壳内山核桃通常是从树上掉到地面后收获的,提出了一种来自土壤接触的食源性病原体污染的潜在途径。壳内山核桃通常在上壳之前进行各种加工或洗涤步骤。这项研究确定了在直接和土壤接种的壳内山核桃上使用抗微生物洗涤液处理后产生志贺毒素的大肠杆菌(STEC)的减少,并评估了处理后用过的山核桃洗涤液的交叉污染潜力。将山核桃直接用STEC鸡尾酒(O157:H7,O157:NM,O121、O26)。通过在山核桃上喷洒STEC混合物来实现直接接种。对于土壤接种山核桃,用STEC鸡尾酒喷洒高压灭菌的土壤,均质化2分钟,用来覆盖壳内山核桃。接种的山核桃在2%乳酸(LA)的处理中洗涤,1000ppm游离氯(次氯酸钠;NaClO),热水(HW;85±2°C),或环境水(C[对照];18±2°C)持续2、5和10分钟,并稀释以计数STEC种群。治疗后,将100mL的用过的洗涤液通过0.45μm的膜进行真空过滤并铺在选择性琼脂上。无论处理时间如何,HW均显着减少了有土壤和没有土壤的山核桃的STEC种群(p<0.05),NaClO比直接接种山核桃的环境对照洗涤减少了STEC种群,但从环境水中减少STEC(C)之间没有显著差异,洛杉矶,和NaClO处理对土壤接种山核桃的影响(p>0.05)。与抗微生物洗液相比,从环境水洗液中列举更大的STEC群体(p<0.05)。HW,洛杉矶,和NaClO处理有效地保持洗涤水的质量,STEC水平通常等于或低于检测极限(<1CFU/100mL),而HW在有和没有土壤涂层的情况下最有效地减少了壳内山核桃的STEC(>5-logCFU/mL减少)。
In-shell pecans are typically harvested after falling from trees to the ground, presenting a potential route of contamination of foodborne pathogens from soil contact. In-shell pecans are often subjected to various processing or washing steps prior to being shelled. This study determined Shiga toxin-producing Escherichia coli (STEC) reductions after treatment with antimicrobial washes on direct and soil-inoculated in-shell pecans and evaluated the cross-contamination potential of the spent pecan washes after treatment. Pecans were directly and soil-inoculated with an STEC cocktail (O157:H7, O157:NM, O121, O26). Direct inoculation was achieved by spraying the STEC cocktail on the pecans. For soil-inoculation pecans, autoclaved soil was sprayed with the STEC cocktail, homogenized for 2 min, and used to coat in-shell pecans. Inoculated pecans were washed in treatments of 2% lactic acid (LA), 1,000 ppm free chlorine (sodium hypochlorite; NaClO), hot water (HW; 85 ± 2 °C), or ambient water (C [control]; 18 ± 2 °C) for 2, 5, and 10 min and diluted to enumerate STEC populations. After treatments, 100 mL of the spent wash was vacuum filtered through a 0.45-µm membrane and plated on selective agar. HW significantly reduced STEC populations from pecans with and without soil regardless of treatment time (p < 0.05), NaClO reduced STEC populations more than the ambient control wash on directly inoculated pecans, but there were no significant differences between STEC reductions from ambient water (C), LA, and NaClO treatments on soil-inoculated pecans (p > 0.05). Larger STEC populations were enumerated from ambient water wash compared to the antimicrobial washes (p < 0.05). The HW, LA, and NaClO treatments were effective at maintaining the quality of the wash water, with STEC levels being generally at or below the detection limit (<1 CFU/100 mL), while HW was the most effective at reducing STEC from in-shell pecans with and without a soil coating (>5-log CFU/mL reductions).