciences Programme, Food Sci. Lab., The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, HKG, China, (2) Pulmuone R&D Center, Pulmuone Co., Ltd., Seodaemun P.O. Box 146, Seodeamun-Ku, Seoul, 120-600, South Korea Different protocols were developed to determine the lysine content in cereals, in which liquid chromatography, reversed-phase high-performance liquid chromatography and biosensors, etc, are often involved. Many of these methods are quite complicated, and involve expensive equipments. In China, the National Standard for the determination of lysine in rice is based on the Dye-Binding Lysine method (DBL). In fact, the method is economical, easy to perform, and used commonly in the past. However, it has the disadvantage of requiring large sample size of 1.2 g per trial. For rice samples collected from breeding experiments, only small number of original grains for lysine analysis is available. Thus, the method is unsuitable. The objective was to develop a simple method requiring small sample size to determine the lysine content in rice. Calrose rice was purchased from the market and milled. Since lysine did not bind to the crocein orange G dye after treated with propionic anhydride, the amount of lysine in the rice sample could be indirectly obtained by the difference in absorbance between the treated and the untreated samples. Several methods were tried by varying the concentrations (1.284 mM and 3.89 mM) of the dye solutions and the sample sizes (ranges: 12 mg to 310 mg per trial). Results showed that the method using 1.284 mM of crocein orange G dye solution with 15.5 mg of sample for each trial was the most reproducible. The lysine content in percentage was 0.336 ± 0.009 by traditional method whereas 0.335 ± 0.019 by the modified method. There was no significant difference between the two groups at p<0.05. This method is especially useful to determine the lysine content in rice when the sample quantity is low (50-100 mg) and when the resources are limited.
Session 15C, Food Chemistry: Food composition and analysis
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