Impingement drying of foods using hot air and superheated steam

Impingement drying is an old technology that has only recently been applied to food products. Tortilla and potato chips, pizza crust, pretzels, cracke rs, and cooks, for example, have been successfully cooked and baked in air- impingement ovens in the Food industry. Granular products (coffee beans, co coa beans, rice, nuts) dry faster and more uniformly when using impingement dryers due to the pseudofluidized bed created by the high-velocity air fro m the nozzles. Tortilla chips and potato chips have been impingement dried using hot air and superheated steam. At higher air temperatures (above 130 degreesC), tortilla chips dry faster when using superheated steam compared to hot air (at the same conditions). Impingement drying with superheated st eam can produce potato chips with less color deterioration and less nutriti onal losses (Vitamin-C) than drying with hot air. Potato chips dry faster a t high superheated steam temperature and high convective heat transfer coef ficients. (C) 2001 Elsevier Science Ltd. All rights reserved.