查看更多>>摘要：Polycyclic aromatic hydrocarbons (PAHs) are a large class of organic compounds produced from incomplete combustion. Many PAHs are mutagenic and some are carcinogenic and pose a health risk to humans. Dietary intake of PAHs is a major route of exposure, where fats and edible oils are important contributors to overall dietary PAH exposure. Composed of hundreds of individual compounds as a complex mixture, only 16 PAHs are typically monitored in food and the environment. In this present study we analyzed 16 commercial olive oil samples from different countries of origin and type (virgin or refined oil) for their content of 45 PAHs using a high-performance liquid chromatograph coupled to a gas chromatograph with a mass spectrometric detector. The content of the 45 PAHs varied between 9.17 and 94.7 mu g/kg (median: 30.1 mu g/kg) in the different olive oil samples. Only one sample didn't meet the regulatory threshold levels for PAHs. The compositional profile of PAHs across the olive oil samples showed a high abundance of PAHs of lower molecular weights, and a large contribution of alkylated PAHs regardless of olive oil type. Direct contact with diesel exhaust emissions from mechanical harvesters has previously shown to affect PAH levels in olive oils. Using diagnostic PAH ratios, biomass/coal combustion and/or petroleum/fossil fuel combustion were indicated as important sources. Source apportionment by Positive Matrix Factorization revealed diesel exhaust emission and biomass combustion as the two major sources of PAHs followed by traffic emissions. This suggests that air quality may have a considerable impact on pollution levels in olive oils and thus indirectly affect dietary exposure.
查看更多>>摘要：This study aimed to determine the enzymatic effect of cellulase, DNase I, and proteinase K on Salmonella enterica Enteritidis biofilms on the stainless steel surface at nutrient availability [tryptic soy broth (TSB) and 20 times diluted TSB (1/20 TSB)] and to evaluate the synergistic effect of proteinase K combined with chlorine (50 ppm for 1 min). The results showed that cellulase and proteinase K degraded S. Enteritidis ME 14 biofilms, regardless of nutrient availability, whereas S. Enteritidis ATCC 13076 biofilms formed in TSB were effectively degraded by all the enzymes tested, but resistant to cellulase and DNase I in 1/20 TSB. Proteinase K or chlorine alone reduced the two S. Enteritidis biofilms formed in TSB by 1.1-1.5 log CFU/cm(2), while the combined treatment with proteinase K followed by chlorine resulted in 3.8-6.1 log reductions, revealing the synergistic effect. On the contrary, both S. Enteritidis biofilms formed in 1/20 TSB were more resistant to proteinase K treatment followed by chlorine than TSB. Furthermore, microscopic observation using Live/Dead (R) assay and scanning electron microscopy (SEM) showed that biofilm morphology was greatly altered by the combined treatment, and pro-teinase K might make it easier for chlorine to penetrate the biofilm matrix. Therefore, these results indicate proteinase K with chlorine-based sanitizer has a potential for effective control of Salmonella biofilms formed on the food contact surface, decreasing the chance of cross-contamination and the risk of salmonellosis.
查看更多>>摘要：Food additive E171 (titanium dioxide, TiO2) is authorized to be used as food colorant in the European Union. E171 is a particulate material, containing a fraction of nanoparticles. A major challenge for food control laboratories is the lack of harmonized, validated analytical methods for measuring the physicochemical properties of nanoparticles in food. This study proposes a generic method for the determination of the number-based size distribution of the constituent particles of E171 in food products based on transmission electron microscopy (TEM). As proof of concept, the protocol was evaluated on 20 food products containing E171 and one personal care product containing titanium dioxide. The total titanium concentration in the products measured by inductively coupled plasma - mass spectrometry (ICP-MS) ranged from 0.1 to 4.0 g/kg, corresponding to 0.2-6.7 g TiO2/kg. The required initial mass of starting product needed for TEM analysis was estimated from the ICP-MS concentration. Sample preparation included matrix digestion, a first centrifugation step to remove the remaining food matrix, sonication to reduce agglomeration, and a second centrifugation step to concentrate the sample. Descriptive TEM analysis showed that five food products, labelled to contain E171, contained smaller rutile TiO2 particles (20-40 nm) coated with mica, which are potassium aluminium silicate-based pearlescent pigments. For 14 other food products and the personal care product, the protocol resulted in a homogenous distribution of the TiO2 particles over the grid surface. In general, variation between products in the number of particles on the grids was limited; on average, 672 +/- 173 particles were measured in 10 images. The median of the minimum Feret diameter distribution varied from 72 +/- 7 nm to 135 +/- 14 nm. The percentage of nanoparticles (minimum Feret diameter smaller than 100 nm) ranged from 23% to 82%. The corresponding mass percentages of these fractions ranged from 3% to 41%. The percentages of E171 particles smaller than 30 nm was very low (3% or less) while corresponding mass fractions were negligible. For only one food product, the TiO2 concentration was too low to apply the protocol without adaptations.
