Jack R. Giacin

Antioxidant ability of BHT‐ and α‐tocopherol‐impregnated LDPE film in packaging of oatmeal

Cereals in general, and particularly oatmeals, are considered rather sensitive to oxidation owing to their relatively high fat content. The addition of antioxidants can sometimes prolong the shelf-life of products. The aim of the present study was to investigate how the rate of lipid oxidation of a packaged oatmeal product was affected by the nature and level of antioxidants incorporated in an LDPE film structure. The stability of the product, which was determined by hexanal analysis using GC–MS and by electronic nose analysis, showed very small variations over the chosen storage period. No oxidation, as determined by hexanal levels in the oatmeal, was initiated during storage, but small variations in volatile profile were seen among the samples analysed by the electronic nose. The product stored in the BHT-impregnated LDPE film had undergone the least change during 10 weeks of storage at 20 °C. α-Tocopherol-impregnated LDPE film did not appear to prolong the shelf-life of the oatmeal at all. © 2000 Society of Chemical Industry

The sorption of water vapor by an amorphous polyamide

Abstract A modified dual-mode sorption model represents the sorption of water vapor by an amorphous polyamide at 23 °C. The Langmuir equation is used to calculate the volume fraction of chemisorbed solute and the Flory-Huggins equation is used instead of Henrys law to calculate the volume fraction of water which is not chemisorbed. This model describes the data over a range of water activities from zero to one and predicts clustering of the sorbant. Fourier Transform Infrared (FTIR) spectroscopy data and dielectric measurements of the gamma relaxation temperature suggest that the water associates with amide groups at low water activities.

The Evaluation of the Aroma Barrier Properties of Polymer Films

HE SHIFT FROM ABSOLUTE BARRIER TYPE PACKAGES, SUCH AS CANS AND bottles, to semi-permeable polymeric packaging systems has created a need to develop a better understanding of the transport of gases, vapors, and other low molecular weight moieties through polymer films. The transport of permeants such as oxygen, carbon dioxide and water vapor through polymer structures has been the subject of numerous investigations, and standard test methods are available for determining transmission rates for these permeants (ASTM E96-66, ASTM D3985-81). In contrast, while the transport of organic penetrants through packaging materials has been the subject of several recent investigations, there is a paucity of data available in this area. This paper will, therefore, focus on the various procedures developed for quantifying the rate of diffusion of organic penetrants through barrier membranes and describe in detail the specific procedures employed in the studies reported. Pye, et al. (1976) described a continuous or isostatic procedure for measuring the diffusivity properties of polymer membranes that employed two gas chromatographs connected to a cell. One chromatograph was equipped with

A determination of solubility coefficient values determined by gravimetric and isostatic permeability techniques

The solubility coefficient (s) values for ethyl acetate in three heat sealant polymer membranes (LDPE, LLDPE and ionomer) were determined over a range of permeant vapour concentrations by a gravimetric procedure and an isostatic permeability technique. The respective solubility coefficient values obtained by the two methods were found to be in good agreement, with no statistically significant difference observed as a function of vapour activity. This agreement suggests that the solubility coefficient values obtained were independent of permeant vapour activity, and the sorption process followed a Henrys law relationship over the vapour concentration range evaluated. Comparison of the solubility coefficient values obtained by the gravimetric and isostatic permeability techniques showed reasonably good agreement over the vapour concentration range considered, with the S values obtained from permeability experiments being approximately 25% higher than those obtained from sorption measurements. Because of the procedural differences between the gravimetric and isostatic permeability techniques, this agreement is considered to be within acceptable limits. For the gravimetric technique, the solubility coefficient value is determined directly from the steady-state portion of the sorption profile curve, while the solubility coefficient value obtained from the permeability experiment is derived from transient state data. Copyright

The Effect of Water Activity and Penetrant Vapor Activity On the Permeation of Toluene Vapor Through a Two-Side Pvdc Coated Opaque Oriented Polypropylene Film

The permeance of toluene vapor through an oriented polypro pylene film coated with a copolymer of vinylidene chloride (PVDC) was evalu ated as a function of water activity and penetrant vapor concentration. It was found that the value of permeance increased as both toluene and water activity increased. Toluene permeance values exhibited a strong dependency on toluene vapor concentration. This concentration dependency was shown to be less intense at high water activity values. Similarly, the effect of water activity-at a specified toluene concentration-on the permeance of toluene diminished as the values of permeant concentration increased. These results illustrate the complex rela tionship of penetrant vapor concentration and water activity on organic vapor permeability through a multilayer structure.

Effect of Flavor Sorption On Adhesive and Cohesive Bond Strengths in Laminations

The effect of sorption of flavor volatiles on the adhesive and cohesive bond strength of multilayer laminations was investigated. Two polyester/polyolefin adhesive laminates coated with a polyvinylidene chloride-polyvinylchloride copoly mer were surface-exposed to lemon juice and a hot sauce product, as well as to food simulant systems at 45°C. Sorption of flavor volatiles resulted in delamination of both laminates following exposure to the respective food products. A Dynamic Headspace Concentrator, interfaced with Capillary Gas Chromatography, identified d-limonene as the primary component sorbed by the laminates upon exposure to lemon juice. Us ing Electron Spectroscopy for Chemical Analysis and Scanning Election Microscopy, adhesive bond failure with the linear low density polyethylene (LLDPE) laminate was identified, while cohesive bond failure occurred within the ethylene vinyl ace tate copolymer (EVA) laminate Bond strength was quantified using a peel test Sig nificant reductions in bond strength occurred upon exposure to the food products.

