RIKILT Wageningen University & Research, P.O. Box 230, 6700 AE Wageningen, The Netherlands.
Wageningen Plant Research, P.O. Box 16, 6700 AA Wageningen, The Netherlands.
Int J Food Microbiol. 2018 Mar 23;269:128-136. doi: 10.1016/j.ijfoodmicro.2018.01.013. Epub 2018 Jan 31.
Controlling water quality is critical in preventing cross-contamination during fresh produce washing. Process wash water (PWW) quality can be controlled by implementing chemical disinfection strategies. The aim of this study was to evaluate the pilot-scale efficacy of chlorine dioxide (ClO) during processing on the reduction of Escherichia coli in the PWW and on processed fresh-cut 'Lollo Rossa' lettuce. The objective was to have a residual target concentration of either 5 or 3 mg/L ClO in the washing tank (3.5 m) before and during 800 kg of lettuce processing (90 min). After 90 min., a nonpathogenic, non-Extended Spectrum Beta-Lactamase (ESBL) E. coli inoculum from an overnight culture broth (37 °C) was added to the tank resulting in an approximate final level of 10 CFU/mL. PWW and lettuce samples for microbiological and chemical analyses were taken before and after the input and supply halted. ClO concentrations quickly decreased after ClO input halted, yet a residual concentration of ≥2.5 mg/L and ≥2.1 mg/L ClO, respectively for 5 and 3 mg/L pilots, was present 12 min after the supply halted. No detectable levels of E. coli (limit of detection 5 log) were determined in the water within 1 min after E. coli was added to the ClO containing wash water. Results demonstrated that ClO use at the semi-commercial pilot scale was able to reduce the E. coli peak contamination in the PWW. After storage (5 days, 4 °C), background microbial communities (i.e., fluorescent Pseudomonads and total heterotrophic bacteria) grew out on lettuce. Overall, ClO decreased the potential for cross-contamination between batches compared to when no sanitizer was used. Chlorate levels of the lettuce sampled before entering the wash water ranged from 7.3-11.6 μg/kg. The chlorate levels of the lettuce sampled after being washed in the ClO containing wash water, as well as after rinsing and centrifugation, ranged from 22.8-60.4 μg/kg; chlorite levels ranged from 1.3-1.6 mg/kg, while perchlorate levels were below the limit of quantification (LOQ, <5 ng/g). In this study, we report the semi-commercial pilot-scale evaluation of ClO, for its ability to maintain the PWW quality and to prevent cross-contamination in the washing tank during fresh-cut lettuce processing. Furthermore, we provide quantitative values of ClO disinfection by-products chlorate and chlorite as well as of perchlorate from PWW and/or lettuce samples.
控制水质对于防止新鲜农产品清洗过程中的交叉污染至关重要。可以通过实施化学消毒策略来控制过程洗涤水（PWW）的质量。本研究的目的是评估二氧化氯（ClO）在处理过程中对 PWW 中大肠杆菌的减少效果，以及对加工后的新鲜切割“Lollo Rossa”生菜的效果。目标是在处理 800 公斤生菜（90 分钟）之前和期间，在洗涤槽中保持 5 或 3mg/L ClO 的残留目标浓度。90 分钟后，将来自过夜培养物（37°C）的非致病性、非扩展谱β-内酰胺酶（ESBL）大肠杆菌接种物添加到水箱中，导致最终水平约为 10 CFU/mL。在输入和供应停止前后，采集 PWW 和生菜样品进行微生物和化学分析。ClO 输入停止后，ClO 浓度迅速下降，但在供应停止后 12 分钟，分别为 5 和 3mg/L 试验的残留浓度≥2.5mg/L 和≥2.1mg/L ClO。在向含有 ClO 的洗涤水中添加大肠杆菌后 1 分钟内，水中未检测到大肠杆菌（检测限为 5 对数）。结果表明，ClO 在半商业规模的试点中能够降低 PWW 中大肠杆菌的峰值污染。在 4°C 下储存 5 天后，生菜上长出了背景微生物群落（即荧光假单胞菌和总异养细菌）。总体而言，与未使用消毒剂相比，ClO 降低了批次之间发生交叉污染的可能性。进入洗涤水之前采集的生菜中氯酸盐的水平范围为 7.3-11.6μg/kg。在含有 ClO 的洗涤水中洗涤后以及洗涤和离心后，从氯酸盐水平范围为 22.8-60.4μg/kg 中采集的生菜中的氯酸盐水平；亚氯酸盐水平范围为 1.3-1.6mg/kg，而过氯酸盐水平低于定量限（LOQ，<5ng/g）。在这项研究中，我们报告了 ClO 的半商业规模试点评估，以评估其维持 PWW 质量并防止新鲜切割生菜加工过程中洗涤罐中交叉污染的能力。此外，我们提供了来自 PWW 和/或生菜样品的 ClO 消毒副产物氯酸盐和亚氯酸盐以及过氯酸盐的定量值。
