Incidence and level of patulin contamination in pure and mixed apple juices marketed in Italy

A survey on the occurrence of patulin was conducted during 2005 on commercial pure apple juices (53 samples) and mixed apple juices (82 samples) marketed in Italy. The current study was undertaken to investigate the possible influence of the agro-food production process employed (conventional or organic), of the fruit percentage in the commercial product (higher or lower than 50%) and of the type of apple juice (clear or cloudy) on the occurrence and level of patulin contamination. Patulin could be quantified in 34.8% of the samples ranging from 1.58 to 55.41 μg kg⁻¹. With the exception of one sample, the level of patulin was lower than 50 μg kg⁻¹, the maximum permitted threshold in fruit juices according to the European legislation. Mean levels of patulin were significantly lower in mixed apple juices (4.54 μg kg⁻¹) than in pure apple juices (9.32 μg kg⁻¹). Levels of patulin contamination were comparable in clear and cloudy juices. A similar incidence of positive samples was found in conventional and organic apple based juices, and the magnitude between the mean contamination levels, although higher in organic (10.92 μg kg⁻¹) than in conventional juices (4.77 μg kg⁻¹), was not statistically significant (p = 0.771; Mann–Whitney test). The magnitude between the means of patulin contamination in juices containing more than 50% fruit (11.26 μg kg⁻¹) and in juices with 50% or less fruit (3.35 μg kg⁻¹) was statistically significant (p = 0.016; Mann–Whitney test).     

Determination of cadmium in tableware leach solution by spectrophotometry using 2,6-dimethylphenyldiazoaminobenzene

A sensitive and selective spectrophotometric method has been developed for determination of trace cadmium in tableware leach solution, the method based on the reaction of cadmium(II) with new reagent 2,6-dimethylphenyldiazoaminobenzene (DMPDAAB). In 0.2 mol l⁻¹ ammonia medium, DMPDAAB reacts with cadmium(II) to form 1:3 red complex with a maximum absorption peak at 523 nm. The apparent molar absorption coefficient of the complex and Sandell’s sensitivity were 2.27 × 10⁵ l mol⁻¹ cm⁻¹ and 0.495 ng cm⁻², respectively. The detection limit for cadmium and relative standard deviation were found to be 0.18 ng/g and 1.06%, respectively. Under optimal conditions, the reaction can complete instantly and absorbance of the complex remain stable for 12 h at least. Absorbance of the complex at 523 nm obey Beer’s law in the cadmium(II) range of 0–0.48 μg/ml. Moreover, we also studied the effect of foreign ions on the determination of cadmium in detail, the results showed the method has excellent selectivity, it has been applied to determine cadmium in tableware leach solution satisfactorily.     

Determination of 3-chloro-1,2-propanediol in soy sauces by capillary electrophoresis with electrochemical detection

A capillary electrophoresis technique with electrochemical detection (CE-ED) for determination of 3-chloro-1,2-propanediol (3-MCPD) in soy sauces was described. Effects of several factors, such as the pH value and the concentration of the running buffer, separation voltage, injection time and the potential applied to the working electrode, were investigated to find the optimum conditions. With a 50 cm length of 25 μm diameter fused-silica capillary, well-defined separation of 3-chloro-1,2-propanediol from propanediol and glycerol was achieved in 30 mmol/L borate (pH 9.24) within 13 min. Operated in a wall-jet configuration, a 0.45 mm copper-disk electrode used as the working electrode exhibits good response at 0.65 V (vs. SCE) for the analyte in 0.05 mol/L sodium hydroxide solution. The linear range for 3-MCPD was from 2 × 10⁻⁴ g/mL to 6.6 × 10⁻⁶ g/mL. Notably, the detection limit (S/N = 3) of 1.3 × 10⁻⁷ g/mL for 3-chloro-1,2-propanediol coincides with the criterion of food safety. This method was successfully used in the rapid analysis of 3-MCPD in soy samples. The average recoveries of 93.8–106.8% indicated that the experimental results were satisfactory.     

