PDF(Pubmed)
Abstract：
This project was undertaken to determine the kinetic parameters of thermal inactivation of Listeria monocytogenes on pecans, macadamia nuts, and sunflower seeds subjected to heat treatments simulating industry processes. Five strains were grown in nonselective medium, mixed, and resuspended before inoculating macadamia nuts, pecans, and sunflower seeds (6 to 9 Log CFU/g). Redried inoculated pecans and macadamia nuts were heated in an oven at a temperature range of 90 to 140°C. Unshelled sunflower seeds were heated in sunflower seed oil. The thermal inactivation was determined by measuring viable cell counts using standard microbiological methods. Average count data were fit to the log-linear model, and thermal-death kinetics were calculated. On pecans, the viable Listeria counts were reduced by 3 and 3.5 Log CFU/g after 40 min at 110°C and 8 min at 140°C, respectively. On macadamia nuts, the L. monocytogenes population was reduced by 5 Log CFU/g after 20 min at 120°C. Unshelled sunflower seeds were subjected to heat treatment via a hot-oil bath. On sunflower seeds, >7 Log CFU/g reductions were observed after 15 min at 120°C. The thermal resistance (D value) for inactivation on pecans at 140°C was 3.1 min and on macadamia nuts at 120°C was 4.4 min. The inactivation of L. monocytogenes was influenced by the kind of nut or seed. These results suggest that L. monocytogenes has a relatively high thermal tolerance. The findings from this study will contribute to the assessment of the effectiveness of heat treatment for control of this pathogen on nuts and seeds. IMPORTANCE Listeria monocytogenes is a major concern for the food industry in ready-to-eat (RTE) foods. In recent years, large-scale recalls have occurred with contaminated sunflower seeds and macadamia nuts that triggered product withdrawals. These events stress the importance of understanding Listeria\'s ability to survive heat treatments in these low-water activity foods. Nuts and seeds are subjected to a variety of thermal treatments typically referred as roasting. To date, no listeriosis outbreak has been linked to nuts and seeds, but the recent recognition that this pathogen can be detected in commercial products stresses the need for research on thermal treatments. The characterization of heat inactivation kinetics at temperatures typically used during roasting processes will be very beneficial for validation studies. This manuscript reports inactivation rates of L. monocytogenes strains inoculated onto macadamia nuts, sunflower seeds, and pecan halves subjected to temperatures between 90 and 140°C.
摘要：
该项目旨在确定山核桃上单核细胞增生李斯特菌热灭活的动力学参数，澳洲坚果,和葵花籽经过模拟工业过程的热处理。五个菌株在非选择性培养基中生长，混合,在接种澳洲坚果之前重新悬浮，山核桃,和葵花籽(6至9LogCFU/g)。将再干燥的接种山核桃和澳洲坚果在90至140°C的温度范围内的烘箱中加热。将无壳葵花籽在葵花籽油中加热。通过使用标准微生物学方法测量活细胞计数来确定热失活。平均计数数据拟合对数线性模型，并计算了热死亡动力学。在山核桃上，在110°C下40分钟和140°C下8分钟后，活李斯特菌计数减少了3和3.5LogCFU/g，分别。在澳洲坚果上，在120°C下20分钟后，单核细胞增生李斯特菌种群减少了5LogCFU/g。通过热油浴对无壳葵花籽进行热处理。在葵花籽上，在120°C下15分钟后观察到>7LogCFU/g减少。山核桃在140°C下失活的热阻（D值）为3.1分钟，澳洲坚果在120°C下失活的热阻（D值）为4.4分钟。单增李斯特菌的失活受坚果或种子种类的影响。这些结果表明单核细胞增生李斯特菌具有相对较高的耐热性。这项研究的结果将有助于评估热处理对控制坚果和种子上这种病原体的有效性。重要性单核细胞增生李斯特菌是即食（RTE）食品中食品工业的主要关注点。近年来,受污染的葵花籽和澳洲坚果发生了大规模召回，导致产品撤回。这些事件强调了了解李斯特菌在这些低水分活度食物中经受热处理的能力的重要性。坚果和种子经受通常称为烘烤的各种热处理。迄今为止,没有李斯特菌病的爆发与坚果和种子有关，但是最近认识到这种病原体可以在商业产品中检测到，这强调了对热处理研究的需要。在焙烧过程中通常使用的温度下的热失活动力学的表征对于验证研究将是非常有益的。该手稿报告了接种到澳洲坚果上的单核细胞增生李斯特菌菌株的失活率，葵花籽,和山核桃一半经受90至140°C之间的温度。
