Survival of Salmonella Enteritidis PT 30 on inoculated almond kernels in hot water treatments

Almonds are blanched by exposure to hot water or steam-injected water to remove the pellicle (skin) from the kernel. This study evaluated the survival of Salmonella Enteritidis PT 30, Salmonella Senftenberg 775W and Enterococcus faecalis on whole raw almond kernels exposed to hot water. Whole, inoculated (7 to 9 log CFU/g) Nonpareil almonds (40 g) were submerged in 25 L of water maintained at 60, 70, 80 and 88 °C. Almonds were heated for up to 12 min, drained for 2 s, and transferred to 80 mL of cold (4 °C) tryptic soy broth. Almonds in broth were stomached at high speed for 2 min, serially diluted, plated onto tryptic soy and bismuth sulfite agars (Salmonella) or bile esculin agar (Enterococcus) and incubated at 37 °C for 24 and 48 h, respectively. D values of 2.6, 1.2, 0.75 and 0.39 min were calculated for exposure of S. Enteritidis PT 30 to water at 60, 70, 80 and 88 °C, respectively; the calculated z value was 35 C°. D values determined for Salmonella Senftenberg 775W and E. faecalis at 88 °C were 0.37 and 0.36 min, respectively. Neither Salmonella serovar could be recovered by enrichment of 1-g samples after almonds inoculated at 5 log CFU/g were heated at 88 °C for 2 min. These data will be useful to validate almond industry blanching processes.     

Destruction of Salmonella Enteriditis inoculated onto raw almonds by high hydrostatic pressure

The effects of continuous (50,000, 60,000 and 70,000 psi with holding times of 5 and 10 min) and discontinuous (oscillatory) (six cycles at 60,000 psi with a holding time of 20 s) high hydrostatic pressure (HHP) treatments on the viability of two Salmonella Enteriditis strains (FDA and PT30) inoculated onto raw almonds were evaluated at 25, 50, and 55 °C. Complete inactivation of the S. Enteriditis was achieved in 0.1% peptone water after continuous pressurization at 60,000 psi and 25 °C for 5 min. Continuous pressurization of raw almonds inoculated with S. Enteriditis at 60,000 psi and 50 °C for 5 min resulted in less than a log reduction (log₁₀ 0.83) of vegetative cells. The decimal reduction time using the continuous pressurization parameters was determined to be 9.78 min. A discontinuous process consisting of six cycles of pressurization at 60,000 psi and 50 °C for 20 s provided greater than a one log reduction (log₁₀ 1.27 for FDA and log₁₀ 1.16 for PT30) of the S. Enteriditis concentration. The low water activity (a_w) of the almonds was found to impart baroprotective attributes on the S. Enteriditis cells. When the almonds were directly suspended in water and then pressurized, a log₁₀ reduction of 3.37 was achieved. HHP of certain dry foods appears to be feasible if the food is directly suspended in the pressurizing medium (water).     

Characterization of Salmonella Enteritidis isolated from human samples

This study aimed to characterize Salmonella Enteritidis (SE) isolated from blood (n = 12) and feces (n = 68) of salmonellosis victims in Southern Brazil. All isolates were submitted to antimicrobial susceptibility testing, PCR-ribotyping, and XbaI macrorestriction Pulsed-Field Gel Eletrophoresis (PFGE). Results demonstrated high levels of ampicillin and nalidixic acid resistance, and strains isolated in different geographic regions were clustered together, presenting a common resistance profile. All strains demonstrated similar and related PCR-ribotyping patterns (R1, R2, and R3); being that the predominant profile R1 grouped 47.5% of the strains. PFGE profile P1 grouped the majority of the strains (96.25%), suggesting a clonal relationship among the strains or inability of molecular typing methods to discriminate strains of this serovar. Results suggested on an increase in antimicrobial resistance and that strains of S. Enteritidis with similar PFGE and PCR-ribotyping profiles were involved in several salmonellosis outbreaks in Southern Brazil.     

