Powering process intensification in an oscillatory flow meso-reactor

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Whey protein gelation: the effect of tryptic hydrolysis

The ability of whey proteins (WP) to form heat induced gels and provide texture is desirable for some “solid like” foods like processed meat, dairy and bakery products. However, this property limits the application of whey proteins in “liquid like” foods including beverages, baby formula and salad dressings [1]. Enzymatic hydrolysis impairs the gelation ability and improves the thermal stability of WP and can be used to expand the applications of WP [2]. From a dietary point of view, the use of whey protein hydrolysates instead of the “whole” protein isolates is interesting to reduce alle rgenicity or improve digestibility. Whey protein hydrolysates are also a important source of bioactive peptides liberated, from native proteins, during the hydrolysis. Once liberated, peptides may act as regulatory compounds with hormonelike activity [3]. In this work, our main objective is to model the gelling properties of whey protein tryptic hydrolysates (WPTH) as a function of the degree of hydrolysis and the protein concentration. An experimental design was applied where protein concentration range between 10 and 17 % (w/w) and hydrolysis degree range between 0,9 and 4,2 %, according to pH-stat methodology. The rheological behaviour of WPTH during heat gelling under small deformation oscillatory shear was investigated using a controlled stress rheometer AR2000 (TA Instruments). Empirical quadratic models were extracted from the experimental results. The statistical results show a dramatic effect of enzymatic hydrolysis on the gelling behaviour and on the gel properties. This study suggests that enzymatic hydrolysates can be designed for specific food formulations according to the desired gel (meat, dairy or bakery products) or liquid character (beverages, salad dressings)

The bubble size distribution and O2 mass transfer in an oscillating, meso-scale tube

This work aims at characterizing bubble size distribution and its control in a small-scale, constricted tube in the presence of an oscillating flow. From previous works, it became clear that the full modelling of the dispersed gas -liquid flow in the constricted tube requires a deeper clarification of the impact of tube geometry and the hydrodynamic parameters on the observed values of the oxygen mass transfer coefficient (kLa). In order to do so, data on the size and shape of the generated bubbles have been obtained with a CCD camera during the steady, continuous operation of a 350 mm constricted tube in the presence of flowing liquid and gas phases, at different combinations of oscillation frequency (f) and amplitude (x0). These data were used to generate bubble size distribution curves. The results demonstrated that the operation at smooth oscillatory flow conditions (f ≤ 10 Hz) leads to a decrease of the bubble size, while for higher values of f (15-20 Hz) the increased oscillatory velocities cause an increase in bubble size. The simultaneous increase of gas hold-up for the same oscillatory flow conditions (f = 15-20 Hz) suggests that the gas hold-up correlates with the bubbles’ diameter for this particular geometry. A correlation between the bubbles’ diameter and the mass transfer coefficient in the liquid, kL, with the oscillatory flow mixing conditions is also presented.Fundação para a Ciência e a Tecnologia (FCT)

The intensification of gas–liquid flows with a periodic, constricted oscillatory-meso tube

The experimental study of gas dispersion in a vertical periodically, constricted, oscillatory meso-tube (OMT) is herein presented. Water was continuously pumped through the OMT in the laminar flow regime along with an oscillatory flow component superimposed into the net flow in a range of fluid oscillation frequency (f) and centre-to-peak amplitude (x0) of and 0–3 mm, respectively, in the presence of a very low superficial gas velocity . Bubble images were recorded with a CCD camera and analysed with Visilog® software. A bimodal distribution of bubble size was in general observed but the bubble size was found strongly dependent on the oscillatory flow mixing conditions imposed into the fluid. A number fraction of micro-bubbles (with an equivalent diameter, Deq, equal or bellow 0.2 mm) up to 60% was generated with increasing values of x0 (i.e. 3 mm) and values of f in the range . Furthermore, it is demonstrated that the Sauter mean diameter, D32, and the specific interfacial area, a, can be fined tune by setting both f and x0 in this studied range. The high number fraction of micro-bubbles was concluded to have a positive impact in enhancing the liquid-side mass transfer coefficient, kL. Globally, the differences in bubbles sizes were found to play a marginal effect in the global enhancement of the kLa in the meso-tube in comparison with the intensive contact experimented by the bubbles rising in the oscillatory flow. The higher order of magnitude of the kL values found in this work (up to ) is promising for running numerous industrial gas–liquid flows processes through smaller and better, while aeration of biotransformations can be run more efficiently, as supported by our recent proof-of-concept studies carried out in the platform.Fundação para a Ciência e a Tecnologia (FCT

