Delimotecan

Chemical sanitizers are usually added to dump tank water to minimize cross-contamination during tomato packing. However, the efficacy of sanitizers continues to be questioned. This study assessed the ability of six commonly used sanitizers (40 ppm of peroxyacetic acid, 40 ppm of mixed peracid, 40 ppm of available chlorine alone or acidified to pH 6.0 with citric acid or T-128, and electrolyzed water containing 40 ppm of available chlorine at pH 6.7) to reduce Salmonella on tomatoes, in wash water, and on equipment surfaces using a pilot-scale processing line. Red round tomatoes (11.3 kg) were dip inoculated to contain Salmonella at ∼6 log CFU/g, air dried for 2 h, treated for 2 min in a 3.3-m-long dump tank and then dried on a roller conveyor, with sanitizer-free water serving as the control. Tomato and water samples were collected at 15-s intervals during washing with additional dump tank, water tank, and roller conveyor surface samples collected after washing. All samples were appropriately neutralized, diluted, and surface plated on Trypticase soy agar containing 0.6% yeast extract, 0.05% ferric ammonium citrate, and 0.03% sodium thiosulfate with or without membrane filtration to enumerate Salmonella. All six sanitizer treatments were more efficacious than the water control (P ≤ 0.05), with chlorine plus citric acid yielding the greatest Salmonella reduction on tomatoes (3.1 log CFU/g). After processing, all sanitizer wash solutions contained significantly lower (P ≤ 0.05) levels of Salmonella than the water control (3.0 log CFU/ml). The four chlorine-based sanitizer treatments yielded significantly lower Salmonella populations (P ≤ 0.05) in the wash solution compared with peroxyacetic acid and mixed peracid. After processing with sanitizers, Salmonella populations decreased to nondetectable levels (<0.2 log CFU/100 cm(2) ) on the equipment surfaces.

Chemical sanitizers are routinely used during commercial flume washing of fresh-cut leafy greens to minimize cross-contamination from the water. This study assessed the efficacy of three chlorine treatments against Escherichia coli O157:H7 on iceberg lettuce, in wash water, and on surfaces of a pilot-scale processing line using flume water containing various organic loads. Iceberg lettuce (5.4 kg) was inoculated to contain 10(6) CFU/g of a 4-strain cocktail of nontoxigenic, green fluorescent protein-labeled, ampicillin-resistant E. coli O157:H7 and held for 24 h at 4°C before processing. Lettuce was shredded using a Urschel TransSlicer, step conveyed to a flume tank, washed for 90 s using water alone or one of three different sanitizing treatments (50 ppm of total chlorine either alone or acidified to pH 6.5 with citric acid or T-128) in water containing organic loads of 0, 2.5, 5, or 10% (wt/vol) blended iceberg lettuce, and then dried using a shaker table and centrifugal dryer. Next, three 5.4-kg batches of uninoculated iceberg lettuce were processed identically. Various product (25 g), water (50 ml), and equipment surface swab (100 cm(2)) samples were homogenized in neutralizing buffer, diluted appropriately, and plated on tryptic soy agar containing 0.6% (wt/vol) yeast extract and 100 ppm of ampicillin without prior 0.45- m m membrane filtration to quantify E. coli O157:H7. Organic load negatively impacted the efficacy of all three chlorine treatments (P < 0.05) at the end of processing, with typical E. coli O157:H7 reductions of >5 and 0.9 to 3.7 log CFU/ml for organic loads of 0 and 10%, respectively. Organic load rarely had a significant impact (P < 0.05) on the efficacy of chlorine, chlorine plus citric acid, or chlorine plus T-128 against E. coli O157:H7 on iceberg lettuce. Reduced sanitizer efficacy generally corresponded to changes in total solids, chemical oxygen demand, turbidity, and maximum filterable volume, indicating that these tests may be effective alternatives to the industry standard of oxygen/reduction potential.