Effects of lactic acid and hot water treatments on Salmonella Typhimurium and Listeria monocytogenes on beef

Uses of Chemical Technologies for Meat Decontamination

Traditional meat preservation techniques such as smoking, drying, and salting have various shortcomings and limitations in effectively reducing microbial loads and maintaining meat quality. Consequently, chemical compounds have gained attention as promising alternatives for decontamination, offering the potential to extend shelf life and minimize physical, chemical, and sensory changes in meat. Chlorine-based compounds, trisodium phosphate, organic acids, bacteriocins, lactoferrin, and peracetic acid are technologies of recent industrial applications that inhibit spoilage and pathogenic microorganisms in meat. This review explores the critical aspects of decontamination and assesses the efficacy of different chemical compounds employed in meat preservation. These compounds exhibit strong microorganism inactivation capabilities, ensuring minimal alterations to the meat matrix and substantially reducing environmental impact.

Susceptibility of Salmonella serotypes isolated from meat and meat contact surfaces to thermal, acidic, and alkaline treatments and disinfectants

The present study was conducted to evaluate the response of 29 Salmonella isolates to exposure to thermal (60°C for 2 min), acidic (pH 2.9 for 30 min), and alkaline (pH 11 for 60 min) treatments and investigate the susceptibility of the isolates and their biofilms to disinfectants. The reductions of Salmonella isolates populations subjected to each treatment were analyzed according to their isolation source, serotype, antibiotic resistance pattern, and biofilm formation ability. Median reductions for all of Salmonella isolates populations after thermal, acidic, and alkaline treatments were 1.8, 2.1, and 0.7 log CFU/ml, respectively. The isolates behavior under stress conditions were not related to their isolation source, serotype, or biofilm formation ability. The median reduction after alkaline treatment in non-MDR (multidrug- resistant) isolates populations was significantly (p < .05) higher than MDR isolates. The median reduction in biofilms of moderate biofilm producers by disinfectants was significantly (p < .05) higher than that of strong biofilm producers. In conclusion, Salmonella isolates showed the highest susceptibility to acidic treatment and MDR isolates were more resistant to alkaline treatment than non-MDR ones. The current study also revealed that the strong biofilm producer isolates were more resistant to disinfectants than moderate biofilm producers. This study facilitated the understanding of the relationship between Salmonella characteristics (isolation source, serotype, antibiotic resistance pattern, and biofilm formation ability) and its susceptibility to thermal, acidic, and alkaline treatments and disinfectants. The findings are helpful for the prevention and control of Salmonella.

A review of food additives to control the proliferation and transmission of pathogenic microorganisms with emphasis on applications to raw meat-based diets for companion animals

Raw meat-based diets (RMBDs) or sometimes described as biologically appropriate raw food (BARFs) are gaining in popularity amongst dog and cat owners. These pet guardians prefer their animals to eat minimally processed and more "natural" foods instead of highly heat-processed diets manufactured with synthetic preservatives. The market for RMBDs for dogs and cats is estimated at $33 million in the United States. This figure is likely underestimated because some pet owners feed their animals raw diets prepared at home. Despite their increasing demand, RMBDs have been plagued with numerous recalls because of contamination from foodborne pathogens like Salmonella, E. coli, or Campylobacter. Existing literature regarding mitigation strategies in RMBD's for dogs/cats are very limited. Thus, a comprehensive search for published research was conducted regarding technologies used in meat and poultry processing and raw materials tangential to this trade (e.g., meats and poultry). In this review paper, we explored multiple non-thermal processes and GRAS approved food additives that can be used as potential antimicrobials alone or in combinations to assert multiple stressors that impede microbial growth, ultimately leading to pathogen inactivation through hurdle technology. This review focuses on use of high-pressure pasteurization, organic acidulants, essential oils, and bacteriophages as possible approaches to commercially pasteurize RMBDs effectively at a relatively low cost. A summary of the different ways these technologies have been used in the past to control foodborne pathogens in meat and poultry related products and how they can be applied successfully to impede growth of enteric pathogens in commercially produced raw diets for companion animals is provided.

