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Modelling migration from paper into a food simulant
Poças, Maria de Fátima; Oliveira, Jorge C.; Pereira, Joel R.; Brandsch, Rainer; Hogg, TimothyThe migration of components from paper into Tenax was studied to determine the influence of molecular size and chemical character of the migrant and the influence of paper characteristics in the migration process. The Weibull model was applied because Fick’s 2nd law of diffusion gave poor fits in some cases. The migration pattern depended on the migrants molecular size and was independent of temperature in the ...
Feasibility study on the use of probabilistic migration modeling in support of ...
Poças, Maria F.; Oliveira, Jorge C.; Brandsch, Rainer; Hogg, TimothyThe use of probabilistic approaches in exposure assessments of contaminants migrating from food packages is of increasing interest but the lack of concentration or migration data is often referred as a limitation. Data accounting for the variability and uncertainty that can be expected in migration, for example, due to heterogeneity in the packaging system, variation of the temperature along the distribution ch...
A critical survey of predictive mathematical models for migration from packaging
Poças, Maria F.; Oliveira, Jorge C; Oliveira, Fernanda A. R.; Hogg, TimothyThe migration of chemicals from food contact materials into foods is an important issue in food safety.The assessment of materials compliance with regulations includes migration monitoring for many monomers and additives. However,it is recognized that predictive mathematical modelling can be used in many cases, to avoid or to reduce the effort on migration experiments. This article reviews the approaches follow...
Dynamic mechanical thermal analysis of aqueous sugar solutions containing fruct...
Cruz, Isabel B.; Oliveira, Jorge C.; MacInnes, William M.The glass transition of glucose, fructose, lactose, maltose and sucrose solutions at maximum cryo-concentration was studied by Dynamic Mechanical Thermal Analysis (DMTA), using the disc bending technique. The glass transition temperatures were determined from the peaks in the loss modulus E′′, which corresponds theoretically to the resonance point (Maxwell model) for several input frequencies. The frequency dep...
Modelling ascorbic acid thermal degradation and browning in orange juice under ...
Manso, Maria C.; Oliveira, Fernanda A.R.; Oliveira, Jorge C.; Frías, Jesús M.The thermal degradation of ascorbic acid (AA) in orange juice was analysed over in a 20–45 °C temperature range. Dehydroascorbic acid (DA), pH and browning were also monitored. Small amounts of AA degradation could be described by first order kinetics, but when only low amounts of AA were retained sigmoidal kinetics were clearly appropriate. The Weibull model was used to describe this pattern (R2adj > 0.995). T...
Determination of the heat transfer coefficient between bulk medium and packed c...
Varga, Szabolcs; Oliveira, Jorge C.The external heat transfer coefficient in steam retort processing was determined experimentally in a pilot scale retort. The heat transfer equations were solved applying finite elements and using the actual retort temperature profile as boundary condition. The instantaneous values of the heat transfer coe cient were determined, to analyse its time-variability along a retort cycle. It was found that reliable res...
Influence of the variability of processing factors on the F-value distribution ...
Varga, Szabolcs; Oliveira, Jorge C.; Oliveira, Fernanda A.R.The F-value distribution in a batch retort processing of in-pack conduction heating foods resulting from the variability of four processing factors (initial temperature, heating time, headspace and external heat transfer coe cient) was determined by mathematical modelling. Three hundred combinations were generated from normally distributed values for each factor, following the Monte Carlo approach. The retort t...
Measurement of glass transition in native wheat flour by dynamic mechanical the...
Pereira, Pedro M.; Oliveira, Jorge C.This work describes a method to study glass transition on native starch powders, based on dynamical mechanical thermal analysis using compression tests, and was applied to wheat flour (13.5% water content). This method will allow the determination of Tg in native (unprocessed) starchy materials, with minimal disturbance of the natural structures. The influence of the test conditions (heating rate, frequency and...
Modelling temperature variability in batch retorts and its impact on lethality ...
Varga, Szabolcs; Oliveira, Jorge C; Smout, Chantal; Hendrickx, Mark E.Experimental time±temperature distributions from two di erent industrial scale retort systems were statistically analysed. The retort temperature was modelled as the sum of a trend value and a residual, with the trend temperatures being simple functions of time. The residuals were modelled using time-series. The resulting impact on the lethality distribution was assessed by calculating the F-value distribution ...
Selection of low swelling materials for protein adsorption from white wines
Sarmento, Miguel R.; Oliveira, Jorge C.; Boulton, Roger B.The protein adsorption capacity of different materials was evaluated to assess their potential efficacy as alternative adsorbents for the removal of proteins from wines, with the purpose of finding suitable low-swelling materials that could be used in a percolated bed. The adsorbents tested were thermally treated sodium bentonite, low-swelling adsorbing clays, ion exchange resins and other protein adsorbents (s...
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