Surface enhanced Raman scattering (SERS) with biopolymer encapsulated silver nanosubstrates for rapid detection of foodborne pathogens

A biopolymer encapsulated with silver nanoparticles was prepared using silver nitrate, polyvinyl alcohol (PVA) solution, and trisodium citrate. It was deposited on a mica sheet to use as SERS substrate. Fresh cultures of Salmonella Typhimurium, Escherichia coli, Staphylococcus aureus and Listeria innocua were washed from chicken rinse and suspended in 10 ml of sterile deionized water. Approximately 5 μl of the bacterial suspensions was placed on the substrate individually and exposed to 785 nm HeNe laser excitation. SERS spectral data were recorded over the Raman shift between 400 and 1800 cm^− 1 from 15 different spots on the substrate for each sample; and three replicates were done on each bacteria type. Principal component analysis (PCA) model was developed to classify foodborne bacteria types. PC1 identified 96% of the variation among the given bacteria specimen, and PC2 identified 3%, resulted in a total of 99% classification accuracy. Soft Independent Modeling of Class Analogies (SIMCA) of validation set gave an overall correct classification of 97%. Comparison of the SERS spectra of different types of gram-negative and gram-positive bacteria indicated that all of them have similar cell walls and cell membrane structures. Conversely, major differences were noted around the nucleic acid and amino acid structure information between 1200 cm^− 1 and 1700 cm^− 1 and at the finger print region between 400 cm^− 1 and 700 cm^− 1. Silver biopolymer nanoparticle substrate could be a promising SERS tool for pathogen detection. Also this study indicates that SERS technology could be used for reliable and rapid detection and classification of food borne pathogens.     

Detection of Omethoate Residues in Peach with Surface-Enhanced Raman Spectroscopy

In this work, surface-enhanced Raman spectroscopy (SERS) was used with silver colloid substrate for rapid detection of omethoate (an organophosphate pesticide) in standard solution and peach extract. The findings demonstrated that the characteristic wavenumber of the pesticide could be precisely identified using the SERS method. The calibration curve was plotted between concentrations and Raman intensities of the target peak at 1649 cm^?1 for the peach extract and at 1647 cm^?1 for the standard solution. The coefficients of determination (R²) of 0.9829 and 0.98 were obtained for standard solution and for peach extract, respectively. The calculated limits of detection for omethoate in standard solution and in peach extracts were 0.001 mg L^?1 and 0.01 mg kg^?1, respectively. This study revealed that the proposed method could be used for the analysis of trace contaminants like omethoate in multifaceted food matrices.     

Determination of 6-Benzylaminopurine and Hg<Superscript>2+</Superscript> in Bean Sprouts and Drinking Mineral Water by Surface-Enhanced Raman Spectroscopy

A novel method for the determination of 6-benzyladenine (6-BA) in bean sprouts and Hg²⁺ in drinking mineral water by surface-enhanced Raman spectroscopy (SERS) was described. 6-BA exhibits obvious SERS signal by using the substrate of silver nanoparticles (AgNPs), and the presence of Hg²⁺ could cause the decrease of SERS signal of 6-BA. The effects of type of aggregation agent, type and level of pH buffer solution, amount of AgNPs, mixing time, concentration of 6-BA, and reaction time on the SERS signals were investigated. Under the optimized experimental conditions, good linear responses were obtained for 6-BA and Hg²⁺ in the concentration ranges of 10–200 μg L^?1 and 5–200 μg L^?1, respectively. By the present method, the limits of detection (LODs) for the determination of 6-BA and Hg²⁺ are 3.3 and 0.20 μg L^?1, and the recoveries of 6-BA and Hg²⁺ in spiked samples are 85.5–113.0 % and 98.2–111.5 %, respectively.     

