In recent years, foodborne viruses, especially human noroviruses (NoV) and hepatitis A virus (HAV), have been increasingly reported as the causes of
foodborne disease outbreaks. Soft red fruits, especially raspberries, have a high incidence among the types of food concerned. Due to low infectious doses and low concentrations of enteric viruses in food samples, it is necessary to have an efficient and rapid detection method to implement prevention measures. A standard method for virus detection and quantification in food, including raspberries (XP CEN ISO/TS 15216-1 and -2, 2013) is currently available. This method proposes a consensus detection approach by RT-real time PCR (RT-qPCR) but also a virus extraction procedure based on the elution-concentration principle. In this study, an alternative method of extraction in which RNAs are directly extracted from food matrices (based on direct
RNA extraction) has been optimized. First, each step was improved to make it a highly rapid, specific and simple method. Second, the standard virus concentration method was compared with the optimized direct
RNA extraction one. Human enteric viral surrogates, Murine Norovirus (MNV) and F-specific RNA bacteriophage GA, were selected according to their adhesion properties and resistance to pH close to our main targets (NoV and HAV). Raspberries were artificially contaminated using two different techniques (immersion and
spotting) in order to define a recovery rate and the amounts of virus recovered. Results showed that the direct
RNA extraction method revealed significantly higher viral extraction efficiency (46.2%) than the elution-concentration method (20.3%), with similar proportions of inhibitors for both. In the same way with inoculation by
spotting, the best recovery rate of GA phage (39.7% against 0.7%) and MNV (42.8% against 0.5%) was observed by direct
RNA extraction. For the lowest concentrations of phage and virus in the immersion bath, only the direct
RNA extraction method allowed their recovery. Direct
RNA extraction proved to be more effective (best recovery rate), faster (<8h) and simpler (fewer steps) than the one proposed in the CEN ISO standard method when it came to detecting enteric viruses on raspberries.