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AIUson, D. W.; 08bourn, D. F. J. Agric. Sci. 1970, 74, 23-26. Chem. €ng. &.pt 12, 1960, 51. Fahle, D. W. M.S. Thesis. Texas Tech Unlverslty, Lubbock, Texas 1978. Harrls. L. E. “Nutrftlon Research Techniques for Domestic and Wkl Animals”; L. E. Harris: Logan, Utah, 1970; Vol. 1. Katal, A.; Schuerch, C. J . Pdym. Sci.: Part A - 1 1966, 4 , 2883-2703. Kiryrlshina, M. F.; Tishchenko. D. V. UDC 674.03, 542.943.5, Consultants Bureau; Plenum Publishing Corp.: New York, 1971. Lantlcan. D. M. Ind. Eng. Chem. Rod. Res. Dev. 1965, 2, 86-70. McCarthy, D. E.; Rlchardson, C. R.; Albln, R. C. Second Chemlcal Congress of the North American Continent, Las Vegas. NV, Aug 1980; American Chemlcai Society: Washlngton. D. C.; Abstr. CELL 121. Millet, M. A.; Baker, A. J.; Satter, R. D. Cellul. Tech. Res. 1975, 6 . 75-105. Moore. W. E.; Effland. M.; Slnha. E.; Bwdick, M. P.; Schuerch, C. TapplI966, 49(5), 206-209. Parker, H. W.; Albln, R. C.; Vernor, T. E.; Fahle, D. W. ”Thermochemlcal Modification of Mesqulte for Rumlnant Rations”; Second Pacific Chemical Engineering Conference, Denver, CO, 1977.
Parker, H. W.; Vernor, T. E.; AIMn, R. C.; Shenod, L. 6.; Summers, C. A. “In Vitro Evaluatlon of Thetmochemlcally Modified Mesquite”; Annual Meeting of the Southern Mvlsion, American Society of Animal Science, Atlanta, GA, Feb 6-9, 1977. Richardson, C. R.; Runte, M. M.; Chang. J.; Tock. R. W.; Horton, J. M. “Ozone and Sulfur Dioxide Treated Mesquite for Orowlng Lambs”; Southern Section, J. Anlm. Scl., Atlanta, GA, 1961. Schuerch, C. J. polvm. Sci., Perf C 1963, 2, 79-95. Sherrod, L. D.; Summers, C. B. h o c . West. Sect., Am. SOC.A n h . Sci. 1974, 25, 358. Tock, R. W.; Parker, H. W.; Rlchardson, C. R. “Pilot Plant Production of a Ruminant Ratkm from S u b Dfoxide-Treated Mesquite”; Texas Tech University. Lubbock, Texas, unpublished data. 1981. Vernor, T. E. M.S. Thesls, Texas Tech Unlversity, Lubbock, Texas 1977.
Received for review July 27, 1981 Accepted October 26, 1981
Migration of BHT Antioxidant from High Density Polyethylene to Foods and Food Simulants Derek E. VII, Danlel J. EhnthoH, Robert C. Reid,’‘ Patrlcla S. Schwarlr,* Kenneth R. Sldman, Arthur D. Schwope, and Richard H. Whelan Arthur D. Llitle, Inc., Acorn Park, Cambrhlge, Massachusetts 02140
The migration of the antioxidant BHT from high density polyethylene (HDPE) was measured in a variety of foods and food simulants. Most slmulant tests were conducted at 40 ‘C,but a few studies were carried out at either 4 or 21 OC to agree with normal food storage conditions. In most instances, the mlgratbn-time data were well correlated by analytical models that assumed the rate-controlling resistance was the diffusion of BHT within the polymer. These models also allowed the estimation of characteristic diffusion coefficients for BHT in HDPE. These diffusion coefficients increased with temperature and depended upon the food/simulant used. Migration was more rapid to 011s and fatty foods than to aqueous materials. Two tests with dry foods, milk and soup mix, led to high migration values.
Part of the mandate of the Food and Drug Administration (FDA) is to ensure that toxic substances are not transferred from packaging materials to food products. Packaging materials based on polymer systems may contain monomers or oligomers from the polymerization process, and antioxidants or other deliberately added species (adjuvants) that are necessary in order to convert the raw polymer to a suitable food packaging material. The detection in food of low levels of these potentially migrant species presents extremely difficult analytical problems. Furthermore, food may be exposed in some packages for long periods of time. For these reasons, it is current practice under FDA guidelines to conduct experiments in which packaging materials are exposed to food simulants at elevated temperatures, thereby permitting the extent of migration to be estimated in a shorter time. This paper summarizes the results of an investigation of the migration of the antioxidant BHT (3,5-di-tert-butyl-4-hydroxytoluene) from HDPE (high density polyethylene) to foods and food simulants. HDPE is widely used for food packaging. The largest single use is in milk bottles and closures. Other applications include packages for edible oils and salad dressings, margarine, frozen desserts and toppings, and institutional Department of Chemical Engineering,Massachusetts Institute of Technology, Cambridge, MA 02139. *Food and Drug Administration, Washington, DC 20204. 0196-4321/82/1221-0106$01.25/0
packs for pickles and shortening. The objective of this study was to develop correlations between the BHT migration measured in foods and those determined with food simulants. Because of the wide variety and complexity of the foods studied, it was found to be necessary to make several simplifying assumptions in order to obtain approximate, but useful, correlations. For example, many of the foods and simulants contain ingredients that would be expected to penetrate HDPE and thereby modify the resulting mobility of BHT within the polymer. There is evidence to indicate that penetration occurs as a Fickian wave with a velocity proportional to t1/2(Figge and Rudolph, 1979). As Knibbe (1971) and Rudolph (1979,1980) have shown, for Fickian penetration of the food or simulant, the migrant has a characteristic diffusivity which is independent of time, position, and concentration of either the migrant or penetrant. This characteristic diffusivity may, however, be significantly different from the intrinsic diffusivity of the migrant in the penetrant-free polymer. In effect, therefore, we have assumed that BHT has an effective diffusion coefficient in HDPE which does not vary with extraction time but is a function of temperature and, possibly, of the food/simulant used. We have also assumed that, for all fluid foods and simulants, there is no significant mass transfer resistance in the fluid phase. The validity of this assertion is not based on actual experimental evidence but rather on estimated mass transfer coefficients with experimentally determined BHT diffusivities and the models developed to test the 0 1982 American Chemical Soclety
Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 1, 1982 107
significance of external phase resistance (Reid et al., 1980). In most experiments involving a well-mixed external phase, the food/simulant behaved as an infinite sink for BHT. Then, for the highly simplified situation where BHT has a constant diffusivity (D,) in the HDPE, and there are no external mass transfer effects of equilibrium partitioning, the solution to Fick's second law leads to an expression for the total BHT lost to the food or simulant per unit area, M,, at time t.
with qn = (2n - 1) 7r/2
(2)
$ = Dpt/L2
(3)
L is the half-thickness of the HDPE plaque for the twosided extraction used in this study. C , is the initial BHT concentration in the plaque, assumed to be constant over the plaque thickness. For cases in which the dimensionless group D,t/L2 is very small (
