Fabric phase sorptive extraction as a reliable tool for rapid screening and detection of freshness markers in oranges.

A simple, fast and sensitive analyte extraction method based on fabric phase sorptive extraction (FPSE) followed by gas chromatography-mass spectrometry (GC-MS) and ultra-performance liquid chromatography-quadrupole time of flight mass spectrometry (UPLC-QTOF-MS) analysis was developed for the analysis of 12 volatile compounds that represent most of the principal chemical families possessing different polarities and volatilities. Five FPSE media coated with different sol-gel sorbent chemistries having different polarities and selectivities were studied: long chain poly(dimethylsiloxane) (PDMS), short chain poly(tetrahydrofuran) (PTHF), Carbowax 20M (CW20M), short chain poly(dimethyl siloxane) (SC PDMS) and polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer (PEG-PPG-PEG). CW20M coated FPSE media was found to be the most efficient extraction media for the analytes of interest in the intended study. The developed methodology was applied to the analysis of orange juice obtained from fresh oranges and oranges after storing at 5°C for two months in order to identify the best chemical markers, both volatiles and non-volatiles, attributed to the freshness of orange. For this purpose, aliquots of the same juice extracts were analysed by GC-MS as well as by UPLC-QTOF-MS. Monoterpenes and terpenoids, such as terpinene, citronellal or estragole were among the volatile compounds that endured the biggest decrease after the extended storage period. Three non-volatile compounds including one amide (subaphyllin) and two flavanoids (tangeretin and nobiletin) also showed a clear decrease in signal intensity (>70%) after orange stored for two months.

Antioxidant effect of an innovative active plastic film containing olive leaves extract on fresh pork meat and its evaluation by Raman spectroscopy.

An antioxidant food packaging material was developed and applied to fresh minced pork meat. The material consists of a multilayer polyethylene film in which 4 different concentrations (2%, 5%, 10%, and 15%) of olive leaves (OL) extract were immobilized in an adhesive formula used to build the multilayer. The antioxidants were not in direct contact with the meat. The packaged meat was kept at 4°C during 16days and finally analyzed by two methods: Raman spectroscopy and thiobarbituric acid reactive substances (TBARS). Raman demonstrated a higher sensitivity for antioxidant evaluation than TBARS. Color of fresh meat packaged with the active film was also measured to evaluate the shelf life of packaged meat. The results showed that active film containing natural antioxidants efficiently enhanced the stability of fresh meat against oxidation processes, thus being a promising way to extend the shelf life of fresh minced meat for about two days.

Phenolic content and antioxidant activity of olive by-products and antioxidant film containing olive leaf extract.

The antioxidant activity of olive leaf (OL) and cake (OC) extracts with different solvents was evaluated. 70% of aqueous ethanol extract of OL was chosen as the most antioxidant extract based on antiradical activity (DPPH) (95.4±0.3%) and oxygen radical absorbance capacity (ORAC) (0.82±0.07g equivalent Trolox per g of solution) assays. This OL extract was incorporated in two multilayer materials consisting of (i) polyethylene/polyethylene (PE/PE) film and (ii) polyethylene/paper (PE/P). These multilayers were exposed to a gas stream enriched in free radicals to evaluate the scavenging capacity of both materials. PE/PE film exhibited the highest scavenging activity of free radicals (78.8%). Migration of the phenolic compounds from olive by-products into two simulants was performed and demonstrated a non-migrating behavior. The limits of detection and quantification for oleuropein were 0.5µgkg(-1) and 1.7µgkg(-1) and for Luteolin-7-O-glucoside 1.3µgkg(-1) and 4.3µg kg(-1) respectively.

Performance of an active paper based on cinnamon essential oil in mushrooms quality.

The antioxidant capacity of two active papers (based on solid and emulsion paraffin) with cinnamon essential oil was studied. Mushroom samples were introduced in macroperforated PET trays covered with the active papers, and weight loss and browning monitored for 9 days. The antioxidant capacity of the different papers was evaluated based on scavenging 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and tyrosinase inhibition kinetics, and the release of aromatic volatile oils was determined by HSPME-GC-MS. Differences in performance were observed: the active papers were more efficient at avoiding weight loss and mushroom browning when compared to the non-active paraffin-based papers. The efficiency increased when the bottom and walls of the trays were covered rather than the bottom alone. Better results were observed when cinnamon was incorporated as emulsion paraffin instead of a solid.

Role of catechins in the antioxidant capacity of an active film containing green tea, green coffee, and grapefruit extracts.

