Abstract: In combination of hot-air drying, vacuum frying was utilized to process peach chips. Vacuum-frying temperature, moisture content after vacuum drying and hot-air drying temperature were recognized as main factors that affect oil content of peach chips. From the results of response surface analysis, it was found that the optimum conditions for the combined vacuum and hot-air drying of peach chips based on oil content of peach chips were sequential operations of 3 min blanching followed by vacuum drying at 87.1 ℃ until a moisture content of 15.9% and hot-air drying at 65.5 ℃ for processing 2 mm thick peach slices. Considering actual operating situations, vacuum-frying temperature, moisture content after vacuum drying and hot-air drying temperature were modified to be 87 ℃, 16% and 66 ℃, respectively, and the other conditions were kept unchanged. Under the modified processing conditions, the actual value of oil content in peach chips after hot-air drying was 12.5%, exhibiting 5.9% relative error when compared to the theoretically predicted value.

Key words: vacuum frying, combined drying, peach chips