Determination of anthocyanin and moisture content of purple sweet potatoes during drying process by their optical properties in the 400-1050 nm range

Abstract

This research investigated the potential of using optical properties to assess quality attributes of purple sweet potatoes (PSPs) during drying process. The absorption (μ_a) and scattering (μ_s^') properties of PSPs during drying were determined at 400-1050 nm using a single integrating sphere system. The absorption spectra were marked by pronounced anthocyanin peaks around 545 nm, and very small water peaks around 980 nm. The average μ_s^' was relatively flat in the 670-1000 nm range, which increased as drying time increased. Good prediction of anthocyanins (determined by pH-differential method) and moisture (determined by oven-drying method) contained in PSPs were obtained using their optical properties through SVM models, with determination coefficients of prediction (R²p) of 0.866-0.917, and residual predictive deviation (RPD) of 2.626-3.190. These results were consistent with correlation results between optical properties and the two quality parameters, suggesting the former can be used for predicting PSP quality during drying.

Keywords: Anthocyanin; Drying process; Integrating sphere; Moisture; Optical properties; Purple sweet potato.