Delaying toxigenesis of Clostridium botulinum by sodium lactate in ‘sous-vide’ products

Microbial Food Safety of Sous Vide Cooking Processes of Chicken and Eggs

Sous vide cooking implies cooking foods, packed under vacuum conditions, at controlled temperatures (<80 °C). Although this method opens a new window of culinary possibilities, it also involves a series of risks, mainly microbiologically related, that must be assessed. The aim of this work was to evaluate the effectiveness of SV processes to inactivate three important foodborne pathogens (Campylobacter, Salmonella, and Clostridium spores) in chicken breast and eggs (omelet). For this purpose, two levels of inoculation (102 and 106 CFU/g), two different recipes, and two distinct treatments (with and without storage) for each food were studied. After treatments and storage, the corresponding microbiological counts were performed with standard methods. Average inactivation rates observed were 1.70, 4.82, and 4.34 log for Clostridium spores, Campylobacter, and Salmonella, respectively. No significant differences in microbial inactivation were perceived between the different recipes (food composition) or treatments, except for Clostridium spores, which showed a higher inactivation rate (2.30 log) when samples were stored. In general, preliminary results showed that, although appropriate levels of inactivation are reached for vegetative pathogenic cells, in some cases (spores in breast and Salmonella in eggs), the remaining microbiological risks should be considered and further studied, especially if long-term storage is planned.

A possible systematic culinary approach for spent duck meat: Sous-vide cuisine and its optimal cooking condition

This study offered a possible systematic culinary approach to spent-laying ducks. Breast meat is suitable for processing due to its amount and completeness. Sous-vide cooking resulted in lower cooking loss than poaching, pan-frying (P < 0.05), and roasting. The sous-vide duck breast had higher gumminess, chewiness, and resilience than other culinary techniques (P < 0.05). Sous-vide cooking at 65°C had a lower cooking loss than 70°C (P < 0.05), and less than 1.5-h sous-vide could keep a lower cooking loss and WB shear value (P < 0.05) as the cooking period extended, the smaller (P < 0.05) quantity of myosin heavy chain and the destroyed sarcomere arrangement were observed. A condition at 65°C for 1.5 h could be the optimal sous-vide cuisine for spent-laying duck breast. These sous-vide products stored at 4°C were still safe for consumption due to no detectible microorganisms and unchangeable physicochemical properties within 7 d.

Sous vide processing: a viable approach for the assurance of microbial food safety

As consumer needs change, innovative food processing techniques are being developed that have minimal impact on food quality and ensure its microbiological safety. Sous vide (SV) is an emerging technology of cooking foods in vacuum pouches at specific temperatures, which results in even heat distribution. Presented here is an overview of the current state of the art in the application of SV techniques for processing and preserving foods. Unlike the conventional thermal food processing approach, the precise nature of the SV method improves food quality, nutrition and shelf-life while destroying microorganisms. Foods processed by SV are usually subjected to temperatures between 50 and 100 °C. Although sufficient for food preparation/processing, its effectiveness in eliminating microbial pathogens, including viruses, parasites, vegetative and spore forms of bacteria, is limited. However, the inactivation of spore-forming microbes can be enhanced by combining the technique with other non-thermal methods that exert negligible impact on the nutritional, flavour and sensory characteristics of foods. In addition to exploring the mechanism of action of SV technology, the challenges related to its implementation in the food industry are also discussed. SV method potential, applications, and impacts on spore-forming microbes and spore inactivation are explored in this review. Through the debate and discussion presented, further research and industrial applications of this food processing method could be guided. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Cardinal parameter growth and growth boundary model for non-proteolytic Clostridium botulinum - Effect of eight environmental factors

A new cardinal parameter growth and growth boundary model for non-proteolytic C. botulinum was developed and validated for fresh and lightly preserved seafood and poultry products. 523 growth rates in broth were used to determine cardinal parameter values and terms for temperature, pH, NaCl/water activity, acetic, benzoic, citric, lactic and sorbic acids. The new growth and growth boundary model included the inhibiting interactive effect between these factors and it was calibrated using growth curves from 10 challenge tests with unprocessed seafood. For model evaluation, 40 challenge tests with well characterized fresh and lightly preserved seafood were performed. Comparison of these observed growth curves and growth rates (μ_max-values) predicted by the new model resulted in a bias factor (B_f) of 1.12 and an accuracy factor (A_f) of 1.40. Furthermore, the new model was evaluated with 94 growth rates and 432 time to toxin formation data extracted from the scientific literature for seafood, poultry, meat, pasta and prepared meals. These data included responses for 36 different toxigenic strains of non-proteolytic C. botulinum. The obtained B_f-/A_f-values were 0.97/2.04 for μ_max-values and 0.96/1.80 for time to toxin formation. The model correctly predicted 93.8% of the growth responses with 5.6% being fail-safe and <1% fail-dangerous. A cocktail of four non-toxin producing Clostridium spp. isolates was used to develop the new model and these isolates had more than 99.8% 16S rRNA gene similarity to non-proteolytic C. botulinum (Group II). The high number of environmental factors included in the new model makes it a flexible tool to facilitate development or reformulation of seafood and poultry products that do not support the growth of non-proteolytic C. botulinum. Further, evaluation of the new model with well characterized products is desirable particularly for meat, vegetables, pasta and prepared meals as well as for dairy products that was not included in the present study.

