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Traditional polysaccharides extraction processes are often performed under heating which makes them time-, energy- and solvent-consuming. The aim of this work was to assess the possibility of using ohmic heating to replace conventional heating in the extraction of seaweed hydrocolloids. This technology is able to heat almost instantaneously the whole volume to be treated, using the ability that most materials have to dissipate energy as heat. As a result, it is energetically much more efficient, with efficiencies well above 95%. In traditional boilers, energetic efficiency is usually around 70-80%. This implies that the energetic efficiency of traditional extraction is below these values, as we have also to account for energy losses in the pipelines and in the extractor. The extraction of agar from Gelidium corneum (sesquipedale) was chosen as a model process due to the high temperatures and energy input needed. All traditional and ohmic extractions were made with a ratio of 50 g of water: 1 g of seaweed at 95 °C, for 2 hours on seaweeds pre-treated with NaOH and neutralized with diluted acetic acid. For the ohmic system, the voltage was set at 600 V and the distance between electrodes was 10 cm. The yields achieved (around 15-20%) were similar in both traditional and ohmic extractions. Gelling ability, sulphate and 3-6-anydrogalactose contents were also in the same range resulting in agars with similar functional properties. Ohmic heating is thus an energetically more efficient alternative to the conventional process of extraction of agar from seaweeds without impairing its functional properties. Besides the evident energy efficiency advantage, steam (and thus boiler blowdown) savings also constitute an important environmental improvement.

The replacement of conventional synthetic films and coatings by biodegradable alternatives reduces the use of non-renewable resources and waste disposal problems. Considering that Portugal is a major producer of leather, and consequently a large producer of related wastes, in this research, bovine hair was tested for the production of biodegradable films directly by thermo-compression, allowing waste valorisation and reduction of environmental pollution. The aim of this study was to determine the influence of the different pre-treatments performed by two processes (removal by mechanical action and removal by chemical process), applied to bovine hair, in order to obtain a biodegradable film with appropriate properties. Mechanical properties for these films were evaluated, namely strain at break, stress at break and Young modulus. Additionally colour, solubility and swelling in water were also studied. The mechanical removal hair only produced films with Na2S treatment. Chemical removed hair (immunization) depends of the pre-treatment and the degreasing with petroleum ether or sodium sulphide pre-treatment leads better mechanical properties. The results obtained indicated that the pre-treatments have an important role in the final properties of biodegradable films.

The gelling ability of whey proteins can be changed by limited hydrolysis and by the presence of other components such as polysaccharides; depending on the environmental conditions it can either be improved or impaired. In this work the effect of LBG on the heat-set gelation of aqueous whey protein hydrolysates (10 % w/w) from pepsin was assessed at pH 7.0 by small deformation rheology. Whey protein concentrate (WPC) and hydrolysates with a degree of hydrolysis (DH) of 1.5, 2.5 and 4.9 % were used. Different LBG concentrations were tested: 0, 0.1, 0.3 and 0.55 % (w/w). The behaviour of gels from whey proteins or whey protein hydrolysates towards the presence of LBG was very similar. The evolution of the viscous and storage moduli followed the general behaviour reported for many biopolymer heat-set gelation processes including whey proteins gelation. The increase in the LBG concentration generally led to a decrease in the gel strength. However, for whey proteins a small amount of LBG (0.1 %) leads to a big enhancement in the gel strength probably due to an increase in the protein concentration of the protein enriched phase. Further increases in the LBG concentration led to a decrease in the gel strength. The gelation process is very sensible to environmental conditions and to processing and often leads to rather coarse data. The factorial planning used allowed validating conclusions using fewer experiments than those needed if no planning had been used, while still getting statistical significance out of the results. However, as many factors are involved, the modelling of the process was not straightforward.