SERS Detection of Insecticide Amitraz Residue in Milk Based on Au@Ag Core-Shell Nanoparticles

A simple, rapid, and environmentally friendly surface-enhanced Raman scattering (SERS) method was developed for the determination of trace amitraz in milk with the use of silver-coated gold nanoparticles (Au@Ag NPs) as enhancing reagent. The normal Raman and SERS spectra of amitraz were analyzed, and the peaks were assigned by density functional theory. The morphology of Au@Ag NPs was characterized and confirmed by transmission electron microscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. The SERS effects of Au@Ag NPs were investigated, including the types of solvents for dissolving amitraz, the volume ratio of the Au@Ag NPs and amitraz, and the concentration of aggregating agent (NaCl) for aggregate Au@Ag NPs. Results show that ethanol exerts the least interference on the SERS spectrum of amitraz and is more environmentally sound than methanol. The strongest SERS signal appeared when the volume ratio of Au@Ag NPs and amitraz was 2:1. Moreover, the strongest SERS signals appeared when the concentration of NaCl was 0.025 mol L^?1 because of appropriate aggregation. Under the optimum conditions, the concentration of amitraz presents a good linear relationship with Raman intensity (723 cm^?1) with a linear range of 9.77 × 10^?4~2.93 × 10^?2 g L^?1. The detected recoveries of amitraz in milk were between 81.7 and 100.5% with a relative standard deviation (RSD) of 2.61~5.51%.     

Simultaneous Detection of Salmonella,Listeria monocytogenes,and Staphylococcus aureus by Multiplex Real-Time PCR Assays Using High-Resolution Melting

A method combining multiplex real-time polymerase chain reaction (PCR) with high-resolution melting (HRM) analysis for rapid and specific simultaneous detection of Salmonella, Listeria monocytogenes, and Staphylococcus aureus was developed. The method included a melting-curve analysis of products and was evaluated by specificity, sensitivity and reproducibility analyses. Sensitivity and reproducibility analyses was both conducted by genomic DNA extracted from serial dilutions for each target pathogen. Assays with artificially inoculated and naturally contaminated samples after enrichment were also conducted. In the specificity test, there was no nonspecific amplification of the 44 nontarget pathogens, whereas the actual T _m values were 79.38?±?0.14, 82.54?±?0.15, and 77.36?±?0.14 °C for Salmonella, L. monocytogenes, and S. aureus, respectively. The sensitivity of the method was 3.5?×?10² CFU ml^?1 for Salmonella and L. monocytogenes and 3.5?×?10³ CFU ml^?1 for S. aureus. The coefficients of variation of T _m values ranged 0.51–1.03 % for Salmonella, 1.63–2.11 % for L. monocytogenes, and 0.75–2.17 % for S. aureus in intraassay, and ranged 0.81–2.43 % for Salmonella, 1.97–2.35 % for L. monocytogenes, and 0.93–3.93 % for S. aureus in interassay. The detection limit in artificially inoculated samples (n?=?50) was 5 CFU (25 g)^?1 food for the three tested pathogens. In the naturally contaminated samples (n?=?120),Salmonella DNA was detected by HRM, sequencing, and conventional culture-based methods at a positive rate of 25.00, 25.00, and 24.17 %, respectively; the corresponding rates for L. monocytogenes were 14.17, 14.17, and 14.17 %, respectively, while those for S. aureus were 16.7, 16.7, and 16.7 %, respectively.     

Antimicrobial Polylactic Acid Packaging Films against Listeria and Salmonella in Culture Medium and on Ready-to-Eat Meat

The contamination of Listeria monocytogenes and Salmonella spp. in ready-to-eat (RTE) meat products has been a concern for the meat industry. In this study, edible chitosan-acid solutions incorporating lauric arginate ester (LAE), sodium lactate (NaL), and sorbic acid (SA) alone or in combinations were developed and coated on polylactic acid (PLA) packaging films. Antimicrobial effects of coated PLA films on the growth of Listeria innocua, L. monocytogenes, and Salmonella Typhimurium in a culture medium (tryptic soy broth, TSB) and on the surface of meat samples were investigated. Antimicrobial PLA films containing 1.94 mg/cm² of chitosan and 1.94 μg/cm² of LAE were the most effective against both Listeria and Salmonella in TSB and reduced them to undetectable level (<0.69 log CFU/ml). The same PLA films with LAE significantly (p?L. innocua, L. monocytogenes, and S. Typhimurium on RTE meat during 3 and 5 weeks’ storage at 10 °C, achieving 2–3 log reduction of Listeria and 1–1.5 log reduction of Salmonella as compared with controls. PLA films coated with 1.94 mg/cm² of chitosan, 0.78 mg/cm² of NaL, and 0.12 mg/cm² of SA significantly reduced the growth of L. innocua but were less effective against Salmonella. The combination of NaL (0.78 mg/cm²) and SA (0.12 mg/cm²) with LAE (1.94 μg/cm²) did not generate additional or synergetic antimicrobial effect against Listeria or Salmonella on the meat surface. L. innocua had a similar sensitivity to the film treatments as L. monocytogenes, suggesting that L. innocua may be used as a surrogate of L. monocytogenes for further scaleup and validation studies. The film treatments were more effective against the microorganisms in TSB culture medium than in RTE meat, which suggests that in vivo studies are a necessary step to develop antimicrobial packaging for applications in foods.     

