Red beet and Swiss chard juice extract as natural nitrate sources for the production of alternatively-cured emulsion-type sausages.

Statements that naturally cured meat products may contain lower residual nitrite levels compared to classical variants led to a closer examination of emulsion-type sausage products in this study, where the input of nitrate from plant extracts (red beet and Swiss chard) was adjusted to typical input levels of nitrite from nitrite curing salt (0.5% NaNO2). The investigations showed that an incubation period of 150 min at 38 °C was necessary to complete the microbial reduction process of nitrate to nitrite and that residual nitrite contents of naturally cured sausages were comparable to the conventionally cured variant, regardless of the nitrate source. During the incubation period, the starter cultures were the dominant microorganisms and showed competitive properties against the natural accompanying flora. In terms of colour development, the variants with Swiss chard juice extract as well as synthetic nitrate showed similar colour formation to conventionally produced emulsion-type sausages. In contrast, colour-providing components of the red beet extract considerably masked the typical appearance.

Inactivation of Listeria monocytogenes in game meat applying sous vide cooking conditions.

This study investigated the effects of sous vide cooking at temperatures between 50 °C and 60 °C on the inactivation kinetics of Listeria (L.) monocytogenes. Nutrient broth and minced game meat (Capreolus capreolus and Sus scrofa) were inoculated with three strains of L. monocytogenes and cooked under sous vide conditions (50, 55 or 60 °C for several hours). Results showed that the decimal reduction values (D-values) were largely dependent on the surrounding matrix. D-values of 125.5, 29.7 and 5.1 min were reached for BHI (brain heart infusion) at 50 °C, 55 °C and 60 °C, respectively. For roe deer, D-values of 49.2, 14.9 and 3.7 min and for wild boar, D-values of 100.2, 23.8 and 4.2 min were reached. It can be concluded that microbiologically safe cooking durations under sous-vide conditions below 60 °C should be considered individually for each meat product due to the dramatic influence of the matrix in comparison to higher temperature conditions.

Inactivation of multidrug-resistant pathogens and Yersinia enterocolitica with cold atmospheric-pressure plasma on stainless-steel surfaces.

The objective of this study was to investigate the impact of cold atmospheric-pressure plasma (CAP) produced by a surface micro-discharge plasma source as a new strategy to combat the transmission of five multidrug-resistant (MDR) pathogens and Yersinia enterocolitica on typical hospital- and food-producing surfaces, e.g. stainless-steel. Approximately 106 CFU/cm2 of vancomycin-resistant Enterococcus faecium, methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli and Y. enterocolitica were inoculated on a 3.14-cm2 stainless-steel surface. Bovine serum albumin (BSA) (3%) was used as a disruptive factor simulating natural organic material. The inoculated surfaces were subsequently exposed to CAP, generated by a peak-to-peak voltage of 10 kV with sinusoidal waveform and a frequency of 2 kHz, for 5, 10 and 20 min, respectively. Fluorescent staining with propidium iodide and SYTOTM 9 was used to demonstrate the manner of bacterial cell damage. Significant (P < 0.05) inactivation of 1.68 ± 0.17 up to 2.80 ± 0.17 log steps was achieved after 5 min of CAP treatment. However, bacterial reduction could be increased to 3.35 ± 0.1 up to 5.17 ± 0.67 log steps after 20 min of CAP treatment. Bacterial cells covered with BSA were statistically significantly less inactivated by CAP. Fluorescent staining showed a predominant level of orange-stained, sublethally damaged bacterial cells after 10 min of CAP treatment. In conclusion, CAP has the ability to inactivate MDR bacterial pathogens on stainless-steel surfaces. Further research is required to investigate the clinical features of CAP.

Inactivation of Salmonella Typhimurium and Listeria monocytogenes on ham with nonthermal atmospheric pressure plasma.