The oxygen radical absorbance capacity (ORAC) method was used to characterize the antioxidant capacity of natural extracts of green tea, green coffee, and grapefruit. These natural extracts were incorporated into a plastic film layer, which was subsequently subjected to a free radical gas stream in order to determine the antioxidant capacity directly in the active film. The green tea extract (GTE) afforded the strongest antioxidant activity. To identify the active compounds in the extract, concentration of the diverse catechins in samples were determined by HPLC-UV analysis. The results showed that the content of catechins in the GTE is around 77% (w/w), the major components being (-)-epigallocatechin gallate, (-)-epicatechin gallate, and (-)-epicatechin. A variation in the concentration profile of catechins was detected during the oxidation process. The chromatographic study demonstrated that (-)-gallocatechin, (-)- epigallocatechin, (+)-catechin, and (-)-catechin gallate exhibited the most radical scavenging.

UPLC-Q-TOF-MS analysis of non-volatile migrants from new active packaging materials.

Ultra-performance liquid chromatography (UPLC) coupled to mass spectrometry (MS) is a useful tool in the analysis of non-volatile compounds, and the use of a quadrupole-time-of-flight (Q-TOF) mass analyzer allows a high sensitivity and accuracy when acquiring full fragment mode, providing a high assurance of correct identification of unknown compounds. In this work, UPLC-Q-TOF-MS technology has been applied to the analysis of non-volatile migrants from new active packaging materials. The materials tested were based on polypropylene (PP), ethylene-vinyl alcohol copolymer (EVOH), and poly(ethylene terephthalate) (PET). The active packaging materials studied were one PP film containing a natural antioxidant, and two PP/EVOH films, two PET/EVOH films and one coextruded PP/EVOH/PP film containing natural antimicrobials. The chemical structure of several compounds was unequivocally identified. The analysis revealed the migration of some of the active substances used in the manufacture of active packaging, such as caffeine (0.07 ± 0.01 µg/g), carvacrol (0.31 ± 0.03 µg/g) and citral (0.20 ± 0.01 µg/g). Unintentionally added substances were also found, such as citral reaction compounds, or citral impurities present in the raw materials.

Atmospheric pressure gas chromatography coupled to quadrupole-time of flight mass spectrometry as a powerful tool for identification of non intentionally added substances in acrylic adhesives used in food packaging materials.

Acrylic adhesives are used to manufacture multilayer laminates that are used in food packaging to form the geometric shape of the package as well as to stick labels on the packages. Once applied on the packaging adhesives can supply potential migrants that could endanger the packaged food. Adhesives are complex matrices where intentionally and non intentionally added substances are present, but the identification of the migrants is required by law. In this study atmospheric pressure gas chromatography coupled to a quadrupole hyphenated to a time of flight mass spectrometer (APGC-MS/Q-TOF) has been explored for identification of unknowns coming from three different acrylic adhesives. The results are compared to those obtained by conventional GC-MS-Q (quadrupole). Sixteen compounds were identified by GC-MS/Q and five of them were confirmed by APGC-MS/Q-TOF as their molecular ions were found. Moreover, additional three new compounds were identified and their structure was elucidated working with the spectra obtained by APGC-MS/Q-TOF. This finding was very relevant as these compounds were biocides suspected to be allergenic and cytotoxic in humans. Migration studies were carried out using Tenax as solid food simulant and the results showed that the three acrylic adhesives tested in this work were safe for being used in food packaging materials since the migration of compounds previously identified was below the limit established in the current legislation.

Analytical methods for the screening of potential volatile migrants from acrylic-base adhesives used in food-contact materials.

Two different analytical techniques were studied for screening the volatile compounds present in pure adhesives and those from the adhesives in different laminates. Three different adhesive formulations were used for the study, all acrylic-based and supplied by different producers. Laminates with polypropylene and paper, polypropylene and polyethylene, and aluminium and polyethylene as substrates were prepared and studied. Adhesives themselves were acetonitrile extracted and volatiles identified by time-of-flight mass spectrometry based on accurate mass measurement of molecular and main fragments. The volatiles in the films themselves were determined by a headspace solid-phase microextraction analysis followed by gas chromatography-mass spectrometry. Significant differences were found within the adhesive formulations. Compounds detected in the screening were assessed in terms of migration through the laminate polypropylene and paper into polyethylene used as a matrix-simulating food. The concentration of the compounds in the polyethylene ranged from 0.04 to 1.6 microg dm(-2) in the polypropylene side, and from 0.27 to 28 microg dm(-2) in the paper side. The most toxic compound detected in the screening, 2,4,7,9-tetramethyl-5-decyne-4, was not found in any of the sides. Analytical features were also calculated to provide the conditions for quantitative purposes. Sensitivity was at low ng dm(-2) of polyethylene and the relative standard deviation was below 10%.

Efficiency of whole and skimmed powdered milk for trapping volatile compounds released from plastic containers in high-temperature applications.