Salmonella contamination of laying-hen flocks in two regions of Algeria

A preliminary epidemiological study of Salmonella contamination in laying-hen flocks was carried out in the regions of Annaba and Eltarf, Algeria, from March to October 2008 and March to November 2009. Our objectives were (i) to estimate the prevalence of infection by Salmonella spp. in seven pooled samples during the hens' laying period (ii) to identify the serotypes and antimicrobial resistance phenotypes of isolates, and (iii) to characterize the factors that may be related to Salmonella contamination in Algerian henhouses. For this purpose, 18 out of 22 operational laying-hen houses were sampled one to three times during these periods: once at the start of laying (pullets aged 22–31 weeks), once in the middle of laying (47–60 week) and once at the end of laying prior to depopulation (70–86 week). The flocks'Salmonella status was assessed by collecting 2754 environmental samples that were analyzed according to the ISO 6579 method. The antibiotic resistance of Salmonella strains was tested as per the guidelines of the Clinical and Laboratory Standards Institute (CLSI). The relationship between each potential risk factor and the Salmonella status of laying-hen flocks was evaluated by calculating the relative risk with 95% confidence intervals. Eight flocks tested positive for Salmonella spp., with a higher prevalence at the end of laying than at either the beginning or middle. Only 19 isolates were recovered from the 2754 samples analyzed and nine different serotypes identified. S. enteritidis (n = 4) was the most prevalent serovar, along with S. Kentucky and S. Hadar (n = 3), followed by S. Heidelberg, S. Manhattan and S. Virchow (n = 2), whereas S. Dublin, S. Typhimurium and S. Albany were found only once. Thirteen isolates were resistant to at least one antimicrobial agent. Of these, six were resistant to at least three different antimicrobial classes. Salmonella serovar Kentucky isolates were resistant to fluoroquinolones with ciprofloxacin MIC ≥ 8 mg/L. Six risk indicators were identified as potentially related to the Salmonella status of layer houses.     

A systematic review and meta-analysis of the effectiveness of biosecurity and vaccination in reducing Salmonella spp. in broiler chickens

Our objective was to estimate the effectiveness of vaccination and biosecurity on the prevalence of Salmonella spp. in broiler chickens using systematic review and meta-analysis. A comprehensive search of the global primary literature was conducted in: Current Contents (1999–2009), Agricola (1924–2009), MEDLINE (1860–2009), Scopus (1960–2009), CAB (1913–2009), and Centre for Agricultural Bioscience Global Health (1971–2009). The search algorithm was (Salmonell*) AND (chicken* OR chick* OR poultry* OR broiler* OR gallus*). Additional studies were identified by contacting five topic experts and hand-scanning bibliographies of recent review articles and a recently published textbook. Studies were included if they were English language and investigated the effects of vaccination and biosecurity on the prevalence of Salmonella spp. in broiler chickens. All study design types were included. Data extraction and methodological assessment were conducted by two reviewers independently. All meta-analyses were based on random-effects models. For biosecurity, sixteen challenge studies (n = 137 treatment-control comparisons) and one controlled study (n = 2) met the inclusion criteria. Significant heterogeneity (Cochran's Q-statistic, p < 0.001) was observed among biosecurity challenge studies examining hydrogen peroxide or polyhexamethylenebiguanide hydrochloride applied to hatching eggs, making it inappropriate to present a summary effects measure. For vaccination, 19 challenge studies (n = 226) and three controlled studies (n = 10) met the inclusion criteria. Among live Salmonella Typhimurium vaccine challenge studies heterogeneity was not significant (p = 0.138). Vaccination with a live Salmonella Typhimurium reduced the risk of Salmonella cecal colonization in the treated broiler group by 35 out of 1000 broilers when compared to the control group (OR = 0.21; 95% CI = 0.06–0.77) and this effect was significant (p = 0.018). One biosecurity study (n = 2 treatment-control comparisons) and three vaccination studies (n = 10) were conducted in a commercial setting. The two included studies in the vaccination meta-analysis were both conducted at research facilities. The live Salmonella Typhimurium vaccine showed the most promise in reducing the prevalence of Salmonella in broiler ceca. However, the meta-analysis included few studies, and these studies challenged the birds with different serotypes. We recommend that more large-scale randomized, blinded trials be conducted with a live Salmonella Typhimurium vaccine on commercial farms.     