Synergistic Antibacterial Mechanism of Mannosylerythritol Lipid-A and Lactic Acid on Listeria monocytogenes Based on Transcriptomic Analysis

Mannosylerythritol lipids-A (MEL-A) is a novel biosurfactant with multiple biological effects. The synergistic antibacterial activity and mechanism of MEL-A and lactic acid (LA) against Listeria monocytogenes were investigated. The synergistic effect resulted in a significant increase in the antibacterial rate compared to LA treatment alone. Genome-wide transcriptomic analysis was applied to deeply investigate the synergistic antibacterial mechanism. Gene Ontology (GO) enrichment analysis showed that the synergy between MEL-A and LA affected many potential cellular responses, including the sugar phosphotransferase system, carbohydrate transport, and ribosomes. KEGG enrichment analysis showed that the PTS system and ribosome-related pathways were significantly enriched. In addition, synergistic treatment affected locomotion and membrane-related cellular responses in GO enrichment analysis and carbohydrate metabolism and amino acid metabolism pathways in KEGG enrichment analysis compared to LA treatment alone. The accuracy of the transcriptome analysis results was verified by qPCR (R² = 0.9903). This study will provide new insights for the prevention and control of L. monocytogenes.

Listeria monocytogenes inhibition by lactic acid bacteria and coliforms in Brazilian fresh white cheese

INTRODUCTION

Minas fresh cheese (MFC), a Brazilian white cheese, is one of the most popular cheeses nationwide. Studies have shown that Listeria monocytogenes occurrence in this product is generally low, while high populations of coliforms can be found. This study aimed to evaluate the influence of coliforms in the behavior of L. monocytogenes in MFC.

METHODS

Pasteurized milk was inoculated with L. monocytogenes and coliforms, and the acidification was made by lactic acid or by the addition of a starter culture. The cheeses of each production were divided into 3 groups and stored at 5 ºC, 12 ºC and cycles of 5 ºC followed by 25 ºC. In predetermined days, samples were taken and L. monocytogenes, coliforms and lactic acid bacteria populations were evaluated, besides the pH, water activity (aw), titratable acidity and NaCl concentration.

RESULTS

The inhibition of L. monocytogenes in the presence of coliforms was observed (p < 0.05), except for those samples prepared with lactic acid and stored at temperature cycles. The values of pH and aw were not sufficiently low to cause inhibition; however, titratable acidity was higher in cheeses containing coliforms. In vitro tests containing lactic acid and L. monocytogenes showed that the bacterium is sensitive to concentration of lactic acid ≥ 0.3%, indicating that lactic acid produced by coliforms strongly influences the population of L. monocytogenes.

CONCLUSIONS

Thus, it can be concluded that coliforms negatively impact populations of L. monocytogenes in MFC. We strongly recommend that producers of MFC adopt good hygiene practices to not only avoid contamination with L. monocytogenes, but also coliforms.

Effect of lactic acid spray on microbial and quality parameters of buffalo meat

We evaluated the effect of lactic acid spray on micro-flora, instrumental color, shelf-life and sensory attributes of buffalo meat displayed under Modified Atmosphere Packaging. Buffalo calf carcasses (n = 12) were sliced into equal sagittal halves, n = 6 halves were randomly assigned to each of four treatments i.e. 2% LA, 4% LA, 6% LA and control. Afterwards, sirloin and tenderloin were vacuum packed and aged for 7 days. Later, steaks were packed in high-oxygen MAP. Microbial load, instrumental color, shelf-life and sensory attributes were evaluated at different days. Aerobic plate count of sprayed carcass and steaks was significantly lower than un-sprayed control. Similarly, though non-significant, redness and chroma value of sprayed carcass meat was found better than un-sprayed control. Lactic acid sprayed meat did not differ in terms of sensory attributes. It is concluded that spraying buffalo carcasses with 2-4% lactic acid after slaughter not only enhances microbial quality but it may also improve its instrumental color.

