Secagem da biomassa de levedura (Rhodotorula glutinis) em camada de espuma (Foam-mat drying)

Abstract

Yeasts, especially the genus Rhodotorula, have the capacity to produce considerable amounts of compounds with high added value, such as carotenoid pigments and lipids, in addition to being considered a source of proteins in human and animal nutrition, but for commercialization it is convenient to apply conservation method. Thus, the objective of this work was to study the drying in foam layer (foam-mat drying) of the biomass of the yeast Rhodotorula glutinis to obtain the powder. The yeast was grown in a bioreactor, amid sugarcane molasses, supplemented with nutrients. The drying was carried out according to the complete factorial design of 2³ + 3 central points, with independent variables: concentration of foaming agent (10, 15 and 20%), stirring time (4, 5 and 6 minutes) and temperature drying (50, 60 and 70 ° C), the influence of these independent variables on the dependent variables (response) of the process (drying time and equilibrium humidity) and on the characterization of the obtained powder was evaluated. The physical characterization of the foam was also evaluated: stability; density; incorporation of air and expansion in the minimum, maximum and central points of the experimental planning. The production of biomass from Rhodotorula glutinis (CTT 2182) was satisfactory, with an average yield of 60 g per batch. The sparkling agent juá was chosen after preliminary tests. In the physical characterization of the foam, the independent variable agitation time, at the upper level of the experimental design, was responsible for the best results for density, volumetric expansion and air incorporation. The foam stability was favored by the increase in the concentration of the sparkling wine. In drying, temperature was the only statistically significant variable at the 95% confidence level. With inversely proportional influence, so that the higher the temperature, the shorter the drying time. For the adjustment of the drying curves, the models that best described the drying phenomenon were Logarithm and Page, with a standard error of the estimate below 0.28%. In the physico-chemical characterizations of the biomass powder of the yeast Rhodotorula glutinis, an average theoretical yield was obtained for the experiments of the central point of 22.36%, an average ascorbic acid content of 41.36 mg / 100 g of powder and solubility greater than 20% in all conditions studied. In the analysis of water activity, all experiments obtained values above 0.6, thus ensuring the viability of the product produced. The drying process in the foam layer of the Rhodotorula glutinis yeast biomass proved to be feasible, with the best temperature conditions being 70 ºC, concentration of the sparkling wine 20 (%) and stirring time of 4 minutes, which showed less drying time and moisture end of the product.