- Email: [email protected]
Migration of organic contaminants into dry powdered food in paper packaging materials and the influencing factors
Journal of Food Engineering 262 (2019) 75–82
Contents lists available at ScienceDirect
Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng
Migration of organic contaminants into dry powdered food in paper packaging materials and the influencing factors
T
Meigui Xuea,∗, Xin-Sheng Chaib, Xiaodong Lia, Runquan Chenc a
Dongguan Polytechnic, Dongguan, Guangdong, 523808, China South China University of Technology, Guangzhou, South China University of Technology, Guangzhou, Guangdong, 530004, China c Dongguan Quality Testing, Dongguan, Guangdong, 523808, China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Paper food packaging dry powdered food Migration performance Influencing factors
The factors affecting the migration of organic contaminants from paper packaging materials into packaged dry powdered food were studied. Based on the molecular structure, volatile, molecular weight, and harm posed to the human body, five organic substances were selected as simulated pollutants. According to EU technical standard BS EN13130-1:2004 (E) migration trough types E manufactured migration cell and completion of migration of simulated contaminants from paper to solid powdered foods at different temperature and times were studied. GC-MS technology was used to detect the content of simulated pollutants in paper and food. Partial least-squares (PLS) method was used to analyze the effects of various factors affecting migration performance. Results showed that the migration of simulated pollutants from paper packaging materials into solid powdered foods was affected by temperature, contact time, molecular weight of organic pollutants, and volatile. Among them, volatile and molecular weight contributed the greatest effects, whereas temperature contributed the least effect. Changes in temperature and contact time were positively correlated with migration performance, whereas volatile, molecular weight, molecular polarity of organic pollutants were negatively correlated. In other words, for the individual factors, higher temperature and longer contact time meant higher migration percentage of organic pollutants from paper-based packaging to packaged dry powdered foods, whereas greater volatile and higher molecular weight of organic pollutants led to poorer migration into food.
1. Introduction Paper and cardboard are widely used as packaging materials for dry solid foods because of their abundant sources, renewability, and natural degradation. However, some organic substances can harm humans are introduced during the manufacture of paper packaging materials and the printing process (Nerín and Asensio, 2004; Aurela et al., 1999, 2001; Johns et al., 1995; Nerín et al., 2007). When these materials are used as food packaging, harmful substances may migrate into food through direct or indirect contact. Accordingly, studying the migration behavior of organic contaminants in paper-based packaging materials into dry powdered foods is very important for the prediction of migration performance, the extension of the products shelf life and effective control of the influencing factors. Extensive studies have been conducted on the migration of organic contaminants from paper-based food packaging materials into the foods
they package. The European Union (EU) has specific instructions on the contact conditions (time and temperature) and simulants for the test conditions of paper-based packaging materials intended to come into contact with foodstuffs. Some examples of these standards are 85/572/ EEC and 87/711/EEC, as well as their revised instructions 93/8/EEC and 97/48/EEC (Regulations and Guidan). Nerín et al. studied the kinetics of migration of organic contaminants from paper into food simulants and found that the length of contact with food simulant and the temperature of the environment are the main factors affecting the migration of organic pollutants (Nerín et al., 2007). Aurela et al. analyzed the migration of phthalate esters in paper-based packages into the food simulants Tenax and white sugar. They found that the mass-to-surface ratio of food simulants and packaging materials, the surface area of the packaging material, the amount of internal standard added during measurement, and the migration device are important factors affecting migration (Aurela et al., 1999). Other studies have shown that the contact time, temperature, and characteristics of organic pollutants
This project was funded by the 2016 Guangdong Province General Colleges and Universities Characteristic Innovative Project (Project Number: 2016KTSCX176). ∗ Corresponding author. E-mail addresses: [email protected], [email protected] (M. Xue). https://doi.org/10.1016/j.jfoodeng.2019.05.018 Received 16 April 2018; Received in revised form 5 December 2018; Accepted 13 May 2019 Available online 17 May 2019 0260-8774/ © 2019 Elsevier Ltd. All rights reserved.
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
2.2. Reagents
(e.g., molecular weight, chemical structure, and volatile) significantly influence migration. The boiling point of organic pollutants and the type and performance of the paper used are also influencing factors (Triantafyllou et al., 2002, 2005, 2006). Recent studies have shown that the volume of migration of organic substances in paper-based packaging materials into foods (mimics) is unrelated to the paper structure (Bradley et al., 2014). Mariani et al. showed that in the process of the migration of the organic pollutant isopropyl naphthalene from recycled cardboard into dry food, when the food is not in direct contact with the packaging paper, the volume of migration is independent of the surface area and fat content of the food and is related only to time. However, in direct contact, the volume of migration is related to the contact time, food characteristics, and initial concentration of pollutants in the paperboard (Boccacci Mariani et al., 1999). Indeed, the process of migration of organic contaminants from paper-based packaging material into packaged dry food and the factors influencing this migration are very complicated. Most previous studies have not analyzed the specific circumstances of each factor's role in the migration process, their interaction with one another, and their relevance. Thus, the specific circumstances of the migration of organic pollutants from paper-based packaging materials into packaged dry foods remain unclear. Moreover, an objective evaluation of migration behavior and various factors affecting such behavior is difficult. Partial least-squares (PLS) regression is a new multivariate statistical data analysis method proposed by Wold et al. (Wold, 1982, 1985). PLS is widely used especially in the fields of chemistry and chemical engineering. This method can effectively solve the problem of multicollinearity of independent variables by considering the information of the independent variables in the process of component extraction and the information of dependent variables. In view of the migration of organic contaminants from paper-based packaging materials into packaged food products, multiple correlations exist among the factors affecting migration performance. Thus, PLS analysis is also suitable for analyzing the effects of various factors on the migration of organic contaminants from paper-based packaging materials into packaged dry foods by calculating the weight values for the effects of various factors. This process effectively links each influencing factor (independent variable) with migration performance (dependent variable), thereby systematically reflecting the impact of various factors on migration performance. In the present work, PLS analysis was used to determine the external environmental (contact time and temperature) and internal factors affecting migration performance, i.e., the characteristics of the migrating substances themselves, such as molecular weight, polarity, and volatile). The date were then combined for comprehensive analysis. This study aimed to examine the migration of organic contaminants from paper-based packaging materials into packaged dry powdered foods, the main factors affecting migration behavior, and the relevance and weight of these factors. Our results can provide theoretical support for the safe use of paper-based food packaging materials, as well as technical guidance for the control of the migration of hazardous substances in paper-based food packaging materials.
The hexane used was from Sinopharm Chemical Reagent Co., Ltd. and was analytical-reagent grade. The acetone used was from Chengdu Kelong Chemical Reagent Plant and was also analytical-reagent grade. To increase observation ability on the migration of organic contaminants in foods, the selected organic contaminants were added to the paper samples as simulated contaminants before migration experiments. To ensure that the selected substances were represented well, previous studies were consulted (Aurela et al., 2001; Nerín et al., 2007; Honkalampi-Hämäläinen et al., 2010; Poças et al., 2010; MAFF, 1999; Lorenzini et al., 2013; Binderup et al., 2002; Sturaro et al., 1994; Xu et al., 2013). Considering the circumstances of molecular structure, volatile, molecular weight, and harm posed to humans, five organic pollutants were identified as simulated pollutants for follow-up migration experiments. The specific conditions are shown in the Table 1. Each simulated contaminant was dissolved in n-hexane and configured to a mixed solution with a concentration of 250 mg/L for use in the subsequent migration experiment.