High prevalence of Clostridium botulinum in vegetarian sausages

Clostridium botulinum is a significant food safety concern due to its ability to produce highly potent neurotoxin and resistant endospores. Vegetarian sausages have become a popular source of plant protein and alternative for meat products. While vegetarian sausages have not been linked to botulism, numerous outbreaks due to preserved vegetables suggest a frequent occurrence of C. botulinum spores in the raw material. The product formulation of vegetarian sausages involves limited NaCl and preservatives, and shelf-lives may be several months. The safety of vegetarian sausages thus relies mainly on heat treatment and chilled storage. The main food safety concern is C. botulinum Group II that can grow and produce toxin at refrigeration temperatures. Here we show a high overall prevalence (32%) of C. botulinum in 74 samples of vegetarian sausages from seven producers. Both Groups I and II strains and genes for neurotoxin types A, B, E and F were detected in the products. The highest cell counts (1200 spores/kg) were observed for C. botulinum Group II in products with remaining shelf-lives of 6 months at the time of purchase. We conclude that vacuum-packaged vegetarian sausage products frequently contain C. botulinum spores and may possess a high risk of C. botulinum growth and toxin production. Chilled storage below 3°C and thorough reheating before consumption are warranted.

New strategies for minimally processed foods. The role of multitarget preservation/Nuevas estrategias para los alimentos mínimamente procesados. La conservación "multiblanco"

Minimally processed foods represent a problem from the point of view of microbiological safety, since their processing implies a loss of extrinsic and intrinsic preservation factors. This paper analyzes the microbiological status of minimally processed foods and the prospects to extend their microbiological safety by the hurdles technology. Some issues to be taken into account for this technology are also considered

Hazard and control of group II (non-proteolytic) Clostridium botulinum in modern food processing

Group II (non-proteolytic) Clostridium botulinum poses a safety hazard in modern food processing, which consists of mild pasteurization treatments, anaerobic packaging, extended shelf lives and chilled storage. The high risk is reflected in the relatively large number of botulism cases due to group II C. botulinum in commercially produced foods during the past decades. Because of the high prevalence of group II C. botulinum in the environment, food raw materials may carry spores. Although group II spores are less heat-resistant than group I (proteolytic) spores, they can tolerate the heat treatments employed in the chilled food industry. Some food components may actually provide spores with protection from heat. Spore heat resistance should therefore be investigated for each food in order to determine the efficiency of industrial heat treatments. Group II strains are psychrotrophic and thus they are able to grow at refrigeration temperatures. Anaerobic packages and extended shelf lives provide C. botulinum with favourable conditions for growth and toxin formation. As the use of salt and other preservatives in these foods is limited, microbiological safety relies mainly on refrigerated storage. This sets great challenges on the production of chilled packaged foods. To ensure the safety of these foods, more than one factor should safeguard against botulinal growth and toxin production.

Growth and germination of proteolytic Clostridium botulinum in vegetable-based media

The growth of proteolytic Clostridium botulinum from spore inocula and changes in spore counts in mushroom, broccoli, and potato purées were monitored. Four strains of proteolytic C. botulinum types A and B were inoculated separately at approximately 10(4) spores per ml in nutrient broth and vegetable purées incubated at 15, 20, and 30 degrees C for up to 52 days. The times for the cell populations to increase 1,000-fold (T1,000) in the tested vegetables (1 to 5 days at 30 degrees C, 3 to 16 days at 20 degrees C, 7 to > 52 days at 15 degrees C) were similar to those for meat or fish. Only temperature significantly influenced growth rate. In contrast, the lag phase depended on the strains and media tested, in addition to temperature. Lag times and T1,000S for proteolytic C. botulinum were longer for potato and broccoli purées than for mushroom purée. These differences were not related to different pHs or redox potentials. The germination level, evaluated as the decrease in the spore count, was low. The addition of a germinant mixture (L-cysteine, L-alanine, and sodium lactate) to some strains inoculated in vegetable purées resulted in an increase in germination, suggesting a lack of germination-triggering agents in the vegetable purées.

