Qualitative and quantitative evaluation of rice component in cereal products by the DNA-based technology

A method based upon the polymerase chain reaction (PCR) has been developed for distinguishing rice species from other cereals. Two specific primer sets designed from 5S ribosomal RNA genes and promoter of rice glutelin genes were able to identify even small amount of DNA fragments in rice. DNA isolated from grain, flour and such products gave similar results. Furthermore, evaluation of quantitative analysis of rice in the samples was accomplished by hybridization with probe designed from promoter of rice glutelin genes. The analysis of a lab-made sample (a mixture of TCW70 rice flour and cassava starch) with nonradioactive labeling probe was performed. The R2 of calibration curve was 0.98 and the calculated amount of rice flour in the sample was very close to the actual value with CV < 3% (n = 2). However, this method is only proper for rice flour, because it is difficult, but necessary, to select a suitable standard that can exhibit rice species and broken situation of DNA about the samples.