Liofilização e secagem em camada de espuma da polpa mista de jambolão e acerola e a elaboração de iogurte concentrado.

Abstract

Lyophilization and drying in a foam layer of the mixed pulp of jambolan and acerola and the elaboration of concentrated yogurt. This work aimed to produce mixed pulp of jambolão and acerola, dehydrated by two dryingprocesses (lyophilization and drying in foam layer) and to use the powders in the elaboration of concentrated yoghurts. For drying in a foam layer, in an oven with forced air circulation at temperatures of 50, 60, 70 and 80 °C, three formulations were made: F1 - composed of mixed pulp + 1% albumin + 0.5% xanthan gum; F2 - mixed pulp + 1% albumin + 0.5% carboxymethylcellulose; and F3 - mixed pulp + 1% albumin + 0.5% guar gum. Foam layer drying kinetics of the formulations were determined by monitoring the loss of water during the process. Lyophilization performed with maltodextrin and added to the mixed pulp in the proportions of 10, 20 and 30% for 72 hours. The mixed pulp of jambolão and acerola was classified as acidic and with a high content of phytochemicals (ascorbic acid, total phenolic compounds, flavonoids and anthocyanins), similar to whole pulps. From the physical analyzes (density, overrun and stability) each formulation had a specific beating time and the foam height of 0.5 cm presented the most satisfactory results for drying in a foam layer. The mixed pulp of jambolão and acerola obtained the classification of acid and with high content of phytochemicals. Foamed formulations in relation to mixed pulp showed a reduction in physicalchemical parameters, however, an increase in sugars and proteins. The application of drying kinetics models established that the Midilli model was the one that presented the best adjustments to the experimental data. The drying process occurred in a decreasing period, with higher temperatures resulted in a decrease in drying time, enthalpy and entropy and an increase in the effective diffusion coefficient and Gibbs free energy. The F1 formulation showed better performance in the drying process in a foam layer at 70 °C, with the lowest water content, Hausner factor, Carr index and angle of rest and, the highest carotenoid content. The lyophilized mixed pulp with 10% maltodextrin showed the best results for phytochemicals. The water adsorption isotherm at 25 °C of all powders obtained type II classification. The Peleg model can estimate the isotherms of the foam layer powders, whereas the GAB model was the one that best fit the experimental data of the lyophilized powders. After storing the selected powders for 180 days, over time there was an increase in water content, water activity and pH, as well as a reduction in the other parameters evaluated. The higher storage temperature showed less stability of the phytochemicals present in the dehydrated samples. The results presented indicate that the freeze-dried powder and storage at 25 °C proved to be more efficient to maintain the quality of the mixed pulp powder. The microbiological analyzes performed on concentrated yogurts were satisfactory in accordance with current legislation. The highlight was the concentrated yoghurts added with mixed pulp powder in terms of physico-chemical parameters. The yogurt with the powder of the freeze-dried mixed pulp without maltodextrin reached the highest levels of bioactive compounds and the formulation with the freeze-dried mixed pulp with maltodextrin the best profile of texture. There was good acceptance of the products regarding the evaluated sensory attributes and purchase intention.