Effects of chilling rate on outgrowth of Clostridium perfringens spores in vacuum-packaged cooked beef and pork

Cooked, chilled beef and cooked, chilled pork were inoculated with three strains of Clostridium perfringens (NCTC 8238 [Hobbs serotype 2], NCTC 8239 [Hobbs serotype 3], and NCTC 10240). Inoculated products were heated to 75 degrees C, held for 10 min in a circulating water bath to heat activate the spores, and then chilled by circulating chilled brine through the water bath. Samples were chilled from 54.4 to 26.6 degrees C in 2 h and from 26.6 to 4.4 degrees C in 5 h. Differences in initial C. perfringens log counts and log counts after chilling were determined and compared with the U.S. Department of Agriculture (USDA) stabilization guidelines requiring that the chilling process allow no more than 1 log total growth of C. perfringens in the finished product. This chilling method resulted in average C. perfringens increases of 0.52 and 0.68 log units in cooked beef and cooked pork, respectively. These log increases were well within the maximum 1-log increase permitted by the USDA, thus meeting the USDA compliance guidelines for the cooling of heat-treated meat and poultry products.

Inhibition of growth of nonproteolytic Clostridium botulinum type B in sous vide cooked meat products is achieved by using thermal processing but not nisin

The safety of refrigerated processed foods of extended durability (REPFEDs) with respect to nonproteolytic Clostridium botulinum is under continuous evaluation. In the present study, mild (P7.0(85.0) values 0 to 2 min [P, pasteurization value; z-value 7.0 degrees C; reference temperature 85.0 degrees C]) and increased (P7.0(85.0) values 67 to 515 min) heat treatments were evaluated in relation to survival of nonproteolytic C. botulinum type B spores in sous vide processed ground beef and pork cubes. The use of two concentrations of nisin in inhibition of growth and toxin production by nonproteolytic C. botulinum in the same products was also evaluated. A total of 96 samples were heat processed and analyzed for C. botulinum by BoNT/B gene-specific polmerase chain reaction and for botulinum toxin by a mouse bioassay after storage of 14 to 28 days at 4 and 8 degrees C. Predictably, after mild processing all samples of both products showed botulinal growth, and one ground beef sample became toxic at 8 degrees C. The increased heat processing, equivalent to 67 min at 85 degrees C. resulted in growth but not toxin production of C. botulinum in one ground beef sample in 21 days at 8 degrees C: in the pork cube samples no growth was detected. The increased heating of both products resulted in higher sensory quality than the milder heat treatment. Nisin did not inhibit the growth of nonproteolytic C. botulinum in either product; growth was detected in both products at 4 and 8 degrees C, and ground beef became toxic with all nisin levels within 21 to 28 days at 8 degrees C. Aerobic and lactic acid bacterial counts were reduced by the addition of nisin at 4 degrees C. The study demonstrates that the mild processing temperatures commonly employed in sous vide technology do not eliminate nonproteolytic C. botulinum type B spores. The intensity of each heat treatment needs to be carefully evaluated individually for each product to ensure product safety in relation to nonproteolytic C. botulinum.

The effect of calcium and sodium lactates on growth from spores of Bacillus cereus and Clostridium perfringens in a 'sous-vide' beef goulash under temperature abuse

The effect of calcium and sodium lactates on growth from spores of Bacillus cereus and Clostridium perfringens at three different concentrations (0, 1.5 and 3% w/w) and at different temperatures (10, 15 and 20 degrees C for B. cereus and 15, 20 and 25 degrees C for C. perfringens) was investigated, using beef goulash as a model system for pasteurised vacuum-packaged convenience foods. Calcium lactate at a level of 3% reduced the pH values of the samples from 6.0 to 5.5. No B. cereus growth was observed at 10 degrees C, but after 7 days at an incubation temperature of 15 degrees C, cell number increased by 1 log cfu/g in the control samples. At this temperature, lactates were seen to be effective at inhibiting growth. Calcium lactate was more inhibitory than sodium lactate as the growth of B. cereus was inhibited at 1.5 and 3% concentrations at 20 degrees C, respectively. Growth of C. perfringens was arrested in the presence of 1.5% calcium lactate at all storage temperatures, whereas growth was inhibited by 3% sodium lactate only at 15 degrees C.

