Pré-tratamentos de fatias de maçã Fuji para desidratação em diferentes temperaturas

Abstract

Dehydration is a technique widely used in the preservation of perishable products, where the moisture content of the food is reduced to very low levels, consequently reducing its deterioration. The present study aimed to analyze qualitatively apple slices submitted to different antioxidant agents and dehydration temperatures, as well as to quantify the loss of mass and the volumetric contraction during the process. In the pre-treatments with antioxidants were used: citric acid (0.5%) and sodium bisulfite (0.5%). The samples were dehydrated in an oven with forced air circulation to the final moisture content of 0.11 ± 0.02 (decimal, b.s.) at temperatures of 50, 70 and 90 ° C. The monitoring of the dehydration process was carried out by mass loss through weighing at predefined time intervals. The three characteristic dimensions of the apple slices were also determined for determination of the volumetric contraction. The qualitative characteristics evaluated were: color, total soluble solids (ºBrix) and sensorial analysis measured by hedonic scale. The results showed that a large part of the slice volume reduction occurred in the first 90 minutes, corresponding to 30% of the time required to complete the process. The contraction at the beginning of dehydration was more significant when using higher temperatures. Pre-treatments had no influence on contraction. The time required to finalize the dehydration up to the pre-established final moisture content, when used at temperatures of 90 and 70 ° C was 18.2 and 9.1%, respectively, lower than the temperature of 50 ° C. The average mass loss was on the order of 83%. The results showed that the temperature that provided the greatest variation of the color attributes of the fruit in natura was at 70 ºC. The pre-treatments were efficient to avoid oxidation. In relation to the total soluble solids, there was no influence of the temperature, but a small tendency of increase of the SST content (ºBrix) was observed when pre-treatment with sodium bisulfite was carried out. The sensorial analysis showed that the highest acceptance of the slices and the prepared tea were at temperatures of 90 and 50 ºC, respectively, both with the pre-treatment of sodium bisulfite.