Dehydration is one of the most effective means to preserve foods in a stable and safe condition for an extended shelf life. Loss of heat sensitive nutrients and other health promoting compounds in dried foods are major concerns in the design and operation of food drying equipment. Scientific information is lacking on the operation of the Refractance Window (RW) drying process. This project provides comprehensive scientific knowledge on this drying process, while quantifying the influence of varying product formulation and drying parameters on product quality, antioxidant activity, and ease of detachment from the drying surface, thereby supporting future optimization of the RW drying system. OBJECTIVES: The objectives of the proposed phase I project are to conduct systematic studies on Refractance Window (RW) drying to obtain sound scientific data on 1) fundamental drying kinetics, 2) influence of glass-liquid transition on product quality and detachment from drying surface, and 3) retention of food quality, including antioxidant activity. Blueberries, being small fruits that contain heat sensitive compounds and distinct pigments that are likely to be lost or discolored during drying, will be used in the project. This research will not only increase competitiveness of a small business, but also introduces a relatively low cost drying method that has potential to maintain food product quality to satisfy the needs of increasingly health conscious consumers. It is expected that the outcome of phase I study will guide dryer design improvements in the next phase that will positively influence the retention of quality in other types of dried food products, including protein, starch, and vegetable. The phase II design improvements targeting the commercialization of RW drying will be facilitated by prototyping and testing auxiliary and alternative product application, product conditioning, and product removal equipment. APPROACH: The research plan consists of: 1) fundamental food engineering studies, 2) studies on the nutritional and health-promoting values of the dried products, and 3) development of formulations that improve product removal and handling characteristics. Drying kinetics of a well-characterized model food system composed of pectin, sugar and minimal amounts of polysaccharide carrier will be obtained, followed by those of blueberry juice/additive formulations. Critical process parameters such as conveyor belt speed, product loading, film thickness, the temperature of process water and that of products will be analyzed in defining the drying kinetics. Glass-liquid transition will be studied to show the influence of additives, product release agents, and levels thereof, on product removal and handling characteristics. Blueberry juice/additive formulations will be analyzed before and after drying to establish the retention of antioxidant activity in comparison with freeze-drying