Discrimination of Salmonella enterica serotypes by Fourier transform infrared spectroscopy

Salmonella continues to be an important cause of foodborne infections in humans throughout the world. The precise nature of the infection depends on the specific combination of host and Salmonella serotypes, some of them being highly pathogenic. Fourier transform infrared (FT-IR) spectroscopy together with chemometric techniques were used in this study to discriminate closely related S. enterica serotypes. Intact cells of 26 different serotypes belonging to serogroups B, C1, C2–C3 and D1 (Enteritidis, Typhimurium, Bredeney, Goldcoast, Rissen, Hadar, Derby, Essen, Virchow, Mbandaka, Menden, Agona, Brikama, Saintpaul, Infantis, Braenderup, Mikawasima, Brandenburg, Heidelberg, Indiana, Norwich, Bardo, Bovismorbificans, Istanbul, Newport and Blockley) were examined by FT-IR spectroscopy in transmittance mode and classified based on the agglutination pattern reactions using the Kauffmann–White classification scheme. Using FT-IR spectra in the 1200–900 cm^? 1 range (outer membrane polysaccharides) allowed to correctly classify all isolates according to the four analysed serogroups. A discrimination analysis applied within each serogroup, demonstrated that it was also possible to differentiate between the different serotypes. Results demonstrate that application of FT-IR spectroscopy together with chemometric methods has considerable potential to effectively fulfil the current requirements for fast and straightforward differentiation of S. enterica serotypes.     

Feasibility of colloidal silver SERS for rapid bacterial screening

This study reports the feasibility of citrate-reduced colloidal silver surface-enhanced Raman scattering (SERS) for differentiating three important food borne pathogens, E. coli, Listeria, and Salmonella. FT-Raman and SERS spectra of both silver colloids and colloid-K₃PO₄ mixtures were collected and analyzed to evaluate the reproducibility and stability of silver colloids fabricated in a batch-production process. The results suggest that the reproducibility of the colloids over the batch process is high and that their binding effectiveness remains consistent over a 60-day storage period. Two specific SERS bands at 712 and 390 cm⁻¹ were identified and used to develop simple 2-band ratios for differentiating E. coli-, Listeria-, and Salmonella-colloid mixtures with a 100% success. These results indicate that colloidal silver SERS technique may be a practical alternative method suitable for routine and rapid screening of E. coli, Listeria, and Salmonella bacteria.     

Detection of Salmonella in Shellfish Using SYBR Green™ I-Based Real-Time Multiplexed PCR Assay Targeting invA and spvB