Variation of bacteriologic and serologic Salmonella enterica prevalence between cohorts within finishing swine production farms

The objective of this study was to evaluate the consistency of bacteriologic and serologic Salmonella enterica prevalence in cohorts of finishing pig lots from multiple production farms. A total of 6 lots of finishing pigs from each of 6 finishing production farms were included in this study. For each lot studied, 30 individual fecal samples were collected directly from the rectum immediately before the pigs were transported to the abattoir, and 50 individual meat samples were collected at slaughter. Individual fecal and meat juice samples were processed for detection of Salmonella and antibodies against Salmonella, respectively. All finishing production farms were Salmonella-positive in at least 2 fecal and 4 meat samplings. The overall bacteriologic prevalence was 12.9% (95% C.I. 8.0–17.8%), whereas the serologic prevalence was 35.4% (95% C.I. 24.5–46.4%; P < 0.05). A wide variation in Salmonella prevalence (bacteriologic and serologic) between different finishing pig lots within production farms was observed, preventing the categorization of the production farms as either high or low Salmonella prevalence. This study shows that bacteriologic and serologic estimates of Salmonella prevalence are not consistent among cohorts within the same production farm, suggesting that point estimates of Salmonella prevalence in swine populations are not reliable.     

Inactivation of Salmonella Enteritidis PT30 on the surface of unpeeled almonds by cold plasma

The contamination of nut products, like almonds, with human pathogens is a reoccurring concern in the food industry. In this study the inactivation of Salmonella Enteritidis PT 30 (ATCC BAA-1045) on the surface of unpeeled almonds by cold atmospheric pressure plasma was investigated. Air, O₂, N₂, CO₂ and 90% CO₂ + 10% Ar were used as process gas. Inoculum preparation and inoculation of almonds was done according to the guidelines recommended by the Almond Board of California. Furthermore, impact of plasma treatment on product color was measured. All plasma treatments inactivated Salmonella. Maximum achieved inactivation depends on the used process gas. Air plasma inactivated > 5.0 log₁₀, O₂ plasma 4.8 and N₂ plasma 2.0 log₁₀ after 15 min treatment. The plasma treatment with air and N₂ resulted in a browning of the unpeeled almond's surface color. Whereas the other used plasma did not alter the color considerably.Industrial RelevanceThe contamination of raw nuts with human pathogens is an on-going food safety concern. The application of cold atmospheric pressure plasma has a high potential as a gentle technology for the surface decontamination. The results of this study suggest that a cold plasma treatment could be an alternative technology for the pasteurization of almonds. The use of air plasma achieved more than a 5 log₁₀, which is in general required by the U.S. Food and Drug Administration for the approval as an alternative inactivation technology for food products. However, the scale up to commercial treatment levels requires the complete understanding of the involved product-plasma interactions.     

Review of Current Technologies for Reduction of Salmonella Populations on Almonds

After the 2001 and 2004 Salmonellosis outbreaks that were associated with raw almonds, ensuring the microbial safety of almonds by treating them to achieve a minimum 4-log reduction of Salmonella population became mandatory in California, the world??s largest almond producer. In this paper, we summarize potential pathways of microbial contamination during almond production and manufacturing. Furthermore, we review sanitization technologies, including chemical, thermal, and non-thermal methods, as well as proprietary systems with regard to microbial and sensory quality of almonds and compare various aspects of their use during almond processing.     