The application of cold atmospheric pressure plasma (CAP) for decontamination of sliced ready-to-eat (RTE) meat products (in this case, rolled fillets of ham), inoculated with Salmonella (S.) Typhimurium and Listeria (L.) monocytogenes was investigated. Cold atmospheric plasma (CAP) is an ionised gas that includes highly reactive species and ozone, interacting with cell membranes and DNA of bacteria. The mode of action of CAPs includes penetration and disruption of the outer cell membrane or intracellular destruction of DNA located in the cytoplasm. Inoculated ham was treated for 10 and 20 min with CAP generated by a surface-micro-discharge-plasma source using cost-effective ambient air as working gas with different humidity levels of 45-50 and 90%. The chosen plasma modes had a peak-to-peak voltage of 6.4 or 10 kV and a frequency of 2 and 10 kHz. Under the tested conditions, the direct effectiveness of CAP on microbial inactivation was limited. Although all treated samples showed significant reductions in the microbial load subsequent to plasma treatment, the maximum inactivation of S. Typhimurium was 1.14 lg steps after 20 min of CAP-treatment (p<0.05), and L. monocytogenes was reduced by 1.02 lg steps (p<0.05) using high peak-to-peak voltage of 10 kV and a frequency of 2 kHz regardless of moisture content. However, effective inactivation was achieved by a combination of CAP-treatment and cold storage at 8°C ± 0.5°C for 7 and 14 days after packaging under sealed high nitrogen gas flush (70% N2, 30% CO2). Synergistic effects of CAP and cold storage for 14 days led to a clearer decrease in the microbial load of 1.84 lg steps for S. Typhimurium (p<0.05) and 2.55 lg steps for L. monocytogenes (p<0.05). In the case of L. monocytogenes, subsequent to CAP-treatment (10 kV, 2 kHz) and cold storage, microbial counts were predominantly below the detection limit. Measurement showed that after CAP-treatment, surface temperature of ham did not exceed the room temperature of 22°C ± 2°C. With the application of humidity levels of 45-50%, the colour distance ΔE increased in CAP treated samples due to a decrease in L* values. In conclusion, effectiveness of CAP-treatment was limited. However, the combination of CAP-treatment and cold storage of samples under modified-atmospheric-conditions up to 14 days could significantly reduce microorganisms on RTE ham. Further investigations are required to improve effectiveness of CAP-treatment.

Effects of parsley extract powder as an alternative for the direct addition of sodium nitrite in the production of mortadella-type sausages - Impact on microbiological, physicochemical and sensory aspects.

Increasing concern about chemical additives in processed meat has led to an increased market of uncured and alternatively cured meat products. However, the use of vegetable extracts or the exclusion of curing salt may increase the risk of greater bacterial growth and alteration of several physicochemical parameters. Therefore, in this study mortadella-type sausages, manufactured with 1.07 (V3), 2.14 (V4) and 4.29 (V5) g parsley extract powder/kg sausage meat were produced. These sausage variants were compared to an uncured (V2) and a traditionally nitrite-cured control (V1). A significantly lower Listeria monocytogenes growth was observed for V5 compared to all other variants during the storage time of 28days (P<0.05). Compared to V1, V5 presented a residual nitrite content reduced by 40% and similar a* values until day 21. Concerning texture parameters, L* and aw values, no differences between the variants were detected. Sensory analysis showed that overall acceptance of V4 and V5 was comparable with V1.

Low temperature cooking of pork meat - Physicochemical and sensory aspects.

Low-temperature cooking is increasingly used in the food sector. This study compared three different low temperature heating methods and one conventional cooking procedure of pork meat in a combi steamer with special emphasis on sensory parameters. Low temperature, long time (LTLT) treatments over 20h at 53°C or 58°C (LTLT 53°C or 58°C) showed considerable effects on meat tenderization. Heating to a core temperature of 60°C (low temperature method=LT) at 60°C oven temperature resulted in less tender but clearly juicier meat. LTLT 53°C and LT were evaluated as being equally acceptable by the panelists. The tenderest meat (LTLT 58°C) was mainly rejected because of a crumbly and dry mouth feeling. Conventional heating to a core temperature of 80°C at 180°C oven temperature resulted in low eating quality due to high toughness and low juiciness.

Low temperature, long time treatment of porcine M. longissimus thoracis et lumborum in a combi steamer under commercial conditions.

