Influence of colour changes and moisture content during banana drying on laser backscattering

Pre-drying treatments are frequently employed to preserve fruit quality. The objective of this research was to monitor colour changes of banana during drying by laser backscattering and to determine the influence of the fruit discolouration on the light distribution into banana tissue. Moreover, to examine the influence of drying on the laser backscatter, the relationship between moisture content and relative laser area of banana slices was analyzed with different degrees of colour degradation. The experiments were conducted at drying air temperature of 63 °C with various pre-treatments like chilling, soaking in ascorbic/citric acid and dipping in distilled water. An untreated sample was used as a control. A laser diode emitting at 670 nm with 3 mW power was used as light source. The backscattering relative laser area was used as an indicator for the light absorption into the tissue. The high result achieved on coefficient of determination R2 (>0.93) confirmed linear relationship between relative laser area and moisture content. Treatment with ascorbic acid gave the best prediction of the moisture content with the standard error of 5.7 and 8.8 for the estimated intercept and slope. The results showed a significant difference of lightness (L* values) during drying according to the different treatments. As a result, colour degradation did not have a significant influence on the absorption of light at 670 nm wavelength