An approach for monitoring the moisture content changes of drying banana slices with laser light backscattering imaging.

摘要

Moisture content is an important quality attribute that directly influences storage stability of fruits and vegetables. Use of a laser light backscattering imaging technique for monitoring drying of banana slices was investigated. A laser diode emitting at 670 nm was used as the light source, and a charge-coupled device camera served as a detector. Photon migration into the tissue was recorded as the average profile of the intensity gradient and expressed by 2 parameters, the size of the total illuminated area (in cm2) on the surface and the radius (in cm) of this area. The 2 attributes correlated with each other (r = 0.97-0.98). Backscattering images of banana slices were acquired each hour throughout drying at 53, 58 or 63 degrees C. The 2 parameters of the intensity profile responded sensitively to changes in moisture content. A significant relationship was found between changes in backscattering area and moisture content, especially at the lower temp. (r = 0.76 at 53 degrees C), when almost no tissue browning occurred. At higher temp., correlations were found between the parameters extracted by image processing and the a* standard colour index, due to tissue browning.