An optimisation framework for drying of heat-sensitive products

An equipment model for a two-stage evaporator system has been presented and validated. A material model incorporating liquid and vapour migration as w ell as the heat transfer in a potato slice, as a model heat-sensitive produ ct, was formulated and validated. Combining the two models, optimisation of the heat pump drying process was conducted for intermittent air temperatur e drying cycles. The independent parameters considered were the mean starti ng temperature, T-m, and the intermittent cycle ratio of the drying air, ta u (on)/tau (cycle). The constraints imposed were the desired moisture conte nt, drying time, ascorbic acid (AA) content and non-enzymatic browning (NEB ). The objective functions were minimising the loss of AA content and NEB d egradation, and maximising the heat recovery of the two-stage evaporator sy stem. The implications of relaxing implicit and explicit constraints on hea t recovery and product quality parameters (AA and NEB) were also studied. ( C) 2001 Elsevier Science Ltd. All rights reserved.