Abstract

To develop a large scale countercurrent single pass heat exchanger for continuous transportation and sterilization of soybean paste, microflora and color value of sterilized soybean paste were examined at various sterile condition. Aerobes, anaerobes, molds, yeasts and lactic acid bacteria were 5.1 x 107 CFU/g, 7.1 x 107 CFU/g, 2.6 x 105 CFU/g, 4.3 x 106 CFU/g, 1.3 x 107 CFU/g, respectively in raw soybean paste. In gold band ampoule test, aerobes and anaerobes of soybean paste were viable up to 90$^{\circ}C$, but become unviable at 100$^{\circ}C$. Molds decreased rapidly and yeasts decreased slowly from 70$^{\circ}C$. Lactic acid bacteria were unviable at 60$^{\circ}C$ within 10 min. In color test, Hunter L, a, and b values of soybean paste were 50.2, +5.6, and +17.8, respectively. After heating in polyethylene film bag at 80$^{\circ}C$, Hunter values were not so much changed and become 50.2, +4.7, and +19.7, respectively. The micorflora and color of soybean paste sterilized in a large scale heat exchanger system resulted in very similar to those of gold band ampoule and polyethylene film bag by effective heat transfer.

Keywords

• soybean paste;
• heat exchanger;
• sterilization