Surface pasteurization of vacuum-sealed precooked ready-to-eat meat products

Treatment of Ready-To-Eat Cooked Meat Products with Cold Atmospheric Plasma to Inactivate Listeria and Escherichia coli

Ready-to-eat meat products have been identified as a potential vehicle for Listeria monocytogenes. Postprocessing contamination (i.e., handling during portioning and packaging) can occur, and subsequent cold storage together with a demand for products with long shelf life can create a hazardous scenario. Good hygienic practice is augmented by intervention measures in controlling post-processing contamination. Among these interventions, the application of 'cold atmospheric plasma' (CAP) has gained interest. The reactive plasma species exert some antibacterial effect, but can also alter the food matrix. We studied the effect of CAP generated from air in a surface barrier discharge system (power densities 0.48 and 0.67 W/cm²) with an electrode-sample distance of 15 mm on sliced, cured, cooked ham and sausage (two brands each), veal pie, and calf liver pâté. Colour of samples was tested immediately before and after CAP exposure. CAP exposure for 5 min effectuated only minor colour changes (ΔE max. 2.7), due to a decrease in redness (a*), and in some cases, an increase in b*. A second set of samples was contaminated with Listeria (L.) monocytogenes, L. innocua and E. coli and then exposed to CAP for 5 min. In cooked cured meats, CAP was more effective in inactivating E. coli (1 to 3 log cycles) than Listeria (from 0.2 to max. 1.5 log cycles). In (non-cured) veal pie and calf liver pâté that had been stored 24 h after CAP exposure, numbers of E. coli were not significantly reduced. Levels of Listeria were significantly reduced in veal pie that had been stored for 24 h (at a level of ca. 0.5 log cycles), but not in calf liver pâté. Antibacterial activity differed between but also within sample types, which requires further studies.

Inactivation of hepatitis A virus and murine norovirus on surfaces of plastic, steel and raspberries using steam-ultrasound treatment

The leading causes of foodborne viral disease outbreaks are human norovirus and hepatitis A virus (HAV). Their environmental persistence enables contamination of kitchen surfaces and crops often consumed raw, such as berries. Many decontamination procedures are inefficient and unsuitable for surfaces of industrial kitchen environments and soft fruits. In this study, we investigated the efficiency of a novel surface decontamination technology, combining steam and ultrasound (steam-ultrasound). Plastic, steel or raspberry surfaces were spiked with the norovirus surrogate, murine norovirus (MNV), and HAV, and steam-ultrasound treated at 85, 90 and 95 °C for 0-5 s. Post treatment viruses were titrated for survival by plaque assay and for genome stability by real-time quantitative PCR (RT-qPCR) of nucleic acid extracts. Survival of viruses were estimated in a log-linear model and the treatment time requirements for each decimal reduction (D value) in viral survival were calculated. The estimated D values of MNV or HAV were 0.4-0.2 or 1.1-0.8 s on plastic, 0.9-0.7 or 1.4-0.8 s on steel and 1.6-1.7 or 3.2-4.7 s on raspberries. No clear trend of genome reduction was observed with tested treatment parameters. Raspberries treated up to 4 s retained its natural texture and visual appeal similar to untreated controls whilst monitored for 7 days. In conclusion, steam-ultrasound treatment can within seconds reduce the titre of foodborne viruses on surfaces of plastic, steel and raspberries. This may particularly benefit industrial scale production of soft fruits for raw consumption and for swift non-hazardous decontamination of industrial kitchen surfaces.

Punica granatum and Citrus spp. Extract Mix Affects Spoilage Microorganisms Growth Rate in Vacuum-Packaged Cooked Sausages Made from Pork Meat, Emmer Wheat (Triticum dicoccum Schübler), Almond (Prunus dulcis Mill.) and Hazelnut (Corylus avellana L.)

Sausage made from pork meat, emmer wheat (Triticum dicoccum Schübler), almond (Prunus dulcis Mill.), and hazelnut (Corylus avellana L.) was integrated with a mix of Punica granatum and Citrus spp. extracts to evaluate the possible effects on the growth and oxidation of spoilage microorganisms. Two concentrations of the mix were added, respectively, during sausage-making, and the final products were compared with a control group, without the extract mix, during storage. The use of the mix, especially at 10 g/1000 g of the whole ingredients, delayed the pH drop and thiobarbituric acid-reactive substances (TBARs) value during storage. Total viable count, lactic acid bacteria and psychrotrophic microbial counts were also affected, as the extract mix lowered the maximum growth rate of the microbial population considered. The sensory analyses revealed an improvement in the shelf-life of 6 and 16 days, respectively, when 5‰ and 10‰ of the mix were used.

