The Use of the RapidChek Listeria NextDay™ Test System to Detect Low Levels of Listeria Species in Brine Samples

Introduction: Different types of brine solutions are used to improve both flavor and the moisture content of different food products. These solutions are also used for food preservation, where they are often used by Ready-to-Eat meat producers to cure meat. The brine solutions are tested to make sure they are free of food pathogens.

Purpose:  The aim of the study is to evaluate the performance of the RapidChek Listeria NextDay test system for the detection of low levels of various Listeria spp. in brine samples.

Methods:  Two types of brine solutions were tested with the Listeria test method, chlorine based and citric acid brine. Hot dogs were cured in both brine solutions for 18 h at 4°C. Each brine solution was spiked with either L. monocytogenes ATCC 19115 (chlorine-based) or L. innocua ATCC 33090 (citric acid brine solution). Thirty brine samples, 20 low-level and 5 high-level spiked samples, and 5 non-spiked samples, of each variety were analyzed by the test method. Brine samples (50 ml) were enriched in 450 ml of the Listeria media and incubated at 30°C for 27 - 48 h. All samples were evaluated with Listeria test strips, and streaked to MOX plates for confirmation.

Results: The Listeria test method detected twenty out of twenty inoculated samples from both types of brine samples. There was no evidence of a matrix or a pH effect on the 27 - 48 h test method.  

Significance: The Listeria test system detected low levels of Listeria spp. in brine samples within the given timeframe of 27 - 48 h with no matrix effect evident on the test. This should enable food producers to quickly and efficiently identify Listeria spp. in brine samples.