Oxygen Permeability Of Films Research Articles

Oxygen Permeability and Mechanical Properties of Films from Hydrolyzed Whey Protein

The effects of whey protein hydrolysis on film oxygen permeability (OP) and mechanical properties at several glycerol-plasticizer levels were studied. Both 5.5% and 10% degree of hydrolysis (DH) whey protein isolate (WPI) had significant effect (p </= 0.05) on film tensile properties compared to unhydrolyzed WPI. Hydrolyzed WPI required less glycerol to achieve the same mechanical properties compared to those of unhydrolyzed WPI. Little or no significant difference (p > 0.05) occurred for film OP between unhydrolyzed WPI, 5.5% DH WPI, and 10% DH WPI films at the same glycerol content. Hydrolyzed WPI films of mechanical properties similar to those of WPI films had better oxygen barrier. Therefore, use of hydrolyzed WPI allowed achievement of desired film flexibility with less glycerol and with smaller increase in OP.

Oxygen permeability in polymers, III. Dependence of the oxygen permeability on the chemical structure of styrene‐maleic acid‐copolymers

AbstractThe paper gives a report on the oxygen permeability in films of poly(styrene‐comaleic acid) halfesters and halfamides as well as other polymers containing carboxylic groups in comparison with commercially available glass forming polymers at room temperature. The presence of oxygen in the polymer layers was proved by the quenching of the delayed fluorescence of pyronin B. The permeability of the halfesters/halfamides (Pox = 2…7.10‐14 cm2/Pa .s) corresponds to that of common polymers like poly(methyl methacrylate) (PMMA) or poly(vinyl acetate) (PVAc), and is nearly one order of magnitude higher than that of poly(acrylic acid) (PAAc), poly(styrene‐comaleic acid) (SMAc) and carboxymethylcellulose (CMC). Presumably, intramolecular hydrogen bonds in the halfester/halfamides compete successfully with the intermolecular interactions and hence cause an increase in permeability as also do bulky substituents. Addition of bases like dimethyl aminopropanol (DMAP) and dimethyl aminopropyl acrylamide (DMAPAA) decreases the permeability to about 1/40 of the initial value. The permeability is then similar to the low permeability of polymers with predominant ionic interaction sodium polyacrylate (NaPAAC), sodium carboxymethylcellulose (NaCMC)).

Electron‐beam irradiation‐induced grafting of acrylonitrile onto polyethylene

AbstractLow‐ and high‐density polyethylene (PE) films were grafted with acrylonitrile (AN) by electron beam prior to irradiation. The distribution of graft chains over the cross section of the sample film was analyzed in terms of the distribution of nitrogen atoms contained in the AN by means of an electron probe microanalyzer (EPMA), and graft sites were studied in relation to the effect of grafting temperature on the percent graft and the oxygen permeability of the sample films. It was found that diffusion of AN into the film was the rate‐limiting step in the grafting process, thus restricting the grafting to the surface of the film in the initial grafting stages. However, the grafting shifted to the center of film as the graft process proceeded, until a uniform distribution of graft chains was observed across the entire film thickness. High‐density polyethylene (HDPE) was found to display a higher percent graft than did low‐density polyethylene (LDPE), and percent graft tended to increase with increasing grafting temperature. On the other hand, film oxygen permeability decreased with increasing percent graft, but this decreasing trend decreased with increasing percent graft. These findings suggest that the grafting is initiated by radicals trapped in the amorphous phase near the crystalline regions and at the surface of crystallites and that graft chains grow toward the amorphous regions. As for the radicals contributing to graft polymerization, it appears that AN permeates deeper near the crystalline surface and that graft chains grow from these sites.

Measurement of the permeability of chilled meat packaging film under conditions of high humidity

SummaryModifications to the American Society for Testing and Materials standard method (D1434) for the determination of film oxygen permeability are described. The method gives results consistent with published data and allows the measurement of permeability under likely food storage humidity conditions.It is recommended that the permeability of hydrophilic materials used for meat packaging should be measured at 100% relative humidity (RH) to permit adequate comparison with other films.

Influence of some preservatives on the quality of prepacked cod fillets in relation to the oxygen permeability of the film.

Summary: The deterioration of prepacked cod fillets in relation to different concentrations of citric acid (HC) and of potassium sorbate (PS) was studied bacteriologically and chemically. Spoilage of fish treated with PS in relation to the oxygen permeability (OP) of the polyethylene film was also examined. The trimethylamine (TMA) and formalin bound nitrogen compounds (FBN) formation at 0° in prepacked cod fillets is inhibited by the addition of HC and PS. A concentration of 0·4% of PS in the cod fillets is sufficient to inhibit the TMA production completely. The OP of the film determines the keeping quality of the cod fillets containing 0·4% of PS. The film with the lowest OP gives the best results, since the spoilage of PS treated fish during the first 12 days is exclusively caused by an increase of FBN. The formation of this fraction at 0° is related directly to the OP of the packing film. From the experiments with PS treated cod fillets it can be deduced that a film with a low OP gives the best results.

Microbiological changes in prepacked cod fillets in relation to the oxygen permeability of the film.

The deterioration of prepacked cod fillets in relation to the oxygen permeability of the polyethylene film was studied bacteriologically and chemically. Spoilage at 0° is not related directly to oxygen permeability (OP). The deterioration curve at higher storage temperatures (3 and 6°) is of the same form as the curve at 0°. Moreover, from the curve it can be deduced that a film with c. 3600 ml/m2/24 h OP gives the best results. A maximum spoilage is observed with an OP c. 1800 ml/m2/24 h. Identical results were obtained with other films. The formation of formalin bound volatile nitrogen compounds is inhibited in prepacked fish whereas the trimethylamine content increases.

The use of an oxidation-reduction indicator to compare the oxygen permeabilities of films for rindless cheese

Slices and blocks of cheese were coloured with aqueous methylene blue solution and vacuum-packed or wrapped in the films to be compared. The extent of bleaching of the dye after 14 days gave a good indication of the extent to which oxygen was excluded by the film. Similar results were obtained with vacuum-packed slices and with wrapped rindless cheeses.With polythene-coated and wax-coated MSAT cellophane films there was little or no reduction of methylene blue on the cheese surface. Similar films, including a lamination of foil or MXXT cellophane, allowed complete or almost complete bleaching.