DECREASE OF REPEATED CONTAMINATION OF PACKED DELI-CIOUS MEAT PRODUCTS

The study considers a problem of repeated contamination of delicious products, ready for consumption. The aim of the work is to study the repeated thermal processing of a ready vacuum-packed whole-muscular meat product for inhibiting a surface microbiota. Today it is urgent for the meat industry, because it influences safety and quality, and also limits a storage term of a product. After bringing a meat product to culinary readiness by thermal processing, it has an unessential amount of microbiota. Microorganisms, including pathogenic and conventionally pathogenic ones, fall on a product after its cooking at cutting, preparation to package and at the package stage itself. Microbiological contamination of a ready meat product results in fast spoilage and is a serious problem for producers, because the microbiota growth shortens its storage life. In its turn, it results in a refuse of a consumer to buy this product and great economic losses for producers. The study is directed on a possibility of solving a problem of contamination of a whole-muscular delicious meat product. The solution is in package of a ready product under vacuum and short-term heating at a high temperature. The work is devoted to the complex study of an influence of repeated pasteurization on safety and quality of a product. There was studied an influence of the repeated thermal processing (post-pasteurization) on microbiological, physical-chemical and also organoleptic parameters of a delicious meat product. The special attention is paid to an influence of post-pasteurization regimes on a microbiological condition of studied samples. Studies of a total amount of microbiota and also the presence of sanitary-representative microorganisms were conducted. It has been proven, that the use of post-pasteurization essentially inhibits a number of microorganisms, and also doesn’t influence physical-chemical parameters outlook of a product and organoleptic characteristics. Based on studying an influence of post-pasteurization, it has been established, that inhibition of a microbiota essentially influences safety and prolongs the storage term of a product.

Employing high-frequency alternating magnetic fields for the non-invasive treatment of prosthetic joint infections

Treatment of prosthetic joint infection (PJI) usually requires surgical replacement of the infected joint and weeks of antibiotic therapy, due to the formation of biofilm. We introduce a non-invasive method for thermal destruction of biofilm on metallic implants using high-frequency (>100 kHz) alternating magnetic fields (AMF). In vitro investigations demonstrate a >5-log reduction in bacterial counts after 5 minutes of AMF exposure. Confocal and scanning electron microscopy confirm removal of biofilm matrix components within 1 minute of AMF exposure, and combination studies of antibiotics and AMF demonstrate a 5-log increase in the sensitivity of Pseudomonas aeruginosa to ciprofloxacin. Finite element analysis (FEA) simulations demonstrate that intermittent AMF exposures can achieve uniform surface heating of a prosthetic knee joint. In vivo studies confirm thermal damage is confined to a localized region (<2 mm) around the implant, and safety can be achieved using acoustic monitoring for the presence of surface boiling. These initial studies support the hypothesis that AMF exposures can eradicate biofilm on metal implants, and may enhance the effectiveness of conventional antibiotics.

Thermal Inactivation Kinetics of Sporolactobacillus nakayamae Spores, a Spoilage Bacterium Isolated from a Model Mashed Potato-Scallion Mixture

Sporolactobacillus species have been occasionally isolated from spoiled foods and environmental sources. Thus, food processors should be aware of their potential presence and characteristics. In this study, the heat resistance and influence of the growth and recovery media on apparent heat resistance of Sporolactobacillus nakayamae spores were studied and described mathematically. For each medium, survivor curves and thermal death curves were generated for different treatment times (0 to 25 min) at different temperatures (70, 75, and 80°C) and Weibull and first-order models were compared. Thermal inactivation data for S. nakayamae spores varied widely depending on the media formulations used, with glucose yeast peptone consistently yielding the highest D-values for the three temperatures tested. For this same medium, the D-values ranged from 25.24 ± 1.57 to 3.45 ± 0.27 min for the first-order model and from 24.18 ± 0.62 to 3.50 ± 0.24 min for the Weibull model at 70 and 80°C, respectively. The z-values determined for S. nakayamae spores were 11.91 ± 0.29°C for the Weibull model and 11.58 ± 0.43°C for the first-order model. The calculated activation energy was 200.5 ± 7.3 kJ/mol for the first-order model and 192.8 ± 22.1 kJ/mol for the Weibull model. The Weibull model consistently produced the best fit for all the survival curves. This study provides novel and precise information on thermal inactivation kinetics of S. nakayamae spores that will enable reliable thermal process calculations for eliminating this spoilage bacterium.

Thermal inactivation kinetics of hepatitis A virus in homogenized clam meat (Mercenaria mercenaria)

AIMS

Epidemiological evidence suggests that hepatitis A virus (HAV) is the most common pathogen transmitted by bivalve molluscs such as clams, cockles, mussels and oysters. This study aimed to generate thermal inactivation kinetics for HAV as a first step to design adequate thermal processes to control clam-associated HAV outbreaks.

