Efficiency of Whole and Skimmed Powdered Milk for Trapping Volatile Compounds Released from Plastic Containers in High-Temperatu

1889

Journal of Food Protection, Vol. 71, No. 9, 2008, Pages 1889–1897 Copyright ᮊ, International Association for Food Protection

Efﬁciency of Whole and Skimmed Powdered Milk for Trapping Volatile Compounds Released from Plastic Containers in High-Temperature Applications

P. LO´ PEZ,* R. BATLLE, J. SALAFRANCA, AND C. NERI´N

Department of Analytical Chemistry, Arago´n Institute of Engineering Research, i3A, CPS-University of Zaragoza, Marı´a de Luna St. 3, E-50018 Zaragoza, Spain Downloaded from http://meridian.allenpress.com/jfp/article-pdf/71/9/1889/1681477/0362-028x-71_9_1889.pdf by guest on 27 September 2021 MS 07-449: Received 28 August 2007/Accepted 6 April 2008

ABSTRACT

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.

Packaging is a crucial element in the food chain. The of rectified olive oil, the established fatty food simulant, is use of plastic materials in high-temperature applications is not feasible for technical reasons under the test conditions continuously increasing in modern society. Typical exam- described by Directive 97/48/EC (17). ples of such applications are baking, reheating precooked Tenax has been widely used in migration studies of food, and generating high local temperatures with micro- various substances of such as inorganic compounds (33), waves (via susceptors). The polymeric matrices used for phthalates (5), Michler’s ketone (40), alkylbenzenes (6), heating are not completely inert, and some chemicals may and volatile organic compounds (VOCs) from polyethylene migrate to the packed food via direct contact or the vapor terephthalate (21) and other plastic containers used in oven phase, thus compromising both the toxicological safety and and microwave applications (28). However, Tenax is an ex- sensory quality of the food (11, 37, 42). pensive polymer, which can be recycled only after exhaus- Migration is both a health issue and a legal problem in tive cleaning with organic solvents, and it has a consider- many countries. In a first attempt to harmonize legislation able electrostatic charge, which makes it difficult to handle. and ensure consumer safety (41), the European Union (EU) Because of these drawbacks, other solid adsorbents such as and the U.S. Food and Drug Administration (FDA) initiated Porapak or some real foodstuffs are being applied in vol- global control by providing lists of allowable raw substanc- atile-sampling applications (1, 27, 35). es for packaging manufacturing and restricting substances In high-temperature applications, VOCs are a group of with toxic potential. When a new plastic material intended substances with high migration potential, and some VOCs for food contact applications is created, migration tests can be harmful even at trace levels. Therefore, very sen- must be performed to ensure the quality and safety of the sitive analytical techniques are needed, and the preferred packaged food (14–18, 47). EU Commission Directive 82/ techniques are those that involve trapping VOCs on a solid 711/EEC and its amendments (14, 16, 17) lay down the adsorbent, desorption, and on-line gas chromatographic basic rules necessary for testing migration. This directive analysis (25, 31, 39). The techniques most commonly used also introduces polyphenylene oxide (MPPO, a porous polymer based on 2,6-diphenylene), commercially known are (i) static headspace, where only a fraction of the vapor as Tenax TA, as an alternative test medium when the use in equilibrium with the sample is introduced into the gas chromatograph, thus failing to provide high sensitivity (19, * Author for correspondence. Tel: (ϩ34) 976 761000, Ext 5296; Fax: 29, 37); (ii) thermal desorption, where traps are directly (ϩ34) 976762388; E-mail: [email protected]. heated and analytes are introduced into the injection port 1890 LO´ PEZ ET AL. J. Food Prot., Vol. 71, No. 9

of the chromatograph, thus maximizing sensitivity but in- with an automatic sample heater was used. Glassware tubes spe- creasing the risk of thermal degradation of the analyte (20, cially adapted for solid samples (150 mm in length and 25-mm 27); and (iii) dynamic headspace techniques or ‘‘purge and inside diameter) and stainless steel needles with four holes in the trap’’ (P&T), where the total mass of VOCs is purged by lower part also were used. Glassware was cleaned with water, Њ an inert gas at moderate temperature and transferred to a methanol, and n-hexane and stored at 220 C until its use to prevent contamination. Blank runs were performed daily to check solid trap from which, in a second step, analytes are ther- that the glassware, autosampler, and trap system were free of con- mally desorbed, thus maximizing sensitivity and preserving tamination. matrix characteristics (10, 22, 32). Chromatographic analysis was performed on an HP 5890 Se- The amount and nature of the released VOCs depend ries II gas chromatograph (Hewlett-Packard, Palo Alto, Calif.) on the type of plastic container. Polypropylene random with an HP 5971A mass selective detector. An HP-624 (94% di- (PPRa), polypropylene copolymer (PPCo), polycarbonate methylsiloxane and 6% cyanopropylphenylsiloxane) capillary col- (PC), and styrene-acrylonitrile copolymer (SAN) are typical umn 25 m in length, 0.32-mm inside diameter, and 1.5-␮m ﬁlm