Comparison of antimicrobial resistance patterns and phage types of Salmonella Typhimurium isolated from pigs,pork and humans in Belgium between 2001 and 2006

Infections with non-typhoid Salmonella represent a major problem in industrialized countries.The emergence and spread of antimicrobial-resistant pathogens, among them Salmonella, has become a serious health hazard worldwide. One of the most commonly isolated non-typhoid Salmonella serovars in pigs, pork and humans is Salmonella Typhimurium. In this study the comparison of the incidences of resistance to nine antimicrobials, resistance patterns and phage types between S. Typhimurium isolated from pigs (n = 581), pork (n = 255) and humans (n = 1870) in Belgium in the period 2001 to 2006 was performed.Resistance to the antimicrobials ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline was frequently observed and varied between 23.5% and 83.1%. Resistance ranged from 15.6% to 20.7% for the combination trimethoprim–sulfonamides and from 3.4% to 5.8% for nalidixic acid. Resistance to the critical important antimicrobials cephalosporins and fluoroquinolones was found sporadically (≤ 1.2%). Resistance to the different antimicrobials was observed to be similar in S. Typhimurium isolates from the various origins. Twenty-seven antimicrobial resistance patterns representing in total 75.2%, 89.0% and 89.6% of the isolates from pigs, pork and humans respectively were found to be common among the three groups and 73 combinations antimicrobial resistance pattern/phage type were found to be common among pork and human isolates, representing 70.1% of the pork isolates and 51.0% of the human isolates. The high percentage of isolates that have a common resistance pattern, and in a less pronounced way a common combination phage type/resistance pattern, are in agreement with the hypothesis of transfer of antimicrobial resistant Salmonella from pigs via the consumption of pork to humans as one of the possible pathways. The most prevalent combination in Belgium within both the pork isolates (7.4%) and the human isolates (13.2%) was S. Typhimurium DT104 resistant to ampicillin, chloramphenicol, streptomycine, sulfonamides and tetracycline.     

Decontamination of Salmonella enterica Typhimurium on green onions using a new formula of sanitizer washing and pulsed UV light (PL)

Pathogenic bacteria such as Salmonella and Shigella flexneri have been linked to green onion contamination. This study was conducted to evaluate decontamination of Salmonella Typhimurium using a new formula of sanitizer washing (0.4 mg/mL thymol and five new formula sanitizers including 300 ppm H₂O₂ + 4% SDS, 2 mg/mL citric acid + 4% SDS, 0.2 mg/mL thymol + 4% SDS, 0.2 mg/mL thymol + 2 mg/mL citric acid and 0.2 mg/mL thymol + 2 mg/mL acetic acid), pulsed UV light (PL) as well as synergy between the sanitizer wash and PL. New formula sanitizers based on decontamination efficacy of single washing solutions (organic acids, hydrogen peroxide (H₂O₂), essential oil or surfactant) were applied to decontaminate spot inoculated green onions. PL, the novel technique, alone has been applied to inactivate Salmonella on both dip and spot inoculated green onions. Salmonella inactivation of PL–new formula sanitizer combinations on dip inoculated green onions was investigated for their potential synergy. As a result, for spot inoculated green onions, 0.4 mg/mL thymol individually and the five new formula sanitizers all achieved higher log reduction of Salmonella (4.5–5.3 log 10 CFU/g reduction) than the 200 ppm chlorine washing. These new formulas of sanitizer would be potential alternatives to chlorine. The 5 s dry PL (4.6 log 10 CFU/g) or 60 s wet PL treatment (3.6 log 10 CFU/g) was better or comparable as chlorine washing. The sanitizer combinations did not provide significantly higher log reduction than PL, and PL has the potential of being used in the green onion industry for decontamination purpose. For dip inoculated green onions, none of our treatment provided > 0.8 log 10 CFU/g (0.6–0.8 log 10 CFU/g) reduction of Salmonella. As a result, the PL–new formula sanitizer combinations had no or minimal synergy to inactivate Salmonella dip inoculated on green onions.     

