Quantification of Process Lethality (5-Log Reduction) of Salmonella and Salt Concentration during Sodium Replacement in Biltong Marinade

Salt (sodium chloride, NaCl) is commonly used in ready-to-eat (RTE) meat products such as biltong, a South African style dried beef product for flavor, enhanced moisture loss, and reduction of microbial growth. However, increased consumption of high sodium content foods is commonly associated with high blood pressure and heart disease. This study evaluated the use of alternative salts, potassium chloride (KCl) and calcium chloride (CaCl2) in the biltong marinade to achieve a ≥ 5-log reduction of Salmonella, a pathogen of concern in beef products. Beef pieces (1.9 cm × 5.1 cm × 7.6 cm) were inoculated with a five-serovar mixture of Salmonella (Salmonella Thompson 120, Salmonella Enteritidis H3527, Salmonella Typhimurium H3380, Salmonella Heidelberg F5038BG1, and Salmonella Hadar MF60404), vacuum-tumbled in a traditional biltong marinade of salt, spices, and vinegar containing either NaCl, KCl or CaCl2 (2.2% concentration) followed by an 8–10 day drying period at 23.9 °C (75 °F) and 55% relative humidity. Microbial enumeration of Salmonella was conducted following inoculation, after marination, and after 2, 4, 6, 8, and 10 days of drying in a humidity/temperature chamber. Biltong produced with CaCl2, NaCl, or KCl achieved a > 5-log reduction of Salmonella after 6, 7, and 8 days, respectively. The Salmonella reduction trends with biltong made with NaCl or CaCl2 were not significantly different (p < 0.05) while both were significantly different from that made with KCl (p > 0.05). Sodium, calcium, and potassium ion concentrations were measured using ion-specific electrode meters following biltong processing and drying. As expected, the biltong made with the corresponding salt had the most abundant ion in the sample. Regardless of the salt used in the marinade, the potassium ion levels were moderately elevated in all samples. This was determined to be from potassium levels naturally present in beef rather than from other ingredients. Sampling of several commercial brands of biltong for sodium content showed that some were significantly above the allowable level of claims made on package ingredient statements. The substitution of NaCl with KCl or CaCl2 during biltong processing can also provide a 5-log reduction of Salmonella to produce a safe product that can be marketed as a more healthy low-sodium food alternative that may appeal to consumers who need to reduce their blood pressure and are conscientious of sodium levels in their diet.

Processing of Biltong (Dried Beef) to Achieve USDA-FSIS 5-log Reduction of Salmonella without a Heat Lethality Step

In the US, dried beef products (beef jerky) are a popular snack product in which the manufacture often requires the use of a heat lethality step to provide adequate reduction of pathogens of concern (i.e., 5-log reduction of Salmonella as recommended by the United States Department of Agriculture Food Safety and Inspection Service (USDA-FSIS)). Biltong, a South African-style dried beef product, is manufactured with low heat and humidity. Our objectives were to examine processes for the manufacture of biltong that achieves a 5-log reduction of Salmonella without a heat lethality step and with, or without, the use of additional antimicrobials. Beef pieces (1.9 cm × 5.1 cm × 7.6 cm) were inoculated with a 5-serovar mixture of Salmonella (Salmonella Thompson 120, Salmonella Heidelberg F5038BG1, Salmonella Hadar MF60404, Salmonella Enteritidis H3527, and Salmonella Typhimurium H3380), dipped in antimicrobial solutions (lactic acid, acidified calcium sulfate, sodium acid sulfate) or water (no additional antimicrobial), and marinaded while vacuum tumbling and/or while held overnight at 5 °C. After marination, beef pieces were hung in an oven set at 22.2 °C (72 °F), 23.9 °C (75 °F), or 25 °C (77 °F) depending on the process, and maintained at 55% relative humidity. Beef samples were enumerated for Salmonella after inoculation, after dip treatment, after marination, and after 2, 4, 6, and 8 days of drying. Water activity was generally <0.85 by the end of 6–8 days of drying and weight loss was as high as 60%. Trials also examined salt concentration (1.7%, 2.2%, 2.7%) and marinade vinegar composition (2%, 3%, 4%) in the raw formulation. Nearly all approaches achieved 5-log10 reduction of Salmonella and was attributed to the manner of microbial enumeration eliminating the effects of microbial concentration on dried beef due to moisture loss. All trials were run as multiple replications and statistical analysis of treatments were determined by repeated measures analysis of variance (RM-ANOVA) to determine significant differences (p < 0.05). We believe this is the first published report of a biltong process achieving >5.0 log10 reduction of Salmonella which is a process validation requirement of USDA-FSIS for the sale of dried beef in the USA.

