REAL-TIME TEMPERATURE DISTRIBUTION IN A H OLDING TUBE OF A STEAM INJECTION TYPE DIRECT HEATING STERILIZER FOR LIQUID FOODS

The steam injection type direct heating sterilizing method is a typica l method among sterilizing operations for liquid foods, together with the plate type indirect heating method. In addition, sterilization is a vital operation for food production and a research on the certainty of this sterilizing method has been required. Despite those facts, how ever, the phenomena that steam injected at high speed into liquid food s abruptly mixes followed by condensation, and that heating to the ste rilizing temperature and holding for the required time are performed i n a holding tube, have been rarely studied. Accordingly, the sterilizi ng efficiency resulted from these phenomena can hardly be determined b eforehand. Therefore, a steam injection type sterilizing machine for e xperiment was assembled using a single nozzle which has been used typi cally. The details of uneven temperature distribution in the holding t ube were measured with multi-points and real-time measuring method as well as velocity variations. In this way, the negative effect of these factors on the sterilization was examined. Moreover, similar measurem ents were carried out on a practical machine, and reproducibility and variation of the sterilizing effect due to the machine size were inves tigated.