Mathematical modeling of gallic acid release from chitosan films with grape seed extract and carvacrol

Controlled release of antimicrobial and antioxidant compounds from packaging films is of utmost importance for extending the shelf-life of perishable foods. This study focused on the mathematical modeling of gallic acid release into an aqueous medium from three chitosan films, formulated with grape seed extract (GSE) and carvacrol. We quantified the release by HPLC technique during 30days at three temperatures (5, 25 and 45°C). The diffusion coefficients, varying with temperature according to an Arrhenius-type relationship, and the respective activation energies for Film-1 and Film-2 were, respectively [Formula: see text] m2s-1 and [Formula: see text] m2s-1, Ea1=58kJmol-1 and Ea2=60kJmol-1 as obtained from the Fickian fit. The low concentrations of gallic acid released by Film-3 could not be detected by HPLC, therefore the respective diffusion coefficient was not estimated. This study will help with the development and optimization of active packaging (AP) films aiming at improved food preservation and shelf-life extension.Javiera F. Rubilar gratefully acknowledges her Ph.D. grant from ErasmusMundus 2008-1022/001 Frame ECW/17, EACEA(European Union), financial support of the Fondecyt-Postdoctoral #3140349 project from CONICYT, and also “Dirección de Investigación e Innovación Escuela de Ingeniería” at Pontificia Universidad Católica de Chile. Rui M. S. Cruz acknowledges grant SFRH/BPD/70036/2010 from Fundac¸ ão para a Ciência e Tecnologia, Portugalinfo:eu-repo/semantics/publishedVersio

Release of additives from packaging plastics

Keywords : migration, diffusion, additives, polymer, low density polyethylene, polymer swelling, Fick, stochastic modellingThe diffusion of small molecules from polymers into food is studied. A better understanding of this process is important for the development of mathematical models to predict migration from packaging plastics into food. To study the effect of food absorption by the plastic on diffusion, the simultaneous diffusion of a migrant (Irganox 1076) and a solvent in low density polyethylene (LDPE) were measured. The migrant diffuses out of the polymer, while the solvent is diffusing inwards. For solvents with low molar mass the diffusion coefficient of Irganox 1076 increases with increasing solvent uptake. No increase in diffusion coefficient was found upon uptake of tri-glycerides such as olive oil. A method using microtoming and GC-analysis is tested for the measurement of migrant concentration profiles inside the polymer. The diffusion of Irganox 1076 and solvent in LDPE have been measured as a function of time. The Fick equation with a migrant diffusivity depending on the solvent concentration gives a good description of the results for isooctane and n -heptane. The description is less good for the measurements with cyclohexane (when the polymer swells strongly). The use of predictive modelling for legislative purposes is evaluated for a deterministic, a worst-case and a new stochastic approach. All approaches give a reasonable, but rough, estimation of the diffusion coefficient. The new stochastic approach has the advantage that an entire probability distribution may be obtained

Influence of solvent absorption on the migration of Irganox 1076 from LDPE

The effect of solvent absorption on additive migration was studied by relating the diffusion coefficient (D) of Irganox 1076 to the maximum solvent absorption of different solvents in low-density polyethylene (LDPE) film. Solvents tested were ethanol, isopropanol, isooctane, ethylacetate, cyclohexane, tributyrin, tricaprylin and olive oil. Diffusion and partition coefficients were determined by fitting the migration curves, i.e. the concentration of Irganox 1076 in solvent as a function of time, with Fick's diffusion equation. The results for the low molecular weight solvents show that with increasing maximum solvent absorption, D of Irganox 1076 is increasing as well. This trend is not observed for the two triglycerides and olive oil. In spite of absorption, no increase in D was observed. The obtained result is the basis of an extended predictive migration model that, besides migrant and polymer properties, is also based on the maximum solvent absorption in the polymer

