Adriana Laca

Controlled malolactic fermentation in cider using Oenococcus oeni immobilized in alginate beads and comparison with free cell fermentation.

Cells of Oenococcus oeni (formerly Leuconostoc oenos) immobilized in alginate beads were used as starter culture to conduct malolactic fermentation in cider production. Concentrations of major organic acids and volatile compounds were monitored during the process, and results were compared to those obtained when using free cells in the same conditions. The rates of malic acid consumption were similar but lower ethanoic acid content and higher concentration of alcohols were detected with immobilized cells. These features have beneficial effects on the organoleptic properties of cider. A comparison between the kinetic behavior in immobilized and free cells, based on the data obtained for the malic acid consumption, has been developed solving the homogeneous diffusion model when it is applied to the system with immobilized cells.

Ethanol and ethyl acetate production during the cider fermentation from laboratory to industrial scale

Abstract Biomass, sugars and ethanol are the main compounds involved in beverage fermentation processes, although many other minor components, such as esters, also play important roles in the flavour and taste of the final product. These compounds were monitored during cider fermentations carried out on laboratory, semipilot and pilot plant scales (100 ml, 13 and 125 l, respectively) and even during a cider industrial fermentation (45 000 l). The behaviour was similar except for fermentations carried out in Erlenmeyer flasks whose ethanol/sugar yield factor was slightly lower and the ethyl acetate concentration achieved was too high due to the different geometry that gave rise to different metabolic pathways. Simple models are developed to predict the evolution of these compounds during the process and they are successfully applied to simulate experimental results.

Catalytic wet oxidation of thiocyanate with homogeneous copper(II) sulphate catalyst

The wet oxidation of thiocyanate has been investigated in a semi-batch reactor at temperatures between 423 and 473 K and pressures between 6.1 x 10(3) and 1.0 x 10(4)kPa in the presence of copper(II) sulphate as catalyst. The effects of copper concentration, initial thiocyanate concentration, pressure and temperature on the reaction rate were analyzed and the main products of reaction were identified. A kinetic model for the Cu-catalyzed reaction is here proposed, including temperature, oxygen concentration, and the reduction of Cu(2+) to Cu(+) that gives an accurate prediction of the oxidation process under the assayed conditions. A mechanistic model based on the formation of a transition complex between a copper cation and two thiocyanate anions has been proposed for the catalytic wet oxidation.

Protein diffusion in alginate beads monitored by confocal microscopy. The application of wavelets for data reconstruction and analysis

A microscopic technique has been developed to obtain the protein profiles inside calcium alginate gel. To do this, the diffusion of BSA, previously marked with FITC, inside calcium alginate beads was observed using confocal laser microscopy, thus obtaining the spatio-temporal evolution of the protein concentration. The technique, however, presents certain limitations and zones where it is impossible to obtain experimental data. Wavelets analysis, commonly used in signal processing and statistics, was employed to reconstruct and subsequently analyse the experimental results. Once the diffusion model was defined, the substrate profiles obtained were used to calculate a diffusivity value for BSA in alginate gel.

Decision criteria for the selection of wet oxidation and conventional biological treatment.

The suitability of wet oxidation or biological treatments for the degradation of industrial wastewaters is here discussed. Advantages of these operations, either singly or in combination, are discussed on the basis of previous experimental results from laboratory and industry. Decision diagrams for the selection of conventional biological treatment, wet oxidation or a combination of both techniques are suggested according to the type of pollutant, its concentration and the wastewater flow rate.

Modelling and description of internal profiles in immobilized cells systems

Abstract Modelling of immobilized cell systems has usually considered a uniform distribution of biomass, although in practice, this is not the case due to the diffusional limitations of substrates, cells and products. When solids distribution inside the beads is examined, different mechanisms of movement appear, In this work, pore diffusion and homogeneous models ans applied in order to simulate the evolution of substrate and cells, including terms for species and cell internal and external diffusion. In practice, these terms have different meanings and correlations depending on the immobilization type. The introduction of the cell diffusion term in the mobelling enables us to obtain four types of profile depending on cell and substrate concentration, ‘diffusion’ and kinetics constants. These profiles have been classified in terms of the classical Thiele modulus for the substrate reaction, and in terms of a new Thiele modulus, based on cells, that we have introduced here. Finally, internal experimental cell profiles, obtained with Serratia marcescens immobilized in calcium alginate beads, are presented, and compared with a theoretical one obtained in some of the previously defined conditions, showing the general applicability of the modelling method.

Analysis and description of the evolution of alginate immobilised cells systems.