examples of plastics used in oven and microwave applica- thickness was used. The oven program was as follows: initial tem- Downloaded from http://meridian.allenpress.com/jfp/article-pdf/71/9/1889/1681477/0362-028x-71_9_1889.pdf by guest on 27 September 2021 tions. The most relevant VOCs released when heating these perature to 40ЊC and hold for 6 min, raise temperature by 3ЊC/ Њ plastic containers were identified in a preliminary work min to 80 C and hold for additional 5 min, and a second ramp at Њ Њ (28). The fat content is a major factor in the accumulation 10 C/min up to 220 C and hold for 1 min. Injector and detector temperatures were 250 and 280ЊC, respectively. of organic contaminants (24, 26) and therefore plays a rel- VOCs were detected in selective ion monitoring mode, and evant role in the sorption of migrants. the selected mass-to-charge ratios for each compound were m/z The aim of this work was to investigate the efficiency 91 and 65 for toluene, m/z 70 and 55 for 1-octene, m/z 106 and of the fat in selected solid sorbents for trapping the volatile 91 for ethylbenzene and xylenes, m/z 104 and 78 for styrene, and compounds released from four types of plastic packaging m/z 146 and 111 for 1,4-dichlorobenzene. materials during heating. In the first step, a full optimization Spiking procedure. Spiked samples were used to optimize procedure for P&T determination of some relevant VOCs the response of P&T and to obtain the calibration curves. For the was developed and analytically validated. The proposed spiking procedure, 10 mg of an n-hexane solution containing a methods were applied to assess the retention capacity of known concentration of each analyte was added to a glass tube powdered skimmed and whole milk at different tempera- containing silanized glass wool (Supelco) and the corresponding tures and for various exposure times. These results were mass of solid sorbent (powdered whole or skimmed milk, Tenax, compared with those obtained when migration tests were or Porapak). The glass tube was kept in a clean room for at least carried out at 121ЊC for 30 min with the alternative test 30 min to allow the complete evaporation of the n-hexane from medium for fatty food simulant (Tenax) and with Porapak the sorbent matrix and to avoid contamination before the tube was Q, another widely used sorbent in such applications. placed in the autosampler. Total evaporation of the solvent was checked on a daily basis by blank analyses. MATERIALS AND METHODS Migration tests. A 6-cm2 piece of each plastic container was Plastic samples, solid dry food, and adsorbents. Several placed in a 10-cm-diameter glass petri dish and covered with 0.4 commercially available plastic containers recommended for high- g of powdered milk, 0.24 g of Tenax, or 0.6 g Porapak, ensuring temperature use were supplied by Curver (Zaragoza, Spain). The that the piece of plastic container was completely covered by the containers were made of PPRa, PPCo, PC, or SAN. sample. The sample dishes were placed in a Star 3400 chromato- Powdered whole milk (23% fat content) and powdered graphic oven (Varian, Palo Alto, Calif.) at the testing temperature skimmed milk (0.3% fat content) (Central Lechera Asturiana, Vil- for the required time. Immediately after the test, the plastic was laviciosa, Spain) were bought in a local market and used without removed and the solid was transferred into the P&T glass tube, any treatment. Tenax TA 60-80 mesh (Supelco, Bellefonte, Pa.) which was already filled with silanized glass wool. This tube was and Porapak Q 80-100 mesh (Supelco) also were used. Both sor- placed in the autosampler and analyzed under the optimized con- bents were previously cleaned with methanol in a Soxhlet appa- ditions. ratus for 8 h and then with n-hexane for another 8 h and air dried ␮Ϯ ͙ in a clean room (30). Blank analyses were performed with the Statistical analysis. Results were calculated as t·s/ n, ␮ four solids to guarantee the absence of ambient contamination. where is the mean of three replicates, s is the standard deviation, and t is the Student’s t test value for n degrees of freedom. Com- Standards. The set of analytes was selected according to parison among adsorbents was made by means of principal com- previous work (27, 28); some analytes had specific restrictions, ponents analysis (PCA). Data were standardized by autoscaling expressed as specific migration limits (SMLs) (18). Toluene (qual- before the statistical analyses (subtraction of the mean and divi- ity 99.5%, CAS no. 108-88-3), 1-octene (98%, 111-66-0, SML 15 sion by the variance). Statistical analyses were performed with the mg/kg), and ethylbenzene (99.5%, 100-42-5) were purchased from Unscrambler software package, version 9.1 (CAMO Software AS, Aldrich (Madrid, Spain). Styrene (99%, 100-42-5, SML 60 mg/ Trondheim, Norway). kg), o-xylene (99%, 95-47-6), m-xylene (99%, 108-38-3), p-xylene (99%, 106-42-3), and dichlorobenzene (99%, 106-46-7, SML RESULTS AND DISCUSSION 12 mg/kg) were supplied by Fluka-Riedel de Haën (Madrid, P&T optimization. The P&T system depends on a Spain). Stock solutions (approximately 1,000 ␮g/g) were prepared large number of variables (9, 25, 50, 51) related to both Њ in n-hexane and stored at 4 C. Working solutions were made by analyte properties and matrix composition. A combination appropriate dilution of stock solutions in n-hexane. of a screening design to identify the statistically relevant Apparatus. A Dorhmann 3100 sample concentrator (Tekmar, factors with a response surface design to optimize the pa- Cincinnati, Ohio) fitted with a Tekmar ALS 2016 autosampler rameters was applied (7, 38). Two optimization criteria J. Food Prot., Vol. 71, No. 9 ROLE OF FAT CONTENT IN TRAPPING VOLATILE COMPOUNDS 1891