A SYBR Green? I-based real-time multiplexed PCR assay was developed targeting invA and spvB for the detection of Salmonella strains in shellfish after both hns and invA genes were identified in all Salmonella strains. Simultaneously, the 16S rRNA gene was used as a PCR internal amplification control (IAC). All 89 Salmonella strains tested in this study exhibited amplification of invA, whereas only 21 (23.6 %) were PCR positive for spvB. The sensitivity of detection of all three targeted genes was 1 ng, which is equivalent to approximately 10⁵ colony-forming unit (CFU) of Salmonella enterica. The analysis showed specific PCR products that were identified by reproducible melt temperature profiles (invA, 84.27?±?1.7 °C; spvB, 88.76?±?1.0 °C; and 16S rRNA gene, 87.16?±?0.8 °C).The sensitivity of detection was 10 pg purified DNA (invA) or 10⁵?CFU in 1 mL pure culture of S. enterica ATCC 14028. The above molecular detection method for Salmonella strains was successfully applied to the oyster homogenates (food matrix). An initial inoculum of 10⁶ and 10²?CFU Salmonella in 1 ml seeded oyster tissue homogenate was detected by multiplexed PCR for all three genes after 5 and 24 h of enrichment, respectively. Natural oysters isolated from Gulf of Mexico during the winter months exhibited negative PCR amplification results suggesting the absence of Salmonella. In contrast to conventional PCR, real-time multiplex PCR assay developed in this study is rapid and sensitive and will help Interstate Shellfish Sanitation Conference undertake appropriate measures to monitor Salmonella in oysters, thereby preventing disease outbreaks and consequently protecting consumer health.     

Rapid Analysis of Multiple Sudan Dyes in Chili Flakes Using Surface-Enhanced Raman Spectroscopy Coupled with Au–Ag Core-Shell Nanospheres

Sudan dyes are often illegally added as colorants into a variety of foodstuffs and have been tied to many food safety issues. In this study, surface-enhanced Raman spectroscopy (SERS) coupled with Au–Ag core-shell nanospheres (Au@Ag) was applied to analyze standard solutions of Sudan I–IV and Sudan dyes in chili flakes. With the use of 90 ± 5 nm Au@Ag (Au seed 20 ± 2 nm) as SERS substrate, the lowest detectible concentrations for Sudan I and II were 0.10 mg/L, for Sudan III was 0.08 mg/L, and for Sudan IV was 0.2 mg/L. The use of principal component analysis (PCA) could successfully classify different Sudan dyes based upon the SERS spectra of their standard solutions. For chili flakes, the use of acetonitrile as extraction solvent led to an overall higher sensitivity for analysis of Sudan dyes with SERS method compared to that of methanol, ethanol, and n-hexane. The lowest detectible concentrations for Sudan I–III in chili flakes were 1 mg/kg and for Sudan IV was 2 mg/kg, which were about ten times as much as that for their standard solutions due to the interference of non-target compounds from sample matrices. Partial least squares (PLS) models developed for quantitative analyses showed relatively high linear correlation between the actual and predicted amounts of Sudan dyes in chili flakes (R ² _cv = 0.869–0.959). The results showed great potential of applying Au@Ag as SERS substrate for qualitative and quantitative analysis of Sudan I–IV with simplified sample preparation method.     

Development and Optimization of a SERS Method for On-site Determination of Nitrite in Foods and Water

A rapid, sensitive, and selective detection method of nitrite in foods and water was established by surface-enhanced Raman spectroscopy (SERS) based on the diazo reaction of nitrite with p-nitroaniline and 1-naphthylamine in acidic solution. The azo dye (4-(4-nitrophenyldiazenyl)naphthalene-1-aminium, NNA), which was derived from the diazo reaction, was determined by SERS using citrate-coated silver nanoparticles (AgNPs) as SERS substrates. The concentrations of nitrite in samples were finally calculated from the intensities of SERS signals generated by NNA in the testing solutions. By using the present method combined with a portable miniature Raman spectrometer, on-site determination of nitrite could be performed easily and efficiently. The effects of several experimental parameters on the intensity of SERS signals, such as the volume of AgNP solution and the mixing time of AgNPs and NNA, were investigated. The linear range of the method was 0.1–10.0 mg L^?1. The limits of detection (LODs) were 0.01, 0.03, and 0.05 mg L^?1 at 720, 1,459, and 1,609 cm^?1, respectively. The method was applied to the determination of nitrite in real food and water samples, with recoveries in the range of 86.9–103.4 % and relative standard deviations (RSDs) less than 9.64 %.     