2.3. Food simulants As shown in the Directive 85/572/EEC on foods and their correspondent simulants, which last amended by Directive 2007/19/EC, no suitable substances are available for dry food simulants in the current migration test (http://eur-lex.europa.eu/, 1985). And in the EU-China trade projection states that the migration of chemicals from the packaging materials may be higher in dry foods than in aqueous simulants (www.euchinawto.org). Another EU regulation states that the migration of substances from food packaging materials into packaged foods is higher than that into food simulants. Accordingly, using real food in the migration test (simulation) was optimal (Grob et al., 2007). Experiments have shown that the thermal stability of the food simulant Porapak was higher than that of Tenax at high experimental temperatures (Nerín et al., 2007). Previous research has shown that the performance of rice powder as a migration test food (simulant) is similar to that of Porapak (Xue and Wang, 2012), and that compared with Porapak, rice powder as a real food can better replace other dry food as a migration test food (simulant). In the present work, rice powder (fat content = 0.62%; purchased from local supermarket) was used as food simulants for subsequent migration experiments. Before the experiment, rice powder was extracted with n-hexane for 8 h, dried for 30 min, cooled to room temperature, and then stored in aluminum-foil packaging for subsequent migration experiments.
2.4. Selection of paper samples Considering that the amount of organic substances that migrated out of the paper-based packaging material was unrelated to the structure of the paper (Bradley et al., 2014), only one Kraft paper commonly used for dry food packaging was selected as a migration test sample. The details were as follows: no recycled pulp, no surface treatment, thickness of 0.369 mm, and grammage of 229 g/m2. And contaminants in the experimental paper samples were analyzed by GC-MS.
2. Experiment section 2.1. Instrument The migration slot was prepared according to the EU standard BS EN13130-1:2004 (E)-migration tank type E, as shown in Fig. 1, which can simulate the actual situation when a packaging material is in singleside contact with food. A gas chromatograph (Trace GC 2000; American Thermo Company) and a mass spectrometer (Trace DSQ, American Thermo Company) were also used.
2.5. Contamination pretreatment of paper samples Paper samples were cut into circular discs with a diameter of 48 mm and placed in a closed container with a mixture of simulated pollutants (250 mg/ L). After allowing to stand for 24 h at room temperature, the discs were air dried for 30 min until use in migration experiments. And the amounts of simulated pollutants contained in the contaminationpretreated paper samples were analyzed by GC-MS. 76
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
Fig. 1. Experimental migration slot.
Table 1 Simulated pollutants used in migration experiments. Simulated pollutant
Molecular weight
Boiling point (°C)
Polarity
Manufacturer and purity
2,6-Dissopropyl naphthalene (2,6-DiPN) Phenol Alkylbenzene
212 86 246
279.3 182 331
Nonpolar Polar Polar
Dibutyl phthalate (DBP) Bis (2-ethylhexyl) phthalate (DEHP)
278 390
340 385
Polar Nonpolar
Tokyo Chemical Industry (TCI), guaranteed reagent Chemical reagents factory of Chongqing East Chemical (Group) Co., Ltd. Tokyo Chemical Industry (TCI), Mixture of various branched alkylbenzenes, guaranteed reagent Chengdu Jinshan Chemical Reagent Co., Ltd., analytical reagent Fluka American Sigma–Aldrich chemical company, chromatographically pure
Fig. 2. Gas chromatograph of experimental paper samples.
Nerín et al., 2007. Migration experiments were then performed using a single-sided contact. The time and temperature conditions for the migration experiments were as follows:
Table 2 Concentrations of simulated pollutants in contaminated pretreated paper samples (mg/L). Paper sample
Phenol
Alkylbenzene
2,6-DiPN
DBP
DEHP
Kraft paper
23.7
31.9
9.13
28.5
42.4
Room temperature (25 °C): 6 h and 1,2,3,4,5,6,7,8,9, and 10 days 50 °C: 15 min, 30 min,1 h, 2 h, 4 h, 6 h, 8 h, 24 h, 32 h, and 48 h 75 °C: 10, 20, 40, 60, 90, 120, 180, 300, and 480 min; 100 °C: 5, 10, 15, 20, 30, 40, 50, 60, 90, 120, and 180 min
2.6. Migration experiments
2.7. Analysis of paper samples
The contaminated paper was placed in the position shown in Fig. 1. To simulate the actual contact of the food with the package,1.29 g of rice powder subjected to extraction treatment was placed in a steel ring based on references Asensio, 2002; EU Project CT 98-4318, 2002 and
After the completion of migration experiments, the paper disc samples were cut into 1 cm × 1 cm pieces, placed in a 50 mL glass vial, and shaken with 5 mL of n-hexane for 30 min at room temperature. 77
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
Table 3 Migration percentage of simulated pollutant from paper to rice powder with time under temperature of 25 °C(%). Pollutant Time (d)
0.25
0.5
1
2
3
4
7
9
10
15
Phenol Alkylbenzene 2,6-DiPN DBP DEHP
29.5 68.5 54.9 59.4 2.3
45.5 81.6 63.3 57.4 7.5
58.8 86.2 72.2 65.0 6.9
60.5 86.9 79.6 75.6 15.0
62.0 87.4 83.9 83.4 14.0
62.5 88.2 85.6 84.8 17.0
62.6 88.0 87.0 84.1 17.4
64.3 88.5 86.5 85.5 18.6
62.5 88.6 87.5 87.4 18.8
64.5 88.0 87.6 88.3 19.8
temperature program was as follows: initial temperature, 60 °C; increased to 240 °C at a rate of 8 °C/min; kept for 4 min; increased again to 280 °C at a rate of 10 °C/min; and kept for 2 min. The GC-MS connection temperature was 280 °C. The MS conditions were as follows: quadrupole type; electron impact ionization source; ionization energy, 70 eV; ion-source temperature, 230 °C; scanning method, full scan; and scanning range, 30–450 amu). Each experiment was repeated three times and the average was taken. The standard curve used for quantitative detection involved serial dilution of the above simulated mixed solution of simulated pollutants with a concentration of 250 mg/L at the following concentrations: 10, 20, 50, 150, and 200 mg/L. 2.8. Analysis of rice powder After completion of the migration experiments, the rice powder was placed in a 50 mL glass vial and extracted with 5 mL of n-hexane with shaking at room temperature for 30 min. After the same procedure was performed three times, the obtained extracts were combined, passed through a microfiltration membrane (pore diameter = 0.4 μm), concentrated to 5 mL, and subjected to GC-MS analysis (the same conditions as above). Each experiment was repeated three times and the average was taken. 2.9. Calculation of migration percentage Considering that the simulated pollutants may volatilize during migration, the migration percentage was calculated according to Equation (1) to ensure that the obtained results represented the “worst” situation.
Q=
Ct , Food × 100% Ct , Food + Ct , paper
(1)
where Q is the percentage of organic simulated pollutants that migrated into rice powder in the paper samples, Ct , Food is the amount of simulated pollutants contained in the rice powder at time t, and Ct , Food + Ct , paper is the amount of simulated pollutants contained in the system (rice powder and paper samples) at time t. 2.10. Statistical analysis 2.10.1. PLS regression analysis PLS regression analysis is a multidimensional data analysis method developed on the basis of principal component regression analysis. PLS analysis draws on the idea of orthogonal decomposition of the matrix of primitive variables when principal component regression analysis is used. Taking this study as an example, when PLS analysis was performed, data consisting of each influencing factor were set as five groups. Matrix X was the independent variable, and data corresponding to the migration performance of each sample was set to 200 groups. Matrix Y was the dependent variable. The independent dataset X = {x1,x2,...,x5[/ Sub]}200×5 and dependent variable dataset Y = {y1,y2[/sub],...,y200}200×1 were expressed as the following linear model: Y = X ⋅Z + E (where Z is the regression coefficient matrix and E
Fig. 3. Migration percentage of simulated pollutant from paper to rice powder with time under different temperatures (50, 75, and 100 °C) (a-e).
After performing the same procedure three times, the resulting extracts were combined, concentrated to 5 mL, and subjected to GC-MS analysis (GC conditions: chromatographic column, DB-5MS capillary column; inlet temperature, 250 °C; automatic, splitless injection; injection volume, 1 μL; carrier gas, helium; and flow rate, 1 mL/min. The column 78
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
Fig. 4. PLS score plot of regression coefficients.
Fig. 5. t/u plan.
Fig. 6. VIP graph of PLS regression.
