Identification of sampling points suitable for the detection of microbial contamination in fresh-cut processing lines

Traditionally, microbiological testing for food safety assurance in fresh-cut industries relied on end product to evaluate compliance with microbial standards. Replacement of end-product testing by a preventive system is being recommended by competent authorities for the production of safe food. In the fresh-cut processing industry, there is still a need for the identification of suitable sampling points which facilitate the detection of a contaminated lot. The goal of this study was to gain insight on the microbial contamination throughout the processing operations involved in fresh-cut leafy green production to identify sampling points and their relation with the microbial contamination of end products. Three Spanish fresh-cut processing companies of baby spinach were visited three times. During the processing schedule, samples from product (raw material and end product), water (pre-wash water, wash water, rinse water and centrifuge water) and surfaces (workers' plastic gloves and equipment surfaces) were taken at three time intervals: at the beginning, in the middle and at the end of the working day. Presence of pathogenic microorganisms such as Listeria monocytogenes, Salmonella spp. and pathogenic Escherichia coli as well as the levels of generic E. coli and coliforms were analysed in all the samples. Enterococcus spp. and Enterobacteriaceae were assessed in water and surface samples, respectively. L. monocytogenes and pathogenic E. coli were not found in any of the samples tested. Salmonella spp. were isolated from two centrifuge effluent water samples. Generic E. coli was only found in centrifuge effluent water samples. To evaluate if the centrifuge water was the most suitable sampling point to detect microbial contamination of the end product, additional lab scale tests were carried out. Baby spinach inoculated with generic E. coli confirmed the potential of centrifuge water as a control point for the detection of microbial contamination. Routine monitoring of this centrifuge water for pathogens and E. coli as the hygiene indicator appears to be a promising tool for the evaluation of product safety. (C) 2015 Elsevier Ltd. All rights reserved.