Plastic food containers used for high-temperature applications are not completely inert, and potentially harmful chemicals may be transferred to foodstuffs when such containers are heated. The aim of this work was to investigate the role of food fat content on the efficiency of trapping volatile organic compounds from heated plastic packaging. Relatively simple food matrices such as powdered skimmed and whole milk were evaluated with respect to their retention of several selected migrants: toluene, 1-octene, ethylbenzene, o-, m-, and p-xylene, styrene, and 1,4-dichlorobenzene released from containers made of polypropylene (random and copolymer), polycarbonate, and styrene-acrylonitrile copolymer, which are all commonly used in high-temperature applications. The analytical method (purge and trap gas chromatography and mass spectrometry) was optimized for each matrix. The developed procedure had detection limits of 0.01 to 1.2 ng, depending on the analyte and sample matrix, and both reproducibility and repeatability (expressed as relative standard deviation) were below 15%. This method was applied to the different plastic materials. The concentrations of the volatile compounds in both matrices were well below the established specific migration limits. Temperature and fat content of powdered milk were the most influential variables in mass transfer processes. These values were compared with those obtained with either Tenax TA (alternative test medium for fatty food simulants) or Porapak Q (another widely used sorbent). Similar results were found in skimmed powdered milk and Tenax TA, but significant differences were observed for whole powdered milk.

Development of flexible antimicrobial films using essential oils as active agents.

The antimicrobial activity in the vapor-phase of laboratory-made flexible films of polypropylene (PP) and polyethylene/ethylene vinyl alcohol copolymer (PE/EVOH) incorporating essential oil of cinnamon ( Cinnamomum zeylanicum), oregano ( Origanum vulgare), clove ( Syzygium aromaticum), or cinnamon fortified with cinnamaldehyde was evaluated against a wide range of microorganisms: the Gram-negative bacteria Escherichia coli, Yersinia enterocolitica, Pseudomonas aeruginosa, and Salmonella choleraesuis; the Gram-positive bacteria Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, and Enterococcus faecalis; the molds Penicillium islandicum, Penicillium roqueforti, Penicillium nalgiovense, Eurotium repens, and A spergillus flavus and the yeasts Candida albicans, Debaryomyces hansenii, and Zigosaccharomyces rouxii. Films with a nominal concentration of 4% (w/w) of fortified cinnamon or oregano essential oil completely inhibited the growth of the fungi; higher concentrations were required to inhibit the Gram-positive bacteria (8 and 10%, respectively), and higher concentrations still were necessary to inhibit the Gram-negative bacteria. PP films were more effective than PE/EVOH films. The atmospheres generated by the antimicrobial films inside Petri dishes were quantitatively analyzed using headspace-single drop microextraction (HS-SDME) in combination with gas chromatography-mass spectrometry (GC-MS). The analyses showed that the oregano-fortified PP films released higher levels of carvacrol and thymol, and the cinnamon-fortified PP films released higher levels of cinnamaldehyde, during the first 3-6 h of incubation, than the corresponding PE/EVOH films. Shelf-life tests were also performed, demonstrating that the antifungal activities of the films persisted for more than two months after their manufacture. In addition, migration tests (overall and specific) were performed, using both aqueous and fatty simulants, to ensure that the films meet EU regulations regarding food contact materials. Following contact with the tested films, the substances that had migrated into the aqueous simulants were recovered by direct immersion-single drop extraction (DI-SDME) and then analyzed by GC-MS. The fatty stimulant (isooctane) was directly injected into the chromatographic system.

Design of a method for generation of gas-phase hydroxyl radicals, and use of HPLC with fluorescence detection to assess the antioxidant capacity of natural essential oils.

The use of natural antioxidants is of increasing importance in the human diet, because they are recognised as compounds essential to health which minimize or delay the aging process. Despite apparent simplicity, however, it is very difficult to measure and quantify such properties, for which a robust analytical method is required. Because oxidation usually is caused by the presence of OH* radicals, a new method involving the in-situ, vapour-phase generation of these radicals and their quantification in the presence and absence of potential antioxidant extracts has been developed. The oxidant atmosphere generated from hydrogen peroxide is carried by an air stream through an empty quartz chamber in which UV radiation promotes the formation of radicals by a photochemical reaction. The products then pass through a cartridge containing the essential oil, finally bubbling into an impinger containing an aqueous solution of salicylic acid, at pH 4.5, which reacts with the OH* radicals forming 2,5-dihydroxybenzoic acid. This solution is quantified by RP-HPLC using UV and fluorescence detectors connected in series. Detection and quantification limits for OH* radicals were approximately 0.01 pg g(-1) air. Description and optimization of the method are discussed, as also is the antioxidant performance of an extract of ginger (Zingiber officinale R.), which reduced the oxidation process by up to 92%.