79
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
3.3. Analysis of migration behavior
is the residual matrix). Then, the least-squares solution was Z = (X T X )−1⋅X T ⋅Y . By applying the influencing factor matrix X and the migration performance matrix Y and performing bilinear decomposition by using the NIPALS algorithm, the decomposed eigenvector expression was X = T ⋅PT + F , Y = U ⋅QT + E (where T and U are matrices X > and Y score vectors, respectively, P and Q are eigenvectors, and F is the residual matrix). T and U were necessary to satisfy as many variations of the influencing-factor matrix and the migration-performance matrix as possible and to make the related degree reach the maximum requirement. PLS analyses, as well as the data preprocessing involved in the statistical analyses, were performed on the software SIMCA-P 11.5Demo.
The migration of organic pollutants from paper-based packaging materials into packaged food is usually expressed in terms of migration percentage, i.e., the ratio of the amount of organic pollutants that migrate into food and the amount in the system (food and packaging), to indirectly describe migration features. Because the time period for the measurement was quite different at different temperatures, e.g., from days to mins, it is difficult to compare the effect of temperature in one figure. So Fig. 3(a–e) only show the percentage of migration of simulated pollutants from paper to rice flour with time when the temperature was 50, 75, and 100 °C, and the data that under temperature of 25 °C are listed in Table 3. Notably, rice powder was brought into contact with the single surface of the pollutant-pretreated paper. As indicated from Table 3, within the migration test time period, with prolonged migration time, the migration percentage of simulated pollutants gradually increased under temperature of 25 °C. Fig. 3(a–e) show that increased temperature accelerate the migration of each simulated pollutant out of the paper. And also demonstrate that with prolonged migration time, except for DEHP, migration percentage of other four simulated pollutants under temperature of 50 °C and 75 °C gradually increased and eventually reached a steady state; however, at the temperature of 100 °C, with prolonged migration time, migration percentage tended to decrease. This finding may be due to the relatively low temperature at 25 °C, the migration of simulated pollutants was slow, and the migration equilibrium was not yet reached within the measurement time range. While at 100 °C, the volatilization of each simulated pollutants caused by high temperature produced an increased amount of losses, resulting in reduced migration to the food simulant. Fig. 3(a) and (b) show that the migrations of phenol and alkylbenzene have the following order when the equilibrium was reached: i.e., M50 °C > M75 °C > M100 °C. It is because the volatilities of these species were relatively high, which caused their more losses (released to environment rather than food) at higher temperature. Due to the lower volatilities of 2,6-DiPN and DBP, the overall migration percentages of them are very close at the equilibrium under different temperature conditions. Fig. 3 also show that the migration behaviors of different simulated pollutants were very different at the same temperature. A smaller molecular weight meant a shorter time to reach the balance of migration. As shown in Fig. 3(a), the initial (but not the final) migration percentage of phenol was the largest, and it was the earliest to reach the balance of migration. Moreover, with the exception of DEHP, the other four simulated pollutants had a higher percentage of migration into foods, whereas DEHP with a larger molecular weight had a slower rate of migration from the paper. Fig. 3 further demonstrates that at temperatures other than 25 °C, when the migration equilibrium was reached, the migration percentage of 2,6-DiPN was the largest, indicating it easily released from the paper and absorbed by the food, this finding may be due to the nonpolarity of 2,6-DiPN that repelled the strongly polar paper packaging material, thereby increasing its diffusion into powdered food (simulant). However, for the nonpolar DEHP, the final equilibrium migration percentage was the lowest at all temperatures. Even in the case of short contact time, migration equilibrium was not reached. These results agreed with those in reference (Xu et al., 2013). The large molecular weight and low volatile of DEHP hindered its release from the pores of paper formed by the large number of interweaved fibers.
2.10.2. Correlation analysis Determining whether a strong correlation existed between the independent variable set X and the dependent variable set Y was the basic condition for evaluating whether a linear regression of Y vs. X can be established. Extracting the principal component u from independent variable X and the principal component t from dependent variable Y yielded a plot of the plane in t/u. If a linear relationship existed between th and uh, a significant correlation obviously existed between X and Y. Thus, using PLS analysis to establish a linear model of Y vs. X was reasonable. 2.10.3. Calculation of weight In PLS analysis, the explanatory power of the independent variable to the dependent variable was measured by the VIP value of the variable projection importance index.
VIPj =
k Rd (y; ;t1, ⋅⋅⋅,tm)
m
∑ Rd (y; th) whj2 h=1
In the formula, whj is the j component of axis wh and used to measure the contribution of x j to the principal component of structure th . Rd (y; th) and Rd (y; t1, t2, ⋅⋅⋅,tm) is the variability accuracy y explained by th and t1, t2, ⋅⋅⋅,tm , respectively, representing the ability of th to interpret y and the cumulative ability of t1, t2, ⋅⋅⋅,tm to interpret y , respectively. For the large x j of VIPj , an important role in interpreting y exists such that the VIP value can be used to select independent variables. 3. Results and discussion This work analyzed the migration behavior of different simulated pollutants in paper-based packaging materials into packaged dry powdered foods by examining under different temperature conditions over time to determine the factors affecting migration behavior. Consequently, the safety control of paper-based food packaging materials can be targeted. 3.1. Analysis of contaminants in the experimental paper samples As shown in the GC analysis of the n-hexane extract from the paper sample (Fig. 2), no other substances existed in the paper except for the solvent peak. 3.2. Analysis of simulated pollutants in the contamination-pretreated paper samples
3.4. Analysis of influencing factors The above analysis showed that the factors affecting the migration performance of simulated pollutants from paper to food mainly included external (i.e., temperature and contact time) and internal (i.e., characteristics of pollutants such as polarity, volatility, and molecular
The amounts of simulated pollutants contained in the contamination-pretreated paper samples were analyzed, and results are shown in Table 2. 80
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
weight of the organic pollutant itself were concluded to greatly influence the migration performance, and these two were the factors that most strongly affected migration performance. Molecular polarity, contact time, and temperature had weaker effects. Safety control recommendations for the migration of organic contaminants to dry powdered foods in paper-based packaging materials. The above analysis revealed that in paper-based packaging materials, the migration of organic pollutants into packaged dry powdered food was affected by internal (molecular weight, volatile, and molecular polarity of organic pollutants) and external (contact time and temperature) factors. Among them, volatile and molecular weight of organic pollutants had the greatest influence on migration performance, whereas temperature had the least influence. In general, the species with lower molecular weight are more volatile, which causes their more loss to the environment, especially at higher temperatures. Therefore, the temperature effect to their migration to food is more significant than the lower volatile species (with higher molecular weights). Accordingly, in the processing, transport, and storage of powdered foods in paper-based packaging, the migration of organic pollutants into the packaged foods decreased with decreased of contact time and ambient temperature. Moreover, because some aspects of food packaging materials such as printing and decorating were indispensable, some organic pollutants were necessary for the presentation of certain effects. During material processing, using substances with good volatile for food packaging can ensure that these organic contaminants were volatilized from the paper-based packaging material prior to packaging processing. Alternatively, using large-molecularweight substances can ensure that throughout the entire process of packaging, transport, and storage, a minimum amount migration of these organic contaminants into the packaged food and reduced the contamination of the food itself caused by food packaging.
weight) factors. However, the influence of each factor on the migration performance was mutually. Consequently, the establishment of an accurate quantitative relationship between a certain factor and migration performance was difficult. Thus, analysis of the comprehensive effect of various influencing factors on the migration performance of simulated pollutants, as well as the specific circumstances of the effects of various influencing factors, can targeted control the migration of organic pollutants from paper-based food packaging materials to the packaged foods with a good guidance function. 3.5. Effects of various factors on PLS analysis Migration percentage is an important indicator used to characterize the degree of migration of pollutants from packaging material to food during studies on migration kinetics. To understand the influence of temperature, contact time, molecular weight, volatile, and molecular polarity of pollutants on the migration of simulated pollutants from paper-based packaging material to food, SIMCA-P statistical analysis software was used to perform coefficient analysis on our data. A standardized PLS regression model coefficient diagram was obtained, as shown in Fig. 4. The coefficient equation was as follows:
Migration percentage % = 0.073 temperature + 0.209 contact time –0.185 molecular polarity–0.792 volatile–1.075 molecular weight The model showed that changes in temperature and contact time were positively correlated with migration performance, whereas volatile, molecular weight, molecular polarity of organic pollutants were negatively correlated. In other words, increased temperature and prolonged contact time meant higher migration percentage of organic pollutants to food, while stronger molecular polarity, greater volatile, and higher molecular weight of organic pollutants meant lower migration percentage to food. The values of the coefficients (of each factor in this model) indicate that the losses of migration percentage to food for the given organic pollutant caused by the volatilization is greater than the increment caused by elevating the temperature. These results are consistent with the above analysis of migration behavior for both phenol and alkylbenzene.
