Foods may be irradiated in their final packaging and this process may affect the composition of the packaging and in turn affect the migration of substances into food. Headspace and liquid injection GC-MS and HPLC with time-of-flight MS have been used to identify and estimate levels of radiolytic products in irradiated finished plastic packaging materials. Fifteen retail packaging materials were studied. Investigations were carried out into the effect of different irradiation types (gamma and electron beam), irradiation doses (1, 3, 7 and 10kGy) and dose rates (5kGys(-1) for electron beam and 0.4 and 1.85kGyh(-1) for gamma) on the radiolytic products. Any differences seen in comparing the two ionising radiation types were attributed largely to the very different dose rates; for electron beam a 10kGy dose was delivered in just 2s whereas using gamma it took 5.4h. Differences were also seen when comparing the same samples irradiated at different doses. Some substances were not affected by irradiation, others decreased in concentration and others were formed upon increasing doses of irradiation. These results confirm that irradiation-induced changes do occur in substances with the potential to migrate and that the safety of the finished packaging material following irradiation should be assessed.

Methods of analysis for 2-dodecylcyclobutanone (2-DCB) using gas chromatography with mass spectrometric detection (GC-MS), liquid chromatography with time-of-flight mass spectrometric detection (LC-TOF-MS) and LC with tandem MS (MS/MS) detection have been developed and optimised for maximum sensitivity to allow very low irradiation doses to be detected. The LC-MS/MS method, following derivatisation with 2,4-dinitrophenylhydrazine, was found to be the most sensitive technique and was used to determine the amount of 2-DCB formed from the model compounds palmitic acid, glyceryl tripalmitate and 1,3-dipalmitoyl-2-oleoylglycerol irradiated over a range of doses by two different irradiation sources (gamma and electron beam). The model compounds were also treated with a number of non-irradiation based processing techniques including heating in the presence and absence of oxygen, light, and redox active metal salts, in a conventional oven, microwave oven and pressure cooker. No 2-DCB was detected in any of the processed non-irradiated model compounds, reaffirming the hypothesis that 2-DCB is a unique radiolytic product that can be used as a marker of irradiation in foodstuffs.

Polyadipate plasticizers can be present in the polyvinylchloride (PVC) gaskets used to seal the lids of glass jars. As the gaskets can come into direct contact with the foodstuffs inside the jar, the potential exists for polyadipate migration into the food. The procedure and performance characteristics of a test method for the analysis of polyadipates in food simulants (3% aqueous acetic acid and 10% aqueous ethanol) and the volatile test media used in substitute fat tests (isooctane and 95% aqueous ethanol) are described. The PVC gaskets were exposed to the food simulants or their substitutes under standard test conditions. Studies were initially carried out using direct measurement of the polyadipate oligomers by liquid chromatography with time-of-flight mass spectrometric detection (LC-TOF-MS) but this was not practical due to the number of peaks detected. Instead, the migrating polyadipates were hydrolysed to adipic acid and measured by liquid chromatography with tandem mass spectrometric detection (LC-MS/MS). The amount of polyadipate that this measurement of adipic acid represents was then calculated. Method performance was assessed by analysis of gaskets from two types of jar lids by single-laboratory validation. Linearity, sensitivity, repeatability, intermediate reproducibility and recovery were determined to be suitable for checking compliance with the 30 mg/kg specific migration limits for polyesters of 1,2-propane diol and/or 1,3- and/or 1,4-butanediol and/or polypropylene-glycol with adipic acid, which may be end-capped with acetic acid or fatty acids C12-C18 or n-octanol and/or n-decanol. The method was found to be much quicker than previous methods involving extraction, clean-up, hydrolysis, esterification, derivatisation and GC measurement, consequently saving time and money.