Aflatoxins in rice – A limited survey of products marketed in Austria

Eighty-one rice samples were purchased from different markets in Vienna and were analysed for their aflatoxin content. The samples were extracted using methanol in water (80/20 v/v) followed by immunoaffinity clean up. The determination was carried out by HPLC–FLD coupled to a Kobracell. Different samples including basmati rice, whole grain rice, long grain rice, short grain rice as well as puffed rice were investigated. Moreover, conventionally and organically produced rice were compared. The results revealed that 24 out of 81 samples contained detectable amounts of aflatoxins. Aflatoxin B₁ could be quantified in 15 samples and aflatoxin B₂ in one sample. The contamination range was noted to be between 0.45 μg kg⁻¹ and 9.86 μg kg⁻¹ for aflatoxin B₁ and 1.5 μg kg⁻¹ for aflatoxin B₂. Aflatoxins G₁ and G₂ were not detected in any sample. Three samples exceeded the maximum levels set in the European Union; having AFB₁ concentrations of 2.16, 2.85 and 9.86 μg kg⁻¹. In the three organic produced rice samples only traces of aflatoxins were found.     

A HPLC with fluorescence detection method for the determination of tetracyclines residues and evaluation of their stability in honey

A high-performance liquid chromatography with fluorescence detection method for the simultaneous determination of oxytetracycline (OTC), tetracycline (TC) and chlortetracycline (CTC) residues in honey was developed and validated. Sample preparation was done in a single solid phase extraction step. The chromatographic separation was performed on a C₈ column. Matrix matched calibration curves showed linearity higher than 0.99. The accuracy values lay between 86% and 111% and the precision was lower than 11%. Limits of detection and quantitation were 8 μg kg⁻¹ and 25 μg kg⁻¹, respectively. The method was employed to evaluate the stability of the tetracyclines in honey during 60 days of storage. The residue levels of OTC, TC and CTC were reduced 97%, 76% and 71%, respectively. Honey samples (n = 22) collected from the retail market were analyzed. No tetracyclines residues were detected.     

Validation of the procedure for the determination of aflatoxin B1 in animal liver using immunoaffinity columns and liquid chromatography with postcolumn derivatisation and fluorescence detection

The validation of the procedure for the determination of aflatoxin B₁ in animal liver (pig, chicken, turkey, beef, calf) was performed. The limit of detection (LOD) and limit of quantification (LOQ) were 2 ng/kg and 7.8 ng/kg, respectively. The repeatability of measurements, represented by the standard deviation (RSD_r) was 7.5%, 7.1%, and 4.8% at the contamination levels of 0.025 μg/kg, 0.050 μg/kg, and 0.075 μg/kg, respectively. The relative standard deviation for the within-laboratory reproducibility (RSD_R) was 18% at the level of 0.025 μg/kg and 22% at the levels of 0.050 μg/kg and 0.075 μg/kg. The measurement uncertainties at the same contamination levels were ±0.007 μg/kg, ±0.016 μg/kg, and ±0.023 μg/kg, respectively. The mean recovery was 72.8%, the decision limit (CCα) 0.063 μg/kg and the detection capability (CCβ) 0.080 μg/kg. The results indicate that the procedure is suitable for the determination of aflatoxin B₁ in animal liver and can be implemented for the routine analysis.     

Effect of combined physico-chemical treatments based on enterocin AS-48 on the control of Listeria monocytogenes and Staphylococcus aureus in a model cooked ham

Enterocin AS-48 was tested alone or in combination with chemical preservatives and/or heat against Listeria monocytogenes and Staphylococcus aureus in a cooked ham model system. AS-48 (20, 40 and 60 μg g⁻¹) alone was active against L. monocytogenes at 5 and 15 °C, but it was not sufficient to avoid regrowth of Listeria during the 60 days storage. Combination of AS-48 (40 μg g⁻¹) with nitrite/nitrate, pentasodium tripolyphosphate, sodium benzoate or potassium sorbate improved the anti-listeria effect during storage at 5 °C. The most effective combination was AS-48-nitrite/nitrate (0.007%) that reduced listeria below detection level from the beginning to end of storage. Although much more resistant, S. aureus was also inhibited by AS-48 alone at 5 °C, and especially in combinations with nitrite/nitrate, pentasodium tripolyphosphate, sodium lactate and sodium acetate. Best results against both pathogens were obtained when sodium pyrophosphate was applied in combination with 60 μg g⁻¹ AS-48. Sub-lethal heat (60 °C, 2 min) clearly increased AS-48 activity against both Listeria and Staphylococcus.     

