Laser-based imaging system for non-invasive monitoring of quality changes of papaya during drying

•A laser-based imaging system for non-invasive monitoring of quality changes is proposed.•Increasing drying temperature resulted in quality changes of papaya.•The use of laser backscattering methods provides a useful tool for quality control in fruit drying processes.

Non-invasive, sensor-based technologies are increasingly considered as preferred methods for evaluating quality attributes of agricultural products. This study investigated the feasibility of a laser light backscattering analysis at three wavelengths (532, 650, 780 nm) for predicting moisture content (MC), shrinkage (S), lightness (L*), chroma (C*) and hue (h*) changes of papaya during drying. Convective hot air drying was conducted at four temperatures (50, 60, 70, 80 °C), during which time the product was sampled and subjected to non-destructive optical analysis as well as reference measurements. From laser images, the illuminated area (AI) and light intensity (IL) were used to assess the backscattering profiles that represent photon migration in the fruit tissue. As expected, drying temperatures significantly affected the quality attributes of dehydrated papayas. Increasing drying temperature resulted in a decrease in MC, L*, and C* values, whereas h* and S values were increased. The results also revealed that each backscattering factor obtained can potentially be used to describe each quality change, except for C* value. In addition, multivariate correlations of measured AI and IL parameters at 650 nm wavelength were found to precisely yield the best fit for MC, L*, and h* predictions (R2 > 0.92). Therefore, the study concludes that the use of laser backscattering methods provides a useful tool for quality control as a rapid, consistent, non-intrusive and objective method for in-line measurement of product quality in fruit drying processes.