Selenite Cystine Agar for Enumeration of Inoculated Salmonella Serovars Recovered from Stressful Conditions during Antimicrobial Validation Studies

Process validation studies often require the inoculation of select foodborne pathogens into targeted foods to determine the lethality of the process or antimicrobial ingredients, and quantitative recovery of surviving inoculum bacteria helps to make those assessments. Such processes introduce various stressors on the inoculated challenge microorganisms whereby traditional selective media are too harsh to enumerate the remaining viable and injured population quantitatively. Innate antibiotic resistance of challenge organisms has often been used to establish simple selective media (i.e., Tryptic Soy Agar/TSA + antibiotics) for recovering inoculated strains, but sometimes antibiotic resistant background microorganisms are higher than desired. Salmonella Thompson 120, Salmonella Heidelberg F5038BG1, Salmonella Hadar MF60404, Salmonella Enteritidis H3527, and Salmonella Typhimurium H3380 were characterized for antibiotic resistance and acid adaptation in Tryptic Soy Broth containing 0%, 0.25%, or 1.0% glucose. Sodium pyruvate was evaluated for recovery after stress but no enhancing effect was observed, possibly because the strains were acid-adapted. Selenite Cystine Broth, traditionally used as a selective enrichment broth, was used as the basis for Selenite Cystine Agar (SCA) in combination with three antibiotics to which our Salmonella are resistant. Serovars of Salmonella, both individually and in mixtures, were enumerated on TSA, SCA, Xylose Lysine Desoxycholate (XLD), and Hektoen Enteric (HE) selective agars (all containing the same antibiotics) after conditions of nutrient starvation, desiccation, acid stress, and thermal stress. The data show that quantitative enumeration of our Salmonella serovars on SCA was not significantly different (p > 0.05) than those achieved on TSA for all tested stress categories. Levels of Salmonella enumerated on XLD and/or HE were significantly different (p < 0.05) than on TSA and SCA and often more than 1–2-log lower, consistent with the inhibition of injured cells. These data confirm that SCA (+ antibiotics) is a suitable selective medium for enumeration of these acid-adapted Salmonella serovars as challenge organisms recovered from various conditions of stress.

Salmonella transmission in poultry farms: The roles of rodents, lizards and formites

Introduction: Salmonellosis constitutes a major threat to poultry industry in Nigeria. The study investigated the roles of rodents, lizards and fomites in the transmission of Salmonella in poultry farms. Methods: A total of 320 samples consisting of litter (n = 70), feed (n = 50), water from drinkers (n = 50), cloacal swabs from chicken (n = 50), faeces from rodents (n = 50) and faeces from lizards (n = 50), were collected from selected poultry farms in Maiduguri, Borno State between March and August, 2011. The samples were subjected to standard bacteriological analyses and presumptive Salmonella isolates were serotyped using slide agglutination technique. Results: A total of 31 (9.7%) Salmonella isolates comprising 7 serovars were obtained. Salmonella serovars Kentucky and Enteritidis were the major serovars recovered from all sample sources and these represent 3.4 % (n= 11) and 3.1 % (n= 10) respectively. These serovars were the predominant in rodents and lizards and were equally isolated from chicken and other samples, however, Salmonella Hadar was only isolated from litters, but not from chicken or other environmental samples (feed or water). Significance: It was concluded that rodents and lizards play significant roles in poultry Salmonella infection via environmental contamination. Farmers should focus more attention on these agents of Salmonella carriage in the poultry environment.