TABLE 1. Experimental range and optimal values found within The optimum values are shown in Table 1. Experi- the experimental domain ments at sampling temperatures higher than 95ЊC were not Powdered milk carried out because of the practical limitation of the P&T Experimental instrument. Variablea domain Skimmed Whole Analytical parameters. The methods were evaluated Prepurge time (tpp, min) 0.5–2 0.5 2 for both types of powdered milk in terms of the limit of Preheating time (tph, min) 1–7 1 1 detection (LOD), limit of quantification (LOQ), linearity, Purge time (tpg, min) 5–20 14.5 5 repeatability, and reproducibility (Tables 2 and 3). Repeat- Desorption time (t , min) 2–6 2 2 ds ability, as the relative standard deviation (RSD) for four Sampling temp (Ts, ЊC) 60–95 60 95 Њ consecutive replicates, and reproducibility, as the RSD from Trap temp (Ttr, C) 10–30 30 30 Њ Ϫ 11 replicates over 15 days, were evaluated by analyzing Cryo temp (Tcr, C) 20 to 10 10 10 spiked skimmed milk (25 ␮g/kg for each analyte) and a Downloaded from http://meridian.allenpress.com/jfp/article-pdf/71/9/1889/1681477/0362-028x-71_9_1889.pdf by guest on 27 September 2021 tpp, time during which the glass tube is purged with helium to whole milk (62.5 ␮g/kg). Recoveries (n ϭ 3) ranging from remove oxygen and prevent oxidation at high temperatures; tph, 84 to 111% were obtained for all the compounds except time needed for sample to reach the sampling temperature; tpg, for toluene in whole powdered milk (128%). Repeatability time during which helium passes through the heated sample and reproducibility were 3.1 to 12.5% and 4.9 to 14.7% in leading the analytes to the trap; t , time during which the an- ds powdered skimmed milk, respectively, and 4.7 to 9.6% and alytes are desorbed from the trap; Ts, temperature of the sample during the purge process; T , temperature of the trap during the 6.2 to 13.8% in powdered whole milk, respectively. tr The method is linear over at least two orders of mag- purge process; Tcr, temperature of the cryo set during the trap desorption process. nitude for all the analytes. Two calibration fittings were necessary for ethylbenzene and styrene because of the high were used: detection of all the analytes and maximal signal, response signals obtained when the migration tests for these which was calculated as the sum of the chromatographic chemicals were carried out with SAN and powdered whole areas of all the analytes. Table 1 shows the selected factors, milk. The mathematical verification of linearity was per- their descriptions, and their experimental domains. The op- formed with a one-way analysis of variance (ANOVA) (Ta- timization experiments comprised the analysis of 0.4 g of ble 3). powdered milk previously spiked to attain a final concen- LODs and LOQs, expressed as absolute amount in- tration of 0.5 mg/kg in food (below the lowest SML for the jected (nanograms), were calculated according to Interna- selected analytes, i.e., 12 mg/kg). tional Union of Pure and Applied Chemistry recommen- ␴ A Plackett-Burman (8, 36) experimental design includ- dations (12) as LOD (LOQ) ϭ 3(10)␴B/Si, where B is the ing the seven experimental variables at two levels was per- standard deviation of the blank analysis and Si is the sen- formed for each type of powdered milk. The dissimilarity sitivity of each analyte. Excluding styrene and 1,4-dichlo- in matrix composition yielded to differences in their trap- robenzene, the LODs of the analytes were slightly lower in ping and sorption behavior, as indicated by the difference skimmed milk (0.01 to 1.0 ng) than in whole milk (0.01 to in significant factors. For skimmed milk, prepurge and 1.2 ng) (Table 3), which demonstrates that fat content is a purge time were the only relevant factors, whereas prepurge major factor in accumulation of organic contaminants. Both time and sample temperature were the factors to be consid- styrene and 1,4-dichlorobenzene, whose boiling points are ered when optimizing the analysis of whole milk. Further slightly higher than those of the other analytes, had differ- optimization of the significant variables was carried out us- ent behavior than the overall trend for P&T optimization ing a response surface modeling (RSM) experimental de- for skimmed milk; sampling temperature (Ts) was the rel- sign, which consisted of a two-variable, three-level full fac- evant parameter. However, the feasibility of the proposed torial model. Correlation coefficients (R2) and predictive method was validated as good enough to achieve the goals coefficients (Q2) were greater than 0.8, which indicates that of this study, and further optimization was not attempted. the model has high predictive power. The potential of the optimized analytical method was

