Occurrence of selected viral and bacterial pathogens and microbiological quality of fresh and frozen strawberries sold in Spain

Strawberry production and exports have been increasing in Spain in recent decades. However, little information is available about their microbiological quality. Due to the growing concern about the microbial safety of these fruits, the objective of this investigation was to study the microbiological quality and the prevalence of the main foodborne pathogens on strawberries sold in Spain. Fresh (n = 152) and frozen (n = 31) samples were obtained from marketplaces and fields in 2017 and 2018. The samples were assayed for total aerobic mesophilic microorganisms (TAM), moulds and yeasts (M&Y), total coliforms (TC), Escherichia coli, Salmonella spp., Listeria monocytogenes as well as Norovirus (NoV) GI and GII. The microbiological counts ranged from <1.70 (detection limit, dl) – 5.89 log10 CFU/g (mean 3.78 log10 CFU/g) for TAM; 2.10–5.86 log10 CFU/g (mean 3.80 log10 CFU/g) for M&Y; and <0.70 (dl) – 4.91 log10 CFU/g (mean 2.15 log10 CFU/g) for TC in fresh strawberries. In frozen strawberries, the counts were <1.70 (dl) – 3.66 log10 CFU/g (mean 2.30 log10 CFU/g) for TAM; <1.70 (dl) – 2.76 log10 CFU/g (mean 1.82 log10 CFU/g) for M&Y; and <0.70(dl) – 1.74 log10 CFU/g (mean 0.77 log10 CFU/g) for TC. All the samples in this study tested negative for Salmonella spp., L. monocytogenes. E. coli and NoV GI and GII genome. A global overview of all the data was executed using Principal Component Analysis (PCA), and the results showed that the scores and loadings according to principal components 1 (PC1) and 2 (PC2) accounted for 75.9% of the total variance, allowing a distinction between fresh and frozen samples. The presence of moulds was significantly higher in the supermarket samples whereas the presence of total coliforms was significantly higher in the field samples (p < 0.05). Although pathogenic microorganisms were not found, preventative measures and prerequisites in the strawberry production chain must be considered in order to avoid possible foodborne diseases related to the microbiological quality of the fruit.info:eu-repo/semantics/acceptedVersio

Effectiveness of a pomegranate peel extract (PGE) in reducing Listeria monocytogenes in vitro and on fresh-cut pear, apple and melon

Pomegranate peel extract (PGE) is a new promising natural alternative control substance with large spectrum of activity against wide range of pathogenic microorganisms. In the present study, PGE was firstly investigated as natural antimicrobial against Listeria monocytogenes both in vitro and on fresh-cut fruits. The in vitro results showed quick and strong bactericidal and bacteriostatic activity against five different strains which were almost completely inhibited by the extract. Furthermore, it significantly decreased growth rate and maximum growth of all tested strains. In vivo trials, confirmed a strong antibacterial activity of the extract that significantly reduced the bacterial load on fresh-cut apple, melon and pear and maintained the population at low levels throughout the storage period (7 days). PGE at 12 g/l reduced L. monocytogenes by 1.24, 1.89, and 0.91 log units soon after treatment and by 3.81, 1.53, and 2.99 log units, after 7 days of storage on apple, pear and melon, respectively. This high antibacterial activity could be mainly related to the high content of polyphenols (ellagitannins) in the extract. Overall, results of this study suggest a potential industrial application of PGE to reduce the growth of the pathogenic microorganisms in fresh-cut fruit and ensure a microbial safety in case of contamination.info:eu-repo/semantics/acceptedVersio

Evaluation of a sanitizing washing step with different chemical disinfectants for the strawberry processing industry