Isostatic and Quasi-Isostatic Methods for Determining the Permeability of Organic Vapors Through Barrier Membranes

Two test methods have been developed which provide quantitative and reliable values for the rate of diffusion of organic vapors through polymer membranes. Method I is based on a quasi-isostatic procedure and utilizes gas chromatography analysis for quantifying the amount of organic vapor that has permeated through the membrane. The permeability of a number of permeant/polymer membrane combinations was determined by this method, with studies being carried out at constant temperature and with varying permeant concentrations. The effect of permeant concentration on the permeability rate, P, permeability constant, P, the apparent diffusion coefficient, D a , and the limiting diffusion coefficient, D 0 , was determined for the diffusion of toluene vapor through oriented polypropylene, Saran, and a Saran-coated oriented polypropylene structure. Method II involved an isostatic procedure, in which a constant and low concentration of permeant is flowed through the upper cell chamber of a permeability cell. Simultaneously, nitrogen carrier gas (N 2 ) of a known flow rate is continually passed through the lower cell chamber of the permeability cell and is conveyed to a gas chromatograph by means of a computer-aided gas sampling valve. The methods developed allow determination of the diffusion of organic aroma constituents through barrier membranes under defined conditions including (1) temperature, (2) permeant concentration, (3) membrane thickness, (4) polymer morphology (percent crystallinity), and, (5) polymer thermal mechanical history (that is, degree orientation), and they will have significant utility in evaluating plastic packaging material for food packaging, particularly as plastics are showing increased usefulness as packaging for fresh and processed food products.

Evaluating the Effect of Temperature and Vapor Concentration on the Organic Vapor Barrier Properties of Polymer Membranes by an Isostatic Procedure

The present study describes the permeability of selected organic vapors through a series of commercially available polymeric films utilizing the MAS Technology Model 2000 Permeability test system and considers the concentration and temperature dependency of the mass transfer process, as well as the application of the Arrhenius expression for estimating permeability coefficient values for high barrier polymer structures. In addition to determining the permeability and diffusion coefficient values, a consistency analysis was performed on experimental permeability data to establish variation in system parameters and to provide a better understanding of the mechanism of the diffusion and sorption processes associated with the permeation process.

Analytical measurements of package components for unintentional migrants

The results of selected studies dealing with the transfer or migration of indirect additives from food contact materials to foodstuffs and/or their appropriate simulants have been reviewed in terms of the polymeric packaging material or packaging article, specific migrant, nature of the contact phase, level of migrant transferred under the conditions of test, and the analytical method employed to monitor com positional changes. The references presented on the analytical procedures developed for quantitation of migrated species are intended as a guide to the literature, where only representative studies have been reviewed.

Permeation of Ethyl Acetate Vapor Through Silica Deposited Polyethylene Terephthalate Film and Composite Structures

The effect of temperature and relative humidity on the permea tion of ethyl acetate vapor through silica deposited polyethylene terephthalate film (SiOx PET) and composite structures was studied by a quasi-isostatic proce dure. For comparison, the permeation of ethyl acetate vapor through an ethyl ene/vinyl alcohol copolymer (EVOH), and an EVOH laminate structure was also determined. Permeability studies were carried out at 50, 65 and 76 ° C with a constant vapor concentration of 300 μg/cc (mass/volume). Results of permeation studies at 65 ° C showed that the transmission profile curve of the EVOH film followed typical Fickian behavior, while the SiOx PET film exhibited atypical behavior during the initial transport period. For the first 24 hours, permeation through SiOx PET was not detectable. Following this initial induction period, a significant increase in the transmission rate was observed; and after 96 hours, mass transport was at steady state. At steady state, the rate of permeation through the SiOx PET was lower than that of the EVOH film. SiOx PET film showed relatively high temperature dependence (Ep = 22.1 kcal/mole) and a low transmission rate. PET also showed relatively high tem perature dependence (23.2 kcal/mole). Based on the activation energy, the EVOH film exhibited very significant temperature dependency (Ep = 48.8 kcal/mole). In over 500 hours of continuous testing, there was no measurable permeation of ethyl acetate vapor through the SiOx PET and EVOH films at 22°C, 56% RH. However, at 87% RH, the EVOH film exhibited a permeation rate of 3.14 x 10-11 kg/m 2·sec for ethyl acetate vapor, while the SiOx PET film was not influenced by sorbed water vapor and showed no measurable permeation of the organic permeant. Analysis by optical microscopy on the SiOx surface showed no effect of temper ature on the structural integrity of the SiOx coating, as evidenced by the absence of cracks or crazing of the SiO x coating. While the functional role of the silica coating is not fully understood, the following mechanism is proposed. For the silica deposited PET film, the barrier properties of the structure are governed by defects, non-homogeneity of both the surface coating thickness and composition, or preferential diffusion paths-all of which can contribute to the observed permeability rates. The permeability of the polymer layers imme diately adjacent to the silica coating are thus critical in determining the effect of such defects.