Grading the pungency of red pepper powder using hyperspectral imaging coupled with multivariate analysis

Abstract

In this study, the spectral image of red pepper powder, which had been prepared in accordance with the standard particle size distribution ratio, was acquired in the short-wave infrared region using a hyperspectral camera. Spectral information was analyzed using multivariate statistical analyses including principal component analysis (PCA) and least partial squares (PLS) analysis. PCA revealed that powders were grouped according to their pungency level, regardless of their particle size distribution (PC1=97%, PC2=2%). The regression coefficient derived in PLS discriminant analysis indicated that 1,201-1,226 nm, 1,387-1,411 nm, and 1,508-1,529 nm are key wavelengths that are affected by the vibration of C-H, O-H, and N-H bonds present in capsaicinoid molecules. Pungency grade was successfully determined, and capsaicinoid content was predicted with high accuracy using PLS analysis of raw data at key wavelength (Rc2=0.9389, Rp2= 0.9261). It was possible to reduce the time required for data calculation and analysis by reducing the amount of spectral data utilized to predict spiciness from 256 to 21 bands. Finally, the distribution of capsaicinoids was mapped visually according to particle size. In conclusion, hyperspectral imaging is a suitable technology for real time, non-destructive monitoring of red pepper powder quality relative to the standard method used during the manufacturing process.