METHODS AND RESULTS

Survivor curves and thermal death curves were generated for different treatment times (0-6 min) at different temperatures (50-72°C) and Weibull and first-order models were compared. D-values for HAV ranged from 47·37 ± 1·23 to 1·55 ± 0·12 min for the first-order model and 64·43 ± 3·47 to 1·25 ± 0·45 min for the Weibull model at temperatures from 50 to 72°C. z-Values for HAV in clams were 12·97 ± 0·59°C and 14·83 ± 0·0·28°C using the Weibull and first-order model respectively. The calculated activation energies for the first-order and Weibull model were 145 and 170 kJ mole(-1) respectively.

CONCLUSION

The Weibull model described the thermal inactivation behaviour of HAV better than the first-order model.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides novel and precise information on thermal inactivation kinetics of HAV in homogenized clams. This will enable reliable thermal process calculations for HAV inactivation in clams and closely related seafood.

Thermal Inactivation of Foodborne Enteric Viruses and Their Viral Surrogates in Foods

Foodborne viruses, in particular human norovirus and hepatitis A virus, are the most common causes of food-associated infections and foodborne illness outbreaks around the world. Since it is currently not possible to cultivate human noroviruses and the wild-type strain of hepatitis A virus in vitro, the use of a variety of viral surrogates is essential to determine appropriate thermal processing conditions to reduce the risk associated with their contamination of food. Therefore, the objectives of this review are to (i) present pertinent characteristics of enteric foodborne viruses and their viral surrogates, (ii) discuss the viral surrogates currently used in thermal inactivation studies and their significance and value, (iii) summarize available data on thermal inactivation kinetics of enteric viruses, (iv) discuss factors affecting the efficacy of thermal treatment, (v) discuss suggested mechanisms of thermal inactivation, and (vi) provide insights on foodborne enteric viruses and viral surrogates for future studies and industrial applications. The overall goal of this review is to contribute to the development of appropriate thermal processing protocols to ensure safe food for human consumption.

Thermal Inactivation Kinetics of Human Norovirus Surrogates and Hepatitis A Virus in Turkey Deli Meat

Human noroviruses (HNoV) and hepatitis A virus (HAV) have been implicated in outbreaks linked to the consumption of presliced ready-to-eat deli meats. The objectives of this research were to determine the thermal inactivation kinetics of HNoV surrogates (murine norovirus 1 [MNV-1] and feline calicivirus strain F9 [FCV-F9]) and HAV in turkey deli meat, compare first-order and Weibull models to describe the data, and calculate Arrhenius activation energy values for each model. The D (decimal reduction time) values in the temperature range of 50 to 72°C calculated from the first-order model were 0.1 ± 0.0 to 9.9 ± 3.9 min for FCV-F9, 0.2 ± 0.0 to 21.0 ± 0.8 min for MNV-1, and 1.0 ± 0.1 to 42.0 ± 5.6 min for HAV. Using the Weibull model, the tD = 1 (time to destroy 1 log) values for FCV-F9, MNV-1, and HAV at the same temperatures ranged from 0.1 ± 0.0 to 11.9 ± 5.1 min, from 0.3 ± 0.1 to 17.8 ± 1.8 min, and from 0.6 ± 0.3 to 25.9 ± 3.7 min, respectively. The z (thermal resistance) values for FCV-F9, MNV-1, and HAV were 11.3 ± 2.1°C, 11.0 ± 1.6°C, and 13.4 ± 2.6°C, respectively, using the Weibull model. The z values using the first-order model were 11.9 ± 1.0°C, 10.9 ± 1.3°C, and 12.8 ± 1.7°C for FCV-F9, MNV-1, and HAV, respectively. For the Weibull model, estimated activation energies for FCV-F9, MNV-1, and HAV were 214 ± 28, 242 ± 36, and 154 ± 19 kJ/mole, respectively, while the calculated activation energies for the first-order model were 181 ± 16, 196 ± 5, and 167 ± 9 kJ/mole, respectively. Precise information on the thermal inactivation of HNoV surrogates and HAV in turkey deli meat was generated. This provided calculations of parameters for more-reliable thermal processes to inactivate viruses in contaminated presliced ready-to-eat deli meats and thus to reduce the risk of foodborne illness outbreaks.