A Micro-Flow-Batch Analyzer Using an In-line Cadmium Sponge Microcolumn for the Photometric Determination of Nitrate and Nitrite in Dairy Samples

In this study, a micro-flow-batch analyzer (μFBA) using an in-line cadmium reduction microcolumn for the photometric determination of nitrate and nitrite in dairy samples is described. The method is based on the Griess-Llosvay reaction and measuring of the absorbance at 540 nm using a green LED integrated into the μFBA built in the urethane-acrylate resin. Initially, the nitrite content of the dairy sample is analyzed in the mixing chamber, while the nitrate is reduced to nitrite in cadmium sponge microcolumn coupled to the microsystem. Nitrate content was calculated from the difference between nitrate plus nitrite (expressed as nitrite) and nitrite content. The analytical curve for nitrate and nitrite was linear in the work range of 10.0–100.0 μg L^?1 with a correlation coefficient of 0.992 and 0.998, respectively. The limit of detection and relative standard deviation were estimated at 0.39 μg L^?1 and <1.7 % (n?=?5) for nitrite and 0.41 μg L^?1 and <1.3 % (n?=?5) for nitrate. Comparing with the reference methods, no statistically significant differences were observed when applying the paired t test at a 95 % confidence level. The accuracy was assessed through recovery test (97.7 to 102.9 %). The proposed microsystem-employed in-line cadmium sponge microcolumn presented satisfactory portability, robustness, flexibility, low-cost device, and reduced chemicals consumption compared to recent methods. Thus, μFBA is potentially useful as an alternative for other automatic determinations using in-line pretreatment steps.     

Application of surface enhanced Raman spectroscopy for analyses of restricted sulfa drugs

The presence of sulfonamide residues in muscle foods is an important concern for consumers and regulatory agencies since these residues may pose potential health risks and result in an increase of drug-resistant bacteria. Surface enhanced Raman spectroscopy (SERS) was applied to analyze three sulfa drugs including sulfamerazine, sulfamethazine and sulfamethoxazole with concentrations ranging from 10 ng mL^?1 to 5 ??g mL^?1. Partial least squares regression (PLS) and principal component analysis (PCA) were used for the spectral data analyses. The three sulfa drugs could be detected at concentration levels as low as 10 ng mL^?1. For the quantitative analyses, the R ² values of actual sulfa drug concentrations versus their concentrations predicted by the PLS models ranged from 0.8149 to 0.9009. Plotting of principal components based upon PCA showed clear, separated clusters between different sulfonamides. This study indicated potential for detection and determination of trace amounts of prohibited or restricted drugs with SERS technology.     

Stimulation of Saccharomyces cerevisiae Cultures by Pulsed Electric Fields

The effects of stimulation of Saccharomyces cerevisiae cells in an aqueous suspension by pulsed electric field (PEF) with electric field strength E?=?20–2,000 V cm^?1 and effective PEF treatment time t _PEF?=?10^?5–1 s were investigated. At relatively high electric field strengths (E?>?1,000 V cm^?1) and moderate times of PEF treatment (t _PEF?>?100 μs), the extraction of ionic components from yeast was observed, which can be related to electroporation of cell membranes. Petri dishes counting revealed dependency of the colony sizes on the time of preliminary fermentation t _f and power consumption W. The “logarithmic” and “saturated” types of electrostimulation were distinguished. At “logarithmic” electrostimulation (10^?7 J mL^?1?W??1 J mL^?1), the viability of yeast cells increased with the increase of power consumption and was higher for longer fermentation (t _f ?=?24 h). However, at “saturated” electrostimulation (10^?1 J mL^?1?W?1 J mL^?1), the viability of yeast cells was noticeably higher for t _f ?=?1 h than for t _f ?=?24 h. The impact of preliminary fermentation time and PEF protocol on biological activity of cells and consumption of nutrients was also discussed.     

Production optimization,purification, and characterization of a novel acid protease from a fusant by Aspergillus oryzae and Aspergillus niger

The production of a novel acid protease was enhanced by 44 % through statistical optimization. The cultural parameters, such as inoculum size, temperature, moisture content, and incubation time, were 8.59 × 10⁵ g^?1 dry koji, 31 °C, 57 %, and 86 h, respectively. This novel acid protease was purified by 17 folds with a recovery yield of 33.56 % and a specific activity of 4,105.49 U mg^?1. Far-UV circular dichroic spectra revealed that this purified protease contained 7.1 % α-helix, 64.1 % β-sheet, and 32 % aperiodic coil. This novel acid protease was active over the temperature range of 35–55 °C with optimum temperature of 40 °C and was stable in the pH range of 2.5–6.5 with optimum pH of 3.5. Mn²⁺ enhanced its activity while Co²⁺ showed inhibitory effect. With casein as substrate, the kinetic parameters of K _m, V _max, energy of activation (E _a), and attenuation index of inactivation velocity by heat inducing (λ) were 0.96 mg mL^?1, 135.14 μmol min^?1 mg^?1, 64.11 kJ mol^?1, and 0.59, respectively.     

