Surface sterilization of dried fishery products in superheated steam and hot air

Dried salmon and dried cuttlefish were treated with superheated steam and hot air. The effects of both treatments in terms of surface sterilization of the products were compared, and evaluations of surface color change and product toughness were conducted. Dried salmon and dried cuttlefish had viable bacteria counts of 10(6) or more cfu/g before treatment. The main bacterial types found were Kocuria genus and Staphylococcus genus, which are resistant to drying conditions. Treatment by hot air circulating in a dryer at 120 degrees C and 180 degrees C for 1 min had little effect in sterilizing dried salmon, but superheated steam treatment of dried salmon using a conveyer system at 120 degrees C for 1 min or 180 degrees C for 30 s decreased viable bacteria counts to less than 300cfu/g, indicating that this treatment was more effective for sterilizing bacteria than the use of hot air. However, the toughness of the fish increased when superheated steam treatment was used. In order to minimize this effect, the superheated steam was blown from a slit to increase the efficiency of heat exchange, and the dried cuttlefish was placed on a net conveyer and passed under the superheated steam. At a temperature of 170 degrees C or 200 degrees C, and with a conveyor belt velocity of 5 cm/s, viable bacteria on the surface of dried cuttlefish decreased less than 10(5) cfu/g, with little change in toughness or surface color. The present study demonstrated that brief treatment with superheated steam resulted in considerable reduction of surface bacteria on dried fishery products with no decrease in quality.