Fat contributes to the buffering capacity of chicken skin and meat but enhances the vulnerability of attached Salmonella cells to acetic acid treatment

Chicken skin and chicken meat display different buffering effects which may impact the survival of Salmonella attached to them when treated with acids. This study investigated the role that differences in fat composition of chicken skin and meat play in their buffering capacity. The survival of Salmonella attached to chicken skin and meat in the presence of fat, and treated with acetic acid was also investigated. Fat was extracted from chicken skin and meat and the buffering capacities of chicken skin, meat, extracted fat and their respective remnants were determined. Two strains of Salmonella Typhimurium and two strains of S. Enteritidis were attached independently to each of the chicken component listed above and enumerated before and after treatment with 0.3 M acetic acid. Chicken skin has a higher fat content as compared to chicken meat. Skin (13 mmol H⁺/(pH1 kg)) had a stronger buffering capacity (p < 0.05) than the extracted fat alone and skin remnants alone (7.0 mmol H⁺/(pH 1 kg) and 6.9 mmol H⁺/(pH 1 kg) respectively). From an initial inoculum (~ 9 log CFU/g), Salmonella cells attached better (p < 0.05) to chicken meat (~ 8 log CFU/g) and chicken skin (~ 7 log CFU/g) than extracted fat (~ 1.5 log CFU/g). Skin remnants without fat were better (p < 0.05) at protecting attached Salmonella than other chicken components. For example S. Typhimurium ATCC 33062 decreased ~ 1 log CFU/g (p < 0.05) on skin remnants after acetic acid treatment while its viable counts on other components decreased from ~ 1.5 to 7 log CFU/g (p < 0.05). We suggest that the fat content present in the skin may enhance the vulnerability of attached cells to acetic acid.     

Effect of γ-irradiation on the physicochemical and sensory properties of raw unpeeled almond kernels (Prunus dulcis)

The present study evaluated the quality of raw unpeeled almonds as a function of irradiation dose in order to determine dose levels causing minimal undesirable changes to almonds. Physicochemical (color, peroxide value, hexanal content, fatty acid composition, volatile compounds) and sensory (color, texture, odor, taste) properties of almonds were determined as a function of irradiation dose.Results showed a ten-fold increase in peroxide value (PV) after irradiation at a dose of 7 kGy. A small but statistically significant (p < 0.05) change was observed in hexanal concentration as a result of irradiation. No statistically significant (p > 0.05) changes were recorded in polyunsaturated fatty acids (PUFA) up to a dose of 7 kGy while monounsaturated fatty acids (MUFA) decreased manifested as a respective increase in saturated fatty acids (SFA) up to 3 kGy. Volatile compounds such as aldehydes, ketones and alcohols increased with increasing irradiation dose indicating enhanced lipid oxidation. Color parameter L^? decreased (p < 0.05) at doses > 3 kGy while color parameters a^? and b^? remained unaffected by irradiation. Sensory analysis showed that almonds remained organoleptically acceptable up to a dose of 3 kGy.Industrial Relevance: Irradiation is very efficient in controlling insects and growth of aflatogenic Aspergillus spp. in dry nuts.     

A meta-analytical estimation of the detection limits of methods for Salmonella in food

The validation of microbial detection methods for foods does not typically state a limit of detection value. Therefore performances of rapid and reference methods for Salmonella detection in foods were compared retrospectively using data from 49 published studies. A total of 576 values for the limit of detection (LOD₅₀) were calculated. The major scientific variables in these independent validation studies were food matrices, Salmonella serovars, and method types (reference, cultural and immunological and nucleic acid based). The basic design feature of the original studies was comparison of the performances of new methods with those of cultural reference methods. A major experimental design variable was the number of laboratories per study. There were 29 single laboratory studies with 20 replicates per level of Salmonella spiked into the food matrix. The 20 multi-laboratory (N ≥ 10) studies had 5–6 replicates per level of Salmonella. The LOD₅₀ values of the dataset had a mean value of 0.021 MPN g^? 1 (standard deviation range (0.013–0.036) and the distribution of their logarithms was symmetrical about the logarithm of the mean if the outlier values were discounted. Eighty-nine percent of the values ranged from 0.01 to 0.04 MPN g^? 1. On this basis about 11% of the values were deemed outliers. About three-quarters of them were > 0.04 MPN g^? 1. The distribution derived in this study can be used as a bench mark against which to evaluate LOD₅₀ data generated in future studies of detection methods for Salmonella in foods and potentially offers a possible way to streamline method validation study experimental design.     

