The in vitro bactericidal effects of the food decontaminants lactic acid and trisodium phoshate

Chemically decontaminating broiler meat for consumer safety is possible with lactic acid (LA) and trisodium phosphate dodecahydrate (TPD). The bactericidal activity of each of these agents in vitro against five different strains of Salmonella spp. was tested. Both agents were bactericidal for all strains in high concentrations, but they were not satisfactorily effective in low concentrations or/and a short duration of activity. The most resistant strain among the tested Salmonella spp. was Salmonella enteritidis serotype pt4, although TPD was more effective than LA. The findings partly explain 1. The reported increases of human foodborne infections from S. enteritidis serotype pt4, thus 2. The increasing need for new methods to effectively decontaminate meat and meat products.     

Microbiological Profile of Goat Meat Inoculated with Lactic Acid Bacteria Cultures and Stored at 30��C for 7?days

The ability of lactic acid bacteria (LAB) cultures to preserve goat meat at 30°C was evaluated in the present study. Strains of Pediococcus pentosaceus GOAT 01 and Lactobacillus plantarum GOAT 012, individually and in combination, were applied as starters on sliced meat samples at 6 log cfu/g and stored for 7 days at 30°C to simulate ambient temperature in Nigeria. They were evaluated for microbiological profile during storage. Reduction in bacterial counts was recorded for enterobacteriaceae, Staphylococcus, yeasts and moulds in starter culture inoculated samples (SCIS), whereas an increase occurred in uninoculated control samples (UCS). In challenge experimental trials, two different sets of meat were inoculated individually with 6 log cfu/g each of pathogenic organisms, Listeria monocytogenes and Salmonella Typhimurium. The inoculated pathogens were monitored during storage to assess the influence of starter cultures on them. Approximately 1 log reduction was recorded in the viable count of L. monocytogenes on day 1, while counts were below detection limit (<2 log) on day 2 in meat samples inoculated with P. pentosaceus alone and in combination with L. plantarum. Counts of Salmonella Typhimurium showed about 2 log reduction in SCIS, inoculated with P. pentosaceus alone and in combination with L. plantarum, on day 2 while an increase by 4 logs was observed in UCS. Our findings suggest that the protective effect of the LAB strains could be exploited in shelf life extension and control of foodborne pathogens in goat meat. If the starter strains could be improved upon, their potential as biopreservatives may be engaged in the preservation of the meat in Nigeria, where storage systems have been very inadequate.     

Investigation of Different Gas Sensor-Based Artificial Olfactory Systems for Screening <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> Contamination in Beef

Two different electronic nose systems (metal oxide and conducting polymer based) were used to identify Salmonella typhimurium contaminated beef strip loin samples (stored at two temperatures). The sensors present in the two systems were ranked based on their Fisher criteria of ranking to evaluate their importance in discriminant analysis. The most informative sensors were then used to develop linear discriminant analysis and quadratic discriminant analysis-based classification models. Further, sensor signals collected from both the sensor systems were combined to improve the classification accuracies. The developed models classified meat samples based on the Salmonella population into “No Salmonella” (microbial counts < 0.7 log₁₀ cfu/g) and “Salmonella inoculated” (microbial counts ≥ 0.7 log₁₀ cfu/g). The performances of the developed models were validated using leave-1-out cross-validation. Classification accuracies of 80% and above were observed for the samples stored at 10 °C using the sensor fusion approach. However, the classification accuracies were relatively low for the meat samples stored at 4 °C when compared to the samples stored at 10 °C. The results indicate that the electronic nose systems could be effectively used as a first stage screening device to identify the meat samples contaminated with S. typhimurium.     