Extreme Heat Resistance of Food Borne Pathogens Campylobacter jejuni, Escherichia coli, and Salmonella typhimurium on Chicken Breast Fillet during Cooking

The aim of this research was to determine the decimal reduction times of bacteria present on chicken fillet in boiling water. The experiments were conducted with Campylobacter jejuni, Salmonella, and Escherichia coli. Whole chicken breast fillets were inoculated with the pathogens, stored overnight (4°C), and subsequently cooked. The surface temperature reached 70°C within 30 sec and 85°C within one minute. Extremely high decimal reduction times of 1.90, 1.97, and 2.20 min were obtained for C. jejuni, E. coli, and S. typhimurium, respectively. Chicken meat and refrigerated storage before cooking enlarged the heat resistance of the food borne pathogens. Additionally, a high challenge temperature or fast heating rate contributed to the level of heat resistance. The data were used to assess the probability of illness (campylobacteriosis) due to consumption of chicken fillet as a function of cooking time. The data revealed that cooking time may be far more critical than previously assumed.

Application of heat in postcook meat chillers reduces Listeria

Electrical air-blowing heaters were used to heat and dry out holding chillers used for postcook commercial processed meats in an attempt to control the presence of Listeria. A baseline study of the prevalence of Listeria in holding chillers in seven facilities was undertaken. Listeria was detected in four of the seven chillers, and swab samples showed Listeria prevalence ranging from 7 (7.8%) of 90 to 6 (20%) of 30, depending on the facility. Two of the facilities with established Listeria contamination (A and E) were chosen for further studies. The heating trials consisted of three individual heating interventions at each of the two facilities, with 2 weeks of postintervention sampling after each treatment. The initial Listeria prevalence in chiller A was 19 (10.6%) of 180, and treatment at 37°C for 36 h reduced prevalence to 3 (1.7%) of 180. The initial Listeria prevalence in chiller E was 7 (7.8%) of 90, and treatment at 50°C for 2 h reduced prevalence to 0 of 90. Both reductions were statistically significant at P < 0.01. The incorporation of these two simple chiller heating protocols into these facilities' good manufacturing practices has effectively reduced prevalence of Listeria in chillers.

Inhibition of Listeria monocytogenes growth in cured ready-to-eat meat products by use of sodium benzoate and sodium diacetate

The effect of sodium benzoate (0.08 to 0.25%) in combination with different concentrations of sodium diacetate (0.05 to 0.15%) and NaClI (0.8 to 2%) and different finished product moisture (55 to 75%) on the growth of Listeria monocytogenes in ready-to-eat meat products was evaluated using a central composite design over 18 weeks of storage at 4 degrees C. The effects of these factors on time to growth were analyzed using a time-to-failure regression method. All main effects were significant except product moisture, which was significant when included in the two- and three-way interactions (P < 0.05). Sodium benzoate was more effective (lengthening time to growth) when used with increasing concentrations of sodium diacetate and salt and decreasing finished product moisture. The model indicated that low-moisture products, e.g., bologna or wieners, could have time-to-growth values longer than 18 weeks if they were formulated with 0.1% sodium benzoate and 0.1% sodium diacetate. Time to growth in high-moisture products, e.g., ham or cured turkey breast at 75% moisture, was predicted to be much shorter for the same basic formulation (0.1% sodium benzoate and 0.1% sodium diacetate). Consequently, high-moisture ready-to-eat products in which sodium benzoate is limited to 0.1% (current standard for generally recognized as safe) may need additional ingredients to effectively inhibit growth of L. monocytogenes.

Pathogen kinetics and heat and mass transfer-based predictive model for Listeria innocua in irregular-shaped poultry products during thermal processing

The increasing demand of ready-to-eat poultry products has led to serious concerns over product safety, and more emphasis has been placed on thorough cooking of products. In this study, processing conditions and thermal inactivation of Listeria innocua in chicken breast meats were evaluated during convection cooking in a pilot-plant scale air-steam impingement oven. A predictive model was developed by integrating heat and mass transfer models with a pathogen kinetics model to predict temperature, water content, product yield, and bacterial inactivation during air-steam impingement cooking. Skinless boneless chicken breasts were cooked at oven air temperatures of 177 and 200 degrees C for 2 to 10 min at a humidity of 70 to 75% (moisture by volume) and an air velocity of 1 m/s at the exit of the nozzles. The reduction in Listeria in chicken breasts after 2 to 5 min of cooking was from 0.3 to 1.4 log CFU/g and from 0.8 to 1.8 log CFU/g at 177 and 200 degrees C, respectively. After cooking for 10 min at both temperatures, no survivors were detected in any of the cooked chicken breasts from an initial bacterial concentration of 10(6) CFU/g. The standard errors of prediction for the endpoint center temperatures after 2 to 10 min of cooking were 2.8 and 3.0 degrees C for air temperatures of 177 and 200 degrees C, respectively. At 177 and 200 degrees C, the median relative errors of prediction for water content were 2.5 and 3.7% and those for product yield were 5.4 and 8.4%, respectively. The developed model can be used as a tool to assist in evaluating thermal processing schedules for poultry products cooked in an air-steam impingement oven.