Information is given concerning the curing characteristics of polyester–polyurethane (PEPU)-based food can coatings and the analysis of the free isocyanate by-products. The behavior of a methyl ethyl ketoxime (MEKO)-blocked isocyanate on heating was studied using thermal analytical techniques. Following this, the curing behavior of a PEPU-based can coating (PEPU01 that contained an aluminum flake pigment) and the MEKO-blocked isocyanate was investigated. A study of the unblocking of the MEKO-blocked isocyanate in the PEPU01 can coatings was undertaken with respect to the migration potential of any residual-free isocyanate compounds that could migrate from the cured PEPU can coatings to the surrounding medium (e.g., foodstuffs).

A methyl ethyl ketone oxime-blocked isocyanate was used as a crosslinking agent in the curing of polyester–polyurethane (PEPU) can coatings. The completeness of cure was assessed from the amount of residual (un-reacted) isophorone diisocyanate (IPDI) trimer that was presented in the coating after curing. This amount of residual trimer depended strongly on the temperature at which the curing was undertaken and time given for curing. The degree of cure was also assessed, correlating with the reduced IPDI trimer migration potential. The amount of residual IPDI trimer that was extractable from a typical PEPU coating rose markedly (15- to 20-fold) if the wet coating was aged up to 6 months before use. The presence of a TiO2 pigment increased the aging effect. An aluminum flake pigment had an even greater effect. The TiO2 pigment increased aging by different degrees according to the type of surface modification that had been applied to the pigment. The grade having the greatest alumina content, as a result of surface modification, gave the greatest aging. The undesirable effects of aging were counteracted by the addition of more catalyst to the aged coating just before the coating was used to coat panels. Deactivation of the acidic polymerization catalyst system (based on organotin compounds) is thought to be the cause of this aging. These findings have allowed improvements to be made to the specifications of the pigments and the catalysts used, with respect to the consistent industrial production of low migration coatings.

A test protocol has been developed that contains a suite of complementary analytical methods to identify and estimate the concentrations of potential chemical migrants in polymeric coatings applied to metal substrates. The capabilities of these techniques (FT-IR, overall migration, headspace GC-MS, GC-MS, and LC-TOF-MS) have been tested for a variety of polymeric coatings, and the results for one particular coating, an epoxy phenolic, are described as an example. The example provided shows both the power and the limitations of current analytical techniques in the evaluation of the total migrate from food contact materials.

Honeys from specified botanical sources often command a premium price due to their organoleptic or pharmacoactive properties. To prevent the fraudulent marketing of honey, analytical techniques are required to confirm its origin.NMR spectroscopy has been used to identify biomarkers of botanical and geographical origin for European honey. One-dimensional H-1 NMR spectra were acquired from 374 authentic European honeys collected during 2 years, with the majority of these (220) taken from the island of Corsica. Biomarkers of sweet chestnut, Corsican spring Maquis and Arbousier (strawberry-tree) honeys were identified. Kynurenic acid was found to be a biomarker of sweet chestnut honey. alpha-Isophorone and 2,5-dihydroxyphenyl-acetic acid were confirmed as markers of strawberry-tree honey. Additional compounds specific to strawberry-tree and Corsican spring Maquis honey were partially characterised. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.

This paper reports the syntheses of individual dendritic branches based on L-lysine and functionalised with either Boc or Bz surface groups. Convergent and divergent synthetic approaches were employed and the preservation of stereochemistry during the syntheses was monitored using polarmetry, NMR and HPLC. In addition, racemic dendritic branches based on D,L-lysine were synthesised for comparative purposes. It was observed that the preservation of stereochemistry in the dendritic peptide was dependent on the method of synthesis, with divergent methodology being preferred. The results are discussed in terms of the known stereochemical outcomes of traditional peptide coupling processes, and are generalised to the synthesis of other dendritic peptides. Such observations about the chirality of dendritic peptides are of relevance to chemists developing dendritic systems for applications where single enantiomer dendrimers would clearly be preferred, such as enantioselective catalysis or pharmaceutical chemistry.

This application illustrates how time-of-flight mass spec- trometry has been used in the studies of interactions at the can coating/food interface of internally coated metal cans intended for use in the food industry. Previously unconfirmed migrants were confidently identified using accurate mass information provided.