Effect of Nanoemulsified and Microencapsulated Mexican Oregano (Lippia graveolens Kunth) Essential Oil Coatings on Quality of Fresh Pork Meat

Fresh meat is a highly perishable food. This work aimed to evaluate the influence of Mexican oregano (Lippia graveolens Kunth) incorporated into active coatings (ACs) spread on fresh pork meat as free (FEO), nanoemulsified (NEO), and microencapsulated (MEO) essential oil (EO), on its microbiological, physicochemical and sensory properties during 15 d at 4 ± 1 °C. Thymol and γ‐terpinene were identified in the EO. In vitro effect of 2.85 mg EO/cm² was tested against Brochothrix thermosphacta, Micrococcus luteus, Lactobacillus plantarum, Pseudomonas fragi, and Salmonella Infantis. FEO antioxidant capacity (DPPH assay) was significantly higher than that of thymol, NEO and MEO (93.53%, 89.92%, 77.79%, and 78.50% inhibition, respectively), and similar to BHA (96.03%) and gallic acid (95.57%). FEO, NEO, and MEO ACs on meat caused growth inhibition of lactic acid bacteria (5 log population reduction) and Pseudomonas spp. (4 log reduction), whereas ≤1.5 log population reduction was observed for B. thermosphacta and Salmonella Infantis. Meat microbiota was more efficiently controlled by MEO than by FEO or NEO. ACs delayed lipid and oxymyoglobin oxidation of fresh pork meat. After 15 d of cold storage meat added with EO coatings was desirable for panelists, whereas untreated (UT) samples were undesirable. Active coatings are a significant alternative method for fresh meat preservation.     

The incidence and antibiotic resistance profiles of Salmonella spp. on Irish retail meat products

Irish retail meat (n=74) and poultry samples (n=106) were tested for the presence of naturally occurring Salmonella spp. The pathogen was detected in 28 poultry (n=106), two pork (n=22) and one cooked meat samples (n=20) examined. Salmonella was not isolated from minced beef or lamb samples tested. Initial counts on samples ranged from 0 to log₁₀2·5 cfu g⁻¹. The most commonly isolated serotype was S. bredeney accounting for 48·4%, followed by S. kentucky (35·5%) and S. enteritidis (6·5%). Salmonella spp. (n=31) isolated from food products were also examined for antibiotic resistance. A total of 155 strains (five strains from each isolate) were tested for resistance to 26 antibiotics using the Bauer method. The percentage of samples showing antibiotic resistance amongstSalmonella isolates were as follows: Riampicin (100%); Tetracycline (92·92%); Oxytetracycline (86·26%); Sulphamethoxazole (86·25%) and Streptomycin (80·92%).     

In-package atmospheric cold plasma inactivation of Salmonella in freeze-dried pet foods: Effect of inoculum population,water activity,and storage

Recently, Salmonella has been linked to numerous low water activity (a_w) food recalls. As an emerging technology, atmospheric cold plasma (ACP) has the potential to reduce Salmonella in low a_w foods. The objective of this study was to evaluate the effects of initial inoculum population of Salmonella (~ 10, 9 and 8 log CFU/cm²), treatment time (2.5, 5, 7.5 and 10 min), water activity (0.13, 0.34, 0.54), and post-treatment storage (0, 7 and 14 days at 21 °C) on the reduction of cocktails of S. Typhimurium and S. Senftenberg on freeze-dried pet food treats. The top surface of pet food was spot inoculated with cocktails of Salmonella with initial cell populations of 10, 9 and 8 log CFU/cm². Inoculated samples were first equilibrated to target a_w values, packaged with modified atmosphere (78% N₂ + 21% O₂ + 1% CO₂), and then in-package ACP treatments were performed. The initial inoculum population, treatment time, and post-treatment storage had significant (P < 0.05) effects on Salmonella inactivation efficacy of ACP. Regardless of the initial inoculum population and storage time, Salmonella equilibrated to 0.13 a_w pet food exhibited the greatest resistant to ACP treatment. ACP treatment for 10 min followed by 7 days storage reduced the Salmonella cells in 0.54 a_w pet food, to below the limit of detection (>4.5 log reduction), when the initial inoculum population was 8.2 log CFU/cm². Regardless of a_w of petfood, peroxide and thiobarbituric acid reactive substance values of 10 min ACP-treated pet foods were significantly increased to 3.44 meq/ kg of fat and 1.53 mg MDA/ kg pet food from 0.87 meq/ kg of fat and 0.50 mg MDA/ kg pet food, respectively. Post-ACP treatment storage of 10 min ACP-treated samples for 14 days further increased the lipid oxidation to 2.58 from 1.53 mg MDA/ kg of pet food, irrespective of the a_w of samples. This study showed that the Salmonella reduction efficacy of in-package ACP treatment in low a_w environment is influenced by various process and product factors.Industrial relevanceFreeze drying is not considered a kill step to inactivate microorganisms on foods. In the future, in-package ACP technology could be used as a potential method for post-packaging decontamination of freeze-dried pet foods in industrial settings after obtaining necessary regulatory approvals.     

