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W Freytag

Publications and source records attributed to W Freytag.

6 recordsLinked to original sources
PubMed1984

Transfer of additives from plastics materials into foodstuffs and into food simulants--a comparison.

The transfer of stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate from high- and low-density polyethylenes and polypropylene as well as that of n-butyl stearate from high-impact polystyrene into several foodstuffs and into different food simulants under normal storage conditions was determined radioanalytically. Additionally, the transfer of these additives into the food simulants under the standard conditions usually requested by the authorities was determined. From these figures 'correction factors' were calculated, relating the amounts of additives transferred from the plastics materials into the foodstuffs under normal conditions of storage to the transfer of these additives from the test specimens into food simulants (e.g. olive oil and HB 307) under the standard test condition of exposure at 40 degrees C for 10 days.

Butylated Hydroxytoluene↗
PubMed1984

Structural organization of (Na+ + K+)-ATPase in purified membranes.

The structural organization of crystalline, membrane-bound (Na+ + K+)-ATPase was studied by negative staining and thin sectioning. The enzyme molecules were induced to form crystalline arrays within fragments of membrane by incubation in defined ionic conditions. The enzyme remained fully active after crystallization. Negative staining and computer processing of images of the crystalline specimens identified two discrete crystalline arrays. The dimensions of the unit cell of one of the arrays were large enough to accommodate an alpha beta protomer; those of the other array, an (alpha beta)2 diprotomer . Thin sections of the crystalline fraction contained a unique membrane complex that was formed from two apposed plasma membranes. The paired membranes in this complex were separated by a center-to-center space of 15 nm containing evenly spaced septa that connected the membrane surfaces; the overall thickness of the entire structure was 22-25 nm. The agglutinin from Ricinus communis, a lectin that binds to the carbohydrate moiety of the beta-subunit of (Na+ + K+)-ATPase, decorated the free surfaces of the complex. Therefore, this complex of paired membranes is the result of interactions between the cytoplasmic domains of the enzyme. From measurements of the dimensions of these structures, we estimate the overall length of the enzyme to be approximately 11.5 nm along the axis perpendicular to the plane of the membrane, and the molecular protrudes more (approximately 5 nm) on the cytoplasmic surface than on the extracytoplasmic surface (approximately 2 nm).

Animals↗
PubMedDate not supplied

Additive migration from various plastics with different processing or properties into test fat HB 307.

The migration of the antioxidant n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate from various plastics into the test fat HB 307 was investigated. Plastics from the following classes were included: high-impact polystyrene (HIPS), polypropylene (PP), high- and low-density polyethylene (HDPE and LDPE), and were found to have distinctly different properties--in particular, different densities, melt flow indices and structural characteristics. Each plastic was processed into test specimens such as pressed and extruded sheets, injection-moulded cups, deep-drawn tubs and blown bottles. The migration out of these specimens was investigated under identical test conditions. The results confirm that the amounts of additive migrating from the different classes of plastics into test fat HB 307 in general decrease in the order LDPE greater than HDPE greater than PP greater than HIPS. Moreover, it seems to be of great importance that the respective amounts of additive migrating from the injection-moulded cups, deep-drawn tubs and blown bottles into test fat were significantly lower in all cases than those from the corresponding pressed or extruded sheets. Presumably, this effect is mainly caused by orientation of the polymer molecules in the injection-moulded, deep-drawn or blown products. It is concluded that the migration of the antioxidant decreases with increasing density of the polymer and that the melt flow index (molecular weight) has hardly any influence. Migration from HIPS into fat increases with the content of impact modifier. In the case of the polyethylenes, the influence of processing on the migration rate decreases with decreasing density of the polymer.

Antioxidants↗