Caracterização da manga Tommy Atkins in natura e após a liofilização

Abstract

Mango (Mangifera indica L.) is a greatly consumed fruit worldwide, it presents tasty fleshy pulp which is highly appreciated, however the fruit suffers quickly deterioration. In order to add value and enhance the shelf life of mangoes, studies have been conducted aiming to develop products without changings in physical, chemical, nutritional and sensorial characteristics. Freeze drying has shown potential maintaining the fruit characteristics. Therefore, the objective of the present work was to characterize mangoes of Tommy Atkins cultivar before and after freeze drying. The fruit was cut in square (5 cm) slices with three different thickness (0.5, 1.0 and 1.5 cm), frozen at -22 °C and freeze dried. Moisture (U, in triplicate, in an oven at 105 °C), water activity (aw, in triplicate, at 25 °C), color (in replicate, reading the values of L*, a* and b*), vitamin C content (in triplicate, by titration) and hardness (in replicate, in N) were determined. It was verified that the average moisture of fresh mango was 85.05 ± 0.02%; and the average moisture of freeze dried with 0.5, 1.0 and 1.5 cm thickness were 2.600 ± 0.004%, 3.800 ± 0.007% and 3.420 ± 0.002%, respectively. Freeze dried fruits presented significant decrease of aw, which values were 0.24 ± 0.02 (0.5 cm thickness), 0.278 ± 0.009 (1.0 cm thickness) and 0.23 ± 0.02 (1.5 cm thickness), pointing the significant free water evaporation from the food. Low values of aw ensure microbiological security and the absence of chemical and enzymatic reactions in the fruit. After freeze drying it was verified a significant decrease in the a* values of the samples, independently of their thickness, showing that freeze dried fruits were less yellow (less red) than fresh fruits, which was expected since the water remove changes the fruits color. The samples presented losses of 94.48% (0.5 cm), 93.27% (1.0 cm) e 91.81% (1.5 cm) of the vitamin C after freeze drying, which could be related to the formation of large ice crystals during frozen, resulting in great destruction of the cellular structure and exposure of the nutrient to oxygen, since the processing results in high porosity of the final product. The hardness of the freeze dried fruits showed proportional to its thickness, ie, as higher the thickness, as higher the hardness. It was concluded that freeze drying was efficient ensuring the microbiological safety of the food, however resulted in severe reduction of the vitamin C content of the mango and possibly in decrease of the carotenoids content.