Determination of Cyanidin-3-Glucoside Content using Visible/Near Infrared Reflectance Spectroscopy (VIS/NIRS) in Black Rice

Brown rice grain pigments of black rice have a higher content of bioactive substances such as anti-mutagenic substance than the non-pigmented rice grain. The major anthocyanin pigment contained in black rice was cyanidin-3-glucoside. This study was conducted to establish a rapid analysis method for determining cyanidin-3-glucoside contents in flour and whole rice seeds of black rice using VIS/NIRS technique. A total of 60 black rice samples were used for VIS/NIRS equation model development and validation. The value of coefficient of determination of external validation (r) and standard error of performance (SEP) in whole rice seed sample were 0.653 and 97.2, respectively. Therefore, the value of it seemed to be difficult to analyze cyanidin-3-glucoside content in whole rice seed samples using VIS/NIRS. However, in rice flour sample, the best accurate equation model was obtained from the partial least square regression (PLS) method. The value of r, SEP and bias were 22.5, 0.922 and -1.45 in the calibration transformed to the N-point smooth of log 1/R signal, 5 factors, respectively. Therefore, the results of our study clearly demonstrate that the VIS/NIRS method would be applicable only for rapid determination of cyanidin-3-glucose content in black rice flour samples.