Novel functional polysaccharides as edible coatings for cheese

One of the problems occurring during cheese ripening and later on, throughout the distribution chain, is the occurrence of molds and the loss of water. Usually, this problem is solved by the use of synthetic coatings where an antimicrobial agent is introduced. Polysaccharide coatings have an oilfree appearance, a low caloric content and can be used to increase the shelf life of foods. The objective of this work was to study the ability of polysaccharides from different and novel sources to be used as coatings for cheese. The tested materials were: chitosan, galactomannan of Gleditsia triacanthos and agar of Glacilariae birdiae. Different formulations were tested with the addition of plasticizer (glycerol and sorbitol), oil and Tween 80. The surface properties of the cheese and the wetting capacity of the coatings on the cheese (in terns of the spreading coefficient) were determined. Based on the values of the spreading coefficient of the polysaccharides solutions the three best solutions for each polysaccharide were chosen. For the chosen solutions, the water, oxygen and carbon dioxide permeability of the films were determined, as well as solubility, opacity and chromaticity. The solutions of G. triacanthos present the best properties to coat the cheese. The O2 consumption and CO2 production rate, as well as the weight loss, of the cheese with and without coating were measured. The gas exchange rates of the cheese were found to decrease in the coated cheese. Also the weight loss from the cheese was lower in the coated cheese.Fundação para a Ciência e Tecnologia (FCT) Queijo Saloio S.A.Valnatura project (EU

Research and characterization of new materials for the production of edible coatings

Tropical fruits are subjected to great losses from harvest to consumption. The main objective of this work was to research and characterize new materials as galactomannans and determine the optimal composition of galactomannan-based coatings in view of their application to extend the shelf life of several tropical fruits. Galactomannans extracted from seeds of Caesalpinea pulcherrima, Adenanthera pavonina, Gleditsia triacanthos and Sophora japonica were characterized as coatings for five tropical fruits: acerola (Malpighia emarginata), cajá (Spondias lutea), mango (Mangifera indica), pitanga (Eugenia uniflora) and seriguela (Spondias purpurea). The intrinsic viscosity of galactomannans solutions with and without glycerol, were determined. The surface properties of fruits was determined, and different formulations of aqueous galactomannan solutions (0.5 %, 1.0 % and 1.5 %) with glycerol (1.0 %; 1.5 % and 2.0 %) were tested in terms of wettability on the five fruits. To analyse the capacity of the galactomannans to decrease the fungal growth, tests using four strains of fungi were performed with: Penicillium commune, Penicillium crustosum, Penicillium roqueforti and Botrytis cinerea. The galactomannan that demonstrated to provide a more significant fungal inhibition was G. triacanthos. The C. pulcherrima seed galactomannan was analysed to determine its sub-chronic toxicity in mice, measuring the evolution of weight, glycemic levels and total cholesterol levels during three months; no toxicity was observed. The weight loss from acerola and mango, coated with galactomannan from C. pulcherrima, during storage time was determined, giving good indications that the use of solutions of this galactomannan and glycerol as coating decreases the weight loss of the fruits. The obtained results confirmed the suitability of galactomannan-based coatings to prolong the shelf life of tropical fruits.Os frutos tropicais são sujeitos a grandes perdas desde a colheita até o consumo. O objectivo principal deste trabalho foi determinar a composição óptima dos revestimentos de galactomananas, tendo como finalidade aumentar o shelf life de frutos tropicais. Galactomananas extraídas de sementes de Caesalpinea pulcherrima, Adenanthera pavonina, Gleditsia triacanthos e Sophora japonica foram solubilizadas e caracterizadas como revestimento de cinco frutos tropicais: acerola (Malpighia emarginata), cajá (Spondias lutea), manga (Mangifera indica), pitanga (Eugenia uniflora) e seriguela (Spondias purpurea). A viscosidade intrinseca foi determinada com soluções de galactomananas com e sem glicerol. As propriedades de superfície dos cinco frutos foram determinadas, e diferentes formulações de soluções aquosas de galactomanana (0.5 %, 1.0 % e 1.5 %) com glicerol (1.0 %; 1.5 % e 2.0 %) foram testadas em termos de wettability nos cinco frutos. Com o objectivo de analisar a capacidade das galactomananas estudadas em decrescer o crescimento fúngico, foram realizados testes com cinco estirpes de fungos: Penicillium commune, Penicillium crustosum, Penicillium roqueforti e Botrytis cinerea. A galactomanana que demonstrou um maior efeito na inibição no crescimento fúngico foi a G. triacanthos. A galactomanana de C. pulcherrima foi usada para determinar a toxicidade sub-crónica, avaliando a evolução dos pesos, colesterol e níveis de glicemia de ratinhos durante 3 meses. Não foi observada toxicidade para a galactomanana de C. pulcherrima quando comparada com o grupo de controlo. Também se avaliou a perda de massa da acerola e da manga durante o seu armazenamento, demonstrando-se que os revestimentos de C. pulcherrima diminuem a perda de massa dos frutos. Os resultados obtidos confirmaram a possibilidade de aplicar os revestimentos de galactomananas em frutos tropicais para lhes aumentar o tempo de prateleira