Strawberries are often consumed fresh or only receive minimal processing, inducing a significant health risk to the consumer if contamination occurs anywhere from farm to fork. Outbreaks of foodborne illness associated with strawberries often involve a broad range of microbiological agents, from viruses (human norovirus) to bacteria (Salmonella spp. and Listeria monocytogenes). The addition of sanitizers to water washes is one of the most commonly studied strategies to remove or inactivate pathogens on berries as well as avoid cross contamination due to reuse of process wash water. The risk posed with the safety issues of by-products from chlorine disinfection in the fruit industry has led to a search for alternative sanitizers. We evaluated the applicability of different chemical sanitizers (peracetic acid (PA), hydrogen peroxide (H2O2), citric acid (CA), lactic acid (LA) and acetic acid (AA)) for the inactivation of S. enterica, L. monocytogenes and murine norovirus (MNV-1) on strawberries. A control treatment with chlorine (NaClO) (100 ppm) was included. For each sanitizer, different doses (40, 80 and 120 ppm for PA and 1, 2.5 and 5% for H2O2, LA, AA and CA) and time (2 and 5 min) were studied in order to optimize the decontamination washing step. The best concentrations were 80 ppm for PA, 5% for H2O2 and 2.5% for organic acids (LA, AA and CA) after 2 min treatment. Results indicate that the sanitizers selected may be a feasible alternative to chlorine (100 ppm) for removing selected pathogenic microorganisms (P > 0.05), with reductions about ≥2 log for bacterial strains and ≥ 1.7 log for MNV-1. As the washing water may also increase the microbial counts by cross-contamination, we observed that no pathogenic bacteria were found in wash water after 5% H2O2 and 80 ppm PA after 2 min treatment. On the other hand, we also reported reductions about total aerobic mesophyll (TAM) (0.0–1.4 log CFU/g) and molds and yeasts (M&Y) (0.3–1.8 log CFU/g) with all alternative sanitizers tested. Strawberries treated did not shown significant differences about physio-chemical parameters compared to the untreated samples (initial). For this study, the optimal sanitizer selected was PA, due to the low concentration and cost needed and its microbiocidal effect in wash water and fruit. Notwithstanding the results obtained, the effect of PA in combination with other non-thermal technologies such as water-assisted ultraviolet (UV-C) light should be studied in future research to improve the disinfection of strawberries.info:eu-repo/semantics/acceptedVersio

Composition, Structure and Tribotechnical Properties of TiN, MoN Single-Layer and TiN/MoN Multilayer Coatings

Results of comprehensive investigations of nanostructed TiN and MoN single layer coatings as well as multilayer coatings consisting of TiN/MoN alternating layers have beenconsidered. The coatings have been deposited by a promising modern method of cathode-arc evaporation (vacuum-arc method). The elemental and phase compositions of coatings, their tribological and physico mechanical properties: friction coefficient, wear, adhesion, hardness, and elastic modulus have been studied and the mechanisms of the coatings fracture have been discussedyesBelgorod State Universit

Evaluation of a sanitizing washing step with different chemical disinfectants for the strawberry processing industry

Strawberries are often consumed fresh or only receive minimal processing, inducing a significant health risk to the consumer if contamination occurs anywhere from farm to fork. Outbreaks of foodborne illness associated with strawberries often involve a broad range of microbiological agents, from viruses (human norovirus) to bacteria (Salmonella spp. and Listeria monocytogenes). The addition of sanitizers to water washes is one of the most commonly studied strategies to remove or inactivate pathogens on berries as well as avoid cross contamination due to reuse of process wash water. The risk posed with the safety issues of by-products from chlorine disinfection in the fruit industry has led to a search for alternative sanitizers. We evaluated the applicability of different chemical sanitizers (peracetic acid (PA), hydrogen peroxide (H2O2), citric acid (CA), lactic acid (LA) and acetic acid (AA)) for the inactivation of S. enterica, L. monocytogenes and murine norovirus (MNV-1) on strawberries. A control treatment with chlorine (NaClO) (100 ppm) was included. For each sanitizer, different doses (40, 80 and 120 ppm for PA and 1, 2.5 and 5% for H2O2, LA, AA and CA) and time (2 and 5 min) were studied in order to optimize the decontamination washing step. The best concentrations were 80 ppm for PA, 5% for H2O2 and 2.5% for organic acids (LA, AA and CA) after 2 min treatment. Results indicate that the sanitizers selected may be a feasible alternative to chlorine (100 ppm) for removing selected pathogenic microorganisms (P > 0.05), with reductions about ≥2 log for bacterial strains and ≥ 1.7 log for MNV-1. As the washing water may also increase the microbial counts by cross-contamination, we observed that no pathogenic bacteria were found in wash water after 5% H2O2 and 80 ppm PA after 2 min treatment. On the other hand, we also reported reductions about total aerobic mesophyll (TAM) (0.0–1.4 log CFU/g) and molds and yeasts (M&Y) (0.3–1.8 log CFU/g) with all alternative sanitizers tested. Strawberries treated did not shown significant differences about physio-chemical parameters compared to the untreated samples (initial). For this study, the optimal sanitizer selected was PA, due to the low concentration and cost needed and its microbiocidal effect in wash water and fruit. Notwithstanding the results obtained, the effect of PA in combination with other non-thermal technologies such as water-assisted ultraviolet (UV-C) light should be studied in future research to improve the disinfection of strawberries.info:eu-repo/semantics/acceptedVersio

