야채에 대한 미생물학적 안전성을 확보하기 위해서 염소수용액과 이산화염소 용액의 농도, 처리시간별로 일반미생물 및 E. coli O157:H7과 Salmonella Typhimurium에 대한 살균효과와 염소 잔류량의 변화를 살펴보았다. 염소수용액과 이산화염소 100ppm용액에 각각 1:10, 1:15, 1:20(w/v)의 비율로 양상추를 5, 10, 30, 60분간 침지 후 양상추 내 염소 또는 이산화염소 잔류량을 측정하였다. 또한 양상추를 염소 농도별(0, 50, 75, 100, 150, 200 ppm), 시간별(1, 5, 10분)로 반응시킨 후 일반미생물 및 인위적으로 접종한 E. coli O157:H7과 S. Typhimurium에 대한 살균효과를 측정하였다. 염소농도 100 ppm에서 1:10, 1:15, 1:20(w/v)의 비율로 양상추를 5분 처리한 결과 상추내의 잔류량은 각각 2.8, 2.4, 2.3ppm으로 나타났다. 반면 동일 농도에서 매회 새로운 양상추를 투입하여 5분간 반응시키는 과정을 5회 반복한 후 염소용액의 잔류량는 50%이상 감소가 되었고 10회 세척 후에는 70%이상의 염소농도가 감소되어지는 것으로 나타났다. 염소농도 100 ppm에서 5분간 처리한 후 양상추의 일반미생물이나 E. coli O157:H7, S. Typhimurium에 대해서는 물로 세척한 경우와 비교하여 1.2 log를 감소시켰으며, 10분간 처리한 경우에는 각각 1.1 log, 1.6 log, 1.5 log를 감소시켰다. 또한 염소농도 75 ppm에서의 5분간 처리는 0.5 log, 1.1 log, 0.9 log를 감소시켰다. 과채소류의 안전성을 확보하기 위해서는 염소 소독하는 것이 병원성미생물을 제어하는데 효과적임을 나타내었다.
Efficacy of aqueous chlorine (NaOCl) and chlorine dioxide (ClO2) for use as sanitizers was evaluated against indigenous bacterial microflora, and streptomycin-resisitant E. coli O157:H7, and streptomycin-resisitant Salmonella Typhimurium on iceburg lettuce inoculated by dip method. Aqueous chlorine and chlorine dioxide at 100 ppm reduced the aerobic mesophiles naturally present on iceberg lettuce by 0.6 and 1.7 log CFU/g for 10 min, respectively. Iceberg lettuce treated with aqueous chlorine dioxide for 10 min showed a reduction in natural flora that was at least 1.1 log CFU/g greater than that of aqueous chlorine treatment. Cut iceberg lettuce dip-inoculated with E. coli O157:H7 and Salmonella Typhimurium was treated with aqueous chlorine and chlorine dioxide for 1, 5, 10 min. Control sample also was included. This treatment was also effective in reducing levels of E. coli O157:H7 and Salmonella Typhimurium. Compared chlorine with chlorine dioxide for bactericidal activity, 100 ppm chlorine for 5 min demonstrated each 0.8 log10 reduction on indigenous bacterial microflora, E. coli O157:H7, and Salmonella Typhimurium. Chlorine dioxide at same condition showed 1.0, 0.8, and 1.2 log10 reduction on natural microflora, E. coli O157:H7, and Salmonella Typhimurium, respectively. However, neither treatment was able to completely inactivate or remove the microorganism from the surface of the iceberg lettuce. Compared to the antimicrobial activity, chlorine dioxide showed higher antimicrobial activity than chlorine on inoculated pathogens. For the residual concentrations of chlorine after treatment of the iceberg lettuce, iodometric method was used. The residual concentration in the washing solution was reduced 50% after 5 times washing at 1:10 w/v and 7 times washing at 1:20 w/v. Chlorine dioxide was appeared rapidly reduced the residual in the treated solution at 1:10 w/v ratio that reduced below 50% at only 3 times washing (1:10 w/v), while it was reduced slowly at 1:15 and 1:20 w/v. The finding of these studies therefore suggest that the use of chlorine dioxide as an antimicrobial rinse for vegetables will be an effective process in the control of E. coli O157:H7, Salmonella Typhimurium, and other background microflora.