Development of Liquid Food Pasteurization Equipment Using Far-infrared Radiation Heating

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1 , Vol. 9, No. 4, pp , Dec , Development of Liquid Food Pasteurization Equipment Using Far-infrared Radiation Heating Noboru SAKAI 1,, Yuko OSHIMA 1, Youko YAMANAKA 1, Mika FUKUOKA 1, and Sumitoshi IMAMICHI 2 1 Tokyo University of Marine Science and Technology, Department of Food Science and Technology, Konan 4-5-7, Minato-ku, Tokyo , Japan 2 Food Sanitary Engineering Association, Konan 4-5-7, Minato-ku, Tokyo , Japan Since heating by infrared radiation can heat directly liquid food, the surface of the food becomes a high temperature, and stainless steel plate which has contacted the food would be maintained a low temperature. As a result it seems to be able to reduce the adhesion of the fouling in the stainless steel plate, which was an important problem in the conventional heat exchanger. In this study we developed the continuous heating equipment using far-infrared radiation, and verified that this system is practically available to pasteurization. In this developed equipment, the liquid food flows down as a thin liquid film, because the penetration of radiation energy to the water is low and the heating of the liquid inside is difficult. Using this equipment, increased temperature of the sample was measured by changing the heating conditions such as supplied electricity to the heater and the liquid flow conditions such as flow rate. The result showed that the increased temperature rises, as liquid film thickness thins, and that the sample temperature could be heated to about 80. Using lactic acid bacteria and yeast, the pasteurization experiments were performed. As the result, the death of the bacterium and the yeast could be confirmed, and the effectiveness of this equipment could be verified. Keywords: Far-infrared radiation, Liquid food, Continuous pasteurization, Thin liquid film Fax: , sakai@kaiyodai.ac.jp 1

2 272 [1] [2] [3] [4] [5] Bacillus subtilis B. cereus Clostridium sporogenes 24 [6,7] Sawai [8] Escherichia coli Staphylococcus aureus Sawai [9] Fig mm 855 mm 30 mm 120 mm 600 mm Fig. 1 Experimental apparatus. Inlet of sample Tank Heating line Far-infrared radiation heater Angle regulator of heating line mm 2.2 Tetragenococcus halophilus T Zygosaccharomyces rouxii Z Candida versatilis Lactobatillus plantarum T Z 2 T Z IAM IAM No. 1676T T IAM No Z

3 K 1100 ml/min Fig. 2 1 kw kw mm 0.28 m/s 1.8 s kw Fig cm 650 Fig. 2 Fig. 2 Relationship between supplied electricity and increased temperature of liquid. Distance between heater and liquid ( 50 mm 90 mm 130 mm). Initial liquid temperature: 22, Liquid flow rate: 1100 ml/min, Angle of the heating unit; 15. Fig. 3 Relationship between flow rate of liquid and its increased temperature. Angle of the heating unit ( ). Initial liquid temperature: 18, Supplied electricity: 3.2 kw.

4 Fig Fig. 4 0 m [10] 3 G 3 1 g cos(90 ) Pa s G m 3 /s kg/m 3 g m/s Fig. 5 Fig. 5 Fig. 3 Fig. 6 Fig. 4 Relationship between flow rate of liquid and its thickness. Angle of the heating unit ( ). Fig. 5 Relationship between flow rate of liquid and its residence time in heating unit. Angle of the heating unit ( ).

5 CFU/ml Z CFU/ml 120 mm mm Fig. 6 Relationship between residence time in heating unit and increased temperature of liquid. Thickness of liquid layer ( mm mm mm mm mm) T Z ml/min mm 30 s 120 mm 4 6 T Z Fig. 7 T Fig. 8 Z T Fig. 7 Viable count and temperature change during heating process in the case of Tetragenococcus halophilus. : Viable count, : Temperature Angle of the heating unit: 1, Heater temperature: 640, Sanple flow rate: 240 ml/min. Fig. 8 Viable count and temperature change during heating process in the case of Zygosaccharomyces rouxii. : Viable count, : Temperature Angle of the heating unit: 1, Heater temperature: 640, Sanple flow rate: 240 ml/min.

6 276 I W/ m 2 I I 0 exp( ax) 2) I 0 W/m 2 a 1/m x m 2.5 m 25 m /m [11] m T Z [1] N. Sakai, W. Mao: Infrared Heating in Thermal Food Processing Edited by D. W. Sun, CRC Press, pp (2006). [2] JIRAReport, 11(6), 1-8 (2000). [3] Bacillus subtilis Aspergillus niger 64(6), (2002). [4].M. 65(2) (2003). [5] (1989). [6] 17(3) (1991). [7] A. Hashimoto, H. Igarashi, M. Shimizu: Effect of Far- Infrared Irradiation of Pasteurization of Bacterial Suspended in Liquid Medium below Lethal Temperature, J. Chem. Eng. Japan, 25, (1992). [8] J. Sawai, K. Sagara, H. Igarashi, A. Hashimoto, T. Kokugan, M. Shimizu: Injury of Escherichia coli in Physiological Phosphate-Buffered Saline Induced by Far-Infrared Irradiation, J. Chem. Eng. Japan, 28(3), , (1995). [9] J. Sawai M. Fujisawa T. Kokugan M. Shimizu H. Igarashi A. Hashimoto H. Kojima: Pasteurization of Bacterial Spores in Liquid Medium by Far-Infrared Irradiation, J. Chem. Eng. Japan, 30, (1997). [10] p.41. [11] 2005 p.20.

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