Changes in color and anthocyanin content of different dried products based on sweet cherries

LORENA FRANCESCHINIS; NATALIA SOSA; CAROLINA SCHEBOR; DANIELA SALVATORI

Mar del Plata

Congreso; Interim Meeting of the International Color Association AIC 2010 “Color and Food”; 2010

It is widely known that quality properties of fruits can be affected by drying processing. 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: -84ºC, vacuum: 0.04 mbar) and by air drying (AD, 24 h, air temperature: 60°C, 10% RH). Color was measured by photocolorimetry, (2° observer, illuminant C, CIELab color space). Measurements were performed on skin and pulp in discs, and in pull in the case of dices. Global color change (ΔE), and hue angle (h) were analyzed in comparison to fresh fruit. Total anthocyanin content (T Acy) in fruit 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 ΔE (> L*, < a*) on skin, due to diffusion of pigments into the solution during osmosis, to the presence of bisulphite in the system, and to the presence of sugar crystals on fruit surface. On the pulp, air-drying caused a darkening of discs (L* decrease), because of browning reactions. In the case of cherry dices not significant differences were observed between ΔE values of samples (p < 0.05). 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. Cutting the fruit in small pieces allowed a better quality product (color and anthocyanin content) than processing the fruit in halves. Overall, the sucrose infusion 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.