Nonproteolytic Clostridium botulinum toxigenesis in cooked turkey stored under modified atmospheres

The ability of nonproteolytic Clostridium botulinum type B spores to grow and produce toxin in cooked, uncured turkey packaged under modified atmospheres was investigated at refrigeration and mild to moderate abuse temperatures. Cook-in-bag turkey breast was carved into small chunks, surface-inoculated with a mixture of nonproteolytic C. botulinum type B spores, packaged in O2-impermeable bags under two modified atmospheres (100% N2 and 30% CO2:70% N2), and stored at 4, 10, and 15 degrees C. Samples were analyzed for botulinal toxin and indigenous microorganisms, as well as subjected to sensory evaluation, on days 0, 7, 14, 28, 42, and 60. Given sufficient incubation time, nonproteolytic C. botulinum type B grew and produced toxin in all temperature and modified atmosphere treatment combinations. At moderate temperature abuse (15 degrees C), toxin was detected by day 7, independent of packaging atmosphere. At mild temperature abuse (10 degrees C), toxin was detected by day 14, also independent of packaging atmosphere. At refrigeration temperature (4 degrees C), toxin was detected by day 14 in product packaged under 100% N2 and by day 28 in product packaged under 30% CO2:70% N2. Reduced storage temperature significantly delayed toxin production and extended the period of sensory acceptability of cooked turkey, but even strict refrigeration did not prevent growth and toxigenesis by nonproteolytic C. botulinum. At all three storage temperatures, toxin detection preceded or coincided with development of sensory characteristics of spoilage, demonstrating the potential for consumption of toxic product when spoilage-signaling sensory cues are absent.

Shelf life of modified atmosphere packed cooked meat products: addition of Na-lactate as a fourth shelf life determinative factor in a model and product validation

Cooked meat products are often post-contaminated because of a packaging and/or slicing step after the pasteurisation process. The shelf life is therefore limited and can be extended by adding Na-lactate. A previously developed model for the spoilage of gas packed cooked meat products, including temperature, water activity and dissolved CO2 as independent variables, was extended with a fourth factor: the Na-lactate concentration in the aqueous phase of the meat product. Models were developed for the maximum specific growth rate mu(max) and the lag phase lambda of the specific spoilage organism Lactobacillus sake subsp. carnosum. Quadratic response surface equations were compared with extended Ratkowsky models. In general, response surface equations fitted the experimental data best but in the case of mu(max) the response surface model predicted illogical growth behaviour at low water activities and high Na-lactate concentrations. A extensive product validation of the mathematical models was performed by means of inoculated as well as naturally contaminated industrially prepared cooked meat products. The deviations of the experimentally determined versus predicted growth parameters in inoculated cooked meat products were in general small. Both types of models were also able to predict the shelf life of naturally contaminated cooked meat products, except for pâté where an under-estimation of the shelf life was predicted by the response surface equations. The validation studies revealed higher accuracy of the extended Ratkowsky models in comparison to the response surface equations. A significant shelf life extending effect of Na-lactate was predicted, which was more pronounced at low refrigerated temperatures. A synergistic effect has also been noticed between Na-lactate and carbon dioxide which, at least partly, could be explained by the pH-decreasing effect of CO2.

Safety evaluation of sous vide-processed products with respect to nonproteolytic Clostridium botulinum by use of challenge studies and predictive microbiological models

Sixteen different types of sous vide-processed products were evaluated for safety with respect to nonproteolytic group II Clostridium botulinum by using challenge tests with low (2. 0-log-CFU/kg) and high (5.3-log-CFU/kg) inocula and two currently available predictive microbiological models, Food MicroModel (FMM) and Pathogen Modeling Program (PMP). After thermal processing, the products were stored at 4 and 8 degrees C and examined for the presence of botulinal spores and neurotoxin on the sell-by date and 7 days after the sell-by date. Most of the thermal processes were found to be inadequate for eliminating spores, even in low-inoculum samples. Only 2 of the 16 products were found to be negative for botulinal spores and neurotoxin at both sampling times. Two products at the high inoculum level showed toxigenesis during storage at 8 degrees C, one of them at the sell-by date. The predictions generated by both the FMM thermal death model and the FMM and PMP growth models were found to be inconsistent with the observed results in a majority of the challenges. The inaccurate predictions were caused by the limited number and range of the controlling factors in the models. Based on this study, it was concluded that the safety of sous vide products needs to be carefully evaluated product by product. Time-temperature combinations used in thermal treatments should be reevaluated to increase the efficiency of processing, and the use of additional antibotulinal hurdles, such as biopreservatives, should be assessed.

