Microbiological risk of pre-packed sweet basil and coriander leaves marketed in Belgium
Nowadays, herbs can be bought as convenient pre-packed cut leaves in retail stores, and as all leafy vegetables grown in open fields, the herbs may be susceptible to microbial contamination. Several screenings of herbs imported mainly from South East Asia resulted in contamination by enteric pathogens.
Scientists at Ghent University (Belgium) have investigated the prevalence of Salmonella spp., Shiga-toxin producing E. coli (STEC - with the main focus on serotype O157, O26, O103, O111, O145), generic E. coli and coliforms on pre-packed basil and coriander leaves both from Belgium (in production season from June to September) and sourced from Israel and Cyprus (year around). Furthermore, the relation between the presence of enteric pathogens on basil and/or coriander and generic E. coli or coliforms as indicator organisms was investigated.
In the period from February 2013 to January 2014, 592 samples (25 g) of fresh pre-packed basil (Ocimum basilicum) and coriander (Coriandrum sativum) leaves originating from Belgium, Israel and Cyprus were analyzed for microbiological risk.
Results showed that Salmonella was detected in 10 out of 592 samples (1.7%; 5 from basil and 5 from coriander), of which two samples were sourced from Israel and eight from Cyprus. The presence of STEC was suspected in 11 out of 592 samples (1.9%; 3 basil and 8 coriander), due to the detection of stx and eae genes, of which one sample originated from Belgium, four from Israel and six from Cyprus. No STEC was isolated by culture techniques, but in three samples a serotype (O26, O103 or O111) with its most likely associated eae-variant (β or θ) was detected by PCR.
Generic E. coli was enumerated in 108 out of 592 samples, whereby 55, 32 and 13 samples respectively between 10–100, 100–1000 and 1000–10,000 cfu/g and 8 samples exceeding 10,000 cfu/g. Coliforms were enumerated in all herb samples at variable levels ranging from 1.6 to 7.5 log cfu/g.
Further statistics indicate that the E. coli class (categorized by level) was significantly correlated with the presence of Salmonella or STEC, while coliform counts were significant correlated with Salmonella presence, but not with STEC. Generic E. coli class is a better indicator for the presence of enteric pathogens than coliforms on fresh herbs, but the relationship between E. coli and Salmonella or STEC was not strong enough to provide a threshold value for E. coli to assure food safety (i.e. no pathogens present).
Scientists conclude that fresh leafy herbs like basil and coriander sourced from different cultivation regions, may contain enteric pathogens and potentially pose a risk for human health.
The present case study for the fresh herbs trading companies can provide objective results and reveals some information on the quality and safety of the products which cannot be visually checked or necessarily deduced from customer complaints and thus contributes to the verification of supplier selection.
Moreover, it may put pressure on the actual production units at the farmers in the sourcing countries to evaluate and improve their own food safety management system. Data collected by the trading companies can be used to build a track record of product control and enable some trend watching over time to verify its own GMP and HACCP plan in ensuring delivery of safe food products to retail and consumers at the end.
The research received funding from the EU FP7 Veg-i-Trade Grant agreement N. 244994. The results of the study are available online from 21th May 2015 at http://www.sciencedirect.com/science/article/pii/S0168160515300076.
Source: Stefanie Delbeke, Siele Ceuppens, Liesbeth Jacxsens, Mieke Uyttendaele, 'Microbiological analysis of pre-packed sweet basil (Ocimum basilicum) and coriander (Coriandrumsativum) leaves for the presence of Salmonella spp. and Shiga toxin-producing E. coli', 2015, International Journal of Food Microbiology, Vol. 208, pages 11–18.
Contacts:
Mieke Uyttendaele
Laboratory of Food Microbiology and Food Preservation, Department of Food Safety and Food Quality
Faculty of Bioscience Engineering, Ghent University
Coupure Links 653, B-9000 Ghent Belgium
Email: mieke.uyttendaele@ugent.be (M. Uyttendaele)