4. Conclusion 1. In the case of the same paper packaging material and with rice flour as a food simulant, the migration behavior of each simulated pollutant was affected by the following factors: temperature, contact time, and nature of pollutant (e.g., molecular weight, molecular polarity, and volatile). Among them, temperature and contact time had a positive effect on migration, whereas volatile, molecular weight, and molecular polarity of organic pollutant had a negative effect. 2. Under the same conditions of paper packaging materials, the characteristics (volatile and molecular weight) of the simulated pollutants had a strong impact on migration performance, whereas external factors (contact time and temperature) had a weaker effect. 3. During the production and processing of paper food packaging, due to the necessity of using certain substances, those with high volatile or molecular weight can ensure quality of the entire packaging throughout transport and storage. During the process, the degree of migration of organic pollutants to the packaged food can be minimized to decrease the risk of contamination of the food caused by the package itself.
3.5.1. Analysis of PLS regression accuracy The above PLS components were extracted, and a total of four principal components were extracted. The explanatory power of these four components for X was 0.91, and the explanatory power for Y was 0.369. Overall, the explanatory power was relatively strong. The crossvalidity Q2 was 0.362, and the critical value was 0.097 (0.362 > 0.097 was relatively high). These data indicated that the constructed model was reasonable. 3.5.2. Correlation analysis Fig. 5 is the t/u floor plan drawn between the principal component t extracted from independent variable X and u extracted from dependent variable Y. A good linear relationship existed between t and u, so X and Y were significantly correlated He and Liu, 2015. Thus, the linear model of Y vs. X established by PLS regression was reasonable.
Funding This project was funded by the 2016 Guangdong Province General Colleges and Universities Characteristic Innovative Project (Project Number: 2016KTSCX176).
3.5.3. Weight analysis Fig. 6 shows the importance (VIP value) of variable projections in explaining migration performance using PLS analysis to analyze the migration behavior data measured in the above experiments. The VIP values of the five factors were relatively large, in which the volatile and the molecular weight of the organic pollutant on the migration performance were greater than 1. The VIP value of molecular polarity, contact time, and temperature affecting the migration performance was between 0.5 and 1. According to the VIP value of the effect of each influencing factor on migration performance, the volatile and molecular
References Anon 1 http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri= CONSLEG:1985L0572:20070420:EN:PDF. Anon 2 www.euchinawto.org. Asensio, E., 2002, 22 November. Title: [Dissertation]. University of Zaragoza, Spain.
81
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
Nerín, C., Contín, E., Asensio, E., 2007. Kinetic migration studies using Porapak as solidfood simulant to assess the safety of paper and board as food-packaging materials. Anal. Bioanal. Chem. 387, 2283–2288. Poças, M.F., Oliveira, J.C., Pereira, J.R., et al., 2010. Consumer exposure to phthalates from paoer packaging: an integrated approach. Food Addit. Contam. 27 (10), 1451–1459. EU Project CT 98-4318, 2002. Programme on the recyclability of food packaging materials with respect to food safety consideration-polyethylene terephthalate (PET), paper and board and plastic covered by functional barriers. EU Regulations and Guidances on Food Contact Materials. Sturaro, A., Parvoli, G., Rella, S., et al., 1994. Food Contamination bydiisopropylnaphthalene from cardboard packages. Int. J. Food Sci. Technol. 29, 593–603. Triantafyllou, Vasileios I., Akrida-Demertzi, Konstantoula, Demertzis, Panagiotis G., 2002. Migration studies from recycled paper packaging materials: development of an analytical method for rapid testing. Anal. Chim. Acta 467, 253–260. Triantafyllou, Vasileios I., Akrida-Demertzi, Konstantoula, Demertzis, Panagiotis G., 2005. Determination of partition behavior of organic surrogate between paperboard packaging materials and air. J. Chromatogr. A 1077, 74–79. Triantafyllou, Vasileios I., Akrida-Demertzi, Konstantoula, Demertzis, Panagiotis G., 2006. A study on the migration of organic pollutants from recycled paperboard packaging materials to solid food matrices. Food Chem. 1, 1–10. Wold, H., 1982. Soft modeling: the basic design and some extensions[A]. K G J Reskog H Wold, Systems under Indirect Observation [C]. Amsterdam, North- Holland, pp. 1–54. Wold, H., 1985. Partial least squares [A]. In: Kotz S Johnson N L. Encyclopedia of Statistical Science [M] 6. John Wiley & Sons, New York, pp. 581–591. Xu, Y., Noonan, G.O., Begley, T.H., 2013. Migration of perfluoroalkyl acids from food packaging to food simulants. Food Addit. Contam. 30 (5), 899–908. Xue, Meigui, Wang, Shuangfei, 2012. Selection of solid food simulants for migration test from paper food packaging materials. Packag. Eng. 33 (21), 51–56.
Aurela, B., Kulmala, H., Söderhjelm, L., 1999. Phthalates in paper and board packaging and their migration into Tenax and sugar. Food Addit. Contam. 16 (12), 571–577. Aurela, B., Ohra-aho, T., Soderhjelm, L., 2001. Migration of alkylbenzenes from packaging into food and Tenax. Packag. Technol. Sci. 14, 71–77. Binderup, M.L., Pedersen, G.A., Vinggaard, A.M., et al., 2002. Toxicity testing and chemical analyses of recycled fibre-based paper for food contact. Food Addit. Contam. 19 (Suppl. 1), 13–28. Boccacci Mariani, M., Chiaccherini, E., Gesumundo, C., 1999. Potential migration of Diisopropyl naphthalenes from recycled paperboard packaging into dry foods. Food Addit. Contam. 16 (5), 207–213. Bradley, E.L., Castle, L., Speck, D.R., 2014. Model studies of migration from paper and board into fruit and vegetables and into Tenax as a food simulant. Food Addit. Contam. A 31 (7), 1301–1309. MAFF, Jaunary, 1999. Diisopropylnaphthalenes in Food Packaging made from Recycled Paper and Board. Food Surveillance Information Sheet, No 169. . Grob, Koni, Pfenninger, Susanne, Pohl, Wolfgang, et al., 2007. European legal limits for migration from food packaging materials:1. Food should prevail over simulants; 2. More realistic conversion from concentrations to limits per surface area. PVC cling films in contact with cheese as an example. Food Control 18 (3), 201–210. He, Xiaoqun, Liu, Wenqing, 2015. Applied Regression Analysis [M]. Renmin University of China Press. Honkalampi-Hämäläinen, U., Bradley, E.L., Castle, L., et al., 2010. Safety evaluation of food contact paper and board using chemical tests and in vitro bioassays: role of known and unknown substances. Food Addit. Contam. 27 (3), 406–415. Johns, S.M., Gramshaw, J.W., Castle, L., et al., 1995. Studies on functional barriers to migration, 1.Transfer of benzophenone from printed paperboard to microwaved food. Dtsch. Lebensm.-Rundsch. 3, 69–73. Lorenzini, R., Biedermann, M., Grob, K., et al., 2013. Migration kinetics of mineral oil hydrocarbons from recycled paperboard to dry food: monitoring of two real cases. Food Addit. Contam. 30 (4), 760–770. Nerín, C., Asensio, E., 2004. Behaviour of organic pollutants in paper and board samples intended to be in contact with food. Analytical Chimmica Acta 508, 185–191.
