Analysis of an Ordinary Process and Development of a New Continuous Smoking Process used for the Processing of Dried Bonito (Katsuo-bushi)

Abstract

The effects of various smoking conditions, especially temperature, relative humidity and smoke density on the quality of Katuo-bushi were investigated. The smoke absorption rate by bonito has been found to increase with the smoke density and to decrease with the smoke velocity. There was no clear correlation between smoke house temperature and relative humidity on smoke absorption of bonito. In the new method of continuous smoking, the cut and boiled bonito meat were continuously dried to harden after the conventional smoking of 2 times repetition. The conditions for the new drying process were 40°C for 2 hours as the first and 50°C for 2-5 hours as the second step. Subsequently cooled until 30°C for 5-7 hours under relative humidity of 80% at 30°C. The amounts of smoke particles (<0.3μm) was about 3-4× 108 per 100ml in smoke house gasses. Air flow rate was 0.2-0.5m/s. This smoking programs were repeated 24 times. The manufacturing term was reduced to one-half by continuous smoking process compared with the conventional smoking process. It was not necessary to take out the Katsuo-bushi from a smokehouse, resulting in the reduction of manual labour. Katsuo-bushi were more effectively and uniformly dehydrated using the continuous smok-ing process. The smoke absorption was sufficiently achieved by this process.