Stochastic modelling of migration from polyolefins

A method is presented to predict diffusion coefficients in polyolefins using stochastic modelling. A large number of experimental diffusion coefficients, published in the literature as one dataset, was used to derive probability distributions of diffusion coefficients in the polymers low-density polyethylene and linear low-density polyethylene, medium- and high-density polyethylene, and polypropylene. An equation is proposed to describe the diffusion coefficient as a function of the molar mass of the migrant. Model parameters and standard deviations are predicted by minimizing the sum of squared errors and the residuals are used to check the assumed types of probability distribution. The experimental data can be described by a log-normal distribution. It is shown how the derived probability distributions can be used as input for migration predictions. The method presented provides information about the most likely migration results for a given packaging¿food simulant combination. This is important for prediction of the probability that a given migration limit may be exceede

Additive Diffusion from LDPE Slabs into Contacting Solvents as a Function of Solvent Absorption

This article describes the simultaneous diffusion of a migrant and a solvent in low density polyethylene (LDPE). The migrant (Irganox 1076) moves out of the slab, while the solvent (isooctane, n-heptane or cyclohexane) moves inwards. Solvent absorption was measured separately by following the increase of the mass of the slab in time. It can be described by the Fick diffusion equation with a diffusivity depending on the solvent concentration, and an interface concentration depending on time. The final absorptions were 12% for isooctane, 14% for n-heptane, and 29% for cyclohexane. Additive concentrations in the slab were determined at different positions by microtoming. Experiments were done for several Contacting times. The concentration profiles were strongly affected by the solvent. A larger local solvent concentration increases the diffusivity of the migrant. The Fick equation with a migrant diffusivity depending on the solvent concentration gives a good description for the results with isooctane and n-heptane. The description is less good for the measurements with cyclohexane (when the polymer swells strongly). (C) 2003 Wiley Periodicals, Inc

Predictive modeling of migration from packaging materials into food products for regulatory purposes

Migration of low-molecular weight compounds is one of the most important problems of packaging plastics and other plastics intended to come into contact with food products. Since migration experiments are time consuming and expensive, predictive modelling has been introduced as a promising alternative. The main objective of this article is to review current knowledge on migration modelling and highlight the consequences of using modelling for regulatory purposes

Direct Measurement of Additive Migration from Low-Density Polyethylene as a Function of Space and Time

A method, based on microtoming and GC analysis, for studying migration of additives inside polymers as a function of space and time was validated for Irganox 1076 migrating from low-density polyethylene to ethanol. The consistency of the mass balance of the total amount of Irganox 1076 in the polymer and the solvent after different incubation times was acceptable considering errors introduced by the analytical procedure. A solution of Fick diffusion equations, fitted to concentration profiles inside the polymer at different incubation times, was found to describe well the transport process as a function of both position and time with a diffusion coefficient of 1.1 x 10(-13) m(2) s(-1). This value corresponded to the diffusion coefficient obtained using conventional measurements of an Irganox 1076 concentration in ethanol as a function of time. Compared to a stationary solvent, no significant effect was observed on the diffusion coefficient by gently shaking the ethanol. Diffusion coefficients measured at different temperatures using the validated method followed an Arrhenius type of relationship with an activation energy of 113 kJ mol(-1). Conclusively, the method was found to be well suitable for studying additive migration in polymers as a function of both space and time. (C) 2002 Wiley Periodicals, Inc

Long-term outcomes of children undergoing video-assisted gastrostomy

Purpose: The aims of this study were to assess the short- and long-term complication rates after video-assisted gastrostomy (VAG), the effects of age and gender on long-term complications and the effect of duration of gastrostomy tube retention on the need for gastroraphy when the gastrostomy device was removed. Methods: This was a retrospective study of children undergoing VAG at a single institution. Children who died or moved from the area were excluded. The rates of short- and long-term complications developing at 3–6 months or 2 or more years, respectively, were compared. Results: A total of 170 children were studied, out of a cohort of 303 children. The median age at surgery was 2 years. The median duration of postoperative long-term follow-up was 5 years (2–9 years). The complications at the respective short and long-term follow-ups were as follows: granulation tissue, leakage, infection and vomiting. There were no differences in the short- versus long-term complication rates for gender and age. Children needing gastroraphy had used a gastrostomy device significantly longer compared with children with spontaneous closure. Conclusion: Complications after VAG decrease over time. A longer duration of gastrostomy device retention leads to increased need for gastroraphy