Convective drying of cambuci, a native fruit from the Brazilian Atlantic Forest: Effect of pretreatments with ethanol and freezing

Cambuci is a native fruit from the Brazilian Atlantic Forest, with high sensorial and nutritional potential. However, this fruit is very perishable, which impairs its exploration and study. This work reported the convective drying of cambuci for the first time, as an approach to achieve stability. Moreover, it also evaluated for the first time the combination of ethanol and freezing pretreatments to convective drying. Pretreatments were performed by immersion of fresh and previously frozen and thawed cambuci slices in ethanol (5 min at 25°C). Pretreated samples were then convectively dried (50°C, 1 m/s). Drying time was reduced up to ~36% by combining the pretreatments, which was associated with the reduction in the external resistance to mass transfer, once the convective mass transfer coefficient increased up to 94%. In contrast, pretreatments that include freezing had a greater influence on reducing the internal resistance to mass transfer, increasing the effective diffusive coefficient. In addition, the thermal surface profile evidenced the temperature increased faster and reached high levels in pretreatments that include freezing, which could be correlated to their higher drying rates and structure modifications. The obtained results corroborate the modifications produced by freezing and the effects of ethanol on the surface of samples significantly accelerate the convective drying of cambuci. Practical Applications: The present investigation shows that convective drying is a feasible alternative for cambuci processing. Further, being this fruit very perishable, with short harvest and production far from the markets, freezing is a common practice to preserve them in the farms. Consequently, the impact of this unit operation was also evaluated. In addition, the proposed pretreatments (freezing and ethanol) have great application potential to improve the conventional convective drying of fruits. It has been shown that the combination of pretreatments accelerated drying, reducing the processing time by 36%. © 2021 Wiley Periodicals LLC.The authors are grateful to the S?o Paulo Research foundation (FAPESP, Brazil): projects n? 2014/12606-3 and 2019/05043-6; GR Carvalho post-doctoral fellowship (2018/17844-0); the ?Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior?Brasil (CAPES)?: BO Gomes (88887.485030/2020-00), JS Guedes (88887.513566/2020-00) and KC Santos (88882.378385/2019-01) M.Sc. and Ph.D. Scholarships; the National Council for Scientific and Technological Development (CNPq, Brazil): BS Bitencourt (132297/2019-1) M.Sc. Scholarship and PED Augusto productivity grant (310839/2020-3); the Fondo Nacional de Desarrollo Cient?fico, Tecnol?gico y de Innovaci?n Tecnol?gica (FONDECYT, Peru) from the ?Consejo Nacional de Ciencia, Tecnolog?a e Innovaci?n Tecnol?gica? (CONCYTEC, Peru): project n? 409-2019-FONDECYT; the Universidad Privada del Norte (UPN, Peru): project n? 20201005. The authors are also grateful for the valuable help of B.Sc. Isabela Silveira and N?colas Gon?alves Borrego, as well as Mr. Paulo Nakanishi from ?Sitio Recanto dos P?ssaros? for providing the fruits