TABLE 2. Quality parameters: repeatability, reproducibility, and recovery Repeatability (RSD, %) Reproducibility (RSD, %) Recovery (mean Ϯ SD, %) (n ϭ 4) (n ϭ 11) (n ϭ 3)

Analyte Skimmed milk Whole milk Skimmed milk Whole milk Skimmed milk Whole milk

Toluene 9.4 8.0 9.9 6.1 108 Ϯ 7 128 Ϯ 5 1-Octene 6.2 4.7 5.2 7.4 109 Ϯ 793Ϯ 4 Ethylbenzene 8.0 9.6 7.3 6.5 74 Ϯ 590Ϯ 6 m-, p-Xylene 6.5 8.7 7.4 14 91 Ϯ 787Ϯ 7 o-Xylene 11 4.9 14 7.3 86 Ϯ 784Ϯ 5 Styrene 12 7.8 10 6.2 84 Ϯ 11 111 Ϯ 3 1,4-Dichlorobenzene 3.4 5.7 4.9 8.1 105 Ϯ 384Ϯ 5 Avg 8.1 7.1 8.6 7.9 94 Ϯ 794Ϯ 5 1892 LO´ PEZ ET AL. J. Food Prot., Vol. 71, No. 9

TABLE 3. Analytical performance

a 2 b Compound LOD (ng) Linear range (ng) Fexp/Ftab R n

Skimmed powdered milk Toluene 1.0 3.3–34 1,443/6.61 0.996 7 1-Octene 0.01 0.03–23 847/6.61 0.993 7 Ethylbenzene 0.07 0.24–25 2,471/7.71 0.998 6 m-, p-Xylene 0.07 0.23–124 2,212/7.71 0.992 6 o-Xylene 0.09 0.31–62 540/5.99 0.990 8 Styrene 0.05 0.17–35 899/10.1 0.996 5 1,4-Dichlorobenzene 0.81 2.7–50 2,232/5.99 0.997 8 Whole powdered milk Toluene 1.2 4.2–33 3,552/10.1 0.999 5 1-Octene 0.02 0.06–51 876/7.71 0.994 6 Downloaded from http://meridian.allenpress.com/jfp/article-pdf/71/9/1889/1681477/0362-028x-71_9_1889.pdf by guest on 27 September 2021 Ethylbenzene 0.21 0.7–6.5 481/10.1 0.992 5 0.20 0.68–260 3,334/5.59 0.998 9 m-, p-Xylene 0.44 1.2–126 1,432/6.61 0.996 7 o-Xylene 0.52 0.96–65 5,877/6.61 0.999 7 Styrene 0.02 0.06–36 503/10.1 0.992 5 0.01 0.03–2,516 1,323/5.99 0.995 8 1,4-Dichlorobenzene 0.43 1.4–53 945/7.71 0.995 6 a Ftab(1,n-2) from critical values of F for a one-tailed ANOVA. b Number of runs. evaluated by determining the correlation of the reported there, migrants partition between air and the different phas- LODs with the established SMLs. In the worst case, toluene es of powdered milk. Diffusion and partition of the volatile in powdered whole milk, the LOD was 1.2 ng, correspond- migrants in the fat encapsulated in the hydrocolloid parti- ing to 3 ng per g of sorbent, i.e., 1,000 times lower than cles of powdered milk add complexity to the process. The the established SML. Therefore, the proposed method may experimental system is not hermetically closed, and zero be considered a useful tool for migration assessment. concentration in the atmosphere is assumed, which means that steady-state conditions are never reached and desorp- Migration tests: efficiency of powdered milk to trap tion of volatiles from the solid sorbent is likely to occur. volatile compounds. Migration tests were carried out in The reduction of migration levels at longer exposure times triplicate experiments at three temperatures (75, 100, and Њ (Tables 4 and 5) supports this hypothesis. 121 C) for three different exposure times (30, 60, and 120 As a general rule, migration was influenced more by min or 60, 120, and 240 min) with each type of plastic temperature than by time, especially when powdered whole container commonly used in high-temperature applications milk was used as the solid sorbent. As the temperature in- and with the two types of powdered milk as potential solid creased, more volatile compounds were released from the test media. Time and temperature values were selected ac- test materials, possibly because of the increased suscepti- cording to Directive 97/48/EC (17). Tests were performed bility of being trapped on the sorbent. Fat content seemed in open systems (petri dishes) to simulate real packaging to play an important role in the migration process. Dry conditions; thus, the equilibrium conditions between the va- powdered milk has no free fat or oil phase on the surface, por phase, the powdered milk, and the plastic were never but as the temperature increases, these components are like- reached. ly to melt and form a thin layer on the surface of the plastic Preliminary tests revealed that powdered milk degrad- material, which means that more mass would be transferred ed at 150 and 175ЊC, as a consequence of processes such to powdered whole milk. The molten fat observed during as the Maillard reaction and lipid peroxidation that occurred tests conducted at 121ЊC can even penetrate into the plastic among its main constituents (carbohydrates, proteins, and matrix structure and conceivably extract contaminants, fa- lipids). This fact imposes certain restrictions in the use of cilitating their mass transfer to the structure and therefore powdered milk as alternative test material in high-temper- increasing migration, as it has been described with limo- ature migration applications. nene and films of low-density polyethylene, PC, and poly- Tables 4 and 5 show the results of migration tests (ex- ethylene terephthlate (48) and with water and ethylene vinyl pressed as micrograms of compound per kilogram of plas- alcohol copolymer films (4). Additional experiments to de- tic). All the migration values were low and well below the termine the sorption of fatty compounds from plastic con- SML values established in the Directive 2002/72/EC (18). tainers should be carried out to validate the use of powdered Results could be explained based on all the mass pro- milk as an alternative test medium for migration assays. cesses involved in the overall migration. Analytes (mi- Traces of 1,4-dichlorobenzene, the least volatile com- grants) diffuse from the core to the package surface, where pound, were not detected. Test conditions were possibly not they are desorbed to the surrounding atmosphere. From stringent enough to release it from the containers. J. Food Prot., Vol. 71, No. 9 ROLE OF FAT CONTENT IN TRAPPING VOLATILE COMPOUNDS 1893 0.05 0.01 0.01 0.02 0.02 0.01 0.004 0.02 0.004 0.003 0.005 0.072 0.003 0.02 0.01 0.02 0.04 0.02 0.002 0.01 0.001 Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 0.04 0.29 0.02 0.10 0.01 0.26 0.002 0.09 0.03 0.15 0.02 0.06 0.01 0.04 0.01 0.04 0.001 0.04 0.30 0.46 0.03 0.10 0.10 0.17 0.01 0.17 0.04 0.10 0.02 0.17 0.004 0.04 0.04 0.06 0.003 0.04 C Њ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 75 degrees of freedom. Downloaded from http://meridian.allenpress.com/jfp/article-pdf/71/9/1889/1681477/0362-028x-71_9_1889.pdf by guest on 27 September 2021 0.08 ND ND 0.02 ND 0.26 0.03 0.27 0.01 0.09 0.03 0.27 0.02 0.09 0.01 ND ND 0.08 0.09 0.04 0.07 0.005 0.03 0.01 0.05 0.01 0.04 0.04 0.70 0.02 0.28 0.02 0.23 0.01 0.10 0.01 0.10 0.10 0.09 0.02 0.04 0.01 0.09 0.01 0.04 n Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 30 min 60 min 120 min test value for t 0.02 0.25 0.01 0.09 0.06 0.28 0.01 0.10 0.03 0.07 0.003 0.03 0.003 0.04 0.02 0.36 0.02 0.27 0.02 0.13 0.01 0.09 0.02 0.08 0.002 0.06 0.004 0.06 0.004 0.05 0.004 0.04 Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ is the Student’s t 0.0 ND 0.11 0.09 0.27 0.01 0.09 0.01 0.41 0.004 0.09 0.04 0.05 0.005 0.03 0.002 0.03 0.05 0.26 0.04 0.26 0.02 0.14 0.004 0.09 0.02 0.07 0.03 ND 0.17 0.002 0.04 0.01 0.04 0.01 0.03 0.001 0.03 C Њ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ g/kg of food) at: 100 ␮ a Migration ( 0.03 0.25 0.01 0.09 0.01 0.27 0.01 0.09 0.01 0.08 0.01 0.03 0.01 0.04 0.09 0.38 0.03 0.28 0.09 0.13 0.01 0.10 0.10 ND ND 0.16 0.01 0.07 0.04 0.15 0.01 0.04 0.03 ND ND 0.38 0.02 0.04 0.02 0.05 0.01 0.04 Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 30 min 60 min 120 min is the standard deviation, and s 0.01 0.29 0.01 0.09 0.01 0.27 0.01 0.09 0.01 0.04 0.01 0.05 0.01 0.05 0.06 0.46 0.03 0.26 0.01 0.17 0.01 0.09 0.17 0.36 0.01 0.08 0.01 0.04 0.01 0.05 0.01 0.08 0.01 0.04 Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 0.01 0.28 0.01 0.10 0.20 0.27 0.08 0.09 0.01 0.06 0.01 0.05 0.05 0.04 0.05 0.41 0.02 0.27 0.03 0.14 0.01 0.10 0.60 0.60 0.01 0.09 0.05 0.06 0.01 0.07 0.02 0.07 0.01 0.04 C Њ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ ND ND 0.20 is the mean of three replicates, 121 ␮ where n, 0.01 0.28 0.02 0.10 0.01 0.37 0.002 0.18 0.02 0.06 0.01 0.04 0.01 0.09 0.11 0.38 0.02 0.27 0.03 0.13 0.01 0.09 0.75 5.3 0.01 0.05 0.01 0.13 0.02 0.08 0.02 0.04 0.01 0.04 c ͙ / s Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ · t 30 min 60 min 120 min ␮Ϯ b Migration of volatile compounds released from plastic packaging to powdered skimmed milk Xylene 0.27 -Xylene 0.26 -Xylene 0.28 -Xylene 0.43 Compound p p p p- -, -, -, -, -Xylene 0.09 -Xylene 0.09 -Xylene 0.15 -Xylene 0.10 o Styrene1,4-DichlorobenzeneToluene1-Octene ND ND ND 0.06 ND ND ND