82
Contents lists available at ScienceDirect
Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng
Migration of organic contaminants into dry powdered food in paper packaging materials and the influencing factors
T
Meigui Xuea,∗, Xin-Sheng Chaib, Xiaodong Lia, Runquan Chenc a
Dongguan Polytechnic, Dongguan, Guangdong, 523808, China South China University of Technology, Guangzhou, South China University of Technology, Guangzhou, Guangdong, 530004, China c Dongguan Quality Testing, Dongguan, Guangdong, 523808, China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Paper food packaging dry powdered food Migration performance Influencing factors
The factors affecting the migration of organic contaminants from paper packaging materials into packaged dry powdered food were studied. Based on the molecular structure, volatile, molecular weight, and harm posed to the human body, five organic substances were selected as simulated pollutants. According to EU technical standard BS EN13130-1:2004 (E) migration trough types E manufactured migration cell and completion of migration of simulated contaminants from paper to solid powdered foods at different temperature and times were studied. GC-MS technology was used to detect the content of simulated pollutants in paper and food. Partial least-squares (PLS) method was used to analyze the effects of various factors affecting migration performance. Results showed that the migration of simulated pollutants from paper packaging materials into solid powdered foods was affected by temperature, contact time, molecular weight of organic pollutants, and volatile. Among them, volatile and molecular weight contributed the greatest effects, whereas temperature contributed the least effect. Changes in temperature and contact time were positively correlated with migration performance, whereas volatile, molecular weight, molecular polarity of organic pollutants were negatively correlated. In other words, for the individual factors, higher temperature and longer contact time meant higher migration percentage of organic pollutants from paper-based packaging to packaged dry powdered foods, whereas greater volatile and higher molecular weight of organic pollutants led to poorer migration into food.
1. Introduction Paper and cardboard are widely used as packaging materials for dry solid foods because of their abundant sources, renewability, and natural degradation. However, some organic substances can harm humans are introduced during the manufacture of paper packaging materials and the printing process (Nerín and Asensio, 2004; Aurela et al., 1999, 2001; Johns et al., 1995; Nerín et al., 2007). When these materials are used as food packaging, harmful substances may migrate into food through direct or indirect contact. Accordingly, studying the migration behavior of organic contaminants in paper-based packaging materials into dry powdered foods is very important for the prediction of migration performance, the extension of the products shelf life and effective control of the influencing factors. Extensive studies have been conducted on the migration of organic contaminants from paper-based food packaging materials into the foods
they package. The European Union (EU) has specific instructions on the contact conditions (time and temperature) and simulants for the test conditions of paper-based packaging materials intended to come into contact with foodstuffs. Some examples of these standards are 85/572/ EEC and 87/711/EEC, as well as their revised instructions 93/8/EEC and 97/48/EEC (Regulations and Guidan). Nerín et al. studied the kinetics of migration of organic contaminants from paper into food simulants and found that the length of contact with food simulant and the temperature of the environment are the main factors affecting the migration of organic pollutants (Nerín et al., 2007). Aurela et al. analyzed the migration of phthalate esters in paper-based packages into the food simulants Tenax and white sugar. They found that the mass-to-surface ratio of food simulants and packaging materials, the surface area of the packaging material, the amount of internal standard added during measurement, and the migration device are important factors affecting migration (Aurela et al., 1999). Other studies have shown that the contact time, temperature, and characteristics of organic pollutants
This project was funded by the 2016 Guangdong Province General Colleges and Universities Characteristic Innovative Project (Project Number: 2016KTSCX176). ∗ Corresponding author. E-mail addresses: [email protected], [email protected] (M. Xue). https://doi.org/10.1016/j.jfoodeng.2019.05.018 Received 16 April 2018; Received in revised form 5 December 2018; Accepted 13 May 2019 Available online 17 May 2019 0260-8774/ © 2019 Elsevier Ltd. All rights reserved.
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
2.2. Reagents
(e.g., molecular weight, chemical structure, and volatile) significantly influence migration. The boiling point of organic pollutants and the type and performance of the paper used are also influencing factors (Triantafyllou et al., 2002, 2005, 2006). Recent studies have shown that the volume of migration of organic substances in paper-based packaging materials into foods (mimics) is unrelated to the paper structure (Bradley et al., 2014). Mariani et al. showed that in the process of the migration of the organic pollutant isopropyl naphthalene from recycled cardboard into dry food, when the food is not in direct contact with the packaging paper, the volume of migration is independent of the surface area and fat content of the food and is related only to time. However, in direct contact, the volume of migration is related to the contact time, food characteristics, and initial concentration of pollutants in the paperboard (Boccacci Mariani et al., 1999). Indeed, the process of migration of organic contaminants from paper-based packaging material into packaged dry food and the factors influencing this migration are very complicated. Most previous studies have not analyzed the specific circumstances of each factor's role in the migration process, their interaction with one another, and their relevance. Thus, the specific circumstances of the migration of organic pollutants from paper-based packaging materials into packaged dry foods remain unclear. Moreover, an objective evaluation of migration behavior and various factors affecting such behavior is difficult. Partial least-squares (PLS) regression is a new multivariate statistical data analysis method proposed by Wold et al. (Wold, 1982, 1985). PLS is widely used especially in the fields of chemistry and chemical engineering. This method can effectively solve the problem of multicollinearity of independent variables by considering the information of the independent variables in the process of component extraction and the information of dependent variables. In view of the migration of organic contaminants from paper-based packaging materials into packaged food products, multiple correlations exist among the factors affecting migration performance. Thus, PLS analysis is also suitable for analyzing the effects of various factors on the migration of organic contaminants from paper-based packaging materials into packaged dry foods by calculating the weight values for the effects of various factors. This process effectively links each influencing factor (independent variable) with migration performance (dependent variable), thereby systematically reflecting the impact of various factors on migration performance. In the present work, PLS analysis was used to determine the external environmental (contact time and temperature) and internal factors affecting migration performance, i.e., the characteristics of the migrating substances themselves, such as molecular weight, polarity, and volatile). The date were then combined for comprehensive analysis. This study aimed to examine the migration of organic contaminants from paper-based packaging materials into packaged dry powdered foods, the main factors affecting migration behavior, and the relevance and weight of these factors. Our results can provide theoretical support for the safe use of paper-based food packaging materials, as well as technical guidance for the control of the migration of hazardous substances in paper-based food packaging materials.
The hexane used was from Sinopharm Chemical Reagent Co., Ltd. and was analytical-reagent grade. The acetone used was from Chengdu Kelong Chemical Reagent Plant and was also analytical-reagent grade. To increase observation ability on the migration of organic contaminants in foods, the selected organic contaminants were added to the paper samples as simulated contaminants before migration experiments. To ensure that the selected substances were represented well, previous studies were consulted (Aurela et al., 2001; Nerín et al., 2007; Honkalampi-Hämäläinen et al., 2010; Poças et al., 2010; MAFF, 1999; Lorenzini et al., 2013; Binderup et al., 2002; Sturaro et al., 1994; Xu et al., 2013). Considering the circumstances of molecular structure, volatile, molecular weight, and harm posed to humans, five organic pollutants were identified as simulated pollutants for follow-up migration experiments. The specific conditions are shown in the Table 1. Each simulated contaminant was dissolved in n-hexane and configured to a mixed solution with a concentration of 250 mg/L for use in the subsequent migration experiment.
2.3. Food simulants As shown in the Directive 85/572/EEC on foods and their correspondent simulants, which last amended by Directive 2007/19/EC, no suitable substances are available for dry food simulants in the current migration test (http://eur-lex.europa.eu/, 1985). And in the EU-China trade projection states that the migration of chemicals from the packaging materials may be higher in dry foods than in aqueous simulants (www.euchinawto.org). Another EU regulation states that the migration of substances from food packaging materials into packaged foods is higher than that into food simulants. Accordingly, using real food in the migration test (simulation) was optimal (Grob et al., 2007). Experiments have shown that the thermal stability of the food simulant Porapak was higher than that of Tenax at high experimental temperatures (Nerín et al., 2007). Previous research has shown that the performance of rice powder as a migration test food (simulant) is similar to that of Porapak (Xue and Wang, 2012), and that compared with Porapak, rice powder as a real food can better replace other dry food as a migration test food (simulant). In the present work, rice powder (fat content = 0.62%; purchased from local supermarket) was used as food simulants for subsequent migration experiments. Before the experiment, rice powder was extracted with n-hexane for 8 h, dried for 30 min, cooled to room temperature, and then stored in aluminum-foil packaging for subsequent migration experiments.