Direct FTIR Analysis of Free Fatty Acids in Edible Oils Using Disposable Polyethylene Films

To simplify a previously reported Fourier transform infrared (FTIR) method for the direct determination of free fatty acid (FFA), a new technique was designed to facilitate mid-FTIR transmission analysis of viscous edible oil samples using disposable polyethylene (PE) films as a spectral acquisition accessory. In the PE-film-based procedures, the viscosities of oil samples were reduced by mixing hexane for allowing the samples to readily deposit onto PE films to form oil films when the solvent evaporated (PE film as spectral background), and the path length of each oil film was normalized to a fixed path length of 0.15 mm. The relationship between FFA content (expressed as percentage of oleic acid) and the absorbance of FFA at 1711 cm^?1 relative to a baseline at 1600 cm^?1 (baseline was 1600 cm^?1) in thenormalized spectra was expressed by a linear calibration equation. To remit the interference from the absorbance due to triglyceride esters (approximately 1,746 cm^?1) in the wave numbers used in FFA determination (1,711 cm^?1), the intensity of the first overtone of the ester vibration (3,471 cm^?1/3,527 cm^?1) in FFA-free oil samples was used to determine the intensity of the interfering signal at 1,711 cm^?1. Moreover, a linear relationship between the two absorbances was established. Consequently, the absorbance measured at 1,711 cm^?1/1,600 cm^?1 by FFA determination in the oil samples was corrected for the linear equation. FFA determination in oil samples with known FFA content (0 to 3 %) was carried out in parallel by using the American Oil Chemists’ Society titrimetric method and the PE-film-based FTIR procedures. A comparison indicated that the PE-film-based FTIR method can be used to determine FFA content in different kinds of edible oils.     

Biocomposite Films Based on κ-Carrageenan/Locust Bean Gum Blends and Clays: Physical and Antimicrobial Properties

The aims of this work were to evaluate the physical and antimicrobial properties of biodegradable films composed of mixtures of κ-carrageenan (κ-car) and locust bean gum (LBG) when organically modified clay Cloisite 30B (C30B) was dispersed in the biopolymer matrix. Film-forming solutions were prepared by adding C30B (ranging from 0 to 16 wt.%) into the κ-car/LBG solution (40/60 wt.%) with 0.3 % (w/v) of glycerol. Barrier properties (water vapour permeability, P _vapour; CO₂ and O₂ permeabilities), mechanical properties (tensile strength, TS, and elongation-at-break, EB) and thermal stability of the resulting films were determined and related with the incorporation of C30B. Also, X-ray diffraction (XRD) was done in order to investigate the effect of C30B in film structure. Antimicrobial effects of these films against Listeria monocytogenes, Escherichia coli and Salmonella enterica were also evaluated. The increase of clay concentration causes a decrease of P _vapour (from 5.34?×?10^?11 to 3.19?×?10^?11 g (m s?Pa)^?1) and an increase of the CO₂ permeability (from 2.26?×?10^?14 to 2.91?×?10^?14 g (m s?Pa)^?1) and did not changed significantly the O₂ permeability for films with 0 and 16 wt.% C30B, respectively. Films with 16 wt.% clay exhibited the highest values of TS (33.82 MPa) and EB (29.82 %). XRD patterns of the films indicated that a degree of exfoliation is attained depending on clay concentration. κ-car/LBG–C30B films exhibited an inhibitory effect only against L. monocytogenes. κ-car/LBG–C30B composite films are a promising alternative to synthetic films in order to improve the shelf life and safety of food products.     

