Abstract Shelf-life is defined as the time a food product retains its desired sensory, chemical, and physical characteristics while also remaining safe for consumption. Bacteria associated with meat spoilage produce off-odors and flavors, tissue discoloration, gas, and slime. The objectives of this study were, 1) to determine the effect of refrigerated-display-case type on the shelf-life and microbial load of the natural flora found on beef steak and chicken breasts and, 2) to evaluate the effect of gravity coil conductive cooling vs. complete conductive cooling on the growth of Escherichia coli K12 artificially inoculated onto beef steak under abusive conditions. In Study 1, beef steak and chicken breasts were placed for 8 or 5 days, respectively, in a conduction cooling gravity assist service case, gravity coil service case with partial conduction coil base deck, gravity coil service case with serpentine assist, or blower coil service case with an additional fogging system. Mesophilic bacteria, Pseudomonas spp. and psychrotrophic bacterial counts on meat surfaces, and meat color, internal meat temperature, case temperature and case relative humidity were determined daily. In Study 2, two of the four types of display case the complete conductive cooling and gravity-coil conduction cooling systems were chosen to evaluate microbial growth on beef steak due to novel conductive cooling technologies. Temperature and weight loss, aerobic plate counts and viable E. coli colony-forming-units on the beef steaks were determined daily. In study 1, the warmest display ambient air temperature was found in the gravity coil service case with partial conduction coil base deck (PCC). The coldest tissue temperatures were observed for steaks and chicken breasts placed in the conduction cooling gravity assist service display case. The lowest RH also tended to occur in the PCC case. Overall, the type of retail display case had no effect on the growth of mesophilic and psychrotrophic bacteria or Pseudomonas on both steaks and chicken breasts. In study 2, the initial numbers of viable E. coli K12 on inoculated steaks were low and remained low through 7 days storage, regardless of display case. The novel conduction cooling gravity assist service display case used in this study has the greatest potential for extending shelf-life due to lower overall tissue temperatures and reduced water loss from meat products held in this case during high traffic and abusive retail conditions.

中文翻译：

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展示柜冷却技术对牛肉和鸡肉保质期的影响

摘要 保质期被定义为食品保持其所需的感官、化学和物理特性，同时还能安全食用的时间。与肉类腐败相关的细菌会产生异味和味道、组织变色、气体和粘液。本研究的目的是，1) 确定冷藏展示柜类型对牛排和鸡胸肉上天然菌群的保质期和微生物负荷的影响，2) 评估重力线圈的影响传导冷却与完全传导冷却对在滥用条件下人工接种到牛排上的大肠杆菌 K12 的生长的影响。在研究 1 中，牛排和鸡胸肉分别放置在传导冷却重力辅助服务箱中 8 或 5 天，带部分传导线圈底座的重力线圈维修箱、带蛇形辅助的重力线圈维修箱或带附加雾化系统的鼓风机线圈维修箱。嗜温细菌，假单胞菌属。和肉表面的嗜冷细菌计数，每天测定肉的颜色、肉的内部温度、箱温和箱相对湿度。在研究 2 中，四种类型的展示柜中的两种，即完全传导冷却和重力线圈传导冷却系统被选择来评估牛排上由于新型传导冷却技术而产生的微生物生长。每天测定牛排上的温度和重量损失、需氧平板计数和可行的大肠杆菌菌落形成单位。在研究 1 中，在带有部分传导线圈底板 (PCC) 的重力线圈服务箱中发现了最温暖的显示环境空气温度。对于放置在传导冷却重力辅助服务展示柜中的牛排和鸡胸肉，观察到最冷的组织温度。最低 RH 也往往出现在 PCC 情况下。总体而言，零售展示柜的类型对牛排和鸡胸肉上的嗜温和嗜冷细菌或假单胞菌的生长没有影响。在研究 2 中，接种牛排上的初始存活大肠杆菌 K12 数量很低，并且在 7 天的储存期间保持低水平，无论陈列柜如何。