Variation of food brittleness of the fruit and vegetable slices during hot air drying process

Objective: Aims at the brittleness regulation of fruit and vegetable slices during hot air drying process. Methods: This article takes fresh potatoes and bananas as the research materials, adopts mechanical and acoustic measuring devices to collect mechanical and acoustic signals generated by the fruit and vegetable slice samples at the mechanical compression mode, which were collected at different drying times during the hot air drying process of 80 ℃, to comprehensively evaluate the fragility of the fruit and vegetable slices. Results: The acoustic emission （AE） signal of the potato slice appeared the drying time of 45 min, and its AE energy increased gradually with the increase of drying time. The stress increased rapidly and then remained stable; The best drying end time of potato was 180 min. At this time, the AE energy and force were 255.38 mV·ms and 20.25 N respectively. The AE signal of the banana slices appeared from the early stage of drying, and its energy increased rapidly with the progress of drying, decreased after 150 min of drying, and remained stable after 200 min. The stress appeared after drying for 60 min, increased rapidly until the peak at 240 min, and remained stable. The optimum drying end time of banana slices was 240 min, and the energy and force were 122.58 mV·ms and 18.01 N, respectively. Conclusion: The mechanical-acoustic detecting method can be used to monitor the crispness variation of the fruit and vegetable slices being dried and to optimize the hot air drying process.