Aims: To study the survival and removal of viruses from fresh fruit and vegetables using the bacteriophage MS2 as a potential surrogate for noroviruses. Method and Results: Survival of MS2 in buffer and on fresh produce was studied at 4, 8 and 22°C. At 4 and 8°C a reduction of <1 log 10 was observed after 50 days in buffer; however a reduction in excess of 1 log 10 occurred within 9 days at 22°C. Similar results were obtained with fresh produce with virus survival times exceeding the shelf life of the produce. In washing experiments, using a chlorine wash (100 ppm), in all but one case <1AE5 log 10 MS2 bacteriophage was removed from fruit and vegetables. The mean across all produce types was 0AE89 log 10 . With potable water, reduction was lower (0AE3 log mean across all produce types). Conclusions: MS2 survived for prolonged periods, both in buffer and on fresh produce, at temperatures relevant to chilled foods. It was not removed effectively by chlorine washing. Significance and Impact of the Study: Bacteriophage MS2 has been evaluated as a potential surrogate for noroviruses on fresh produce. Experimental results together with current knowledge of norovirus resistance and survival indicate that MS2 could be used as an effective surrogate in future evaluations.

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The effectiveness of power ultrasound for the microbial decontamination of minimally processed fruits and vegetables was studied. Reductions in Salmonella typhimurium attached to iceberg lettuce obtained by cleaning with water, chlorinated water, ultrasound with water and ultrasound with chlorinated water were 0.7, 1.7, 1.5 and 2.7 logs, respectively, for small‐scale (2 L) trials. The cleaning action of cavitation appears to remove cells attached to the surface of fresh produce, rendering the pathogens more susceptible to the sanitizer. For large‐scale (40 L) trials, the addition of chlorine to water in the tank gave a systematic difference in Escherichia coli decontamination efficiency. However, the frequency of ultrasound treatment (25, 32–40, 62–70 kHz) had no significant effect on decontamination efficiency (P > 0.69). With the potentially high capital expenditure together with the expensive process of optimization and water treatment, it is unlikely that the fresh produce industry would be willing to take up this technology. Furthermore, the additional one log reduction achieved by applying ultrasound to a chlorinated water wash does not completely eliminate the risk of pathogens on fresh produce.

Saccharomyces cerevisiae displays very strong induction of a single ATP-binding cassette (ABC) transporter, Pdr12p, when stressed with certain weak organic acids. This is a plasma membrane pump catalysing active efflux of the organic acid anion from the cell. Pdr12p action probably allows S. cerevisiae to maintain lower intracellular levels of several weak organic acid preservatives than would be expected on the basis of the free equilibration of the acid across the cell membrane. This in turn facilitates growth in the presence of these preservatives and therefore yeast spoilage of food materials. Pdr12p appears to confer resistance to those carboxylic acids that, to a reasonable degree, partition into both the lipid bilayer and aqueous phases. Its gene (PDR12 ) is strongly induced by sorbate, benzoate and certain other moderately lipophilic carboxylate compounds, but not by organic alcohols or high levels of acetate. PDR12 induction reflects the operation of a previously uncharacterized S. cerevisiae stress response, for which the induction signal is probably a high intracellular pool of the organic acid anion.

Gene mutations in APC, K-ras, and p53 are thought to be essential events for colorectal cancer development. Recent data seem to indicate that K-ras and p53 mutations rarely co-exist in the same tumor, indicating that these alterations do not represent a synergistic evolutionary pathway. Moreover, an inverse relation between K-ras gene activation and BRAF mutations has been demonstrated, suggesting alternative pathways for colorectal cancer transformation. To reconstruct the chronological modulation of these gene mutations during cell transformation and colorectal cancer progression, mutations of p53, K-ras, and BRAF genes were analyzed by Single Strand Conformation Polymorphism (SSCP) or sequencing analysis in 100 colorectal cancer samples, evenly distributed among different Dukes' stages. We found mutations in p53, K-ras, and BRAF genes in 35%, 30%, and 4% of tumors, respectively, and observed a minimal or no co-presence of these gene alterations. Moreover, the frequency of molecular p53 mutations increased as tumor stage increased, suggesting an important role for this gene in the progression of colorectal cancer. Conversely, K-ras or BRAF genes were not related to tumor stage or location. These data seem to indicate the absence of a co-presence of the genes, highlighting the possibility of multiple pathways for colorectal tumor progression. Moreover, mutations in p53, K-ras, and BRAF are not present in about one-third of colorectal cancers and therefore other gene mutations need to be investigated to better understand molecular mechanisms at the basis of cell transformation and the progression of colorectal cancer.