Department Food Science and Technology, University of Nebraska-Lincoln, NE 68588, USA; The Food Processing Center, University of Nebraska-Lincoln, NE 68588, USA.
Department Food Science and Technology, University of Nebraska-Lincoln, NE 68588, USA; Department of Agronomy and Horticulture, University of Nebraska-Lincoln, NE 68583, USA.
Int J Food Microbiol. 2020 Jan 16;313:108381. doi: 10.1016/j.ijfoodmicro.2019.108381. Epub 2019 Oct 22.
As a raw agricultural commodity, wheat is exposed to microbial contamination; therefore, enteric pathogens may be among its microbiota creating a food safety risk in milled products. This research evaluates (1) the effectiveness of organic acids dissolved in saline solutions to reduce the counts of pathogenic microorganisms in soft and hard wheat, and also investigates the effect of seasonal temperature on (2) survivability of pathogens in wheat kernels and on (3) pathogen inactivation during tempering with saline organic acid solutions. Wheat samples were inoculated with cocktails of either 5 serovars of Salmonella enterica, 5 E. coli O157:H7 or 6 non-O157 Shiga toxin-producing E. coli (STEC) strains to achieve a concentration of 7 log CFU/g. Inoculated samples were allowed to stand for 7-days at temperatures (2.0, 10.8, 24.2, 32 °C) corresponding to those experienced during winter, spring/fall, and summer (average and maximum) in the main wheat growing regions in the state of Nebraska, USA. Besides water, solutions containing acid (acetic or lactic 2.5% or 5.0% v/v) and NaCl (26% w/v) were used for tempering the wheat to 15.0% (soft) and 15.5% (hard) moisture at the different seasonal temperatures. The survival of pathogenic microorganisms throughout the resting period, and before and after tempering was analyzed by plating samples on injury-recovery media. The survival rate of pathogenic microorganisms on wheat kernels was higher at temperatures experienced during the winter (2.0 °C) and spring/fall (10.8 °C) months. Regardless of tempering temperature, the initial pathogen load was reduced significantly by all solutions when compared to the control tempered with water (P ≤ .05). The combination of lactic acid (5.0%) and NaCl was the most effective treatment against Salmonella enterica, E. coli O157:H7 and non-O157 STEC, with average reduction values of 1.8, 1.8 and 1.6 log CFU/g for soft wheat and 2.6, 2.4 and 2.4 log CFU/g for hard wheat, respectively. Implementation of organic acids and NaCl in tempering water may have the potential to reduce the risk of pathogen contamination in milled products.
作为一种原始农产品，小麦容易受到微生物污染；因此，肠病原体可能存在于其微生物群中，从而给加工产品带来食品安全风险。本研究评估了（1）溶解在盐溶液中的有机酸降低软质和硬质小麦中致病性微生物数量的有效性，还调查了季节性温度对（2）小麦籽粒中病原体的存活能力和（3）用盐有机酸溶液调温时病原体失活的影响。将沙门氏菌属 5 个血清型、大肠杆菌 O157:H7 5 个或非 O157 产志贺毒素大肠杆菌（STEC）6 个菌株的混合物接种到小麦样品中，以实现约 7 log CFU/g 的浓度。将接种的样品在 2.0、10.8、24.2 和 32°C（对应于美国内布拉斯加州主要小麦种植区冬季、春季/秋季和夏季的平均和最高温度）的温度下放置 7 天。除了水之外，还使用含有酸（乙酸或乳酸 2.5%或 5.0%v/v）和 NaCl（~26%w/v）的溶液将小麦调至 15.0%（软质）和 15.5%（硬质）水分，在不同的季节性温度下。通过在损伤恢复培养基上平板分析整个休眠期以及调温前后样品中致病性微生物的存活情况。在冬季（2.0°C）和春季/秋季（10.8°C）月份经历的温度下，致病性微生物在小麦籽粒上的存活率更高。无论调温温度如何，与用温水调温的对照相比，所有溶液都显著降低了初始病原体负荷（P≤.05）。与水相比，乳酸（5.0%）和 NaCl 的组合对肠炎沙门氏菌、大肠杆菌 O157:H7 和非 O157 STEC 最有效，软质小麦的平均减少值分别为 1.8、1.8 和 1.6 log CFU/g，硬质小麦的分别为 2.6、2.4 和 2.4 log CFU/g。在调温水时添加有机酸和 NaCl 可能有助于降低加工产品中病原体污染的风险。
