Effect of Vacuum and Modified Atmosphere Packaging on the Shelf Life and Quality of Gutted Rainbow Trout (Oncorhynchus mykiss) during Refrigerated Storage

The quality changes of gutted rainbow trout in vacuum packaging (VP) and modified atmosphere packaging (MAP) with 40% CO2 + 60% N2 (MAP1), 60% CO2 + 40% N2 (MAP2), and 90% CO2 + 10% N2 (MAP3) were evaluated. The samples were stored at 3 ± 0.5 °C, and on days 1, 4, 7, 10, 13, and 16 of storage, microbiological, chemical, and sensory testing was performed. The aerobic plate count (APC) and psychrotrophic bacteria count (PBC) in VP fish exceeded the conventional limit of 7 log cfu/g on day 10, and in MAP1 and MAP2 fish on day 16, whereas in MAP3 fish, their number remained below that limit during the experiment. MAP significantly slowed down the growth of Enterobacteriaceae in trout, and the degree of inhibition increased with increasing CO2 concentration in the gas mixture. The lowest lactic acid bacteria numbers were detected in VP fish, whereas the highest numbers were determined in trout packaged in MAP2 and MAP3. Significantly lower numbers of hydrogen sulfide-producing (H2S) bacteria were detected in fish packed in MAP. Distinct patterns were observed for pH among treatments. The lowest increase in TBARS values was detected in VP and MAP3 fish, whereas in MAP1 and MAP2 fish, the TBARS values were higher than 1 mg MDA/kg on day 16 of storage when a rancid odor was detected. MAP inhibited the increase in total volatile basic nitrogen (TVB-N) content of trout compared to trout packaged in a vacuum. The sensory attributes of trout perceived by the sensory panel changed significantly in all experimental groups during storage. Based primarily on sensory, but also microbial, and chemical parameters, MAP has great potential for preserving fish quality and extending the shelf life of gutted rainbow trout from 7 days in VP to 13 days in MAP1 and MAP2, and to 16 days in MAP3.

Seasonal Prevalence of Shiga Toxin-Producing Escherichia coli on Pork Carcasses for Three Steps of the Harvest Process at Two Commercial Processing Plants in the United States

Shiga toxin-producing Escherichia coli (STEC) is a foodborne pathogen that has a significant impact on public health, with strains possessing the attachment factor intimin referred to as enterohemorrhagic E. coli (EHEC) and associated with life-threatening illnesses. Cattle and beef are considered typical sources of STEC, but their presence in pork products is a growing concern. Therefore, carcasses (n = 1,536) at two U.S. pork processors were sampled once per season at three stages of harvest (poststunning skins, postscald carcasses, and chilled carcasses) and then examined using PCR for Shiga toxin genes (stx), intimin genes (eae), aerobic plate count (APC), and Enterobacteriaceae counts (EBC). The prevalence of stx on skins, postscald, and chilled carcasses was 85.3, 17.5, and 5.4%, respectively, with 82.3, 7.8, and 1.7% of swabs, respectively, having stx and eae present. All stx-positive samples were subjected to culture isolation that resulted in 368 STEC and 46 EHEC isolates. The most frequently identified STEC were serogroups O121, O8, and O91 (63, 6.7, and 6.0% of total STEC, respectively). The most frequently isolated EHEC was serotype O157:H7 (63% of total EHEC). Results showed that scalding significantly reduced (P < 0.05) carcass APC and EBC by 3.00- and 2.50-log10 CFU/100 cm2, respectively. A seasonal effect was observed, with STEC prevalence lower (P < 0.05) in winter. The data from this study show significant (P < 0.05) reduction in the incidence of STEC (stx) from 85.3% to 5.4% and of EHEC (stx plus eae) from 82.3% to 1.7% within the slaughter-to-chilling continuum, respectively, and that potential EHEC can be confirmed present throughout using culture isolation.IMPORTANCE Seven serogroups of STEC are responsible for most (>75%) cases of severe illnesses caused by STEC and are considered adulterants of beef. However, some STEC outbreaks have been attributed to pork products, although the same E. coli are not considered adulterants in pork because little is known of their prevalence along the pork chain. The significance of the work presented here is that it identifies disease-causing STEC, EHEC, demonstrating that these same organisms are a food safety hazard in pork as well as beef. The results show that most STEC isolated from pork are not likely to cause severe disease in humans and that processes used in pork harvest, such as scalding, offer a significant control point to reduce contamination. The results will assist the pork processing industry and regulatory agencies to optimize interventions to improve the safety of pork products.

