Effect of relative humidity on shrinkage and color changes in dehydrated strawberry

LINA M. AGUDELO; NURIA ACEVEDO; CAROLINA SCHEBOR; MARÍA DEL PILAR BUERA

The World of Food Science

IUFOST-IFT

Año: 2010 vol. 11 p. 1 - 4

Dehydrated fruits are prone to suffer discoloration during storage. Many natural pigments are unstable in dried media, and also brown pigments can be formed. The objective of this work was to evaluate shrinkage and color changes in freeze-dried strawberry slices as a function of relative humidity (RH) employing a computer vision system. Fruit discs were stored at 45ºC and color and area changes were recorded with time. Strawberries presented heterogeneous color distribution. Besides analysing the global color variables (L*, a* and b*), the disk areas were divided into four different zones according to their a* values and segmented image analysis was performed. The heat treatment caused browning and anthocyanin destruction. The color changes in strawberry were better represented by the a* variable, which decreased during storage. Also, at the highest RH analysed, the strawberry slices became homogeneous. The main radial area reduction (shrinkage) was observed after 14 days of humidification at 20ºC and it increased as RH increased. Computer vision analysis is a useful tool to assess optical properties and allows the analysis of heterogeneous materials. The segmented image analysis was appropriate to evaluate some relevant characteristics of the visual appearance changes occurring in dehydrated strawberries, related to the humidification level and storage time. Water mobility seems to be involved in drastic shrinkage and color changes.