2.4. Selection of paper samples Considering that the amount of organic substances that migrated out of the paper-based packaging material was unrelated to the structure of the paper (Bradley et al., 2014), only one Kraft paper commonly used for dry food packaging was selected as a migration test sample. The details were as follows: no recycled pulp, no surface treatment, thickness of 0.369 mm, and grammage of 229 g/m2. And contaminants in the experimental paper samples were analyzed by GC-MS.
2. Experiment section 2.1. Instrument The migration slot was prepared according to the EU standard BS EN13130-1:2004 (E)-migration tank type E, as shown in Fig. 1, which can simulate the actual situation when a packaging material is in singleside contact with food. A gas chromatograph (Trace GC 2000; American Thermo Company) and a mass spectrometer (Trace DSQ, American Thermo Company) were also used.
2.5. Contamination pretreatment of paper samples Paper samples were cut into circular discs with a diameter of 48 mm and placed in a closed container with a mixture of simulated pollutants (250 mg/ L). After allowing to stand for 24 h at room temperature, the discs were air dried for 30 min until use in migration experiments. And the amounts of simulated pollutants contained in the contaminationpretreated paper samples were analyzed by GC-MS. 76
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
Fig. 1. Experimental migration slot.
Table 1 Simulated pollutants used in migration experiments. Simulated pollutant
Molecular weight
Boiling point (°C)
Polarity
Manufacturer and purity
2,6-Dissopropyl naphthalene (2,6-DiPN) Phenol Alkylbenzene
212 86 246
279.3 182 331
Nonpolar Polar Polar
Dibutyl phthalate (DBP) Bis (2-ethylhexyl) phthalate (DEHP)
278 390
340 385
Polar Nonpolar
Tokyo Chemical Industry (TCI), guaranteed reagent Chemical reagents factory of Chongqing East Chemical (Group) Co., Ltd. Tokyo Chemical Industry (TCI), Mixture of various branched alkylbenzenes, guaranteed reagent Chengdu Jinshan Chemical Reagent Co., Ltd., analytical reagent Fluka American Sigma–Aldrich chemical company, chromatographically pure
Fig. 2. Gas chromatograph of experimental paper samples.
Nerín et al., 2007. Migration experiments were then performed using a single-sided contact. The time and temperature conditions for the migration experiments were as follows:
Table 2 Concentrations of simulated pollutants in contaminated pretreated paper samples (mg/L). Paper sample
Phenol
Alkylbenzene
2,6-DiPN
DBP
DEHP
Kraft paper
23.7
31.9
9.13
28.5
42.4
Room temperature (25 °C): 6 h and 1,2,3,4,5,6,7,8,9, and 10 days 50 °C: 15 min, 30 min,1 h, 2 h, 4 h, 6 h, 8 h, 24 h, 32 h, and 48 h 75 °C: 10, 20, 40, 60, 90, 120, 180, 300, and 480 min; 100 °C: 5, 10, 15, 20, 30, 40, 50, 60, 90, 120, and 180 min
2.6. Migration experiments
2.7. Analysis of paper samples
The contaminated paper was placed in the position shown in Fig. 1. To simulate the actual contact of the food with the package,1.29 g of rice powder subjected to extraction treatment was placed in a steel ring based on references Asensio, 2002; EU Project CT 98-4318, 2002 and
After the completion of migration experiments, the paper disc samples were cut into 1 cm × 1 cm pieces, placed in a 50 mL glass vial, and shaken with 5 mL of n-hexane for 30 min at room temperature. 77
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
Table 3 Migration percentage of simulated pollutant from paper to rice powder with time under temperature of 25 °C(%). Pollutant Time (d)
0.25
0.5
1
2
3
4
7
9
10
15
Phenol Alkylbenzene 2,6-DiPN DBP DEHP
29.5 68.5 54.9 59.4 2.3
45.5 81.6 63.3 57.4 7.5
58.8 86.2 72.2 65.0 6.9
60.5 86.9 79.6 75.6 15.0
62.0 87.4 83.9 83.4 14.0
62.5 88.2 85.6 84.8 17.0
62.6 88.0 87.0 84.1 17.4
64.3 88.5 86.5 85.5 18.6
62.5 88.6 87.5 87.4 18.8
64.5 88.0 87.6 88.3 19.8
temperature program was as follows: initial temperature, 60 °C; increased to 240 °C at a rate of 8 °C/min; kept for 4 min; increased again to 280 °C at a rate of 10 °C/min; and kept for 2 min. The GC-MS connection temperature was 280 °C. The MS conditions were as follows: quadrupole type; electron impact ionization source; ionization energy, 70 eV; ion-source temperature, 230 °C; scanning method, full scan; and scanning range, 30–450 amu). Each experiment was repeated three times and the average was taken. The standard curve used for quantitative detection involved serial dilution of the above simulated mixed solution of simulated pollutants with a concentration of 250 mg/L at the following concentrations: 10, 20, 50, 150, and 200 mg/L. 2.8. Analysis of rice powder After completion of the migration experiments, the rice powder was placed in a 50 mL glass vial and extracted with 5 mL of n-hexane with shaking at room temperature for 30 min. After the same procedure was performed three times, the obtained extracts were combined, passed through a microfiltration membrane (pore diameter = 0.4 μm), concentrated to 5 mL, and subjected to GC-MS analysis (the same conditions as above). Each experiment was repeated three times and the average was taken. 2.9. Calculation of migration percentage Considering that the simulated pollutants may volatilize during migration, the migration percentage was calculated according to Equation (1) to ensure that the obtained results represented the “worst” situation.
Q=
Ct , Food × 100% Ct , Food + Ct , paper
(1)
where Q is the percentage of organic simulated pollutants that migrated into rice powder in the paper samples, Ct , Food is the amount of simulated pollutants contained in the rice powder at time t, and Ct , Food + Ct , paper is the amount of simulated pollutants contained in the system (rice powder and paper samples) at time t. 2.10. Statistical analysis 2.10.1. PLS regression analysis PLS regression analysis is a multidimensional data analysis method developed on the basis of principal component regression analysis. PLS analysis draws on the idea of orthogonal decomposition of the matrix of primitive variables when principal component regression analysis is used. Taking this study as an example, when PLS analysis was performed, data consisting of each influencing factor were set as five groups. Matrix X was the independent variable, and data corresponding to the migration performance of each sample was set to 200 groups. Matrix Y was the dependent variable. The independent dataset X = {x1,x2,...,x5[/ Sub]}200×5 and dependent variable dataset Y = {y1,y2[/sub],...,y200}200×1 were expressed as the following linear model: Y = X ⋅Z + E (where Z is the regression coefficient matrix and E
Fig. 3. Migration percentage of simulated pollutant from paper to rice powder with time under different temperatures (50, 75, and 100 °C) (a-e).
After performing the same procedure three times, the resulting extracts were combined, concentrated to 5 mL, and subjected to GC-MS analysis (GC conditions: chromatographic column, DB-5MS capillary column; inlet temperature, 250 °C; automatic, splitless injection; injection volume, 1 μL; carrier gas, helium; and flow rate, 1 mL/min. The column 78
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
Fig. 4. PLS score plot of regression coefficients.
Fig. 5. t/u plan.
Fig. 6. VIP graph of PLS regression.