Cus, FrancCesnik, Helena BasaBolta, Spela Velikonja
7页
查看更多>>摘要：The aim of this study was to compare pesticide residues, copper and biogenic amines concentrations in conventional and organic wines. For each type of wine production, 20 samples were collected. We used two multiresidual methods employing GC/MS (92 pesticides) and LC/MS/MS (112 pesticides) detection. Copper residues and biogenic amines were measured by standard FAAS and HPLC methods. We confirmed lower numbers and concentrations of pesticide residues in organic wines. The most frequently determined pesticide was dimethomorph, followed by boscalid, fenhexamid, metalaxyl + metalaxyl-M, iprovalicarb and pyrimethanil. Also, higher levels of copper were observed in the groups of conventional wines. For biogenic amines, we could not confirm a clear trend. It is unacceptable that some pesticide residues in organic wines were detected, which are not allowed in this type of production. Nevertheless, we can confirm the trend of added value in organic wine production in terms of reducing pesticide residues and copper in bottled wines.
查看更多>>摘要：Non-enzymatic browning (NEB) is the major quality deterioration of Choerospondias axillaris fruit cake (CAFC) occurred during drying. The evolution of NEB, 5-Hydroxymethyl furfural (5-HMF), total phenols and ascorbic acid contents of CAFCs during hot air drying at various temperatures (50, 60, 70, 80 and 90 degrees C) were studied, and the anti-browning agents for inhibiting NEB were evaluated. The results showed that the browning index and 5HMF content separately increased from 26.40 to 39.33 and 25.29-208.87 mg/kg; while the reductions of ascorbic acid and total phenols contents increased from 15.12 to 64.02 mg/100g and 10.54-35.40 mg GAE/100 g as the drying temperature increased from 50 to 90 degrees C. Drying at the programmed temperature (80-60-50 degrees C) could effectively decrease the browning of CAFC. Pearson correlation and Path-coefficient analysis further indicated that Maillard reaction was mainly responsible for the NEB of CAFCs. Adding 0.03%-0.05% sodium bisulfite showed the best effect on the NEB of CAFC, followed by 0.12% ferulic acid and 0.08% phytic acid. The ferulic acid and phytic acid could be used as a substitute of sodium bisulfite to improve the color of CAFCs.
Giagkazoglou, ZoeGriffiths, Andrew M.Imsiridou, AnastasiaChatzispyrou, Archontia...
8页
查看更多>>摘要：Mislabeling of seafood products and marketing of protected species remains a worldwide issue despite the labeling regulations set at a local, European and International level. DNA barcoding has proven to be the most popular and accurate method of detection of fraudulent seafood products. This study investigated the batoid meat market of Greece, the mislabeling rates and the protected species occurrence. A total of 114 ray products were collected from fishmongers, open markets, supermarkets, and restaurants across eight Greek cities. The cytochrome oxidase subunit I (COI) gene was used to analyze samples, and the sequences were compared against genetic databases for species identification. At least 13 species across nine genera were identified. The results did not indicate significant differences in species utilization among cities, retailers, and labels. However, in the pairwise comparisons, Athens differed from all other locations and a similar trend was followed by the label "salachi". Moderate mislabeling levels were recorded (13.5%), while 3.5% of the identified samples belonged to species with prohibitions on landings, confirming an ongoing market for protected species. Overall, 19.8% of the samples originated from species that are locally listed in threatened categories of the IUCN Red List of species.
