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- Kinetics of the adsorption of bovine serum albumin contained in a model wine solution by non-swelling ion-exchange resinsPublication . Sarmento, M.R.; Oliveira, J.C.; M. Slatner, M.; Boulton, R.B.Adsorption of wine proteins is an essential step in the production of white and rosé wines. In order to develop environmentally friendly adsorption processes, non-swelling adsorbents are required. The performance of selected non-swelling ion-exchange resins (Macro-Prep™ 50S and Streamline® SP) was studied by describing the process kinetics of the adsorption of BSA in a model wine solution. The process was assumed to be diffusion controlled and a shrinking core model was applied. Experiments were performed in the 5–35°C temperature range and with different equilibrium partition coefficients. The results obtained with the shrinking core model were theoretically consistent and the apparent diffusivity values correlated very well with theoretically estimated effective diffusivities combined with a linear dependence of porosity with temperature. Separating the temperature effect on porosity, the apparent diffusivity followed an Arrhenius type dependency with temperature with 16.9 kJ/mole activation energy.
- Development of perforation-mediated modified atmosphere packaging to preserve fresh fruit and vegetable quality after harvestPublication . Oliveira, F.A.R.; Fonseca, S.C.; Oliveira, J.C.; Brecht, J.K.; Chau, K.V.The use of perforations as a means of obtaining large size containers suitable for modified atmosphere packaging (MAP) would greatly enhance the applicability of this technology for storage and distribution of fresh and minimally processed products. General concepts of MAP, and advantages and drawbacks of using perforations to achieve it are discussed. Products for which perforated packages can be used are listed. The variables that affect this type of package are presented and the methodology for designing an adequate package is described and illustrated with the case study of shredded cabbage.
- Influence of intrinsic factors on conventional wine protein stability testsPublication . Sarmento, M.R.; Oliveira, J.C.; Slatner, M.; Boulton, R.B.The influence of intrinsic factors on the results of ethanol, tannin and heat tests, routinely used to assess wine protein stability, was studied. Experiments were performed on 23 Portuguese and Austrian wines. The factors considered were total protein content, pH, ethanol content and the amount of several relevant cations (calcium, iron, copper, sodium and potassium). The protein pro®les were analysed by HPLC fractionation. The heat test was a good indicator of total protein content while the ethanol and the tannin tests showed signi®cant interference by the other factors. A factorial design at two levels in selected samples was also performed to assess the influence of pH, storage temperature, tannin concentration and ethanol concentration on the development of turbidity. Results indicated that ethanol content had no significant infuence, and that pH and storage temperature had a significant infuence, though only when tannin was added.
- Degradation of ascorbic acid during drying processesPublication . Frias, J.M.; Oliveira, J.C.
- Rheological properties of heated cross-linked waxy maize starch dispersionsPublication . Silva, Pedro M. S. da; Oliveira, J.C.; Rao, M.A.The effect of starch concentration on time-dependent, steady shear, and dynamic shear rheological properties of heated cross-linked waxy maize starch (CWM) starch dispersions was studied. The influence of storage time at 5°C on the rheological properties, the applicability of the Cox-Merz rule, and the sol-gel transition of a 5% (w/w) were also examined. The heated CWM starch dispersions exhibited antithixotropic and shear-thinning with yield stress behaviors. The former behavior increased with both starch concentration and shear rate between 100s-1 and 400s-1. As expected, the apparent viscosity at a fixed shear rate and the yield stress increased with starch concentration. Because the Cox-Merz rule was not applicable, the dispersions may be classified as weak gels. Both differential scanning calorimetry and thermo-rheological data showed that the onset of starch gelatinization temperature was 63°C.
- Consumer exposure to phthalates from paper packaging: an integrated approachPublication . Poças, M.F.; Oliveira, J.C.; Pereira, J.R; Hogg, T.This paper presents an integrated approach to estimate the exposure of the Portuguese population to phthalates as a contaminant originating from paperboard packaging. The approach combined data of migrant concentration in the foods resulting from a stochastic simulation with consumption data of food packaged in paperboard. The results from the exposure model were validated with experimental values actually found in the food. A short surveillance exercise was conducted with samples collection from market shelves to identify and quantify the phthalates present in both the packages and the food. The distribution of values for the di-butyl phthalate concentration in the packages was used as the input of the initial concentration in the Weibull model to estimate the concentration of this phthalate in the foods. This distribution of occurrence data was then combined with the packaging usage data in a probabilistic simulation with a Monte Carlo sampling method. Exposure values ranged between zero and 8.95 mg day 1 kgbw, a value close to the tolerable daily intake established by the European Food Safety Authority (EFSA) – 10 mg day 1 kgbw. However, the 97.5th percentile and the average were 1.82 and 0.44 day 1 kgbw, respectively, indicating that further refinement of the estimates is not necessary. Other phthalates were also detected in the packaging samples: di-isobutyl phthalate and di-ethylhexyl phthalate. The latter was present in all packaging samples collected and was detected in a few food samples at values requiring further investigation.
- New paradigm for patterns of home packaged food intakePublication . Poças, M.F.F.; Oliveira, J.C.; Pinto, H. J.; Hogg, T.Purpose – The purpose of this paper is to describe a pilot study characterizing the domestic usage of food packaging (amount and type) at the household level. Design/methodology/approach – Collection and detailed characterization is carried out, from a sample of Portuguese consumers, of packages used at home during a seven-day period. Findings – The daily intake of domestically consumed, packaged food ranged from 5 to 50 g/kgbw. The average intake value for children below 12 years old was 26 g/kgbw. Considering all packaging materials, package usage ranged from 0.1dm2/day.kgbw to 0.6dm2/day.kgbw. Packaging usage factors and food-type distribution factors for each packaging material were estimated. Research limitations/implications – The period of packaging collection and the size of the sample limit the degree of generalized conclusions that can be drawn. Practical implications – The data collected are the base for the development of a framework and could make an important contribution to the assessment of consumer exposure to substances migrating from packages into food, in this case of the Portuguese consumer. Originality/value – The results achieved are analysed in relation to the current assumptions made for the safety assessment of materials in the relevant European legislation. Furthermore, the results achieved can be used in a probabilistic approach to these assessments as the distributions of values, and not only the per capita values, are known.
- Influence of operating conditions on the extent of enzymatic conversion of rice starch in wet extrusionPublication . Tomás, R.L.; Oliveira, J.C.; McCarthy, K.L.Rice starch mixtures with 550–650g water per kg rice flour were extruded in a co-rotating twin-screw extruder with thermostable á-amylase mixed in the feed slurry in concentrations between 0.1–1.0g enzyme per kg rice flour, at temperatures between 70 and 100 °C. The extent of starch hydrolysis promoted by the resulting combination of extrusion and enzymatic activity was monitored by measuring the DE (dextrose equivalent) values of the extruded material. DE values between 20 and 90 were observed, with the control of operating conditions providing for a good control of starch hydrolysis. Nonenzymatic extrusion yielded DE values around 5. The experimental design followed a full three-level factorial plan, allowing a conclusion to be made that interactive effects between the factors studied (temperature, enzyme concentration and water content) were not relevant, while a quadratic effect of water content was evident, corresponding to a maximum starch hydrolysis at 600 g water per kg rice flour. The results were adequately fitted to a multi-linear response-surface model, with a correlation coefficient of 0.89.