Fourier transform infrared spectroscopy (FTIR) as a tool for discriminating <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> contaminated beef

Detection of beef contamination from harmful pathogens will be helpful in protecting the consumer safety and controlling the outbreaks. In this paper, the potential of Fourier transform infrared spectroscopy (FTIR) was investigated to discriminate the Salmonella contaminated packed beef. A suitable headspace sampling system was designed and used to collect the headspace volatiles from the packed meat to the FTIR gas cell. Spectral signatures of headspace volatiles of meat packages were used to classify the packed meat samples as contaminated or not. FTIR spectrum was divided into several regions in order to reduce the dimensionality as well as to select the regions based on the absorbance properties of various volatiles present in headspace of meat package. Principal component analysis was performed on the entire spectrum (4000–500 cm⁻¹) as well as on the selected sub-regions of entire spectrum. Two statistical classification techniques (linear and quadratic discriminate analysis) were used to develop classification models. The statistical models were validated using bootstrap cross validation technique. The total average classification accuracies were evaluated in terms of coefficient of variance (% CV). Based on the mean of total average classification accuracies and its % CV calculated from five similarly conducted experiments, it was found that the statistical models developed on a part of the spectra (500–850 cm⁻¹) and full spectra (4000–500 cm⁻¹) can be used as potential classification models for non-destructive discrimination of Salmonella contaminated packed beef samples from uncontaminated ones. These results need to be further validated on dataset with larger sample size.     

Co-production of Lactic Acid and <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> Cells from Whey Permeate with Nutrient Supplements

Lactic acid and cell production from whey permeate by Lactobacillus rhamnosus with different nutrient supplements were investigated in this study. Yeast extract was identified as the most effective nutrient affecting lactic acid production. Increase in inoculum size from 0.05% to 1% (v/v) resulted in a substantial increase in lactic acid productivity from 0.66 to 0.83 g L⁻¹ h⁻¹ (P < 0.001). The optimal temperature for lactic acid production was 37 °C, while the highest cell production was obtained at 42 °C. When whey permeate and yeast extract concentrations were 6.8% (w/v) and 3 g L⁻¹, respectively, lactic acid productivity reached 0.85 g L⁻¹ h⁻¹ after 48-h cultivation, which is 3.40 times of those without nutrient supplements.     

Microbiological Properties of Pork Cheek Meat as Affected by Acetic Acid and Temperature

Our objective was to determine the effect of acetic acid (AA) and temperature in inhibiting Salmonella typhimurium, aerobic plate counts (APCs) and total coliforms on pork cheek meat. Compared with initial APCs of control cheeks, a reduction in log₁₀ CFU/cm² APC by more than 78.6% was found in all samples that were treated with 20 and 40° acetic acid (P < 0.05). Additionally, total coliforms for acidtreated cheeks were lower for both AA treatments (P < 0.05). Cheeks (n = 10/treatment) were also sprayed in a commercial pork slaughter facility carcass wash with 2% AA (25°) and compared to control (non-treated) cheeks. The incidence of Salmonella decreased by 67% for acid-treated cheeks (P < 0.05). A significant decrease in APCs and coliforms occurred for the acid-treated cheeks (P < 0.05).     