Detection of Roundup Ready soybean by loop-mediated isothermal amplification combined with a lateral-flow dipstick

LAMP–LFD, loop-mediated isothermal amplification (LAMP) combined with a lateral-flow dipstick (LFD), was developed and evaluated as a new method for the detection of Roundup Ready soybean (RRS). Biotinylated LAMP amplicons were produced by two sets of six designed primers that specifically recognized the endogenous gene (Lec1) and the event-specific 5′ -junction region (G35S) of RRS followed by hybridization with FITC-labeled probes and LFD detection. The following optimized conditions for the LAMP assay were used: deoxynucleotide triphosphate (dNTP) concentrations ranging from 0.6 to 3.2 mM, 6 mM Mg²⁺, 4 U Bst DNA polymerase and a 1:6 ratio of outer to inner primers. The LAMP–LFD results were generated within 50 min. The detection limit of LAMP–LFD was 2.4 copies of the linearized plasmid pTLH10 and was 20 times more sensitive than conventional PCR. We demonstrated the high specificity of LAMP–LFD by testing processed soybean products, genetically modified (GM) maize and Bt-cotton meal. The novel LAMP–LFD setup presented here is simple, rapid, and has the potential for future use in the detection of GM ingredients in feed and food products.     

A sensitive and validated method for determination of melamine residue in liquid milk by reversed phase high-performance liquid chromatography with solid-phase extraction

A sensitive and validated method for the determination of melamine residue in liquid milk is developed using reversed phase high-performance liquid chromatography-diode array detection (RP-HPLC-DAD) with solid-phase extraction (SPE). The conditions of the extraction, SPE and HPLC were investigated and optimized. The linearity is satisfactory in the range of 0.1–50 μg/mL with a correlation coefficient of 0.9998. Under the optimal conditions, the method limit of detection (LOD) and method limit of quantification (LOQ) were 18 μg/kg and 60 μg/kg, respectively. The recovery of melamine for milk samples spiked with 0.10–3 mg/kg was in the range of 85.5–99.3% with the RSDs (n = 3) of 2.3–3.7%. The intra-day assay precision (RSD) was 5.6% for five replicates of quality control milk sample at 2 mg/kg level. Confirmation of the identities of melamine was achieved by monitoring the two transitions in multiple-reaction monitoring (MRM) mode, and has been applied successfully for the determination of melamine residue in liquid milk samples. The confirmatory method can permit the detection of melamine residues at levels as low as 60 μg/kg in different liquid milks.     

Exposure assessment of mycotoxins in dairy milk

The objective of this study was to develop a quantitative Monte Carlo exposure assessment model for mycotoxins in dairy milk and to assess the potential human exposure levels. Mean concentrations of mycotoxins in milk were estimated using the simulation model (Aflatoxin M1 = 0.0161 μg/kg, Ochratoxin A = 0.0002 μg/kg, Deoxynivalenol = 1 μg/kg, Fumonisin B1 = 0.36 μg/kg, Zearalenone = 0.39 μg/kg, T-2 = 0.0722 μg/kg) while the simulated tolerable daily intakes (TDIs) from milk for males and females all fell below European Union guidelines. Aflatoxin M1 was the toxin of greatest concern as it had potential to exceed the EU limit of 0.05 μg/kg in milk. The sensitivity analysis identified the concentration of toxins in maize as the area which needs most attention in relation to crop management and agricultural practice. The sensitivity analysis assessed also identified the carry over rate as a factor closely related to risk and as a factor which required further research.     

