Modern food industry dictates strict conditions on energy use and application, preventing unnecessary energy dissipation. Energy demanding processes such as distillation and drying have to be optimised to the highest extent, while retaining or improving the final product quality. Pretreatments to drying can be used in order to optimize drying, and some of cranberry pretreatments such as chemical, mechanical and osmotic dehydration were optimized. Chemical pretreatment consisted of dipping cranberries into solution of ethyl oleate and sodium hydroxide at different temperatures, and process times. Mechanical pretreatment was cutting of berries into halves or quarters. Tested parameters for osmotic dehydration were the duration of process, osmotic agent type and its concentration. / Once the appropriate pretreatment was selected, cranberries were subjected to hybrid drying under subatmospheric pressure and using microwaves as an energy source. Evaluated process parameters were microwave power level, microwave power mode, and the operating pressure of process. This drying method showed good potential, but in order to verify the results obtained, it was compared to microwave/convective drying. Slight advantages of the microwave/vacuum process over the microwave/convective process were apparent in almost all product quality parameters, as well as in process efficiency.

Since cranberry skin is thick and has low porosity, skin pretreatments were considered before drying in order to facilitate water diffusion. Mechanical and chemical pretreatments were considered, by cutting the fruits in half, by making pin holes in each cranberry, and by dipping the fruits in an alkaline solution. / A second pretreatment seemed necessary when drying cranberries in order to reduce their tartness. Cranberries were osmotically dehydrated, by immersing them in osmotic solutions of sucrose or high fructose corn syrup. / Once the pretreatment conditions were selected, four drying methods were tested on the pretreated cranberries. These methods included hot air drying, freeze-drying, vacuum drying and a combination of hot air and microwaves. A quality evaluation of the dried samples was also performed, including evaluation of overall appearance, taste, color, water activity, rehydration capacity and texture. (Abstract shortened by UMI.)

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