Use of Caprylic Acid in Broiler Chickens: Effect on Campylobacter jejuni

The effect of caprylic acid (CA) on Campylobacter jejuni in chickens was evaluated using two approaches: dietary supplementation or surface treatment of chilled chicken carcasses. To analyze the dietary effect of CA, individually housed broiler chickens (n = 48) were artificially infected with C. jejuni VFU612 (10(6) colony-forming units [CFU]/bird) on the 21st and 35th days of life. Dietary CA (2.5 and 5 g/kg of feed, fed throughout the entire experiment) significantly decreased C. jejuni shedding (p<0.05). However, the effect only lasted for 3-7 days after infection. The numbers of Campylobacter shed by the positive control birds reached its maximum on the 37th day of life, while on that same day, both Treatment I and Treatment II groups shed significantly lower (p<0.05) numbers of Campylobacter (by 0.8 and 1.8 log10 CFU/g, respectively). Also, peak shedding was delayed by 1 day in both treated groups. After euthanasia of each chicken on the 42nd day of life, no differences in Campylobacter counts in the crop, gizzard, ileum, and cecum were found between the positive control and the treated groups (p>0.05). Surface contamination of the chilled chicken halves was performed with C. jejuni VFU612 (clinical isolate) and CCM6214 (collection strain). Surface treatment with CA at 1.25 and 2.5 mg/mL for 1 min significantly reduced C. jejuni VFU612 contamination of chicken skin (p<0.05) by 0.29-0.53 and 1.14-1.58 log10 CFU/g of skin, respectively. Counts of C. jejuni CCM6214 were reduced by 0.68-1.65 log10 CFU/g of skin). In conclusion, dietary CA affected numbers of C. jejuni in the gastrointestinal contents of chickens, whereas surface treatment reduced C. jejuni contamination in processed chicken carcasses.

Antimicrobial Effect of Calcium Chloride Alone and Combined with Lactic Acid Injected into Chicken Breast Meat

Chicken breast meat was injected with calcium chloride alone and in combination with lactic acid (0.01% and 0.002%, respectively). The inhibitory effects of the treatments on microbial growth were determined in the injected chicken breast meat stored at 4°C under aerobic packaging condition for 0, 3, and 7 d. Calcium chloride combined with 0.002% and 0.01% lactic acid reduced microbial counts by 0.14 and 1.08 Log CFU/g, respectively, however, calcium chloride alone was unable to inhibit microbial growth. Calcium chloride combined with 0.01% lactic acid was the most effective antimicrobial treatment and resulted in the highest initial redness value. Calcium chloride alone and combined with lactic acid suppressed changes in pH and the Hunter color values during storage. However, injection of calcium chloride and lactic acid had adverse effects on lipid oxidation and sensory characteristics. The higher TBARS values were observed in samples treated with calcium chloride and lactic acid when compared to control over the storage period. Addition of calcium chloride and lactic acid resulted in lower sensory scores for parameters tested, except odor and color, compared to control samples. Therefore, the formulation should be improved in order to overcome such defects prior to industrial application.

Controlling Vibrio vulnificus and spoilage bacteria in fresh shucked oysters using natural antimicrobials

This study evaluated the efficacy of grape seed extract (GE), citric acid (CA) and lactic acid (LA) on the inactivation of Vibrio vulnificus and inherent microflora in fresh shucked oysters. The minimum inhibitory concentration (MIC) of GE, CA or LA against V. vulnificus was determined. Furthermore, the shucked oysters were artificially inoculated with V. vulnificus. The inoculated shucked oysters (25 g) were then dipped in 250 ml GE, CA or LA solutions for 10 min. The population of V. vulnificus in shucked oysters was determined. The effects of the treatments with GE, CA or LA solutions on the inherent microbiota in fresh shucked oysters during storage at 5°C for 20 days were also studied. The MICs of GE, CA or LA against V. vulnificus were 10.0, 5.0 or 1.0 mg ml(-1), respectively. The concentrations of 500, 300 or 150 mg ml(-1) GE, CA or LA solutions were needed to reduce the population of V. vulnificus to below the detection level (1.0 log g(-1)). Treatment with 500, 300, 150 mg ml(-1) GE, CA or LA significantly reduced the initial inherent microbiota in fresh shucked oysters, and inherent levels were significantly (P < 0.05) lower than the control sample throughout refrigerated storage for 20 days.

SIGNIFICANCE AND IMPACT OF THE STUDY

Oysters filter large volume of seawater during their feeding activities that concentrate bacteria such as Vibrio vulnificus in their body. The presence of V. vulnificus in oysters has a serious impact on public health and international trade. There is increasing concern over the use of chemical preservatives. Furthermore, the food industry is looking for new natural preservation methods. This study indicated that lactic acid and citric acid wash solutions could offer an inexpensive, natural and strong approach to control V. vulnificus and spoilage bacteria in fresh shucked for the oyster industry.