Trace element levels of mushroom species from East Black Sea region of Turkey

The levels of trace metals of mushroom samples collected from East Black Sea region of Turkey were determined by flame and graphite furnace atomic absorption spectrometry after microwave digestion method. The accuracy of the method was corrected by standard reference material (NIST SRM 1573a Tomato Leaves). The contents of investigated trace metals in mushroom samples were found to be in the range of 18.9–64.8 μg/g for copper, 53.5–130 μg/g for manganese, 44.7–198 μg/g for zinc, 187–985 μg/g for iron, 0.54–10.8 μg/g for selenium and 0.9–2.5 μg/g for cadmium. Mushrooms species in the highest levels of trace elements were found Entoloma sinuatum for Cu and Zn, Leucoagaricus leucothites for Mn, Amanita pantherina for Fe and Se, Agaricus arvensis for Cd.     

Occurrence of aflatoxin M1 in pasteurised,UHT milk and milk powder from goat origin

In the present study, 36 samples of pasteurised, ultra-high-temperature (UHT) treated and goat milk powder traded in the city of Campinas, Brazil, were analysed for aflatoxin M₁ (AFM₁), from October to December 2004 and March to May 2005. Results showed 25 (69.4%) positive samples for AFM₁ at levels of 0.011–0.161 μg L⁻¹ of milk, which were below the tolerance limit of 0.500 μg L⁻¹ as adopted for AFM₁ in milk by Brazilian regulations. Mean levels of AFM₁ in pasteurised, UHT and goat milk powder were 0.072 ± 0.048, 0.058 ± 0.044 and 0.056 ± 0.031 μg L⁻¹, respectively. It is concluded that the incidence of AFM₁ in goat milk traded in Campinas is high, but at levels that probably leads to a non-significant human exposure to AFM₁ by consumption of goat milks.     

Optimization of the liquid–liquid extraction method and low temperature purification (LLE–LTP) for pesticide residue analysis in honey samples by gas chromatography

This work optimized a simple and practical method for identification and quantification of the pesticides chlorpyrifos, λ-cyhalothrin, cypermethrin and deltamethrin in honey samples. The method was based on liquid–liquid extraction and low temperature purification using acetonitrile: ethyl acetate (6.5 mL:1.5 mL) as the solvent for extraction. A final clean up step with 2 g florisil was performed before analysis by gas chromatography using electron-capture-detector. The technique was proven satisfactory with efficiency exceeding 85% and linear chromatographic response for the tested pesticides, ranging from 0.033 to 1.7 μg g⁻¹ with correlation coefficients above 0.99. Detection and quantification limits were lower than 0.016 and 0.032 μg g⁻¹, respectively. The proposed method was applied to 11 honey samples. Chlorpyrifos and λ-cyhalothrin residues were found in two samples at concentrations below maximum residue limit (MRL) established for food products. The presence of these compounds was confirmed by mass spectrometry in SIM mode (GC–MS-SIM).     

Effects of Zataria multiflora Boiss. essential oil and nisin on Bacillus cereus ATCC 11778

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO, 0.0%, 0.005%, 0.015%, 0.03% and 0.045%) and nisin (N, 0.0, 0.25, 0.5, 1.5 and 2.5 μg ml⁻¹), pH values (7.4, 6.5 and 6.0), temperatures (Ts, 10, 20 and 30 °C) and storage times (Ds, up to 43 days) on log₁₀ probability percentage of growth initiation (log P%) of one vegetative cell of Bacillus cereus in brain heart infusion broth were evaluated in a factorial design study. The log P% of the organism was significantly affected (P < 0.01) by the values of EO, N, pH, T and D.The combinations of T ⩾ 20 °C, EO ⩽ 0.03% and pH values (7.4, 6.5 and 6.0) could not obviously affect the growth of the organism in this study. Whereas, the strong inhibitory action was observed by increasing EO concentration to 0.045 at T ⩾ 20 °C and selected pH values (7.4, 6.5 and 6.0) and by decreasing temperature to 10 °C at EO ⩾ 0.015% and pH values used in this study. The inhibitory effect of N also was enhanced by decreasing storage temperature to 10 °C at the selected pH values (7.4, 6.5 and 6.0) in this study.The growth of the organisms was strongly affected by increasing EO concentration to 0.03% in combination with N concentrations used at the selected temperatures in this study. The growth of the organism was completely inhibited at combinations EO ⩾ 0.015%, N ⩾ 1.5 μg ml⁻¹, T ⩽ 30 °C and pH ⩽ 7.4 during 43 days of storage in this study. This synergistic effect of EO and N was enhanced in lower pH values (6.5 and 6.0) in the present study. The growth of organism was completely inhibited at combinations of EO ⩾ 0.005 and N ⩾ 1.5 μg ml⁻¹ at pH = 6.0, and EO ⩾ 0.03 and N ⩾ 0.5 μg ml⁻¹ at pH ⩽ 6.5 during the study at the selected Ts (30, 20 and 10 °C).     

