Inactivation of Clostridium sporogenes in Clover Honey by Pulsed UV-light Treatment

Abstract

Honey has naturally low levels of microorganisms due to its low water content and high concentration of sugars. However, it has been known to contain the spores of yeast, mold, and bacteria resulting in spoilage of the product. Clostridium botulinum, is associated with honey and is known to cause a disease called botulism. Heat pasteurization, pressure treatment, and irradiation have all been studied as methods of killing the spores, but have been found lacking. Pulsed Ultraviolet (UV)-Light Sterilization is a novel processing method used for microbial inactivation. For the experimentation, spores of C. sporogenes were prepared from cooked meat medium cultures grown in an anaerobic jar for 7 days at 37oC. Honey was inoculated with 0.1 ml of C. sporogenes spore suspension per 20 g honey, and mixed well. Pulsed light was applied to the inoculated honey using the SteriPulse XL® 3000 Pulsed Light Sterilization System provided by NASA Commercial Food Technology Center. The following parameters were analyzed: 1) the number of pulses 2) the distance between the food product and lamp 3) depth of honey. Treated and untreated (control) honey was analyzed for C. sporogenes. Increasing the number of pulses (or treatment time) also appears to be effective at inactivating the spores. When the depth of honey was decreased from 8 to 2 mm at the 20 cm shelf height, the spore kill increased for the same number of pulses. Even though varying these three parameters enhanced the inactivation of C. sporogenes up to 90%, it failed to inactivate the spores completely due to insufficient penetration of UV-light into honey.