Purpose: The purpose of this study was to evaluate the efficacy of compositing frozen vegetables using multiple detection methods for Listeria monocytogenes at low and medium inoculation levels.
Methods: A four-strain Listeria monocytogenes cocktail was used to spike 25 g, 125 g and 375 g samples of frozen vegetables at low and medium levels. Samples were enriched for each test method with volumes of pre-enrichment modified to accommodate the 125 g and 375 g samples sizes. Data were analyzed using the chi squared test to determine statistical significance.
Results: At the medium inoculation level, Listeria monocytogenes was detected by all methods in all 25 g, 125 g and 375 g samples. When considering all vegetables and methods using the low inoculation level, the ability to detect Listeria monocytogenes in the 375 g samples was significantly lower than the 25 g samples.
Significance: This study provides data for evaluating the use of sample compositing of frozen vegetables using multiple methods of detection for Listeria monocytogenes.