EFFECTS OF CONTINUOUS WAVE LASER RADIATION AGAINST PATHOGENIC BACTERIA ESCHERICHIA COLI O157: H7 IN IRANIAN PROBIOTIC DOOGH

Background and Aim:Food contamination draws a lot of attention as one of the major challenges in the food industry. Methods used for reducing these risks are heat, drying, freezing and additives. The non-thermal treatments that can be cited are (PEF) Pulsed Electric Field, (PLT) Pulsed Light and ultraviolet and infrared radiation.Methods:Strong optical radiation has been used as a protective technique to treat the contamination levels of food through the destruction of microorganisms in the wavelength of 200 to 1000 nm. The homogenized milk with 1.5% fat was pasteurized in 90°C. It was cooled down to 43°C. Then, Streptococcus thermophiles, Lactobacillus delbrueckii subsp bulgaricus, and 2% of salt were added. It was incubated with the starter solution in 42°C and the fermentation was continued until the pH reached over 4.6. Laser with constant wavelength produced by a diode laser with a wavelength of 437 nm and intensity of 50 w/cm2 was radiated to the Iranian probiotic Doogh samples (with Lactobacillus casei, E. coli and control).Results:The results of the study demonstrated that the survival of the pathogen bacteria during different days of storage had meaningful statistical differences (p<0.05). Laser treatment in different times had meaningful statistical differences in pathogen bacteria decrease comparing to the control group (p<0.05).Conclusion:Due to the effects of thermal treatment on the nutritional and organoleptic properties of dairy products such as milk therefore, this method can be used for decontamination and reduction of microbial load in milk.

Keywords:

E. coli , Iranian Doogh , Probiotic , Laser Radiation , organoleptic properties