Interpretive Summary: This research developed a new processing method using sequential infrared predehydration and freeze-drying to produce high quality, crispy fruit and vegetable products with reduced drying time and energy use. The reduced drying time and energy use should significantly reduce the production cost and promote the consumption of fruits and vegetables and improve the human heath.

Technical Abstract:
Dried fruit pieces are increasingly popular as snacks or add-ins in breakfast cereals. They are typically produced by using freeze-drying or hot air drying. Freeze-drying can maintain the product texture, but it is a very slow drying process. Hot air drying provides a higher drying rate than freeze-drying, but the product quality is poor. In order to produce high quality dried fruits and vegetables with reduced drying time and improved energy efficiency, a new drying method that uses sequential infrared radiation and freeze drying (SIRFD) was researched. The objective of this study was to determine the drying characteristics of strawberry slices with the SIRFD method. Strawberry slices of 2, 4, and 6 mm thickness were dried using a catalytic infrared (CIR) dryer to achieve 30%, 40%, and 50% moisture removal under each of the three radiation intensities, 3000, 4000, and 5000 W/m2. Then the pre-dehydrated strawberry slices were frozen and dried with a freeze dryer to achieve a final moisture content of about 5%. The drying times and rates of SIRFD with different processing conditions were measured and the quality of finished products was also evaluated. The results showed that infrared drying alone could remove 30% of moisture in 6, 5, and 4 minutes with 3000, 4000, and 5000 W/m2 intensity, respectively. Additionally, the SIRDF method could significantly reduce the overall drying time and produce high quality product compared to regular freeze-drying. Because of reduced drying time, the SIRDF method showed it’s a great energy saving potential for drying fruits and vegetables.