As the interest in low temperature, long time (LTLT) treatment of meat, as well as the use of modern combi steamer technology is growing, this study characterized the effects of LTLT treatments on porcine Musculus longissimus thoracis et lumborum in a combi steamer. Upon heating for 10 and 20 h at 53°C or 58°C, weight loss increased with both time and temperature, while no significant changes over time could be reached between 20 and 30 h. Redness only varied with temperature, showing lower a* values at 53°C. Shear force values at 58°C remained at a stable level over time and were lower than values at 53°C after 10 and 20 h. In contrast, at 53°C, shear force was reduced with increasing treatment time, until after 30 h both temperatures showed similar shear force values. Inoculation experiments revealed that already the lowest LTLT condition (53°C, 10h) inactivated 5 log10 cfu/g of certain indicator pathogens confirming the safety of these treatments.

Inactivation of a foodborne norovirus outbreak strain with nonthermal atmospheric pressure plasma.

UNLABELLED: Human norovirus (NoV) is the most frequent cause of epidemic nonbacterial acute gastroenteritis worldwide. We investigated the impact of nonthermal or cold atmospheric pressure plasma (CAPP) on the inactivation of a clinical human outbreak NoV, GII.4. Three different dilutions of a NoV-positive stool sample were prepared and subsequently treated with CAPP for various lengths of time, up to 15 min. NoV viral loads were quantified by quantitative real-time reverse transcription PCR (RT-qPCR). Increased CAPP treatment time led to increased NoV reduction; samples treated for the longest time had the lowest viral load. From the initial starting quantity of 2.36 × 10(4) genomic equivalents/ml, sample exposure to CAPP reduced this value by 1.23 log10 and 1.69 log10 genomic equivalents/ml after 10 and 15 min, respectively (P < 0.01). CAPP treatment of surfaces carrying a lower viral load reduced NoV by at least 1 log10 after CAPP exposure for 2 min (P < 0.05) and 1 min (P < 0.05), respectively. Our results suggest that NoV can be inactivated by CAPP treatment. The lack of cell culture assays prevents our ability to estimate infectivity. It is possible that some detectable, intact virus particles were rendered noninfectious. We conclude that CAPP treatment of surfaces may be a useful strategy to reduce the risk of NoV transmission in crowded environments. IMPORTANCE: Human gastroenteritis is most frequently caused by noroviruses, which are spread person to person and via surfaces, often in facilities with crowds of people. Disinfection of surfaces that come into contact with infected humans is critical for the prevention of cross-contamination and further transmission of the virus. However, effective disinfection cannot be done easily in mass catering environments or health care facilities. We evaluated the efficacy of cold atmospheric pressure plasma, an innovative airborne disinfection method, on surfaces inoculated with norovirus. We used a clinically relevant strain of norovirus from an outbreak in Germany. Cold plasma was able to inactivate the virus on the tested surfaces, suggesting that this method could be used for continuous disinfection of contaminated surfaces. The use of a clinical strain of norovirus strengthens the reliability of our results as it is a strain relevant to outbreaks in humans.

Effect of pulsed electric fields on microbial inactivation and physico-chemical properties of whole porcine blood.

The objective of this study was to determine the lethal effectiveness of pulsed electric fields on the inactivation of the porcine blood endogenous microflora. Furthermore, the impact of pulsed electric field application on physico-chemical and sensory properties in this medium should be proved. Blood samples from a commercial abattoir in Germany were processed by a continuous pilot plant-pulsed electric field system at electric field strength of 11 kV/cm for treatment times of 163 and 209 µs. The applied pulse frequencies of 134 and 175 Hz correspond to an energy input of 91 and 114 kJ/kg, respectively. In these conditions, the effectiveness of pulsed electric field processing on microbial inactivation was limited: 1.35 log10 CFU/mL reduction of total aerobic plate count (p < 0.05), 1.0 log10 CFU/mL for Pseudomonas spp. (p < 0.05), 0.97 and 0.66 log10 CFU/mL reduction for Enterobacteriaceae and sulfite-reducing anaerobic bacteria, respectively. However, the storage experiment (14 days at +3 ) showed a significant reduced growth of total aerobic plate count (p < 0.05) and Pseudomonas spp. (p < 0.05) in the pulsed electric field-treated blood samples. Pulsed electric field processing leads to a complete hemolysis of the red blood cells, in addition significant decreased L* (lightness), a* (redness) and b* (yellowness) values (p < 0.0001) were observed. Furthermore, changes in the sensory attributes color (changed from red to dark brown) and odor (changed from fresh to musty and tangy) were noticed.