Orange slice drying enhancement by intervention of control atmosphere coupled with vacuum condition—A new design and optimization strategy

Abstract

The present study aimed to improve the quality of dried orange slices by modifying a conventional vacuum dryer in which nitrogen gas is injected into the dryer chamber. The orange slices were dried in a vacuum dryer with two different normal and controlled atmosphere (CAtm) methods. Next, the parameters of effective moisture diffusivity (Deff ), total energy consumption, color indices (ΔL*, Δa*, Δb*, and BI), antioxidant capacity (AC), total phenolics content (TPC), and ascorbic acid (AA) were measured for all samples during the drying process. Finally, both methods were optimized by the central composite design (CCD). The results showed that the CAtm at optimum performance increased Deff about twice, and the energy consumption of the CAtm system was almost half of the normal atmospheric method. Also, AC at optimum points in the CAtm method was about twice more than the normal atmosphere. Although the temperature effect on TPC was nonlinear under NAtm, it was moderate under CAtm. Overall, the AA was more stable when the orange slice was dried by the CAtm method. Furthermore, CAtm decreased the Δa*, and the effect of temperature on ΔL*, Δb*, and BI was nonsignificant.