Indirect impedance has been used for the detection and enumeration of bacteria, however there is limited data regarding the ability of the method to measure growth and inhibition of microorganisms in food in response to preservatives. The aim of this study was to evaluate the suitability of the technique to determine maximum growth rates of Listeria innocua (used as a surrogate for Listeria monocytogenes) in complex food matrices to which multiple preservative factors had been applied and assess the suitability of the data for use in predictive microbiology. Growth of L. innocua in laboratory medium (BHI broth) and two food matrices (zucchini purée and béarnaise sauce) under varying conditions of pH (5 & 5.3), water activity (0.93, 0.96 & 0.98) and acetic and propionic acid concentration (0, 1 & 2 mM) was monitored by the conductimetric Rapid Automated Bacterial Impedance Technology (R.A.B.I.T) system by means of CO2 emission for up to 120 h. Growth rates of L. innocua were determined for several conditions across the three test matrices and a good correlation between detection times and initial inoculum level was observed in most cases (R2 ≥ 0.82). However, growth of L. innocua was not detected in a large number of conditions and comparison of growth rates determined by indirect impedance to those determined by plate counts indicated that in general, the R.A.B.I.T. system under-estimated growth. This study demonstrates that there are limitations associated with the technology, and as a result the system may be unsuitable for measuring microbial growth rates in complex food matrices under the environmental conditions tested and within the time duration of the study.

中文翻译：

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预测和阻抗确定的复杂食品基质中无毒李斯特菌生长的比较。

间接阻抗已用于细菌的检测和计数，但是关于该方法测量响应防腐剂的食物中微生物的生长和抑制的能力的数据有限。这项研究的目的是评估该技术的适用性，以确定在应用了多种防腐剂的复杂食品基质中无病李斯特菌（用作单核细胞增生李斯特菌的替代品）的最大生长速率，并评估该数据的适用性。用于预测微生物学。在pH（5＆5.3），水分活度（0.93、0.96＆0.98）和乙酸和丙酸浓度（ 0、1＆电导率快速自动细菌阻抗技术（RABIT）系统通过CO2排放监测了2 mM）长达120 h。在三个测试矩阵中的几种条件下确定了无毒李斯特菌的生长速率，并且在大多数情况下，观察到检测时间与初始接种量之间具有良好的相关性（R2≥0.82）。但是，在许多情况下均未检测到无毒李斯特菌的生长，并且通过间接阻抗确定的生长速率与通过平板计数确定的生长速率的比较表明，总体而言，RABIT系统低估了生长。这项研究表明，这项技术存在一些局限性，