Suitability of novel galactomannans as edible coatings for tropical fruits

The main objective of this work was to determine the optimal composition of edible coatings in view of their application to extend the shelf life of several tropical fruits. Coatings constituted by galactomannans from different sources (Caesalpinia pulcherrima and Adenanthera pavonina) and glycerol were characterized as coatings for five tropical fruits: acerola (Malpighia emarginata), cajá (Spondias lutea), mango (Mangifera indica), pitanga (Eugenia uniflora) and seriguela (Spondias purpurea). The surface properties of the five fruits were determined and different aqueous galactomannan solutions (0.5%, 1.0% and 1.5%) with glycerol (1.0%, 1.5% and 2.0%) were tested for their wettability on fruits. For the solutions having a better wettability, films were casted and water vapour permeability, oxygen permeability, carbon dioxide permeability, tensile strength and elongation at break were determined. Taking into account the surface and permeability properties of the obtained films, four compositions were selected as the best coatings to the studied fruits: acerola – 0.5% of A. pavonina galactomannan and 1.0% of glycerol; cajá – 1.0% of A. pavonina galactomannan and 1.0% of glycerol; mango and pitanga – 1.5% of A. pavonina galactomannan and 1.0% of glycerol; and seriguela – 0.5% of C. pulcherrima galactomannan and 1.5% of glycerol. For the coating, the values of the measured properties were as follows: wettability ranged from −36.33 ± 3.39 to −26.45 ± 4.58 mN · m−1; water vapour permeability ranged from 4.89 ± 0.11 to 6.25 ± 0.20 × 10−11 g m−1 s−1 Pa−1; oxygen permeability ranged from 0.31 ± 0.01 to 0.99 ± 0.13 × 10−15 g m (Pa s m2)−1; carbon dioxide permeability ranged from 28.81 ± 3.08 to 61.19 ± 1.44 × 10−15 g m (Pa s m2)−1; tensile strength ranged from 2.56 ± 0.15 to 3.96 ± 0.43 MPa; and elongation at break ranged from 28.26 ± 4.53% to 46.36 ± 2.29%.αLFA VALNATURA Project of the Europe Aid Cooperation OfficeFundação para a Ciência e Tecnologia (FC

Customization of an optical probe device and validation of a signal processing procedure to study gas-liquid-solid flows. Application to a three-phase internal-loop Gas-lift Bioreactor

The study of local hydrodynamic properties of three-phase bioreactors in biotechnology processes is of great importance, mainly because of the complex interaction between bioreactor and microorganisms. However, classical techniques used for measuring local hydrodynamic properties such as single needle probes are mainly limited to two-phase flows. In this work it was developed and validated a new system, based on the customization of an optical probe initially designed in LEGI. The necessity of a new system was due to the agglomeration of the solid-phase (spent grains which are used as the micro-organisms carrier for the targeted application) around the optical tip, which influences the measurements. This new system allows for the measurement of the main local gas-phase properties in a complex gas-liquid-solid mixture. The new system was first validated for air-water system in an internal loop gas-lift reactor and then applied to a spent grains-air-water mixture at low solid load in an internal gas lift reactor. In addition, experiments using complementary techniques (as high speed camera and PIV) were performed that allowed for the validation of the new system and the explanation of possible physical mechanisms that are underlying on this multiphase system. The system developed has the potential for improvement and use in several biotechnology applications.The authors gratefully acknowledge the financial support from FCT (Fundacao para a Ciencia e Tecnologia, SFRH/BD/37082/2007 and SFRH/BPD/45637/2008)