ND ND ND ND ND ND ND ND ND 0.10 ND ND ND ND 0.11 ND ND o Styrene1,4-Dichlorobenzene ND ND ND ND ND ND ND ND ND ND ND ND 0.15 ND ND ND 1-Octene 0.06 Ethylbenzene 0.04 m Ethylbenzene 0.04 m o o Styrene 4.0 Styrene1,4-DichlorobenzeneToluene1-Octene ND ND ND 0.08 ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND 0.54 1-Octene 0.05 Ethylbenzene 0.07 Ethylbenzene 0.04 m m 1,4-DichlorobenzeneToluene ND ND ND ND ND ND ND ND 0.21 ND ND ND ND Toluene ND Results were calculated as PPCo, polypropylene copolymer; PPRa, polypropylene random; SAN, styrene-acrylonitrile copolymer; PC, polycarbonate. ND, not detected. PPRa SAN PC TABLE 4. PPCo a b c 1894 LO´ PEZ ET AL. J. Food Prot., Vol. 71, No. 9 0.03 0.01 0.00 0.00 0.01 0.02 0.02 0.00 0.43 0.03 0.02 0.01 0.00 0.04 0.03 0.01 Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 0.02 0.07 0.00 0.13 0.00 0.11 0.00 0.11 0.02 0.06 0.00 0.04 0.01 0.07 0.02 0.12 0.20 2.2 0.01 0.13 0.02 0.08 0.00 0.12 0.02 0.03 0.04 0.18 0.00 0.08 0.01 0.03 C Њ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 75 degrees of freedom. Downloaded from http://meridian.allenpress.com/jfp/article-pdf/71/9/1889/1681477/0362-028x-71_9_1889.pdf by guest on 27 September 2021 0.02 0.16 0.00 0.12 0.0 0.12 0.01 0.11 0.00 0.08 0.00 0.03 0.00 0.07 0.00 0.15 1.1 2.8 0.01 0.13 0.04 0.09 0.00 0.11 0.00 0.04 0.21 0.20 0.00 0.05 0.00 0.03 n Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 30 min 60 min 120 min test value for t 0.01 0.13 0.07 0.13 0.01 0.03 0.00 0.11 0.01 0.11 0.07 0.06 0.03 0.04 0.01 0.06 0.01 0.12 1.4 9.6 0.01 0.12 0.07 0.11 0.01 0.12 0.03 0.48 0.03 0.07 0.01 0.03 Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ is the Student’s t 0.26 0.11 0.01 0.21 0.00 0.03 0.01 0.11 0.01 0.12 0.00 0.14 0.05 ND ND ND ND 0.01 0.06 0.00 0.13 0.01 0.13 2.6 5.7 0.02 0.22 0.06 0.14 0.00 0.11 0.20 0.14 0.01 0.08 0.01 0.11 C Њ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ g/kg of food) at: 100 ␮ a Migration ( 0.12 0.35 0.37 0.31 0.01 0.15 0.001 0.03 0.00 0.11 0.00 0.11 0.01 0.07 0.004 0.04 0.00 0.06 0.01 0.13 0.71 7.3 0.03 0.14 0.03 0.13 0.01 0.11 0.01 0.07 0.00 0.03 Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ 30 min 60 min 120 min is the standard deviation, and s 0.01 0.72 0.04 2.5 0.02 0.12 0.04 ND ND ND ND ND ND 0.01 0.03 0.02 0.12 0.01 0.10 0.05 0.06 0.06 ND 0.13 0.01 0.03 0.01 0.05 0.05 0.13 3.0 10 0.01 0.12 0.00 0.12 0.00 0.11 0.01 0.06 0.00 0.02 Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ ND ND ND ND ND ND ND 0.08 0.15 2.5 0.42 0.08 0.19 0.04 0.26 0.01 0.11 0.04 0.13 0.02 0.16 0.01 0.12 0.02 0.19 0.03 0.06 0.01 0.09 0.08 0.23 26 28 0.04 0.18 0.01 0.07 0.01 0.12 0.02 0.08 0.02 0.06 c C Њ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ is the mean of three replicates, 121 ␮ where n, 0.04 0.22 4.2 9.3 0.04 0.20 0.03 0.27 0.00 0.26 0.23 0.12 0.06 0.36 0.01 0.05 0.14 0.08 0.00 0.28 21 151 0.38 0.16 0.01 0.08 0.01 0.12 0.01 0.08 0.11 0.04 0.19 ND ͙ / s Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ Ϯ · t 30 min 60 min 120 min ␮Ϯ b Migration of volatile compounds released from plastic packaging to powdered whole milk -Xylene 0.19 -Xylene 0.16 -Xylene 0.26 -Xylene 0.60 Compound p p p p -, -, -, -, -Xylene 0.08 -Xylene 0.13 -Xylene 0.38 -Xylene 0.08 m o 1,4-DichlorobenzeneToluene1-Octene NDEthylbenzene ND 11 ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND 1,4-DichlorobenzeneToluene ND ND ND ND 0.57 ND ND ND ND ND ND 1-OcteneEthylbenzene 0.11 ND ND ND ND ND ND ND ND ND Styrene 0.11 m Styrene 0.35 o 1,4-DichlorobenzeneToluene ND ND ND ND 0.29 ND ND ND Below LOD ND ND 1-OcteneEthylbenzene 0.04 ND ND ND ND ND ND ND ND ND o Styrene 214 1,4-Dichlorobenzene ND ND ND ND ND ND ND ND ND m o Styrene 0.12 m 1-OcteneEthylbenzene 0.31 ND ND ND ND ND ND ND ND ND Toluene 0.65 Results were calculated as PPCo, polypropylene copolymer; PPRa, polypropylene random; SAN, styrene-acrylonitrile copolymer; PC, polycarbonate. ND, not detected. SAN PPRa PC TABLE 5. PPCo a b c J. Food Prot., Vol. 71, No. 9 ROLE OF FAT CONTENT IN TRAPPING VOLATILE COMPOUNDS 1895 Downloaded from http://meridian.allenpress.com/jfp/article-pdf/71/9/1889/1681477/0362-028x-71_9_1889.pdf by guest on 27 September 2021

