CONICET | Buscador de Institutos y Recursos Humanos

The objective of this work was to analyze the effect of different pretreatments and dehydration methods on color and anthocyanin content of two products obtained from sweet cherries (Lapins var.). Fruits were cut in halves and in eighth pieces in order to obtain different dried product geometries: discs and dices. Sucrose infusion (SI) and blanching (B) were applied prior to drying. Dehydration was performed by freeze-drying (FD, 48 h, condenser temperature: -84°C) Color was measured by photocolorimetry (2° observer, C illuminant, CIELAB color space). Measurements were performed on skin and pulp in discs and in pull in the case of dices. Global color change and hue angle were analyzed in comparison to fresh fruit. Total anthocyanin content (T Acy) was determined using the pH-differential method, and Acy degradation index (ADI) was calculated. The applied pretreatments and drying methods caused different effects on color and anthocyanin retention when compared to the fresh fruit. The SI pretreatment in discs caused the greatest on skin, due to diffusion of pigments into the solution during osmosis, to the addition of bisulphite to the system and to the presence of sugar crystals on fruit surface. On the pulp, air-drying caused a darkening of discs (L* decrease). Both products, discs and dices, exhibited in general an increase in h values upon dehydration, in agreement with Acy pigment decrease. For a certain pretreatment, FD samples showed a greater Acy retention than the respective AD samples. Moreover, AD-SI samples presented the highest ADI values. Fruit cut in small pieces allowed obtaining a better quality product (color and anthocyanin content) than processing it in halves. Overall, the SI pretreatment caused an important decrease in anthocyanin pigments retention and a clearer appearance. Therefore, this procedure should be carefully performed in berries in order to keep the nutritional quality of the product.

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