79
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
3.3. Analysis of migration behavior
is the residual matrix). Then, the least-squares solution was Z = (X T X )−1⋅X T ⋅Y . By applying the influencing factor matrix X and the migration performance matrix Y and performing bilinear decomposition by using the NIPALS algorithm, the decomposed eigenvector expression was X = T ⋅PT + F , Y = U ⋅QT + E (where T and U are matrices X > and Y score vectors, respectively, P and Q are eigenvectors, and F is the residual matrix). T and U were necessary to satisfy as many variations of the influencing-factor matrix and the migration-performance matrix as possible and to make the related degree reach the maximum requirement. PLS analyses, as well as the data preprocessing involved in the statistical analyses, were performed on the software SIMCA-P 11.5Demo.
The migration of organic pollutants from paper-based packaging materials into packaged food is usually expressed in terms of migration percentage, i.e., the ratio of the amount of organic pollutants that migrate into food and the amount in the system (food and packaging), to indirectly describe migration features. Because the time period for the measurement was quite different at different temperatures, e.g., from days to mins, it is difficult to compare the effect of temperature in one figure. So Fig. 3(a–e) only show the percentage of migration of simulated pollutants from paper to rice flour with time when the temperature was 50, 75, and 100 °C, and the data that under temperature of 25 °C are listed in Table 3. Notably, rice powder was brought into contact with the single surface of the pollutant-pretreated paper. As indicated from Table 3, within the migration test time period, with prolonged migration time, the migration percentage of simulated pollutants gradually increased under temperature of 25 °C. Fig. 3(a–e) show that increased temperature accelerate the migration of each simulated pollutant out of the paper. And also demonstrate that with prolonged migration time, except for DEHP, migration percentage of other four simulated pollutants under temperature of 50 °C and 75 °C gradually increased and eventually reached a steady state; however, at the temperature of 100 °C, with prolonged migration time, migration percentage tended to decrease. This finding may be due to the relatively low temperature at 25 °C, the migration of simulated pollutants was slow, and the migration equilibrium was not yet reached within the measurement time range. While at 100 °C, the volatilization of each simulated pollutants caused by high temperature produced an increased amount of losses, resulting in reduced migration to the food simulant. Fig. 3(a) and (b) show that the migrations of phenol and alkylbenzene have the following order when the equilibrium was reached: i.e., M50 °C > M75 °C > M100 °C. It is because the volatilities of these species were relatively high, which caused their more losses (released to environment rather than food) at higher temperature. Due to the lower volatilities of 2,6-DiPN and DBP, the overall migration percentages of them are very close at the equilibrium under different temperature conditions. Fig. 3 also show that the migration behaviors of different simulated pollutants were very different at the same temperature. A smaller molecular weight meant a shorter time to reach the balance of migration. As shown in Fig. 3(a), the initial (but not the final) migration percentage of phenol was the largest, and it was the earliest to reach the balance of migration. Moreover, with the exception of DEHP, the other four simulated pollutants had a higher percentage of migration into foods, whereas DEHP with a larger molecular weight had a slower rate of migration from the paper. Fig. 3 further demonstrates that at temperatures other than 25 °C, when the migration equilibrium was reached, the migration percentage of 2,6-DiPN was the largest, indicating it easily released from the paper and absorbed by the food, this finding may be due to the nonpolarity of 2,6-DiPN that repelled the strongly polar paper packaging material, thereby increasing its diffusion into powdered food (simulant). However, for the nonpolar DEHP, the final equilibrium migration percentage was the lowest at all temperatures. Even in the case of short contact time, migration equilibrium was not reached. These results agreed with those in reference (Xu et al., 2013). The large molecular weight and low volatile of DEHP hindered its release from the pores of paper formed by the large number of interweaved fibers.
2.10.2. Correlation analysis Determining whether a strong correlation existed between the independent variable set X and the dependent variable set Y was the basic condition for evaluating whether a linear regression of Y vs. X can be established. Extracting the principal component u from independent variable X and the principal component t from dependent variable Y yielded a plot of the plane in t/u. If a linear relationship existed between th and uh, a significant correlation obviously existed between X and Y. Thus, using PLS analysis to establish a linear model of Y vs. X was reasonable. 2.10.3. Calculation of weight In PLS analysis, the explanatory power of the independent variable to the dependent variable was measured by the VIP value of the variable projection importance index.
VIPj =
k Rd (y; ;t1, ⋅⋅⋅,tm)
m
∑ Rd (y; th) whj2 h=1
In the formula, whj is the j component of axis wh and used to measure the contribution of x j to the principal component of structure th . Rd (y; th) and Rd (y; t1, t2, ⋅⋅⋅,tm) is the variability accuracy y explained by th and t1, t2, ⋅⋅⋅,tm , respectively, representing the ability of th to interpret y and the cumulative ability of t1, t2, ⋅⋅⋅,tm to interpret y , respectively. For the large x j of VIPj , an important role in interpreting y exists such that the VIP value can be used to select independent variables. 3. Results and discussion This work analyzed the migration behavior of different simulated pollutants in paper-based packaging materials into packaged dry powdered foods by examining under different temperature conditions over time to determine the factors affecting migration behavior. Consequently, the safety control of paper-based food packaging materials can be targeted. 3.1. Analysis of contaminants in the experimental paper samples As shown in the GC analysis of the n-hexane extract from the paper sample (Fig. 2), no other substances existed in the paper except for the solvent peak. 3.2. Analysis of simulated pollutants in the contamination-pretreated paper samples
3.4. Analysis of influencing factors The above analysis showed that the factors affecting the migration performance of simulated pollutants from paper to food mainly included external (i.e., temperature and contact time) and internal (i.e., characteristics of pollutants such as polarity, volatility, and molecular
The amounts of simulated pollutants contained in the contamination-pretreated paper samples were analyzed, and results are shown in Table 2. 80
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
weight of the organic pollutant itself were concluded to greatly influence the migration performance, and these two were the factors that most strongly affected migration performance. Molecular polarity, contact time, and temperature had weaker effects. Safety control recommendations for the migration of organic contaminants to dry powdered foods in paper-based packaging materials. The above analysis revealed that in paper-based packaging materials, the migration of organic pollutants into packaged dry powdered food was affected by internal (molecular weight, volatile, and molecular polarity of organic pollutants) and external (contact time and temperature) factors. Among them, volatile and molecular weight of organic pollutants had the greatest influence on migration performance, whereas temperature had the least influence. In general, the species with lower molecular weight are more volatile, which causes their more loss to the environment, especially at higher temperatures. Therefore, the temperature effect to their migration to food is more significant than the lower volatile species (with higher molecular weights). Accordingly, in the processing, transport, and storage of powdered foods in paper-based packaging, the migration of organic pollutants into the packaged foods decreased with decreased of contact time and ambient temperature. Moreover, because some aspects of food packaging materials such as printing and decorating were indispensable, some organic pollutants were necessary for the presentation of certain effects. During material processing, using substances with good volatile for food packaging can ensure that these organic contaminants were volatilized from the paper-based packaging material prior to packaging processing. Alternatively, using large-molecularweight substances can ensure that throughout the entire process of packaging, transport, and storage, a minimum amount migration of these organic contaminants into the packaged food and reduced the contamination of the food itself caused by food packaging.
weight) factors. However, the influence of each factor on the migration performance was mutually. Consequently, the establishment of an accurate quantitative relationship between a certain factor and migration performance was difficult. Thus, analysis of the comprehensive effect of various influencing factors on the migration performance of simulated pollutants, as well as the specific circumstances of the effects of various influencing factors, can targeted control the migration of organic pollutants from paper-based food packaging materials to the packaged foods with a good guidance function. 3.5. Effects of various factors on PLS analysis Migration percentage is an important indicator used to characterize the degree of migration of pollutants from packaging material to food during studies on migration kinetics. To understand the influence of temperature, contact time, molecular weight, volatile, and molecular polarity of pollutants on the migration of simulated pollutants from paper-based packaging material to food, SIMCA-P statistical analysis software was used to perform coefficient analysis on our data. A standardized PLS regression model coefficient diagram was obtained, as shown in Fig. 4. The coefficient equation was as follows:
Migration percentage % = 0.073 temperature + 0.209 contact time –0.185 molecular polarity–0.792 volatile–1.075 molecular weight The model showed that changes in temperature and contact time were positively correlated with migration performance, whereas volatile, molecular weight, molecular polarity of organic pollutants were negatively correlated. In other words, increased temperature and prolonged contact time meant higher migration percentage of organic pollutants to food, while stronger molecular polarity, greater volatile, and higher molecular weight of organic pollutants meant lower migration percentage to food. The values of the coefficients (of each factor in this model) indicate that the losses of migration percentage to food for the given organic pollutant caused by the volatilization is greater than the increment caused by elevating the temperature. These results are consistent with the above analysis of migration behavior for both phenol and alkylbenzene.
