Examination of microorganisms in plantation white sugar and their disinfection in syrup by ultraviolet radiation
1997
Sirivatana Chittrepol
Microorganisms were isolated from 37 plantation white sugar factories, however, yeast and fungi including pathogenic bacteria were not detected. Eighty four thermophilic bacteria were found in 27 factories Bacillus coagulans being the dominant species. This species is a major food spoilage causing bacteria, thus, B. coagulans was used for further studies of ultraviolet disinfection in syrup. The equipment was installed with a commercial 36 watt lamp that emits an output of about 12.5 watt ultraviolet radiation at 253.7 nm. The syrup concentrations of 40, 50, 60 and 64 deg Brix were innoculated with vegetative cells of bacteria 9.9*10*[3), 8.5*10*[4), 8.0*10*[5), 5.4*10*[6) cells/ml and spore of bacteria 3.69*10*[3), 8.6*10*[4) and 5.4*10*[5) spores/ml then radiated at the flow rate of 5, 7, 10, 12, 15, 17, 20, 22 and 25 liter/min which were equivalent to the residence time of 11.52, 8.23, 5.76, 4.80, 3.84, 3.38, 2.88, 2.62 and 2.30 minutes respectively. The results revealed that the most extent of disinfection was found in the lowest sugar concentration of 40 deg Brix even accompanied with high cell concentration of 5.4*10*[6) cells/ml and gave the inactivation rate (k) of 0.0025/sec. High sugar concentration with high viscosity resulted lower disinfection. Disinfection of vegetative cell required 5.01 to 9.90 minute per log with dose (D10) at 242.86 to 479.78 mW-sec/square cm while for the disinfection of spores twice the above values were needed.
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