Antimicrobial properties of selected essential oils in vapour phase against foodborne bacteria

The aim of this study was to identify antimicrobial properties of essential oils in vapour phase. In vitro antibacterial activity against five foodborne bacteria (Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enteritidis, Staphylococcus aureus) was evaluated by disc volatilization method. The results were expressed as minimum inhibitory concentrations (MIC) in μl/cm³ of air. Thirteen of the 27 essential oils were active at least against one bacterial strain in the range of tested concentrations (0.0083–0.53 μl/cm³). The best results were shown by Armoracia rusticana (MIC 0.0083 μl/cm³) against all of the strains, followed by Allium sativum > Origanum vulgare > Thymus vulgaris > Satureja montana, Thymus pulegioides > Thymus serpyllum > Origanum majorana > Caryopteris x clandonensis, Hyssopus officinalis, Mentha villosa, Nepeta x faassenii, Ocimum basilicum var. grant verte. In conclusion, certain essential oils are highly effective in vapour phase and could be used in control of foodborne bacterial pathogens.     

Pentocin 31-1, a novel meat-borne bacteriocin and its application as biopreservative in chill-stored tray-packaged pork meat

Pentocin 31-1 was produced by Lactobacillus pentosus 31-1, isolated from the traditional China fermented Xuan-Wei Ham. In this work, study on its application as biopreservative in chill-stored nonvacuum-tray-packaged pork meat was carried out. Pentocin 31-1 was prepared by pH-adsorption in 5 l stainless steel fermentor. Each 200 ml semi-purified bacteriocin was obtained from one fermentation, and the specific activity was 1280 AU/ml. The effects of pentocin 31-1 on microbiological counts, physicochemical change and sensory quality of chilled pork in the period of preservation at 4 °C was investigated. Results showed that pentocin 31-1 could substantially inhibit the accumulation of VBN and generally suppress the growth of microflora, especially Listeria and Pseudomonas, during chilled pork storage. Microbiological counts, physicochemical parameters and sensory characteristics of the treatments (40 AU/ml pentocin 31-1 or 75 AU/ml nisin) had exceeded the limitation of Chinese hygienic standard for fresh meat of livestock by day 15. 80 AU/ml pentocin could extend the shelf life to 15 days and the meat showed good sensory characteristics. These results suggest the potential of pentocin 31-1 as a biopreservative in tray-packaged chilled pork storage.     

Dissipation of propisochlor and residue analysis in rice,soil and water under field conditions

The analytical method for the residues of a new herbicide propisochlor and its dissipation and residual amounts in soil, water and rice plants in field conditions (rice cropping system) were studied. The chloroacetanilide herbicide, propisochlor (72% w/w EC) was applied at two dosages, 108 g a.i. ha⁻¹ (recommended) and 162 g a.i. ha⁻¹ (1.5 times of the recommended dosage) seven days after transplanting rice seedlings in the experimental fields in both Beijing and Fujian provinces (experimental localities). Soil, water and rice plant samples were collected at intervals and analyzed for propisochlor residues. The detection limit (LOD) of propisochlor is 0.2 μg kg⁻¹ and the limit of quantification (LOQ) was established as 1 μg kg⁻¹. At three different spiking levels, mean recoveries and relative standard deviation (RSD) from fortified samples in three replicated experiments for each matrix were in the range 81–109% and 1.3–13.1%, respectively. The results showed that the half-lives of propisochlor in water, soil and rice plant from Beijing were 0.56, 5.25 and 1.46 days respectively, and the half-lives of propisochlor in water, soil and rice plant from Fujian were 0.62, 5.12 and 0.81 days. At harvest, soil, straw, rice hull and husked rice samples were found to contain propisochlor well below the limit of detection (LOD) following the recommended dosage and 1.5 times dosage.     