Inactivation of Escherichia coli O157:H7, Salmonella and human norovirus surrogate on artificially contaminated strawberries and raspberries by water-assisted pulsed light treatment

This study investigated the inactivation of Escherichia coli O157:H7, Salmonella and murine norovirus (MNV-1), a human norovirus surrogate, on strawberries and raspberries using a water-assisted pulsed light (WPL) treatment. The effects of combinations of WPL treatment with 1% hydrogen peroxide (H₂O₂) or 100 ppm sodium dodecyl sulfate (SDS) were also evaluated. Strawberries and raspberries were inoculated with E. coli O157:H7 and treated by WPL for 5–60 s. E. coli O157:H7 on both strawberries and raspberries was significantly reduced in a time-dependent manner with 60-s WPL treatments reducing E. coli O157:H7 by 2.4 and 4.5 log CFU/g, respectively. Significantly higher reductions of E. coli O157:H7 were obtained using 60-s WPL treatment than washing with 10 ppm chlorine. Compared with washing with chlorine, SDS and H₂O₂, the combination of WPL treatment with 1% H₂O₂ for 60 s showed significantly higher efficacy by reducing E. coli O157:H7 on strawberries and raspberries by 3.3- and 5.3-log units, respectively. Similarly, Salmonella on strawberries and raspberries was inactivated by 2.8- and 4.9-log units after 60-s WPL–H₂O₂ treatments. For decontamination of MNV-1, a 60-s WPL treatment reduced the viral titers on strawberries and raspberries by 1.8- and 3.6-log units, respectively and the combination of WPL and H₂O₂ did not enhance the treatment efficiency. These results demonstrated that the WPL treatment can be a promising chemical-free alternative to chlorine washing for decontamination of berries destined for fresh-cut and frozen berry products. WPL–H₂O₂ treatment was the most effective treatment in our study for decontamination of bacterial pathogens on berries, providing an enhanced degree of microbiological safety for berries.     

Comparison of multiple chemical sanitizers for reducing Salmonella and Escherichia coli O157:H7 on spinach (Spinacia oleracea) leaves

Effectiveness of multiple chemical sanitizers on the reduction of Salmonella spp. and Escherichia coli O157:H7 on spinach was compared. Fresh spinach (Spinacia oleracea) was inoculated with a bacterial suspension containing multiple strains of rifampin-resistant Salmonella and E. coli O157:H7. Inoculated spinach leaves were treated with a water wash or water wash followed by 2% L-lactic acid at 55 °C, peroxyacetic acid (80 mg/L), calcium hypochlorite (200 mg/L), ozonated water (mg/L) or ClO₂ gas (1.2 or 2.1 mg/L). The l-lactic acid produced a 2.7 log CFU/g reduction for E. coli O157:H7 and a 2.3 log CFU/g reduction for Salmonella, statistically significant compared to water wash alone (P < 0.05), which resulted in a reduction of 0.7 log CFU/g for both pathogens. These findings indicate that 2% l-lactic acid at 55 °C may be an effective treatment for reducing pathogens on spinach leaves.     

