Monitoring of Extraction Efficiency by a Sample Process Control Virus Added Immediately Upon Sample Receipt

When analysing food samples for enteric viruses, a sample process control virus (SPCV) must be added at the commencement of the analytical procedure, to verify that the analysis has been performed correctly. Samples can on occasion arrive at the laboratory late in the working day or week. The analyst may consequently have insufficient time to commence and complete the complex procedure, and the samples must consequently be stored. To maintain the validity of the analytical result, it will be necessary to consider storage as part of the process, and the analytical procedure as commencing on sample receipt. The aim of this study was to verify that an SPCV can be recovered after sample storage, and thus indicate the effective recovery of enteric viruses. Two types of samples (fresh and frozen raspberries) and two types of storage (refrigerated and frozen) were studied using Mengovirus vMC0 as SPCV. SPCV recovery was not significantly different (P > 0.5) regardless of sample type or duration of storage (up to 14 days at -20 °C). Accordingly, samples can be stored without a significant effect on the performance of the analysis. The results of this study should assist the analyst by demonstrating that they can verify that viruses can be extracted from food samples even if samples have been stored.