Freeze Concentration – Steam-Based
Industry: Fruit and Vegetables (NAICS 3114) Dairy (NAICS 3115)
Process Brief: Water is removed by chilling a product so that the moisture can be filtered as ice crystals.
Energy source: Electricity
Freeze concentration is useful to concentrate foods that are especially temperature sensitive such as diary products, juices, and coffee. Simply described, in freeze concentration the product is chilled to the point where ice crystals can be removed by filtration. In a typical application, fruit juice is chilled in a scraped surface freezer to the point that tiny ice crystals begin to form. The chilled product is scraped from the surface and transferred to a recrystalizing vessel, where the small crystals melt and reform larger crystals in a ripening process. The crystals are removed in a wash column and the concentrate is removed to the recrystalizing vessel. Freeze concentration is used to make instant coffee by combining this process with spray drying.
Freeze concentration systems are more expensive than thermal processes and are used only for high value products. One dairy plant installed a freeze concentration system that could remove 1/3 of the water in 275 gallons of milk per hour and the cost of the system was about $1.0 million.