Potential migration release of volatile compounds from plastic containers destined for food use in microwave ovens.

Several commercially available plastic containers of polycarbonate, polypropylene-copolymer, polypropylene-20% talcum, polypropylene random and styrene-acrylonitrile designed for heating food in microwave ovens were studied. The analytical procedure based on a purge & trap (P&T) GC-MS was optimized. It consisted of heating the materials at 100 degrees C in a P&T system coupled in line with GC-MS equipment. The compounds released from the materials were then identified through their mass spectra. Variables such as the time of purge using helium as the carrier gas in the system, sample temperature, the type of solid trap, the desorption temperature and the time as well as chromatographic separation of all the compounds released from the plastic were optimized. Compounds such as methylbenzene, ethylbenzene, 1-octene, xylene, styrene and 1,4-dichlorobenzene were found in all the containers. Quantitative analysis and potential migrations are reported and discussed.

Use of solid-phase microextraction for the analysis of bisphenol A and bisphenol A diglycidyl ether in food simulants.

A new method has been developed to simultaneously analyse bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) in aqueous based food simulants. The method consists on direct immersion solid-phase microextraction (SPME) of the analytes from the liquid matrix and subsequent chromatographic analysis by gas chromatography-mass spectrometry. Using the proposed method, a whole analysis (including chromatographic step) can be completed in less than 40 min, with minimum sample handling. The SPME method shows good analytical performance for simultaneous BPA and BADGE analysis, except for BADGE determination in the aqueous alcohol (simulant C) solution. Detection limits ranging from 0.1 to 2.0 ng/g for BPA and from 13 to 15 ng/g from BADGE were obtained, with a linear range from the low-ng/g to several-microg/g range for BPA and from 0.1 microg/g to 40 microg/g for BADGE. A possible optimisation method has been also developed and introduced.

A systematic approach to optimize solid-phase microextraction. Determination of pesticides in ethanol/water mixtures used as food simulants.

The optimization of solid-phase microextraction (SPME) of several organochlorine and organophosphorus pesticides is presented, and the influence of variables is discussed. The optimized method is applied to several selected ethanol/water mixtures used as food simulants, and the influence of the ethanol content on the SPME performance is also discussed. Detection limits ranging from 0.02 to 0.04 ng/g for water simulant and from 38.7 to 205.5 ng/g for 95% ethanol simulant were obtained. The relative standard deviation (% RSD) was <20% in all cases. The optimized method is compared with classical liquid-liquid extraction (LLE).

Speciation of ionic alkyllead compounds in human urine by gas chromatography-mass spectrometry after butylation through a Grignard reaction.

One analytical procedure for the determination of ionic alkyllead in human urine has been studied. The system consists of the extraction of Me3Pb+, Et3Pb+ and Pb2+ at pH 9.0 with diethyldithiocarbamate to an organic phase. Then, the ionic compounds are butylated with BuMgCl and the final organic solution is analyzed by GC-MS-SIM. The elimination of both foam and gels in the extraction step and the general procedure for the urine are discussed. The recovery of compounds ranges from 105.1% for Me3Pb+ to 97.2% for Et3Pb+ using hexane as extracting agent and detection limits are 18.4 pg/ml of Me3Pb+ and 19.2 pg/ml of Et3Pb+ in urine. The speciation of ionic alkylleads in the urine of a petrol station worker showed a value of 27.9 pg/ml of Me3Pb+ in urine and Et3Pb+ was below the detection limit.

Parts-per-trillion determination of styrene in yoghurt by purge-and-trap gas chromatography with mass spectrometry detection.

Headspace sampling methods prior to capillary gas chromatography have been widely used for the determination of volatile compounds present in very different kinds of samples. This paper describes an automated and rapid system to determine volatiles from yoghurt. Thirty-five volatile organic compounds (VOCs) were identified in polystyrene cups used for yoghurt packaging and 42 VOCs from yoghurt samples. Quantitation of styrene in several samples from the Spanish retail market was carried out.

Plasticizers from printing inks in a selection of food packagings and their migration to food.

A survey of plasticizers in printing inks present in a selection of food packaging including confectionery, snacks, crisps, potatoes, chocolate bars and biscuits, has been carried out both in England and Spain. The identification of the polymer used as packaging showed that almost all of them were oriented polypropylene. Printing inks that are always used on the outer surface contain phthalates as major plasticizers, N-ethyl- and N-methyl-toluenesulphonamides and tris(2-ethylhexyl)trimellitate were found in some of the samples studied. Several food samples were also analysed to check the level of plasticizers migrating from printing inks.