Meat species identification using DNA-redox electrostatic interactions and non-specific adsorption on graphene biochips

This study describes the development of a novel electrochemical biosensor for meat species identification using DNA-redox electrostatic interactions and the nonspecific adsorption of these molecules on graphene biochips. The ruthenium hexamine molecule [Ru(NH₃)₆]³⁺, or RuHex, was observed to form complexes with free DNA in solution that adsorbed onto graphene surfaces, enabling the development of a rapid, high-sensitivity DNA biosensor. Reproducible cathodic current signals were generated from these low-cost graphene biochips, both in the presence and absence of dsDNA and loop-mediated isothermal amplification (LAMP) amplicons. The combination of the DNA-redox molecule complexes and the graphene surface therefore provided a novel detection strategy. This new biosensor was able to identify different meat species based on the isothermal amplification of target genes followed by electrochemical detection with square wave voltammetry. To optimize the specificity and sensitivity of the biosensor, the LAMP parameters were investigated under varying isothermal conditions using varying concentrations of reagents and target DNA, and with different combinations of newly designed loop primers. Using these novel biomarkers along with the new on-chip detection strategy, we observed limits of detection of target DNA of 1 pg/μL and 100 pg/μL for chicken and pork species, respectively.     

HPLC determination for prostaglandins from seaweed Gracilaria gigas

Seaweed (Gracilaria gigas) is an edible red alga and occasionally induces food poisoning cases. Prostaglandin E₂ (PGE₂) has been reported to be possible causative agent. In this study, a simple, sensitive, rapid and accurate HPLC method was developed for quantifying prostaglandins in seaweed. The mobile phase was gradient acetonitrile (35–60%) and 0.017 M phosphoric acid at flow rate of 1 mL/min within 30 min. The standard curves of prostaglandins were extremely linear (R² > 0.999) with low correlation coefficients (less than 4.7) in the range of 5–50 μg/mL. To obtain maximum prostaglandins amount, the optimal ratio of seaweed (wet weight) to arachidonic acid was 10 g:2 mg and oxygen was needed in reaction.     

Microbiological quality of legume-based traditional fermented foods marketed in West Bengal,India

A total of 105 samples of six different types of legume-based popular fermented foods, namely amriti, dhokla, dosa, idli, papad and wadi, purchased from retail outlets in West Bengal, was analysed to determine their microbiological safety status. While dhokla and idli were of high-moisture foods (62 g (100 g)⁻¹), others had a lower moisture level (14–27 g (100 g)⁻¹). Papad was alkaline (pH 8.7), whereas all the other foods were acidic (pH 4.4–5.8). Every sample was found contaminated with total aerobic mesophilic bacteria (detection limit, 10 cfu g⁻¹); 38% (40/105) of the samples contained more than 10⁶ cfu g⁻¹. Aerobic mesophilic bacterial spores were found in 88% (92/105) of the samples (detection limit, 100 cfu g⁻¹), whereas their anaerobic counterparts were present in 39% (41/105) of the samples (detection limit, 10 cfu g⁻¹). Although all the samples, excepting one, were free from Staphylococcus aureus (detection limit, 100 cfu g⁻¹), 20% (21/105) of the samples were found contaminated with Bacillus cereus (detection limit, 100 cfu g⁻¹). Enterobacteriaceae were found in 46% (48/105) of the samples (detection limit, 10 cfu g⁻¹). Of the Enterobacteriaceae isolates, 92% were coliforms and 57% were faecal coliforms. Escherichia coli (detection limit, 10 cfu g⁻¹) was found in only one sample each of wadi and idli, at a load of 10³–10⁴ g⁻¹. Salmonella (detection limit, 1 cell (25 g)⁻¹) occurred in 12 samples of wadi, idli and papad, however was absent in the other three products. Clostridium perfringens (detection limit, 10 cfu g⁻¹) and Shigella (detection limit, 1 cell (25 g)⁻¹) could not be detected. The results obtained in the present study indicated that these foods were manufactured using poor-quality starting materials, processed under unhygienic conditions, or/and temperature-abused during transportation and storage. Based on these results, a guideline is recommended for obtaining safe products.