Mycotoxin in the food supply chain-implications for public health program

Mycotoxins are a group of naturally occurring toxic chemical substances, produced mainly by microscopic filamentous fungal species. Regarding potential synergisms or even mitigating effects between toxic elements, mycotoxin contamination will continue to be an area of concern for producers, manufacturers, regulatory agencies, researchers, and consumers in the future. In Serbia, recent drought and then flooding confirmed that mycotoxins are one of the foodborne hazards most susceptible to climate change. In this article, we review key aspects of mycotoxin contamination of the food supply chain and implications for public health from the Serbian perspective.

Treatment of cattle hides with Shellac-in-ethanol solution to reduce bacterial transferability--a preliminary study

A solution of natural, food-grade resin (Shellac) in ethanol was evaluated to treat samples of visually clean and dry cattle hides with the aim to reduce bacterial removability from the hides by swabbing. Hide treatment by 23% Shellac-in-ethanol solution reduced sponge-swabbing recoveries of general microflora (TVC) by a factor of 6.6 logs (>1000-fold larger than the 2.9 log reduction observed by ethanol alone), and of generic Escherichia coli and Enterobacteriaceae by factors of at least 2.9 and 4.8 logs, respectively. These reductions were superior to those achieved by a sanitizer rinse-vacuum hide treatment. Significantly greater reductions of TVC recoveries from hides were achieved when using higher Shellac concentrations (23 and 30% rather than 4.8-16.7%) and when Shellac solution temperatures were 20-40 degrees C rather than 50-60 degrees C. Furthermore, the Shellac-based treatment also markedly reduced the E. coli O157 prevalence (3.7-fold reduction) on natural, uninoculated hides, as well as the counts of E. coli O157 on artificially inoculated hides (2.1 log reduction). This preliminary study indicated that a "bacterial on-hide immobilisation" approach to reducing transmission of microorganisms from cattle hide is promising and so will be further explored.

The occurrence of Escherichia coli O157 in/on faeces, carcasses and fresh meats from cattle

The aim of this study was to investigate whether Escherichia coli O157 is present in/on raw beef in Serbia. Correlated faecal and carcasses samples from 115 slaughtered cattle plus 26 uncorrelated carcass samples were examined. E. coli O157 detection and identification was performed using selective enrichment and immunomagnetic separation followed by selective media-plating and biochemical tests. The E. coli O157 occurrences were 2.6% in faeces and 2.8% on carcasses. The E. coli O157 occurrences were 0%, 6.2% and 2.1%, respectively, in 106 samples of beef trimmings, 48 samples of minced beef and 48 samples of batter intended for production of raw, fermented sausages. The results confirmed that faecal contamination is very important for the occurrence of E. coli O157 on beef carcasses. Furthermore, the present study revealed occasional presence of the pathogen in raw materials used for producing raw, fermented beef sausages.

Occurrence of Escherichia coli O157 on hides of slaughtered cattle

AIMS

To obtain the first information on the occurrence of Escherichia coli O157 on hides of slaughtered cattle in Serbia.

METHODS AND RESULTS

A total of 355 swabs were taken on the slaughterline from five areas of hide of each of the 71 cattle in a single commercial abattoir in Serbia. Using an ISO method incorporating enrichment and immunomagnetic separation steps, E. coli O157 was isolated from the hides of 20 animals (28 x 2%). With respect to different areas of the hides, the occurrence of the pathogen was, in decreasing order: hooves (11 x 3%), brisket (8 x 4%), rump (7 x 0%), neck (4 x 2) and flank (2 x 8%). In addition, factors that had more or less effects on the occurrence included visible dirtiness of the hide, cattle's age category, geographical origin of the animals and season.

CONCLUSIONS

This study revealed the presence of E. coli O157 in the beef chain in Serbia and confirmed hide as an important potential source of related contamination of beef carcasses. Therefore, incorporation of preskinning hide decontamination treatments into HACCP-based slaughterline hygiene control measures could be very useful.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results will enable further optimization of necessary measures along the beef chain to reduce the E. coli O157 risks in Serbia.