Biopreservation of fresh-cut pear using Lactobacillus rhamnosus GG and effect on quality and volatile compounds

In recent years, the consumption of minimally processed fruit has increased. However, unfortunately, these products could be an appropriate vehicle for the transmission of foodborne pathogens. In this study, the antagonistic capacity of the probiotic strain Lactobacillus rhamnosus GG against a cocktail of 5 serovars of Salmonella and 5 serovars of Listeria monocytogenes on fresh-cut pear at conditions simulating commercial application was assessed. Moreover, its effect on fruit quality, particularly on the volatile profile, was determined, during 9 days of storage at 5 C. L. monocytogenes population was reduced by approximately 1.8 log-units when co-inoculated with L. rhamnosus GG. However, no effect was observed in Salmonella. Fruit quality (soluble solids content and titratable acidity) did not change when the probiotic was present. A total of 48 volatile compounds were identified using gas chromatography. Twelve of the compounds allowed to discriminate L. rhamnosus GG-treated and untreated pears. Considering their odour descriptors, their increases could be positive in the flavour perception of L. rhamnosus GG-treated pear. The probiotic was able to control L. monocytogenes population on fresh-cut pear, which could be a vehicle of probiotic microorganisms as quality of fruit was not affected when the probiotic was presentinfo:eu-repo/semantics/acceptedVersio

3D-to-2D morphology manipulation of sputter-deposited nanoscale silver films on weakly interacting substrates via selective nitrogen deployment for multifunctional metal contacts

The ability to reverse the inherent tendency of noble metals to grow in an uncontrolled three-dimensional (3D) fashion on weakly interacting substrates, including two-dimensional (2D) materials and oxides, is essential for the fabrication of high-quality multifunctional metal contacts in key enabling devices. In this study, we show that this can be effectively achieved by deploying nitrogen (N2) gas with high temporal precision during magnetron sputtering of nanoscale silver (Ag) islands and layers on silicon dioxide (SiO2) substrates. We employ real-time in situ film growth monitoring using spectroscopic ellipsometry, along with optical modeling in the framework of the finite-difference time-domain method, and establish that localized surface plasmon resonance (LSPR) from nanoscale Ag islands can be used to gauge the evolution of surface morphology of discontinuous layers up to a SiO2 substrate area coverage of ∼70%. Such analysis, in combination with data on the evolution of room-temperature resistivity of electrically conductive layers, reveals that presence of N2 in the sputtering gas atmosphere throughout all film-formation stages: (i) promotes 2D growth and smooth film surfaces and (ii) leads to an increase of the continuous-layer electrical resistivity by ∼30% compared to Ag films grown in a pure argon (Ar) ambient atmosphere. Detailed ex situ nanoscale structural analyses suggest that N2 favors 2D morphology by suppressing island coalescence rates during initial growth stages, while it causes interruption of local epitaxial growth on Ag crystals. Using these insights, we deposit Ag layers by deploying N2 selectively, either during the early precoalescence growth stages or after coalescence completion. We show that early N2 deployment leads to 2D morphology without affecting the Ag-layer resistivity, while postcoalescence introduction of N2 in the gas atmosphere further promotes formation of three-dimensional (3D) nanostructures and roughness at the film growth front. In a broader context this study generates knowledge that is relevant for the development of (i) single-step growth manipulation strategies based on selective deployment of surfactant species and (ii) real-time methodologies for tracking film and nanostructure morphological evolution using LSPR