FIGURE 1. Principal components analysis of the migration of toluene (1), 1-octene (2), ethylbenzene (3), m- and p-xylene (4), o-xylene (5), styrene (6), and 1,4-dichlorobenzene (7) at 121ЊC for 30 min from polypropylene copolymer (PPCo), polypropylene random (PPRa), styrene-acrylonitrile copolymer (SAN), and polycarbonate (PC) to solid dry sorbents: Tenax (Tx), Porapak (Pk), powdered whole milk (Wm), and powdered skimmed milk (Sm).

Although 1-octene is the least polar analyte the partitioning of migrants. Therefore, a migration test to ϭ (log Koctanol-water 4.57), it was not detected in powdered assess a food packaging material should be carried out with whole milk but was detected in powdered skimmed milk. the final product. In that sense, theoretical approaches such Because 1-octene is a very reactive ␣-olefin that is widely as the quantitative structure-property relationship method used in polymerization reactions (3, 34, 49), at the tested could be of interest (45). temperatures it might be involved in oligomerization reactions with other constituents of the fatty matrix, such as Migration tests: comparison among different solid organic short-chain esters (13). adsorbents. The results obtained when using powdered The concentrations of ethylbenzene and the three iso- milk were compared by PCA with those obtained with the mers of xylene were higher in powdered whole milk than other two adsorbents, Tenax and Porapak. Tenax is one of in powdered skimmed milk. This finding indicates that the the alternative test media proposed in EU legislation (17), fat content of the food matrix is of paramount importance. and Porapak has been widely used as an adsorbent in vol- Because styrene is one of the main components of the atile-sampling applications (1, 27, 35). Tests were carried Њ SAN, its migration was expected, especially for powdered out at 121 C for 30 min. Operational conditions for P&T whole milk. However, its migration values never exceeded were adjusted according to some previous studies, which the SML (Table 5). The daily styrene exposure is estimated were conducted by other members of the research group as 18.2 to 55.2 ␮g per person per day, which corresponds (28). to an annual exposure of 6.7 to 20.2 mg per person (2). An PCA has been widely applied in data treatment to in- individual would have to eat at least 3 kg of powdered vestigate the underlying structure and to extract a maximum whole milk that had been previously heated in contact with amount of information from large data matrices. In PCA, SAN to reach a total daily intake of 18 ␮g of styrene, which new orthogonal variables (latent variables or principal com- is quite unlikely to occur. The migration value at 121ЊC ponents) are obtained by combining the original variables was much higher than that at 100ЊC. Although the maxi- with the criterion of maximizing the variance of the data. mum temperature at which the SAN container should be Two principal components were needed to explain 83% of used is 130ЊC (according to the manufacturer’s specifica- the variance (principal component 1, 50% of the variance; tions), the degradation of polymer chains and the release of principal component 2, 33% of the variance). Principal styrene might occur to some extent at 121ЊC. Ethylbenzene, component 1 was directly correlated with the content of whose presence is also linked to the composition of SAN xylenes in the sorbent, whereas principal component 2 dis- (43), followed trends similar to those for styrene. criminated experiments with a higher concentration of sty- Food matrices and fat content play a critical role in the rene and ethylbenzene. Both powdered milks and Porapak migration process by retaining compounds with similar had similar behavior for the migration of toluene, 1-octene, physicochemical properties. Because migration into food and the three isomers of xylene (Fig. 1). Nevertheless, the occurs through the environment, factors other than fat con- retention of styrene and ethylbenzene released from SAN tent (e.g., food structure) could have a significant effect. containers in powdered whole milk was the highest. The Food morphology, thickness, and crystallinity also affect positive correlation between the fat content of the matrix 1896 LO´ PEZ ET AL. J. Food Prot., Vol. 71, No. 9 and the concentration of styrene and ethylbenzene due to 6. Aurela, B., T. Ohra-aho, and L. Soderhjelm. 2001. Migration of al- their lipid solubility had been previously reported (20, 23, kylbenzenes from packaging into food and Tenax (R). Pack. Technol. Sci. 14:71–77. 