4. Conclusion 1. In the case of the same paper packaging material and with rice flour as a food simulant, the migration behavior of each simulated pollutant was affected by the following factors: temperature, contact time, and nature of pollutant (e.g., molecular weight, molecular polarity, and volatile). Among them, temperature and contact time had a positive effect on migration, whereas volatile, molecular weight, and molecular polarity of organic pollutant had a negative effect. 2. Under the same conditions of paper packaging materials, the characteristics (volatile and molecular weight) of the simulated pollutants had a strong impact on migration performance, whereas external factors (contact time and temperature) had a weaker effect. 3. During the production and processing of paper food packaging, due to the necessity of using certain substances, those with high volatile or molecular weight can ensure quality of the entire packaging throughout transport and storage. During the process, the degree of migration of organic pollutants to the packaged food can be minimized to decrease the risk of contamination of the food caused by the package itself.
3.5.1. Analysis of PLS regression accuracy The above PLS components were extracted, and a total of four principal components were extracted. The explanatory power of these four components for X was 0.91, and the explanatory power for Y was 0.369. Overall, the explanatory power was relatively strong. The crossvalidity Q2 was 0.362, and the critical value was 0.097 (0.362 > 0.097 was relatively high). These data indicated that the constructed model was reasonable. 3.5.2. Correlation analysis Fig. 5 is the t/u floor plan drawn between the principal component t extracted from independent variable X and u extracted from dependent variable Y. A good linear relationship existed between t and u, so X and Y were significantly correlated He and Liu, 2015. Thus, the linear model of Y vs. X established by PLS regression was reasonable.
Funding This project was funded by the 2016 Guangdong Province General Colleges and Universities Characteristic Innovative Project (Project Number: 2016KTSCX176).
3.5.3. Weight analysis Fig. 6 shows the importance (VIP value) of variable projections in explaining migration performance using PLS analysis to analyze the migration behavior data measured in the above experiments. The VIP values of the five factors were relatively large, in which the volatile and the molecular weight of the organic pollutant on the migration performance were greater than 1. The VIP value of molecular polarity, contact time, and temperature affecting the migration performance was between 0.5 and 1. According to the VIP value of the effect of each influencing factor on migration performance, the volatile and molecular
References Anon 1 http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri= CONSLEG:1985L0572:20070420:EN:PDF. Anon 2 www.euchinawto.org. Asensio, E., 2002, 22 November. Title: [Dissertation]. University of Zaragoza, Spain.
81
Journal of Food Engineering 262 (2019) 75–82
M. Xue, et al.
Nerín, C., Contín, E., Asensio, E., 2007. Kinetic migration studies using Porapak as solidfood simulant to assess the safety of paper and board as food-packaging materials. Anal. Bioanal. Chem. 387, 2283–2288. Poças, M.F., Oliveira, J.C., Pereira, J.R., et al., 2010. Consumer exposure to phthalates from paoer packaging: an integrated approach. Food Addit. Contam. 27 (10), 1451–1459. EU Project CT 98-4318, 2002. Programme on the recyclability of food packaging materials with respect to food safety consideration-polyethylene terephthalate (PET), paper and board and plastic covered by functional barriers. EU Regulations and Guidances on Food Contact Materials. Sturaro, A., Parvoli, G., Rella, S., et al., 1994. Food Contamination bydiisopropylnaphthalene from cardboard packages. Int. J. Food Sci. Technol. 29, 593–603. Triantafyllou, Vasileios I., Akrida-Demertzi, Konstantoula, Demertzis, Panagiotis G., 2002. Migration studies from recycled paper packaging materials: development of an analytical method for rapid testing. Anal. Chim. Acta 467, 253–260. Triantafyllou, Vasileios I., Akrida-Demertzi, Konstantoula, Demertzis, Panagiotis G., 2005. Determination of partition behavior of organic surrogate between paperboard packaging materials and air. J. Chromatogr. A 1077, 74–79. Triantafyllou, Vasileios I., Akrida-Demertzi, Konstantoula, Demertzis, Panagiotis G., 2006. A study on the migration of organic pollutants from recycled paperboard packaging materials to solid food matrices. Food Chem. 1, 1–10. Wold, H., 1982. Soft modeling: the basic design and some extensions[A]. K G J Reskog H Wold, Systems under Indirect Observation [C]. Amsterdam, North- Holland, pp. 1–54. Wold, H., 1985. Partial least squares [A]. In: Kotz S Johnson N L. Encyclopedia of Statistical Science [M] 6. John Wiley & Sons, New York, pp. 581–591. Xu, Y., Noonan, G.O., Begley, T.H., 2013. Migration of perfluoroalkyl acids from food packaging to food simulants. Food Addit. Contam. 30 (5), 899–908. Xue, Meigui, Wang, Shuangfei, 2012. Selection of solid food simulants for migration test from paper food packaging materials. Packag. Eng. 33 (21), 51–56.
Aurela, B., Kulmala, H., Söderhjelm, L., 1999. Phthalates in paper and board packaging and their migration into Tenax and sugar. Food Addit. Contam. 16 (12), 571–577. Aurela, B., Ohra-aho, T., Soderhjelm, L., 2001. Migration of alkylbenzenes from packaging into food and Tenax. Packag. Technol. Sci. 14, 71–77. Binderup, M.L., Pedersen, G.A., Vinggaard, A.M., et al., 2002. Toxicity testing and chemical analyses of recycled fibre-based paper for food contact. Food Addit. Contam. 19 (Suppl. 1), 13–28. Boccacci Mariani, M., Chiaccherini, E., Gesumundo, C., 1999. Potential migration of Diisopropyl naphthalenes from recycled paperboard packaging into dry foods. Food Addit. Contam. 16 (5), 207–213. Bradley, E.L., Castle, L., Speck, D.R., 2014. Model studies of migration from paper and board into fruit and vegetables and into Tenax as a food simulant. Food Addit. Contam. A 31 (7), 1301–1309. MAFF, Jaunary, 1999. Diisopropylnaphthalenes in Food Packaging made from Recycled Paper and Board. Food Surveillance Information Sheet, No 169. . Grob, Koni, Pfenninger, Susanne, Pohl, Wolfgang, et al., 2007. European legal limits for migration from food packaging materials:1. Food should prevail over simulants; 2. More realistic conversion from concentrations to limits per surface area. PVC cling films in contact with cheese as an example. Food Control 18 (3), 201–210. He, Xiaoqun, Liu, Wenqing, 2015. Applied Regression Analysis [M]. Renmin University of China Press. Honkalampi-Hämäläinen, U., Bradley, E.L., Castle, L., et al., 2010. Safety evaluation of food contact paper and board using chemical tests and in vitro bioassays: role of known and unknown substances. Food Addit. Contam. 27 (3), 406–415. Johns, S.M., Gramshaw, J.W., Castle, L., et al., 1995. Studies on functional barriers to migration, 1.Transfer of benzophenone from printed paperboard to microwaved food. Dtsch. Lebensm.-Rundsch. 3, 69–73. Lorenzini, R., Biedermann, M., Grob, K., et al., 2013. Migration kinetics of mineral oil hydrocarbons from recycled paperboard to dry food: monitoring of two real cases. Food Addit. Contam. 30 (4), 760–770. Nerín, C., Asensio, E., 2004. Behaviour of organic pollutants in paper and board samples intended to be in contact with food. Analytical Chimmica Acta 508, 185–191.
82