The survey of expression levels of virulent genes in Salmonella strains isolated in retail meats in Hanoi

Salmonella is one of the major causes of food poisoning worldwide, especially in developing countries. The virulence of Salmonella is a complex process involving between their virulence factors and the host defenses. The purpose of this study was to detect virulent genes and to assess the level of expression of these genes in five Salmonella strains (including Enteritidis, Albany, Typhimurium, Hadar, and Derby), which were isolated from meat samples at the retail markets in Hanoi. As a result, Salmonella Enteritidis and Salmonella Typhimurium were 100% positive with seven virulent genes, e.g., spiA, spvB, sitC, sifA, sipB, pagC, and invA genes. Salmonella Hadar and Salmonella Derby positive with six genes, except spvB, whereas Salmonella Albany was positive with only the pagC gene. The comparision of the expression levels of these seven virulent genes and the 16S rRNA control gene showed a significantly difference among Salmonella strains (P<0.05). The result of gene expression of seven virulent genes indicate that Salmonella Hadar has the highest gene expression, followed by Salmonella Enteritidis, Salmonella Derby, Salmonella Typhimurium and finally Salmonella Albany. The results of molecular biology analysis will provide additional data on the expression of virulent genes in Salmonella strains isolated from retail meats in Hanoi.

Influence of lactic acid on the survival of Salmonella on poultry carcass surfaces

The aim of this study was to determine the influence of Salmonella by different lactic acid concentrations in microbiological media and on the surfaces of the chicken carcasses. Contamination of samples were used strains: Salmonella Enteritidis, Salmonella Typhimurium , Salmonella Hadar, Salmonella Infantis and Salmonella Virchow. Each strain from each dilution was placed on nutrient agar without the addition of chemical substances (the control), and on nutrient agar with various amounts of substances added 0,02%, 0,05%, 0,1%, 0,25%, 0,5%, 1%, 2% solutions of lactic acid. A concentration of up to 0.02% of lactic acid did not have a significant effect on the quantitative growth of Salmonella spp. .Lactic acid, starting from the con-centration of 0.1 %, completely inhibits growth of all the studied strains of Salmonella. 150 samples from broiler chicken breasts, was immersed for 2 minutes in 80 ml of Salmonella suspension containing 107 CFU. The sam-ples were then transferred to sterile beakers with 250 ml of 2% and 5% solutions of lactic acid for a period of 5 minutes. At a lactic acid concentration of 2%, the number of Salmonella, compared to the control, reductions ranging from 0,18 to 1,21 log. At the lactic acid concentration of 5%, the number of Salmonella, compared to the control, reductions ranging for from 2,69 log to 3,67 log. .

Effect of Temperature and Gamma Radiation on Salmonella Hadar Biofilm Production on Different Food Contact Surfaces

Salmonella is a pathogen transmitted by foods and it is one of the most important target bacteria in food irradiation studies. Few works were carried out on the effectiveness of gamma radiation against biofilms formed by this bacterium. Salmonella can form a biofilm on different material surfaces. The physicochemical properties of surfaces and environmental factors influence the adhesion of this pathogen. The present study investigated the effect of gamma radiation (1 and 2 kGy) and temperature (28°C and 37°C) on the development of Salmonella Hadar biofilm on polyvinyl chloride (PVC), glass, cellophane paper (CELLO), and polystyrene (POLY). The obtained results indicated that biofilm production is surface and temperature dependent. In addition, biofilm formation decreased significantly after gamma irradiation at either 1 or 2 kGy doses. However, the agfD and adrA genes expression did not demonstrate significant decrease. This work highlighted that gamma radiation treatment could reduce the biofilm formation of Salmonella enterica serovar Hadar on different food contact surfaces.