Secagem por refractance window de cará-roxo (dioscorea trifida) visando a obtenção de compostos de importância tecnológica

Abstract

The purple yam (Dioscorea trifida) is a tuber rich in nutritional and medicinal components available at low cost. The North and Northeast of Brazil are the largest producers of the Dioscorea genus. However, a Dioscorea trifida species, despite its attractive potential, is still poorly studied. The consumption of this tuber generally includes family farming and sales at open markets. In addition, the high moisture content reduces the time of use and industrial possibilities. Much of the available information in the databases is on starch extraction and physical, compound and technological properties, production of biodegradable films from the flour of these tubers, few reports on extraction and characterization of antioxidant compounds. None of it reports data on drying with the tuber. Therefore, the objective of this work was to evaluate the effects of drying in Refractance Window on the purple yam and to verify the technological potential of the purple yam after drying. Dioscorea trifida tubers were processed and drilled to dry in Refractance Window at temperatures of 70, 80 and 90 ºC. Another part of the processed Dioscorea trifida mass was subjected to freeze-drying. Heat transfer and drying mass parameters were transferred, in addition to the physical-chemical effect and antioxidant capacity of the dry sample. The moisture diffusivity and the mass transfer coefficient were determined using the Dincer and Dost model. With the results, it was observed that the dehydration process of the samples occurred in a short time. The diffusivity coefficients ranged from 2,91 × 10-7 to 6,81 × 10-7 m2.s-1 and the mass transfer coefficient ranged from 1,16 × 10-4 to 1,34 × 10-4ms -1. The activation energy was obtained at 44,16 kJ.mol-1. The results of the thermodynamic properties pointed to a non-spontaneous process, with positive values of enthalpy and Gibbs free energy and negative values of entropy. In the Dioscorea trifida powders obtained after drying in Refractance Window, they showed carbohydrate as the main constituent (85,66 to 86,47 %) with a starch content greater than 69,0 %. Among the technological properties, the oil absorption index of the powder was strongly dependent on the drying temperature RW. The highest retention rate of bioactive compounds (> 50 %) in powders occurred at temperatures of 70 and 80 °C. RW drying is a viable technique for drying tubers of Dioscorea trifida. The powder resulting from drying, despite expected losses with drying, presented an industrial potential for application in food. Due to its nutritional valuable andantioxidant properties, purple yam (Dioscorea trifida) has a wide variety of applications and can be explored in terms of its bioactive components.