Non-destructive analysis of the moisture content in shiitake mushrooms (Lentinula edodes) using near-infrared imaging at 1450 nm

Moisture content (MC) is an important factor in the freshness of shiitake mushrooms (Lentinula edodes). In this study, we developed a simple prediction method for MC of shiitake mushrooms using near-infrared (NIR) imaging at 1450 nm, as the band at 1450 nm is strongly correlated with OH groups. First, a NIR image was captured by an InGaAs sensor with a bandpass filter of 1450 nm; the captured image was then calibrated using an image taken at 1100 nm to remove shade and shape effects of mushrooms. The actual MC of shiitake mushrooms was measured using an oven-drying method, and a calibration curve was obtained for the cap surface and the gill side, respectively. The correlation coefficient reached more than 0.85, and the standard error of calibration ranged from 3.1% to 8.2%. Non-destructive MC images were quantified using the constructed calibration curves, and the experimental results showed that differences in the water-holding property can be visualized over 6 h for each side using our method.