Water content effect on the chromatic attributes of dehydrated strawberries during storage, as evaluated by image analysis

The changes of chromatic attributes due to different hydration degree, anthocyanins degradation and browning development were studied in dehydrated strawberries. Strawberry slices were freeze-dried, equilibrated at different relative humidities and stored at 45 °C. The changes of several functions of the CIELAB color space were analyzed using a computer vision system, employing segmented image analysis. Darkening promoted by browning reactions could be evaluated through the decrease of luminosity and increase of hue angle and yellow coordinate in the whitish sections of the samples. During humidification the anthocyanin degradation increased as increasing water content. Of the several color functions, only the red coordinate values of the reddish sections of the samples correlated with anthocyanin degradation, but at relative humidities values higher than 43%. Light diffusion in the dried material caused a lighter appearance up to 75% relative humidity, while browning reaction and pigment degradation were accelerated at this relative humidity. These effects were related with the appearance of mobile water populations in the material, as detected by 1H NMR.

► The segmented image analysis was appropriate to evaluate the visual appearance.
► The destruction of anthocyanins could be followed by the chromatic attribute a*.
► The formation of brown pigments could be followed by L* and b* attributes.
► Appearance changes could be related to water molecular mobility by 1H NMR.