Konstantoula Akrida-Demertzi

Migration studies from recycled paper packaging materials: development of an analytical method for rapid testing

Abstract The safe use of recycled paper and board material for food packaging applications is a major area of investigation. Studies on the migration of contaminants into foods and food simulants have been carried out to evaluate the suitability of recycled paperboard for direct food contact applications. In the present study, the kinetics of migration of selected model contaminants (surrogates) from paper packaging samples into an alternative or substitute fatty food simulant (Tenax) was studied with the aim of developing a rapid test method based on solvent extraction, gas chromatography (GC)–mass spectrometry (MS) identification and GC–flame ionization detector (FID) quantification. These tested substances represent a large number of molecular sizes and polarities and are among those that may be present in fiber material. Crucial data about the time needed to reach equilibrium between paper samples and the food simulant were obtained. The results of the study indicate that time and temperature conditions are the most important variables with respect to the actual mass transfer during contact with food simulants. The proposed quick test method seems to be suitable for compliance testing of paper and board samples if migration limits are applied in future legislation.

Gas chromatographic studies on polymer-plasticizer compatibility: Interactions between food-grade PVC and epoxidized soybean oil

Abstract The technique of inverse gas chromatography was applied to study the miscibility (compatibility) of the system of PVC with epoxidized soybean oil (ESO). The PVC-ESO thermodynamic interaction parameters, χ + 23 , were determined from the measured retention data for various vapour-phase “probes” in stationary phase mixtures of the components covering the entire composition range. Experiments were run in the range 90–110°C. In accordance with previous studies on polymer-polymer and polymer-plasticizer blends, the interaction parameters were found to be dependent on the temperature, the chemical nature of the probe and the blend composition. χ + 23 values were mostly negative or slightly positive up to 0.40 weight fraction of ESO, indicating relatively high compatibility of PVC and ESO for this range of compositions. They then increased with increasing plasticizer content and, at ca 0.70 weight fraction of ESO, exceeded 0.5 which is considered as the “compatibility limit value”.

Study of compatibility of PVC and polyester-type plasticizer blends by inverse gas chromatography

The technique of inverse gas chromatography has been applied to a thermodynamic study of the miscibility (compatibility) of PVC and a polymeric (polyadipate ester) plasticizer. A number of organic solvents (probes) were used to evaluate the Flory-Huggins parameters for the PVC-plasticizer interaction in stationary phase mixtures of the two components covering the entire composition range for each component (0–100%). Experiments were carried out in the range 90–120°. The interaction parameter values were found to be dependent on the chemical nature of the probes, the temperature and the composition of the mixed (binary) phase. The results predict good polymer-plasticizer compatibility for a wide range of the above mixture (up to ca 0.55 weight fraction of plasticizer).

Differences in concentration of essential and toxic elements in peanuts and peanut oil

Abstract Two varieties of peanut ( Arachis hypogeaea ), which grow in two different areas of Greece, were analysed for essential and toxic elements by atomic absorption spectroscopy (AAS). Differences in concentrations, probably depending on the growing area, were observed for seven elements (Ca, Mg, Cu, Fe, Zn, Co and Pb). Higher concentrations of Ca, Mg, Co and Pb were found in the oil-free material of the Serron variety (continental area), while the Kalamon variety (coastal area) showed higher concentrations of Cu, Fe and Zn. The contents of these elements in the peanut oil are significantly different in the two varieties. Significant variations also appear in the concentrations of the water-and fat-soluble salts of the elements studied. Discussion of the results is based on statistical treatment of the data.

Wine production using free and immobilized kefir culture on natural supports

The aim of the present study was to perform simultaneous alcoholic and malolactic wine fermentations using free or immobilized kefir culture at a wide temperature range (5-45 °C). Repeated batch fermentations were carried out for a period up to 29 months, suggesting a high operational stability of the systems, while malic acid conversion and ethanol productivity up to 70.9% and 36.9 g/(Ld) were noted. Volatile acidity was at levels typically found in wines (<1.0 g acetic acid/L) in most cases, although increased values were recorded in wines produced at 5 °C, but no vinegar taint was detected. Fusel alcohols were at levels usually found in wines, but were reduced at 5 °C. Application of PCA to minor volatiles showed that the fermentation temperature rather than the nature of kefir culture had a significant effect. Noticeably, all products were accepted by the panel during the preliminary sensory evaluation.

Effect of adsorbent particle size on the water-ethanol separation by cellulosic substrates

Abstract Inverse gas chromatography was used to study the adsorption of water and ethanol on two fractions of wheat straw with two different particle size compositions (80–100 and 100–120 mesh), in the temperature range 50–90°C, before and after its regeneration by thermal treatment at 140°C for 24 h. From the chromatographic retention data it was possible to calculate the separation factor (s) of the two solutes and to obtain the values for Gibbs free energy (ΔGs) and enthalpy (ΔHs) of adsorption. The results showed that water was adsorbed more strongly than ethanol by both fractions, at all temperatures, both for the untreated and thermally treated wheat straw. In addition, it was found that adsorption of both solutes was more spontaneous at lower temperatures, at which the separation factor had the higher values. Adsorption of both solutes was slightly stronger on wheat straw of 100–120 mesh particle size, whereas values for the separation factor were similar for both fractions. Thermal treatment had no effect on the adsorption of ethanol on both fractions. On the other had adsorption of water was stronger on the untreated wheat straw, thus leading to a decrease of the separation factor for the thermally treated material.

Saccharomyces cerevisiae and Kefir Production Using Waste Pomegranate Juice, Molasses, and Whey

The growth of Saccharomyces cerevisiae (bakers yeast) and kefir was studied in substrates containing pomegranate juice, molasses, and cheese whey, at various conditions such as fermentation temperature, air supply, initial sugar concentration, and substrate composition. The results showed that, in the case of kefir, the highest production yield of biomass (0.24 g/g of utilised sugar) and productivity (6.5 g/l/day) was obtained in 40/60 and 20/80% of pomegranate/ cheese whey. S. cerevisiae grew easily on all substrates with higher cell mass yields (0.34 g/g) and productivities (13.1 g/l/day) compared to kefir, with the best results obtained at the ratio of 40/60 and 20/80% of pomegranate/ molasses. These results are promising regarding the exploitation of non-conventional substrates, such as the juice from discarded pomegranate fruits of a currently significantly increasing market, for microbial biomass production.

Water and ethanol adsorption on starchy substrates as biomass separation systems

Abstract Adsorption of water and ethanol on corn meal and wheat flour has been studied in the temperature range of 50–90°C. using inverse gas chromatography (IGC). The results showed that adsorption of water was affected more significantly by the kind of starchy adsorber than the adsorption of ethanol. Values for thermodynamic parameters such as Gibbs free energy (ΔGs) and enthalpy (heat) (ΔHs) corresponding to sorption of water and ethanol by the substrates have been calculated using chromatographic retention data. It was found that adsorption was more spontaneous at lower temperatures as expected.