APPLICATION OF HEAT-PUMP DRYER TO THE SMO KING PROCESSING OF THE DRIED BONITO (KATSUO-BUSHI)

The main purposes of smoking in manufacturing of dried bonito (Katsuo- bushi) were drying, flavoring and antioxidizing. We previously found t hat flavoring and antioxidizing were accomplished in the middle of smo king process. Drying was the most dominant in the last of smoking proc ess. So, in the smoking, the drying by smoke could be substituted by h ot dry air. Since heat pump drying system gave a energy saving with it s high efficiency, we applied to the last of smoking process. Followin g results were obtained: (1) In a conventional smoking process, the pr ocess was repeated 9 times until the cut bonito meat (fillets) became harden. In the new method of smoking using a heat pump dryer, the fill ets were continuously dried for 48 hours to harden after the 5 times r epitition of conventional smoking. The conditions for the drying proce ss were relative humidity (RH) of 80% at 50 degrees C for 12 hours (at the start), RH of 75% for 12 similar to 24 hours (in the middle) and RH of 70% for 24 similar to 48 hours (in the last). The new method sho rtened the manufacturing period of 17 days to 9 days. (2) The browning of the Katuo-bushi flakes was suppressed by the heat pump process. Th e color of Katsuo-bushi was clearer than that of the conventional one. There was no difference in the flavor of Katsuo-bushi dried by the he at pump process and that of the conventional one. (3) By heat pump dry er, Katsuo-bushi were more effectively and uniformly dehydrated. The b reakdown of the Katsuo-bushi flakes during the shaving process was red uced because the surface of the Katsuo-bushi was not excessively dried . The yield of the Katsuo-bushi flakes was improved by about 103% of t hat by the conventional method. It was unnecessary to take out the Kat suo-bushi from the smokehouse when it was smoked every one day and pil ed for 1 to 3 days for making the water content uniformly. Further mor e, the fuel cost was reduced by reduction of an So amounts of firewood by about 30%.