Design and Characterization of Corn Starch Edible Films Including Beeswax and Natural Antimicrobials

The effectiveness of edible films (EFs) used as coatings to maintain the quality and safety of fresh produce for long time depends on their functional properties characterization. This study was aimed to design and evaluate physicochemical, barrier, mechanical, and antimicrobial properties of EFs based on corn starch (acetylated cross-linked (ACLS) or oxidized (OS)), micro-emulsified beeswax (BW, 0–1 % w/w), and two natural antimicrobials (lauric arginate (LAE, 400–4000 mg/L) and natamycin (NAT, 80–800 mg/L)). EFs based on ACLS or OS made with 1 % BW microemulsion produced homogeneous EFs surface and did not show changes in thickness or opacity. Water vapor permeability (WVP, 0.57 ± 0.04 g mm m^?2 h^?1 kPa^?1 for ACLS, and 0.56 ± 0.05 g mm m^?2 h^?1 kPa^?1 for OS) was reduced; tensile strength (TS, 51.48 ± 5.92 MPa for ACLS, and 40.96 ± 4.98 MPa for OS), and elastic modulus (EM, 211.30 ± 7.85 MPa for ACLS, and 203.50 ± 5.35 MPa for OS) were decreased, whereas elongation at break (E, 4.59 ± 1.11 % for ACLS, and 4.76 ± 4.98 % for OS) increased. The additive effect showed by the combination of natural antimicrobials (2000 mg/L of LAE plus 400 mg/L of NAT) incorporated into EFs with 1 % BW completely inhibited Rhizopus stolonifer, Colletotrichum gloeosporioides, Botrytis cinerea, and Salmonella Saintpaul. These properties of corn starch EFs used as coatings represent an excellent alternative to extend the shelf life of fresh produce.     

Wood–water relations of chestnut wood used for structural purposes

Hygroscopic properties and water vapour permeability of chestnut (Castanea sativa Mill.) wood were studied using saturated salt solutions, and the results were analyzed using the Hailwood–Horrobin model. At 20 °C/65 % the equilibrium moisture content (MC _eq ) and density were 11.5 ± 0.1 % and 576.6 ± 10.2 kg m^?3, respectively, and the fiber saturation point was 20.83 %. The average water vapour permeability was 0.320 kg m^?1 s^?1 Pa^?110⁸, lower than that of Radiata pine (0.726 kg m^?1 s^?1 Pa^?110⁸). Furthermore, there was no difference in permeability between tangential and radial cuts. This low permeability is explained by the scant development of the multilayer of the Hailwood–Horrobin model. This is attributed to the wood extractives, which reduce the void space and hindered condensation. Chestnut wood has different vapour sorption and vapour permeability than conifers normally used in construction.     

Determination of Tricyclazole Content in Paddy Rice by Surface Enhanced Raman Spectroscopy

Abstract: An ultrasensitive method based on Surface enhanced Raman scattering (SERS) has been developed to determine content of a pesticide which is tricyclazole in paddy rice using sliver colloid as a substrate and pyridine as an internal standard. The peaks at 424 and 1035 cm^?1 in a SERS spectrum were selected as analytic and internal peaks, respectively, and their intensity ratio I_t/I_p was used to calculate the regression concentration of tricyclazole. The correlation between I_t/I_p and concentration showed significant linear relationship with a correlation coefficient of R²= 0.995 in a concentration range of 0.05 to 0.70 mg/L and the tricyclazole solution can be detected to be low as 0.002 mg/L by SERS. The method was applied to determine tricyclazole contents of 3 real rice samples with a standard addition method in order to eliminate interference of matrix. The errors of SERS measurements for the 3 samples were 0.0008 to 0.0246, 0.0013 to 0.0028, and 0.0129 to 0.0304 mg/kg, respectively, compared with the results obtained by high performance liquid chromatography method. This also showed a good reproducibility with low values of relative standard deviation (n= 3) for the 3 samples ranged from 3.63% to 4.64%. Practical Application: SERS is a simple, rapid, and sensitive method to detect pesticides residue in agricultural food. Our results demonstrate that coupled with silver colloid, SERS is able to rapidly determine tricyclazole residue in paddy rice, indicating that SERS can provide rapid, accurate, and reproducible results for tricyclazole determination at trace level in paddy rice.