Non-Destructive Analysis of Anthocyanin Content and Antioxidant Activity in Single Purple Corn Kernels By Near-Infrared Reflectance Spectroscopy.

Anthocyanins are a class of flavonoids that are the most widespread secondary metabolites in plant tissues. Purple corn contains anthocyanins in the pericarp, and the pigments have 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity. Anthocyanins are high-functional pigments, and could be utilized as a new type of agricultural product. In Japan, breeders are targeting purple corn cultivars with a high content of anthocyanins. Conventionally, the contents of anthocyanins and their DPPH radical-scavenging activity are measured spectrophotometrically. NIR spectroscopy has advantages of easy handling, and quick and nondestructive measurement. If a calibration equation for determining anthocyanin contents and DPPH radical-scavenging activity could be established nondestructively in single corn kernels by NIR spectroscopy, the analyzed corn kernels could be seeded in the field. In this study, a total of 120 corn kernels were obtained in Japan in 2014. The 1200 log 1/R values (at 1-nm intervals, from 1200 to 2400 nm) were recorded using a Spectra Star 2400 NIR spectrophotometer (BLtec K.K., Osaka, Japan). After the scan, the kernels were pulverized using a crushing mill. The powder samples were individually treated with water-concentrated trifluoroacetic acid (99/1, v/v) for 24 hrs at room temperature. The final concentration of the mixtures was 20 mg/mL. Anthocyanin contents and DPPH radical-scavenging activity were calculated from measurements made using a UV-vis spectrometer. Partial least squares regression (PLSR) was used to develop calibration and validation models from the NIR spectra for the composition results. According to our study, the calibration provided the lowest SEP (3.04 umol Cy3Glc eq/g D.W. and 1.66 umol Trolox eq/g D.W.). The validation correlation and standard deviation/square error of validation values (RPD) and the coefficient of determination for validation (R2v) were determined as follows: anthocyanin content, 0.84 and 2.5; DPPH radical-scavenging activity, 0.87 and 2.7. These results indicated that the content of anthocyanins and the DPPH radical-scavenging activity of single purple corn kernels could be measured nondestructively using NIR spectroscopy.