Different immobilised cells models, including very simple ones, can be useful in the fitting of experimental results. However, goodness or the ability to extrapolate results needs to be in accordance with basic observations and these will also suggest models to be proposed. In this paper, observations of calcium alginate/bacteria systems are used to show the ability of basic models to fit classic observations, as well as how new observations, in this case from electronic microscopy, oblige us to think about more complex mechanisms and mathematical treatments. Nevertheless it is not only important to discuss the model type, but also the type of kinetics assumed in the interior of the beads, as well as the internal structure, the boundary conditions related to bead shredding and cell escape and finally, geometrical effects.

Eggshell waste as catalyst: A review

Agricultural wastes are some of the most emerging problems in food industries because of their disposal cost. However, it is also an opportunity for the bioeconomy society if new uses for these residual materials can be found. Eggshells, considered a hazardous waste by UE regulations, are discarded, amounting hundreds of thousands of tonnes worldwide. This egg processing waste is a valuable source material, which can be used in different fields such as fodder or fertilizer production. Additionally, this residue offers interesting characteristics to be used in other applications, like its employment as an environment-friendly catalyst. In the present review we provide a global view of eggshell waste uses as catalyst in different processes. According to reviewed researching works, a huge variety of added value products can be obtained by using this catalyst which emphasised the interest of further investigations in order to widen the possible uses of this cheap green catalyst.

Simultaneous oxidation of cyanide and thiocyanate at high pressure and temperature

Thiocyanate and cyanide are important contaminants that frequently appear mixed in industrial effluents. In this work the wet oxidation of mixtures of both compounds, simulating real compositions, was carried out in a semi-batch reactor at temperature between 393 K and 483 K and pressure in the range of 2.0-8.0 MPa. The presence of cyanide (3.85 mM) increased the kinetic constant of thiocyanate degradation by a factor of 1.6, in comparison to the value obtained for the individual degradation of thiocyanate, (5.95 ± 0.05) × 10(-5)s(-1). On the other hand, the addition of thiocyanate (0.98 mM) decreased the degradation rate of cyanide by 16%. This revealed the existence of synergistic and inhibitory phenomena between these two species. Additionally, cyanide was identified as an intermediate in the oxidation of thiocyanate, and formate, ammonia and sulfate were found to be the main reaction products. Taking into account the experimental data, a reaction pathway for the simultaneous wet oxidation of both pollutants was proposed. Two parallel reactions beginning from cyanate as intermediate were considered, one yielding ammonia and formate and the other giving carbon dioxide and nitrogen as final products.

Environmental impact of a traditional cooked dish at four different manufacturing scales: from ready meal industry and catering company to traditional restaurant and homemade

PurposeThe environmental burdens of the same dish (a traditional hot stew with pulses and pieces of pork sausages and ham) cooked at four different production scales was analyzed by life cycle assessment (LCA): (a) canned, industrially manufactured and consumed at home; (b) catering company, serving the product for schools; (c) restaurant, cooked in a traditional way and served; and (d) homemade, cooked, and consumed at household level.MethodsThe LCA methodology was applied following the ISO 14044:2006 guidelines. For the inventory analysis, industrial data were obtained from a ready meals factory. Other primary data were directly obtained from the systems analyzed (catering, restaurant and homemade levels). Databases (Ecoinvent, LCA Food DK, BUWAL250, IDEMAT 2001, ETH-ESU 96) were used together with the SimaPro v7.3.3. For the impact assessment, the Eco-indicator 99 method and the CML 2 baseline method were used. In cases (c) and (d), different scenarios for the origin of raw materials and source of energy for cooking were considered. In level (a), an additional scenario considering a 50% reduction of food wastes was also investigated.Results and discussionThe main contribution was meat ingredients, followed by energy consumption. Despite the higher environmental loads in transportation, the factory showed an environmental performance similar to cooking at home with gas. These results can be explained by the implementation of heat recovery systems at industrial scale. The restaurant showed the worst environmental performance. The main reason was that all the energy consumed in the restaurant (even not directly related to cooking) was attributed to the exclusive purpose of serving the food, since no other activities were carried out in the business. Consumer’s choices such as the preference for eating in a restaurant or the energy used for cooking turned out to be important differentiating factors.Conclusions and recommendationsLCA allowed critical aspects to be identified in order to improve sustainable food production and consumption patterns. Electricity consumption and the amount of wastes sent to landfill turned out to be critical control points. In the case of complex dishes such as stews, the higher scale systems in the study (the factory and catering company), with proper energy and environmental practices, can have lower environmental burdens than small-scale systems, such as homemade cooking using a ceramic-glass cooktop or consumption in traditional restaurants. To reinforce the role of education, specific programs on the need to save food and the environmental impact of dietary choices must be implemented at schools.