44). However, the detected values of toluene, 1-octene, and 7. Batlle, R., H. Carlsson, P. Tollba¨ck, A. Colmsjo¨, and C. Crescenzi. the three xylene isomers in Tenax were higher than those 2003. Enhanced detection of nitroaromatic explosive vapors com- in food (here, powdered milk), which was in agreement bining solid-phase extraction–air sampling, supercritical fluid extrac- with results of other studies (5, 6). tion, and large-volume injection–GC. Anal. Chem. 75:3137–3144. Tenax has been confirmed to be a suitable food simu- 8. Beres, D. L., and D. M. Hawkins. 2001. Plackett-Burman techniques lant for dry foods with low and intermediate fat content for sensitivity analysis of many-parametered models. Ecol. Model. 141:171–183. (30), such as powdered skimmed milk or semolina (46). 9. Bianchi, F., M. Careri, E. Marengo, and M. Musci. 2003. Use of Nevertheless, dry food with a higher fat content, such as experimental design for the purge-and-trap–gas chromatography– powdered whole milk, retains higher amounts of certain mass spectrometry determination of methyl tert-butyl ether, tert-bu- migrants with high lipid solubility. tyl alcohol and BTEX in groundwater at trace level. J. Chromatogr. A 975:113–121. In summary, a practical optimization scheme for the Downloaded from http://meridian.allenpress.com/jfp/article-pdf/71/9/1889/1681477/0362-028x-71_9_1889.pdf by guest on 27 September 2021 10. Castle, L., S. M. Jickells, J. Gilbert, and N. Harrison. 1990. Migra- extraction of volatile compounds from different matrices tion testing of plastics and microwave-active materials for high-tem- using a P&T technique was developed. Relevant variables perature food-use applications. Food Addit. Contam. 7:779–796. were identified. Optimum values were related to both the 11. Castle, L., S. M. Jickells, M. Sharman, J. W. Gramshaw, and J. analyte and food matrix characteristics. P&T gas chroma- Gilbert. 1988. Migration of the plasticizer acetyltributyl citrate from tography with mass spectrometry in selective ion monitor- plastic film into foods during microwave cooking and other domestic use. J. Food Prot. 51:916–919. ing mode was an extremely sensitive technique for specific 12. Currie, L. A. 1999. Nomenclature in evaluation of analytical meth- migration testing of volatile compounds. ods including detection and quantification capabilities (IUPAC rec- All the food containers studied (PC, PPRa, PPCo, and ommendations 1995). Anal. Chim. Acta 391:105–126. SAN) gave very low migration values that were well below 13. de Klerk, A. 2006. Reactivity differences of octenes over solid phos- the established SML. The transfer rate, or migration speed phoric acid. Ind. Eng. Chem. Res. 45:578–584. of each analyte to each adsorbent, depends on mass transfer 14. European Commission. 1982. Council Directive 82/711/EEC of 18 October 1982 laying down the basic rules necessary for testing mi- processes and temperature, whereas total amount is also a gration of the constituents of plastic materials and articles intended function of analyte solubility in the matrix. The role of fat to come into contact with foodstuffs. European Commission of the content is of paramount importance in the trapping effi- European Union, Brussels. ciency of the volatile compounds. 15. European Commission. 1985. Council Directive 85/572/EEC of 19 Tenax, the alternative fatty test medium proposed by December 1985 laying down the list of simulants to be used for testing migration of constituents of plastic materials and articles in- the EU, provides an underestimation of some lipophilic an- tended to come into contact with foodstuffs. European Commission alytes. For those applications where the operating temper- of the European Union, Brussels. ature is below 121ЊC, powdered whole milk could be a 16. European Commission. 1993. Commission Directive 93/8/EEC of 15 useful tool from an analytical point of view and for eco- March 1993 amending Council Directive 82/711/EEC laying down nomical and handling reasons. the basic rules necessary for testing migration of constituents of plastic materials and articles intended to come into contact with food- ACKNOWLEDGMENTS stuffs. European Commission of the European Union, Brussels. 17. European Commission. 1997. Commission Directive 97/48/EC of 29 This work was financed by Spanish project AGL 2001-1808 of the July 1997 amending for the second time Council Directive 82/711/ Spanish Ministry of Science and Technology and by project P060-2001 EEC laying down the basic rules necessary for testing migration of of the Government of Aragon (DGA). R. 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