Institute of Environmental Science and Research, P.O. Box 29181, Christchurch 8540, New Zealand (ORCID: https://orcid.org/0000-0002-5939-7255 [J.M.K.]).
New Zealand Food Safety, Ministry for Primary Industries, P.O. Box 2526, Wellington 6140, New Zealand.
J Food Prot. 2019 Dec;82(12):2161-2168. doi: 10.4315/0362-028X.JFP-19-251.
The influence of egg storage temperature on contamination of eggs is a key consideration in determining storage and shelf life recommendations for eggs. In this study, experiments assessed the survival of isolates on and in eggs at storage temperatures (15 and 22°C) currently used in New Zealand. Eggshell surfaces were inoculated with a cocktail of 10 isolates comprising five serotypes, at a concentration of ∼10 CFU per egg (for determining shell surface survival) or ∼10 CFU per egg (for determining internalization). Additionally, a subset of eggs was artificially contaminated with sterile chicken feces prior to inoculation. Inoculated eggs were incubated at 15 and 22°C. At 0, 21, and 35 days of incubation, eggshells were enumerated for and egg contents were tested for presence or absence (yolk) or most probable number (albumen). Higher levels of were recovered from eggshells following incubation at 15°C (31% relative humidity [RH]) compared with 22°C (45% RH) after both 21 and 35 days of incubation. Recoverable numbers of from visibly clean eggshell surfaces declined over time at both storage temperatures and were at, or below, the limit of detection from eggs stored at 22°C and 45% RH for 35 days. A substantially higher concentration of viable was recovered from eggshells that were experimentally contaminated with chicken feces compared with those without, particularly from eggs stored at 15°C and 31% RH for 35 days (2.38 log higher CFU from eggs containing feces). No was detected in egg contents (albumen or yolk) at any incubation temperature or time point, regardless of the presence of feces. Findings emphasize the importance of current regulations that require eggs sold at retail to be visibly clean and will inform risk management decisions regarding egg storage times and temperatures with respect to control in and on New Zealand eggs at retail.
鸡蛋储存温度对鸡蛋污染的影响是确定鸡蛋储存和货架期建议的关键因素。在这项研究中，实验评估了在新西兰目前使用的储存温度（15°C 和 22°C）下，细菌在鸡蛋内外的存活情况。蛋壳表面用包含五个血清型的 10 个分离株混合物进行接种，每个鸡蛋的浓度约为 10 CFU（用于确定蛋壳表面存活情况）或每个鸡蛋的浓度约为 10 CFU（用于确定内化情况）。此外，一部分鸡蛋在接种前用无菌鸡粪进行人工污染。接种后的鸡蛋在 15°C 和 22°C 下孵育。在孵育 0、21 和 35 天时，对蛋壳进行计数，并对鸡蛋内容物进行检测，以确定 是否存在（蛋黄）或最可能数量（蛋清）。在孵育 21 和 35 天后，在 15°C（相对湿度 31%）下孵育的鸡蛋壳中回收的 数量明显高于在 22°C（相对湿度 45%）下的回收数量。在两种储存温度下，从可见清洁蛋壳表面回收的可回收 数量随着时间的推移而下降，并且在 22°C 和 45% RH 下储存 35 天后， 的数量达到或低于检测限。与未污染的鸡蛋相比，用鸡粪实验污染的蛋壳中回收的活 数量要高得多，尤其是在 35 天孵育时在 15°C 和 31% RH 下储存的鸡蛋（来自含有粪便的鸡蛋的 CFU 高 2.38 个对数级）。在任何孵育温度或时间点，无论是否存在粪便，都未在鸡蛋内容物（蛋清或蛋黄）中检测到 。这些发现强调了现行法规的重要性，这些法规要求零售销售的鸡蛋必须肉眼清洁，并将为新西兰零售鸡蛋中 的控制提供有关鸡蛋储存时间和温度的风险管理决策信息。
