Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2008
Publication Date: 6/25/2008
Citation: Olson, D.A., Avena-Bustillos, R.D., Muy-Rangel, M.D., Pan, Z., Mc Hugh, T.H. 2008. Improved Energy and Processing Efficiencies of Strawberry Drying Using Sequential Infrared Freeze-Drying Method. Annual Meeting of the Institute of Food Technologists.
Technical Abstract: Strawberries are rich in nutrients but highly perishable. Freeze-drying is an excellent dehydration method for strawberry preservation. However, freeze-drying is an expensive dehydration process due to slow drying rates, high capital operating costs and low energy efficiency. Strawberry slice weight reduction can improve color and texture of freeze-dried slices while reducing the freeze-drying time. Sequential infrared radiation is a potential efficient method to reduce moisture content of strawberry slices prior to freeze-drying. The objective of our study was to quantify energy savings during sequential infrared freeze-drying of strawberries. A catalytic gas emitter infrared heating system was used to achieve 40% weight reduction of sliced strawberries. Surface temperature and wavelength of infrared emitters was 472°C and 3.89 µm, respectively. Strawberry slices with 4 mm thickness were loaded on trays for 4 min static infrared heating. Single layer slices on trays were frozen and freeze-dried using programmable cycle steps for different periods of time. A power meter was used to measure integrated energy in Kw-h every 5 min in the freeze-drier and then converted to MJ/Kg of fresh strawberries. Weight loss, moisture content and Aw were also measured. Freeze-drying of fresh strawberries was used as control. Total energy for 4 min infrared heating of strawberry slices was 1.9 MJ/Kg. Electric energy used in the freeze dryer was significantly reduced by using sequential infrared dried than fresh strawberries slices to achieve the same final freeze-dried products, moisture (5%) and Aw (0.266). The freeze-drying time for fresh versus sequential infrared dried strawberries slices was reduced from 12 h to 10 h, resulting in 324 MJ/Kg energy savings. Sequential infrared freeze-drying is an energy efficient method to dry strawberry slices.