Infrared pasteurization of raw almonds

Due to outbreaks of salmonellosis associated with whole raw almonds, an infrared (IR) pasteurization process was investigated for its efficacy in improving the safety of raw almonds. After almonds were heated to 100, 110 and 120 °C with IR, they were cooled at ambient temperature to a holding temperature of 70, 80 or 90 °C before being transferred to a custom-designed holding device for different time periods up to 60 min. We observed that holding almonds at 90 °C for 10-15 min reduced the Pediococcus population size by more than 5-log and holding at 80 °C for longer than 22 min provided more than 4-log reduction, thus satisfying the targeted 4-log reduction required in the almond industry. The L^∗a^∗b^∗ color values of whole almonds were not affected significantly (P > 0.05) by the IR process whereas the a^∗ and b^∗ color values of ground almonds changed significantly (P < 0.05). The sensory panel did not detect any significant difference (P > 0.01) in appearance, texture, flavor and overall quality of pasteurized almonds compared with untreated samples.     

Salmonella in meat from hunted game: A Central European perspective

The occurrence of Salmonella in meat from game hunted in Europe is reviewed, with a focus on Central Europe. Prevalence in fecal samples is different according to region and game species, ranging from < 5 (wild ruminants) to ca. 20% (wild boar). The pathogen is rarely recovered from carcasses or meat cuts of wild ruminants (< 1%). Prevalences on wild boar carcasses have been reported to range from < 1 to ca. 7%, the tonsils presumably constituting a main reservoir on the eviscerated carcass. On meat cuts from game, recent German and EU (EFSA) reports indicate a prevalence of < 1%. A number of Salmonella enterica serovars can be isolated, with highest prevalences of S. Typhimurium and S. Enteritidis. Persistence of these pathogens in wildlife is a less pressing issue for biology and wildlife conservation than for public health experts, which has been recognized in the framework of zoonoses legislation. On one hand, wildlife is exposed to salmonellae originating from farm animals and humans, and on the other hand, game can be a source of Salmonella in farm animals. Breeding game under intensified conditions (farmed game) as well as extensive breeding of farm animals, notably pigs, can create new epidemiological situations. The pathway of Salmonella from intestinal content of the live animal to individual meat cuts can be described in qualitative terms, yet the relative contribution of the various factors remains to be quantified, which complicates proper risk assessment. Control of Salmonella in the game meat chain is in part based on Good Hygiene Practice from killing and evisceration to chilling and skinning, whereas more detailed data are needed in order to allow risk-based meat inspection.     

High-pressure and temperature effects on the inactivation of Bacillus amyloliquefaciens,alkaline phosphatase and storage stability of conjugated linoleic acid in milk

Milk rich in conjugated linoleic acid (CLA, 42 ± 3 mg g^− 1 fat) was used to evaluate the impact of high-pressure sterilization (HPS). The pressure, temperature and time needed to reduce 7-log of Bacillus amyloliquefaciens endospores were determined in the presence of nisin (4–64 mg L^− 1). In addition, the inactivation of alkaline phosphatase was evaluated. After HPS treatment, the remaining CLA and formation of hydroperoxides were monitored during storage up to 60 d at 25 °C. The addition of nisin (≥ 16 mg L^− 1) to milk significantly enhanced the inactivation of B. amyloliquefaciens (7-log reduction) after treatment at 600 MPa, 120 °C and 5 min of holding time. These conditions were selected to evaluate the impact of HPS on the CLA retention and hydroperoxides formation. Milk with the addition of nisin and treated with HPS delivered higher retention of CLA and a lower concentration of hydroperoxides compared with the UHT equivalent process (125 °C/15 s and 135 °C/10 s).Industrial relevanceHigh-pressure sterilization is a valuable alternative to produce superior quality milk products in cases where traditional thermal treatments have failed. This study evaluated the impact of processing conditions on the conjugated linoleic acid content at conditions where commercial sterilization has been achieved (7-log reduction of B. amyloliquefaciens). The outcomes of this study are considered as a step further for the development of high-pressure sterilized milk.     