Antimicrobial activity of propolis nanoparticles against some common meat contamination bacteria

Raw meat is a highly perishable product that requires a great amount of care, from its handling to the conservation conditions at low temperatures. The reduction of microbial proliferation in meat is necessary to achieve an increase of shelf life, food safety, while maintaining product features. For this reason, a technology based on natural antimicrobial agent may offer a potential alternative to protect and control the proliferation of microorganisms on food products. Propolis is a natural resinous substance collected from the leaf buds of different tree species by honeybees and known for its biological properties (antibacterial, antifungal, antioxidant) (Koo et. al, 2000). The aim of this work was to evaluate the antimicrobial activity of propolis nanoparticles in comparison with ethanol-propolis extract against some common meat contamination bacteria. The ethanol-propolis extract was obtained from green propolis resin, in absolute ethanol under agitation during 15 days. To obtain the propolis nanoparticles, ethanol-propolis extract at 13.75% (w/v) was mixed with polyvinyl-alcohol solution at 0.1% (w/v). Antimicrobial activity of propolis nanoparticles and ethanol-propolis extract was tested against 8 microorganisms typically present in meat. Minimum inhibitory concentrations (MIC) of both solutions were evaluated by agar-well diffusion method; all strains were susceptible and MIC values ranged from 0.57 to 2.29% (w/v) for propolis nanoparticles and from 0.68 to 6.88% (w/v) for ethanol-propolis extract. The MIC of propolis nanoparticles for Escherichia coli, Staphylococcus aureus, Salmonella thompson, Listeria monocytogenes, Enterococcus faecalis, Enterobacter helveticus, Lactobacillus bucheneri and Leuconostoc mesenteroideswas 1.15%, 0.57%, 2.29%, 1.72%, 1.72%, 2.29%, 2.29%, 1.72%, respectively, and the MIC for ethanol-propolis extract to the same species was 3.44%, 0.68%, 3.44%, 3.44%, 3.44%, 6.88%, 6.88%, 3.44%, respectively. The shown antimicrobial activity of propolis nanoparticles is of potential interest for food applications (e.g. in edible coatings formulation). Therefore, results obtained in this study, set the bases for future studies, using films as support for propolis nanoparticles, for application in meat products. References Koo, H.; Gomes, B.P.F.A.; Rosalen, P. L.; Ambrosano, G.M.B.; Park, Y. K.; Cury, J. A. (2000) In vitro antimicrobial activity of propolis and Arnica montana against oral pathogens. Archives of Oral Biology 45: 141-14

Effect of moderate electric fields in the permeation properties of chitosan coatings

Edible films and coatings can provide additional protection for food, while being a fully biodegradable, environmentally friendly packaging system. Preliminary works have shown that the presence of a moderate electric field during the preparation of chitosan coating solutions may influence e.g. their transport properties. If such effect is confirmed, moderate electric fields could be used to tailor edible films and coatings for specific applications. The aim of this work was to determine the effect of field strength on functional properties of chitosan coatings (obtained from lobster from the Cuban coasts). Four different field strengths were tested (50, 100, 150, 200 V cm−1) and, for each electric field treatment, the water vapor, oxygen and carbon dioxide permeabilities of the films formed were determined, together with their color, opacity and solubility in water. The surface microstructure of the films was analyzed using atomic force microscopy (AFM). The results showed that ohmic heating had statistically significant effects on film's physical properties and structure. In general, the most pronounced effect of the field strength was observed for treatments made at 100 V cm−1 or higher, a positive correlation being found between the water vapor, oxygen and carbon dioxide permeability coefficients and field strength. The AFM results show that the surface of chitosan films is much more uniform when an electric field is applied, which may be related with a more uniform gel structure leading to the differences observed in terms of transport properties.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Europe Aid Cooperation Office - αLFA VALNATURA ProjectFundação para a Ciência e a Tecnologia (FCT