Microbiological quality of cooked chicken breasts containing commercially available shelf-life extenders

Experiments were conducted to determine the effect of various shelf-life extenders on the aerobic plate counts (APC) of cooked chicken breast meat stored at refrigeration temperatures. Fresh chicken breast meat obtained from local grocers was injected with either 0.5, 1, 1.5, or 2% sodium lactate; 0.63, 1.25, 1.88, or 2.51 g/kg of a liquid smoke flavoring; 0.33, 0.66, 1, or 1.33% Per/Lac 1901, a fermented whey product; or 0.25, 0.5, 0.75, or 1% Alta 2341, a fermented corn syrup product. The samples were cooked at 85 C dry bulb, 77.8 C wet bulb to an internal temperature of 76.7 C. The cooked chicken breasts were cut into 20-g samples and aseptically placed into Ziploc bags. Initial APC were enumerated following 2-d incubation at 30 C. Additional stored samples (2 C) were subsequently evaluated for APC every week for 5 wk. Only one of the four ingredients, Alta 2341, significantly extended cooked breast meat shelf-life over that of the controls. Using Alta 2341 would be beneficial in extending the refrigerated shelf-life of cooked chicken breast meat up to 5 wk.

Predictive model of the effect of temperature, pH and sodium chloride on growth from spores of non-proteolytic Clostridium botulinum

Non-proteolytic strains of Clostridium botulinum are capable of growth at chill temperatures and thus pose a potential hazard in minimally-processed chilled foods. The combined effect of pH (5.0-7.3), NaCl concentration (0.1-5.0%) and temperature (4-30 degrees C) on growth of non-proteolytic C. botulinum in laboratory media was studied. Growth curves at various combinations of pH, NaCl concentration and temperature were fitted by the Gompertz and Baranyi models, and parameters derived from the curve-fit were modelled. Predictions of growth from the models were compared with data in the literature and this showed them to be suitable for use with fish, meat and poultry products. This model should contribute to ensuring the safety of minimally-processed foods with respect to non-proteolytic C. botulinum.

Growth of and toxin production by nonproteolytic Clostridium botulinum in cooked puréed vegetables at refrigeration temperatures

Seven strains of nonproteolytic Clostridium botulinum (types B, E, and F) were each inoculated into a range of anaerobic cooked puréed vegetables. After incubation at 10 degrees C for 15 to 60 days, all seven strains formed toxin in mushrooms, five did so in broccoli, four did so in cauliflower, three did so in asparagus, and one did so in kale. Growth kinetics of nonproteolytic C. botulinum type B in cooked mushrooms, cauliflower, and potatoes were determined at 16, 10, 8, and 5 degrees C. Growth and toxin production occurred in cooked cauliflower and mushrooms at all temperatures and in potatoes at 16 and 8 degrees C. The C. botulinum neurotoxin was detected within 3 to 5 days at 16 degrees C, 11 to 13 days at 10 degrees C, 10 to 34 days at 8 degrees C, and 17 to 20 days at 5 degrees C.

Effect of heat treatment on survival of, and growth from, spores of nonproteolytic Clostridium botulinum at refrigeration temperatures

Spores of five type B, five type E, and two type F strains of nonproteolytic Clostridium botulinum were inoculated into tubes of an anaerobic meat medium plus lysozyme to give approximately 10(6) spores per tube. Sets of tubes were then subjected to a heat treatment, cooled, and incubated at 6, 8, 10, 12, and 25 degrees C for up to 60 days. Treatments equivalent to heating at 65 degrees C for 364 min, 70 degrees C for 8 min, and 75 degrees C for 27 min had little effect on growth and toxin formation. After a treatment equivalent to heating at 85 degrees C for 23 min, growth occurred at 6 and 8 degrees C within 28 to 40 days. After a treatment equivalent to heating at 80 degrees C for 19 min, growth occurred in some tubes at 6, 8, 10, or 12 degrees C within 28 to 53 days and at 25 degrees C in all tubes within 15 days. Following a treatment equivalent to heating at 95 degrees C for 15 mine, growth was detected in some tubes incubated at 25 degrees C for fewer than 60 days but not in tubes incubated at 6 to 12 degrees C. The results indicate that heat treatment of processed foods equivalent to maintenance at 85 degrees C for 19 min combined with storage below 12 degrees C and a shelf life of not more than 28 days would reduce the risk of growth from spores of nonproteolytic C. botulinum by a factor of 10(6).(ABSTRACT TRUNCATED AT 250 WORDS)