Water activity change at elevated temperatures and thermal resistance of Salmonella in all purpose wheat flour and peanut butter

Water activity (a_w) is a major factor affecting pathogen heat resistance in low-moisture foods. However, there is a lack of data for a_w at elevated temperatures that occur during actual thermal processing conditions, and its influence on thermal tolerance of pathogens. The objective of this study was to gain an in-depth understanding of the relationship between temperature-induced changes in a_w and thermal resistance of Salmonella in all purpose flour and peanut butter at elevated temperatures (80 ^oC). Equilibrium water sorption isotherms (water content vs. water activity) for all purpose wheat flour and peanut butter over the range of 20 to 80 °C were generated using a vapor sorption analyzer and a newly developed thermal cell. The thermal resistance (D₈₀-values) of Salmonella in all purpose wheat flour and peanut butter with initial a_w of 0.45 (measured at room temperature, ~ 20 °C) was determined via isothermal treatment of small (< 1 g) samples. When increasing sample temperature from 20 to 80 °C in sealed cells, the a_w of all purpose flour increased from 0.45 to 0.80, but the a_w of peanut butter decreased from 0.45 to 0.04. The corresponding estimated D₈₀-values of Salmonella in all purpose flour and peanut butter with 20 ^oC a_w of 0.45 were 6.9 ± 0.7 min and 17.0 ± 0.9 min, respectively. The significantly (P < 0.05) higher D₈₀-value of Salmonella in peanut butter than in all purpose flour may be partially attributed to the reduced a_w in peanut butter in comparison to the increased a_w in all purpose flour at 80 °C. The improved understanding of temperature-induced changes in a_w of low-moisture products of different composition provides a new insight into seemly unpredictable results, when using heat treatments to control Salmonella in such food systems.     

Effects of carob bean gum on performance,nutrient digestibility and Salmonella enterica var. Enteritidis colonisation in chickens

Salmonella is presently one of the microorganisms of higher concern for food safety in poultry products. The present study examined the effect of feeding galactomannans from carob bean gum on nutrient digestibility and performance in chickens, and on the prevalence of Salmonella enterica var. Enteritidis in challenged animals. Four experiments were performed with either broiler or leghorn chickens, challenged with 10⁶ CFU (colony-forming units) of S. Enteritidis at 1 day of life, and feeding carob bean gum at different concentrations (25, 50 or 100 g/kg, depending on the experiment), alone or in combination with β-mannanase, cellulase or α-galactosidase at 8.3 U/g; or feeding D-mannose at 25 g/kg, or depolymerized carob bean gum or guar gum at 100 mg/kg. Trials lasted 3 or 4 weeks. Body weight and feed intake were determined and feed conversion ratio calculated (feed:gain). Faeces were collected during the last week on trial for evaluation of nutrient balance (energy, lipids and protein), using chromium oxide as inert marker. Viscosity of the ileal content was also determined at the end of the second experiment. Salmonella presence in caeca was determined two and 3 weeks after challenge. Performance and nutritive value of diets were impaired in birds fed carob bean gum, with higher effect at higher inclusion rates. D-mannose impaired performance variables only whereas depolymerized gums did not affect bird performance or nutritive value of the diets. Of the enzymes tested, only β-mannanase significantly decreased the viscosity of the intestinal contents of birds fed carob bean gum and partly counteracted the impairment in bird performance and the reduction in the nutritive value of the diets. The number of Salmonella-positive birds varied among experiments and was lower in the third week post-challenge compared to the second week post-challenge. However, the reduction in the number of Salmonella-positive birds was more constant and marked when carob bean gum was present in the diet. The inclusion of carob bean gum in the diet of chickens at the high concentrations used in the present experiment reduced the presence of Salmonella in challenged birds, but it also impaired performance and nutrient digestibility. These impairments were partially counteracted by the addition of β-mannanase to the diet. Carob bean gum might be used to reduce the incidence of Salmonella in chickens, while its negative effects on performance and nutrient digestibility could be counteracted by β-mannanase.