Effect of steam and lactic acid treatments on the survival of Salmonella Enteritidis and Campylobacter jejuni inoculated on chicken skin

Campylobacteriosis and salmonellosis are the most frequently reported zoonotic infectious diseases. The present work evaluated the effectiveness of steam treatment at 100 °C for 8s, a 5% lactic acid treatment for 1 min and their combination for inactivating Salmonella Enteritidis and Campylobacter jejuni inoculated on chicken skin. The impact of each treatment on the total aerobic mesophilic bacteria and the effect of rinsing after contact with lactic acid were also evaluated. Residual bacteria were counted immediately after treatment or after seven days of storage at 4 °C. Results demonstrated the immediate efficiency of the steam and the combined treatments with reductions of approximately 6 and 5 log cfu/cm2 respectively for S. Enteritidis and C. jejuni. They also showed significant reductions (equal to or >3.2 log cfu/cm2) in the total aerobic mesophilic plate count. Lactic acid had a persistent effect on pathogen growth during storage which was significantly higher when the skin was not rinsed, reaching reductions of 3.8 log cfu/cm2 for both S. Enteritidis and C. jejuni. Only the combined treatments significantly reduced the recovery of the total aerobic mesophilic bacteria during storage. The significant reductions in both pathogens and total aerobic mesophilic bacteria on treated chicken skins are possible ways to improve the safety and shelf life of the product although high levels of indigenous non-pathogenic bacteria may be beneficial due to their protective effect against potential re-contamination of chicken skin.

Validation of a lactic acid- and citric acid-based antimicrobial product for the reduction of Escherichia coli O157: H7 and Salmonella on beef tips and whole chicken carcasses

The objectives of this study were to determine the effects of a lactic acid- and citric acid-based antimicrobial product on the reduction of Salmonella on whole broiler carcasses during processing and the reduction of Salmonella and Escherichia coli O157:H7 on beef trim. Freshly harvested broiler carcasses were inoculated with an inoculum of Salmonella strains to yield a 10(5) CFU/ml pathogen load on the surface of the carcass. The beef tips were inoculated as well with an inoculum of either E. coli O157:H7 or Salmonella to yield 10(4) CFU/100 cm(2). After 30 min for attachment, the broiler carcasses were treated with Chicxide applied for 5 s via a spray or immersed in Chicxide for 5, 10, or 20 s. Broiler carcasses were rinsed in poultry rinse bags with 400 ml of Butterfield's phosphate buffer in which Salmonella was enumerated from the diluents and Butterfield's phosphate. Chicxide significantly reduced Salmonella by 1.3 log CFU/ml with spray treatment and 2.3 log CFU/ml for all dip treatments. Following 30 min of attachment, the beef tips were placed into a spray cabinet with either Beefxide or sterilized water (control) and sprayed at 1 ft/2.5 s chain speed at 40 lb/in(2). The external surface of each beef tip was swabbed (100 cm(2)) to determine pathogen loads. Beefxide significantly reduced E. coli O157:H7 by 1.4 log CFU/100 cm(2) and Salmonella by 1.1 log CFU/100 cm(2) (P < 0.05) compared with the control samples.

Effectiveness of lemon juice in the elimination of Salmonella Typhimurium in stuffed mussels

Street foods are becoming more and more prominent in countries all over the world. There are many reports of disease due to consumption of street foods contaminated by pathogens. With the modern trend toward more natural preservatives, the use of organic acids can achieve a good microbiological safety in food. In the present study, stuffed mussels were inoculated with Salmonella Typhimurium suspension to provide initial populations of approximately 6 and 3 log CFU/g. After inoculation, samples were treated with fresh lemon juice and lemon dressing for 0, 5, and 15 min, and pathogens were enumerated by using direct plating on brilliant green agar. Treatment of stuffed mussels inoculated at high inoculum level, with lemon juice and lemon dressing for different exposure times caused reduction ranging between 0.25 and 0.56 log CFU/g and 0.5 and 0.69 log CFU/g, respectively, whereas in stuffed-mussel samples inoculated at low level, lemon juice and lemon dressing caused 0.08 to 0.25 log CFU/g and 0.22 to 0.78 log CFU/g reductions, respectively. Results of the study showed that both lemon juice and lemon dressing used as flavoring and acidifying agents for stuffed mussels caused slight decrease in Salmonella Typhimurium as an immediate inhibitor, but this effect increased by time. However, treatment of stuffed mussels with the inhibitors until 15 min is not enough to prevent Salmonella Typhimurium outbreaks related to stuffed mussels.