查看更多>>摘要：Nuclear magnetic resonance (NMR), and in particular transverse relaxation (T-2), has been used to characterize meat and seafood products for decades. Despite many years of research, it is still not possible to reproducibly correlate the transverse relaxation of muscle foods to attributes that determine their quality and value. Instead of directly trying to interpret the T-2 spectrum itself, typically chemometrics is used to try to relate the relaxation distributions to other measured properties on the sample. As muscle tissue is a porous medium, it is tempting to use equations developed to analyze other porous systems to provide a more direct, quantitative description of the tissue. However, the standard equations used to characterize porous materials have been developed for pre-dominantly geological systems. This article discusses the foundations of transverse relaxation theory in porous media and the challenges that arise when attempting to adapt the equations to a biological system like tissue. One of the biggest issues that needs to be overcome before porous media theory can be reliably applied to characterize meat and seafood is to determine the source of relaxivity in the tissue. In order to better understand how the NMR signal originates, T-2, diffusion, T-1-T-2 correlation and T-2-T-2 exchange experiments were performed on Atlantic cod (Gadus morhua) tissue in a variety of states (e.g. fresh, thawed, homogenized, etc.). In the literature, typically four T-2 peaks are reported for meat and seafood samples. Results of this study indicate that the fastest relaxation peak is attributable to hydrogen within the protein itself and therefore arises from dipolar coupling. The T-2B peak appears to belong to a type of bound water in protein called "buried water", and its relaxation stems from a combination of restricted motion and interaction with the hydrogen in the protein. For the T-21 peak, attributed to fluid in myofibrils, the main relaxation mechanism is the interaction between water molecules and the hydrogen in myosin/actin matrix. The T-22 peak arises predominantly from the interaction of water with dissolved protein in the sarcoplasm. An important finding from the study is the need to include both surface sinks and volume sinks in the interpretation of T-2 relaxation results. Given these sources of the transverse relaxation in tissue, it is highly likely that changes to the T-2 distribution that have been attributed to micro-structural changes in the tissue are in reality due to a combination of changes in microstructure, surface relaxation and fluid properties. These findings aid in better interpreting T-2 measurements in meat and seafood products and present a step towards a systematic approach for using transverse relaxation to quantitatively describe changes in tissue, with the ultimate aim of eventually predicting product quality and value from NMR relaxometry.
查看更多>>摘要：This study investigated the antimicrobial activity of lime oil (LO) at 50, 100, and 200 mu l to control microbial spoilage and the survival of Listeria monocytogenes on ready-to-eat (RTE) mixed vegetable salads in 1-L glass boxes for 7 days in a refrigerator (similar to 4 degrees C). The bacteriostatic properties of L. monocytogenes were investigated by cell constituent release analysis and crystal violet assays, which are related to the bacterial cell wall and cell membrane. Scanning electron microscopy (SEM) was used to study the morphology of L. Monocytogenes, and the components of LO in treated RTE mixed vegetable salads using were studied by gas chromatography-mass spectrometry (GC-MS). The results indicated that LO at 100 mu l L-1 could inhibit cell cultures and reduce the growth of L. monocytogenes (similar to 10(4) cfu ml(-1)) on RTE salads in refrigerated conditions by 0.6-1.5 log(10) cfu g(-1). The results revealed that LO affected bacterial cell permeability and cell membrane integrity. The treated cells showed serious detrimental defects in their membrane morphology. Furthermore, alpha-terpineol, terpineol and limonene were confirmed as the key components that inhibited bacteria during cold storage. The quality of RTE salads stored with LO in a 1-L glass box showed good results, and the consumers also accepted the salads with a hedonic score (similar to 6.1 +/- 0.7) rated as 'like slightly' for sensory evaluation.
Oh, JiwonKim, HoikyungBeuchat, Larry R.Ryu, Jee-Hoon...
6页
查看更多>>摘要：The objectives of this study were to screen essential oil (EO) vapors for inhibitory activities against Staphylococcus aureus on a laboratory medium and to validate their antibacterial effects on dried black peppercorns (Piper nigrum). Among 84 commercially available EOs, using a vapor disc assay, vapors from caraway seed, carrot seed, cinnamon bark, citronella, kanuka, lemongrass, may chang, oregano, and thyme thymol EOs were found to be more inhibitory to S. aureus. The minimal inhibitory concentration (MIC) and minimal lethal concentration (MLC) of nine EO vapors from these plant materials were measured on a laboratory medium. Citronella, lemongrass, and oregano EO vapors had the lowest MIC and MLC values, at 0.0781 and 0.1563 mu L/mL, respectively. Using a checkerboard assay, partial synergism in inhibitory activity of a combination of citronella and lemongrass EO vapors was observed (fractional inhibitory concentration index = 0.6250). When tested against S. aureus on black peppercorns, citronella, lemongrass, and oregano EO vapors, both individually and in combination, showed a significant antibacterial effect (P < 0.05). Notably, a combination of citronella and lemongrass EO vapors (1:4 vol ratio) showed significant synergistic activity, reducing the S. aureus population by ca. >= 1.3-1.8 log CFU/g more than treatment with single EOs (P < 0.05). The results of this study provide important basic information for developing technologies to control S. aureus on the surfaces of dried foods using EO vapors.
NSTL
Elsevier