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Human norovirus (HuNoV) is the leading causative agent of foodborne outbreaks and is associated with the second most prevalent cause of waterborne infections in the United States. The goal of this research was to investigate the antiviral activity of chitosan microparticles (CM) against HuNoV GII.4 Sydney and its cultivable surrogate, Tulane virus (TuV), in suspensions mimicking fecally-contaminated water. CM was prepared by crosslinking chitosan molecules with sodium sulfate, and then its anti-noroviral activity was assessed using infectivity assay on TuV and RT-qPCR on TuV and HuNoV. A 3% CM suspension in PBS (pH 7.2) showed binding to TuV particles but with a negligible impact on virus infectivity (p>0.05). TuV and HuNoV suspended in fecal suspensions showed a 1.5-log10 reduction in genomic copies per ml following a 10-min contact time (p

Cold-smoked salmon (CSS) is a potentially hazardous ready-to-eat food product due to the high risk of contamination with Listeria monocytogenes and lack of a listericidal step. We investigated the antilisterial property of liquid smokes (LS) against Listeria innocua ATCC 33090 (surrogate to L. monocytogenes) as a potential supplement to vacuum-packaged CSS. A full-strength LS (Code 10-Poly), and three commercially refined fractions (AM-3, AM-10, and 1291) having less color and flavor (lower content of phenols and carbonyl-containing compounds) were tested. In vitro assays showed strong inhibition for all LS except for 1291. The CSS strips were surface coated with AM-3 and AM-10 at 1% LS (vol/wt) with an L-shaped glass rod and then inoculated with L. innocua at 3.5 log CFU/g, vacuum packaged, and stored at 4°C. The LS did not completely eliminate L. innocua but provided a 2-log reduction by day 14, with no growth up to 35 days of refrigerated storage. A simple difference sensory test by 180 untrained panelists showed the application of AM-3 did not significantly influence the overall sensorial quality of CSS. In essence, the application of the refined LS as an antilisterial additive to CSS is recommended.

The biogenic amine content and related bacterial changes (Pseudomonas spp., psychrotrophic and mesophilic counts) in whole farmed rainbow trout (Oncorhynchus mykiss) were monitored during ice storage for 18 days (at 0, 3, 6, 9, 12, 15 and 18 days). Levels of putrescine, cadaverine and histamine, and bacterial loads, increased (P < 0.05) during storage, but tyramine was not detected in any of the tested samples. Concentration of putrescine ranged from 0.4 initially to 8.97 μg/g, and psychrotrophic microorganisms were dominant. The best linear regressions (correlations) were for putrescine and Pseudomonas spp. and psychrotrophs (r = 0.98), and for cadaverine with Pseudomonas spp. (r = 0.82). Putrescine content was a good quality marker. Histamine was detected only at later stages of storage and was therefore less suitable than the other biogenic amines as freshness indicator.