Determination of Histamine in Some Foods by Isotachophoretic Method with Simple Sample Preparation

A one-dimensional capillary isotachophoretic method in cationic system of the separation has been applied for histamine determination in food samples. The proposed electrolyte system consisted of 0.01 M potassium hydroxide with l-valine to pH = 9.9 as the leading electrolyte and 0.02 M 2-amino-2-hydroxymethyl-propane-1,3-diol adjusted to pH = 8.3 with 0.1 M hydrochloric acid as terminating electrolyte. Proposed method was characterized by linearity range 5–50 mg L⁻¹ and R ² = 0.9982, accuracy (recoveries ranged from 95% to 102%), detection (2.10 mg L⁻¹), and quantification (7.01 mg L⁻¹) limits. The sample preparation for proposed electrophoretic method included only simple extraction with trichloroacetic acid with filtration and derivatisation stage are avoided. The histamine concentration was determined in meat (turkey, chicken, beef and pork) and meat products (ripened sausage and dry-cured ham), fish (smoked salmon and mackerel), and different kind of mildew and mold ripened cheeses samples. The histamine content ranged from not detected level for fresh meat to 29.63 mg 100 g⁻¹ for cheese samples. The reversed phase HPLC was applied as reference method and the F-Snedecor test and the t test were employed to compare the precision and accuracy of the both methods. Positive correlations were found between the two analytical methods for histamine determination in food products. The obtained results indicate that the proposed electrophoretic method is simple, precise, accurate, and convenient.     

Low gamma irradiation of raw meat. II. Bacteriological effects on samples from butcheries

One hundred and twenty samples of raw ground meat, a component of ‘filet américain’ consumed raw in some European countries, were investigated, both directly and after gamma irradiation with a dose of 1 kGy. Moreover, the meat was checked serologically for presence of other type beside beef.Salmonella were isolated from 23 (19.2%) non-irradiated samples, MPN counts ranged from 40 to 2 × 10³ organisms/100 g. Only 1 sample was Salmonella-positive after irradiation, at an amount of 2.3 × 10²/100 g.Yersinia enterocolitica was found in 60 (50%) samples of raw meat but this organism was not isolated from irradiated samples.From none of the investigated samples of raw meat could Campylobacter jejuni be isolated.The average reduction after irradiation of the total aerobic count and Enterobacteriaceae was 2.18 and 4.00 log cycles, respectively.In 5 of 120 samples of raw ground meat intended for preparation of filet américain the presence of pork was demonstrated.Based on the results of this study it may be concluded that irradiation of raw meat with a dose of 1 kGy eliminated of reduced some pathogens of public health concern to acceptable levels.     

Evaluation of modified casings and chitosan‐PVA packaging on the physicochemical properties of cooked Sichuan sausages during long‐term storage

The effects of a modified casing and chitosan‐poly‐vinyl alcohol antimicrobial packaging (CP packaging) on sausage colour, texture, microbial spoilage and volatile compounds after 29‐days storage were investigated. Casings were modified by surfactant solution (composed of soy lecithin and soy oil) and lactic acid. For samples stored in CP packaging, there were no significant differences between day 1 and day 29 in relation to sausage hardness and springiness (P > 0.05). Redness increased over storage time regardless of treatments and packagings. Total plate counts of samples packaged by CP packaging were lower than 1 log cfu g^?1 during 29‐days storage. Cyclohexene, 1‐methyl‐4‐(1‐methylethylidene)‐ and α‐copaene were found in samples with control casings and CP packaging after 15‐days storage. The improved characteristics of the natural casing will enable meat processors or manufactures to enhance sausage production with a low sausage burst incidence, while the CP packaging will inhibit the intensive microbial growth.     

The Application of NIR FT-Raman Spectroscopy to Monitor Starch Retrogradation and Crumb Firmness in Semolina Bread

In this study, the potential application of near-infrared (NIR) Fourier-transform (FT)-Raman spectroscopy to monitor starch retrogradation in stored bread crumb was investigated. Semolina-based bread was made and cut into slices, which were stored under controlled conditions in sealed plastic bags. The aging of the bread crumb was monitored by both NIR FT-Raman spectroscopy and a texture analysis over a period of 20 days. Two-dimensional correlation analysis in the spectral range of 390–975 cm⁻¹ revealed characteristic differences among the spectra collected over time for bands that peaked at 480, 765, and 850 cm⁻¹. The band at 480 cm⁻¹ is studied here in detail. During the storage, the peak frequency of this band shifted towards lower wavenumbers, and its full width at half height decreased. Both of these parameters are highly correlated (R ² = 0.921 and R ² = 0.949, respectively) to crumb hardness measured by the texture analyzer.     

Study of pulsed light inactivation and growth dynamics during storage of Escherichia coli ATCC 35218, Listeria innocua ATCC 33090, Salmonella Enteritidis MA44 and Saccharomyces cerevisiae KE162 and native flora in apple,orange and strawberry juices

The response of some inoculated strains and native flora to PL treatment (Xenon lamp, 3 pulses s^?1, 10 cm distance from the lamp, 71.6 J cm^?2) in apple, orange and strawberry fresh juices with different absorbance, turbidity and particle size was investigated. Microbial growth dynamics during 12‐day storage (5 °C) of PL‐treated juices was also evaluated. PL treatments provoked 0.3–2.6 log reductions for inoculated microorganisms and 0.1–0.7 for native flora. High turbidity and particles with high UV absorbance seemed to play a major role in the PL efficiency compared to particle size. Cold storage of PL‐processed juices provoked an increase in Salmonella Enteritidis and Listeria innocua inactivation, achieving 5.0–8.0 log reductions, while no recovery of Escherichia coli and retardation for yeast growth was observed, compared to untreated samples. This study gives valuable information regarding the influence of juice variables on PL effectiveness and emphasises the beneficial effect of a postcold storage on microbial safety of PL‐treated juices.     

Inhibitory effect of acid concentration,aging, and different packaging on Escherichia coli O157:H7 and on color stability of beef

The presence of pathogens such as Escherichia coli O157:H7 (EC) represents risks to public health and to economy of Brazilian beef industry. In this context, the application of lactic acid (LA) is an efficient practice employed to reduce bacterial count without compromising consumer safety. Our aim was to verify the inhibitory effect of LA application combined with aging and different packaging on EC and its effects on beef color. The LA effect on EC counts was concentration dependent during aging and storage, with T2 (10% of LA added) demonstrating greater (p < .05) reductions than T1 (5% of LA added). Aging did not affect (p > .05) EC counts, however reduced (p < .05) the total aerobic mesophilic bacteria. LA application promoted a decrease on beef redness (p > .05) after application and during storage. LA treatment (T2) promoted a reduction in E. coli O157:H7, despite the effects on beef color.

Practical applications

The present data evidence a breakthrough in lactic acid (LA) researches once evaluate the inhibitory effect of aging, LA concentration and package on Escherichia coli O157:H7 and the influence of these technologies in beef color. Moreover, the data presented allow clarifying the meat industry about the potential use of LA preservation on beef.     

Detection of Raw Pork Targeting Porcine-Specific Mitochondrial Cytochrome B Gene by Molecular Beacon Probe Real-Time Polymerase Chain Reaction

Pork identification in raw meat using real-time polymerase chain reaction (PCR) was developed. Total DNA from meat samples were successfully extracted and found to be of high quality and produced clear PCR products. Porcine-specific molecular beacon probe and primers that amplifies 119 bp of the cytochrome b gene fragment of swine (Sus scrofa domestica) was used. Analysis of data showed that the C _q (quantification cycle) from 10 ng/μl porcine DNA is (18.70 ± 0.12 to 19.08 ± 0.06). Meanwhile, the other samples exhibited negative result, which confirmed the specificity of the primers. The method also showed that the limit of detection of pork was 0.0001 ng. Based on the regression analysis of the standard curve, the 96% efficiency of real-time PCR was achieved with high correlation coefficient (r ² = 0.9989). Sensitivity of the assay in discriminating pork as low as 0.1% (w/w) pork in pork–beef mixtures was also obtained. Reproducibility of the assay was successfully validated by applying sample and experimental replicates in every assay being conducted. Thus, this methodology could serve as a fast and sensitive method for detection of pork for meat species verification.     

Microbiological attributes and biogenic amine content of probiotic Turkish fermented sausage

Microbiological attributes and biogenic amine content of Turkish fermented sausage manufactured by using probiotic starter cultures (Lactobacillus casei, L. acidophilus or their combination) were investigated before and after fermentation-drying period and during refrigerated storage at 4 ± 1 °C for 8 months at 2 month intervals. As results of the study, during fermentation and storage biogenic amine content (histamine, putrescine, cadaverine and tyramine) of the samples were increased significantly. Salmonella, Staphylococcus aureus, coliform and fecal coliform microorganisms were not detected during fermentation and storage. Probiotic microorganism counts of all samples were higher than the lower limit of 6.0 log cfu/g which is requested for probiotic foods.     

Effect of carvacrol and thymol on Salmonella spp. biofilms on polypropylene

The present study evaluated the effects of carvacrol and thymol against Salmonella spp. biofilm on polypropylene. The efficacy of the compounds was assessed by quantifying Salmonella spp. cells during and after biofilm formation on polypropylene and performing scanning electron microscopy. During biofilm formation, carvacrol and thymol, at subinhibitory concentrations, reduced bacterial counts about 1–2 log, while established Salmonella spp. biofilms were reduced about 1–5 log by carvacrol and thymol, at MIC or 2× MIC. The greatest reduction in carvacrol‐treated biofilms, about 5 log, was observed with 156 and 312 μg mL^?1 (MIC and 2× MIC) in established Salmonella Typhimurium ATCC 14028 biofilms. Thymol showed the greatest reduction, about 4 log, at 624 μg mL^?1 (2× MIC) against mature Salmonella Enteritidis biofilm. Carvacrol and thymol reduced the number of Salmonella spp. cells on polypropylene, suggesting their potential for the control of Salmonella spp. biofilms.     

Evaluation of Protease-producing Ability of Fish Gut Isolate Bacillus cereus for Aqua Feed

Extracellular protease production by Bacillus cereus isolated from the intestine of fish Mugil cephalus has been investigated in shake-flask experiment using different preparations of tuna-processing waste such as raw fish meat, defatted fish meat, alkali hydrolysate, and acid hydrolysate as nitrogen source. Among the tuna preparations tested, defatted fish meat supported the maximum protease production (134.57 ± 0.47 U ml⁻¹), and 3% concentration of the same was found to be optimum for maximizing the protease production (178.50 ± 0.28 U ml⁻¹). Effect of carbon sources on protease production in the optimized concentration of defatted tuna fish meat revealed that galactose aided the higher protease production (259.83 ± 0.04 U ml^–1) than the other tested carbon sources and a concentration of 1.5% galactose registered as optimum to enhance the protease production (289.40 ± 0.16 U ml⁻¹). The halotolerancy of B. cereus for protease production indicated that 3% of sodium chloride was optimum to yield maximum protease (301.63 ± 0.20 U ml⁻¹). Among the surfactants tested, protease production was high in Triton X 100-added medium (298.63 ± 0.12 U ml⁻¹) when compared to other surfactants, and its optimum concentration recorded was 0.8% (320.57 ± 0.17 U ml⁻¹) for more protease production. Partial characterization of crude enzyme revealed that pH 7.0 (278.90 ± 0.08 U ml⁻¹) and 60°C temperature (332.37 ± 0.18 U ml⁻¹) were optimum for better protease activity by B. cereus.     

Effect of Minimal Processing on Quality of Jackfruit (Artocarpus heterophyllus L.) Bulbs Using Response Surface Methodology

Jackfruit (Artocarpus heterophyllus L.) bulbs were minimally processed using variables such as CaCl₂ concentration (0.13–1.47%), ascorbic acid (AA) concentration (0.005–0.03%), and treatment time (8–43 min). Second-order polynomial model was proposed with regard to effect of independent variables on responses such as juice leakage, firmness, browning index, L value, and overall acceptability by response surface methodology (RSM) using a central-composite experimental design. The established models for responses showed a good fit with the experimental data (R ² > 0.896), describing the effect of independent variables on the quality parameters of minimally processed jackfruit bulbs. The recommended processing conditions for maximizing firmness, L value and overall acceptability and minimizing juice leakage, and browning index in the samples at the end of 20 days of low temperature storage were found to be 1% CaCl₂, 0.02% AA, and 30 min of treatment time. The RSM was found to be an effective tool to model the effect of minimal processing treatments on jackfruit bulbs quality.