CHISA 2008 - 18th International Congress of Chemical and Process Engineering (CD-ROM of Full Texts), info:eu-repo/semantics/publishedVersion

The gelling ability of whey proteins can be changed by limited hydrolysis, and depending on the environmental conditions it can either be improved or impaired. Rheological studies are useful to evaluate the gelling ability of biological macromolecules; in particular, they allow accessing the structure of the gel, evaluating its texture, controlling the gelling behaviour or complementing the information provided by sensory methods. The heat-induced gelling properties of whey protein concentrate (WPC) and whey protein hydrolysates (WPH) from trypsin and pepsin with different degrees of hydrolysis - 1.0 (T1.0) and 3.5 % (T3.5) for tryptic hydrolysates and 1.5 (P1.5), 2.5 (P2.5) and 4.9 % (P4.9) for peptic hydrolysates - at different concentrations were studied at pH 7.0 by small deformation rheology. At WPC concentrations close to the gelling point, stronger gels with lower gelation temperatures were achieved with limited hydrolysis of whey proteins. G was higher for P1.5 (138 Pa) followed by P2.5 (58 Pa) and T1 (17 Pa), for hydrolysates concentration of 7.5 % w/w. All three were stronger than WPC at this concentration (G=5.7 Pa). They were also more elastic as the loss angle was smaller. However, at higher protein concentrations this effect was impaired. The expected increase in gel strength was smaller for the hydrolysates than for the intact proteins. A similar increase in protein concentration corresponds to a lower increase of the amount of protein with effective gelation ability in the case of the hydrolysates. Gels from hydrolysates ruptured at lower strains than gels from WPC (i.e. more particulate gels with a coarser network structure). The results show that protein systems with many different textures can be tailored by manipulating the hydrolysis conditions and the type of the enzyme used to produce protein hydrolysates., info:eu-repo/semantics/publishedVersion

Tese de Doutoramento em Engenharia Química e Biológica, Cheese whey is a waste effluent with a hig-, polluting content that cannot disposed directly into the environment and can become an environmental and economical problem for dairy industries Cheese whey treatment for disposal can be expensive and laborious as it is highly putrescible and has a very low solid concentration. Valorisation of dairy by-products is thus of great interest for economic and environmental reasons. Bovine milk whey proteins are widely used in food formulations due to their nutritional and functional properties. In fact, whey proteins have a hig-, nutritional capacity and balanced amino acid content, particularly essential amino acids. Furthermore, major whey proteins, a.-Iactalbumin and rl-Iactoglobulin, are an important source of bioactive peptides, compounds with a health promoting potential The functional applications of whey proteins include emulsification, gelation, foaming and filler/water binder The wish of the food industry to convert waste products into value-added, high-priced commodities has inspired a !?lowing interest in the development of processes for the enhancement of whey protein functionality. Thus, the modification of whey proteins to improve their functional properties in specific food systems has become a focus of current research. One market that is in huge expansion is lhat of health-promoting foods. However, such novel products have to meet consumer acceptance, in terms of efficacy, organoleptic properties and price Therefa-e the development of health-promoting foods comprises a range of processes which need to be integrated, including optimisation of protein hydrolysis, peptide characterization, sbJdy of peptides' physical-chemical properties and interactions with other food components (Iipids, pOlysaccharides, salts and others) and establishment of a standard methodolo~ to determine biological activity in wvo. Based on the premises described in the previous para!?laphs, the work presented in this document is the result of a plan that aimed at studying the hydrolysis of whey proteins for food applications In particular, lhe research undertaken was directed to the hydrolysis of whey proteins (aiming at changing their functional properties) and to the study of rheological interactions between whey proteins/hydrolysates and galactomannans, with the final goal of obtaining new textures, with hig-, protein content or with interesting (eg bioactive) peptides that can be used in existing food formulations or in the development of new food products The hydrolysis of whey proteins was performed with the aid of enzymes, both free and immobilized in different carriers. A comparison was established for the various conditions tested based on the enzyme's activity and specificity, kinetic parameters and peptide profile of the hydrolysates produced. The gelling properties of the hydrolysates were tested and the hydrolysates were combined with a polysaccharide (Iocust bean ~m), in arder to evaluate the interaction of lhose components in terms of possible new functional properties The work performed allowed to conclude lhat the choice of lhe hydrolysis enzyme is particularly important in determining the properties of the resulting hydrolysates. Besides choosing the type of enzyme it is also important to select an adequate fa-m of the chosen enzyme with the adequate purity and treatment (for instance a treated trypsin with low chymotryptic activity) for the desired application, as different hydrolysates are achieved with different forms of the enzyme The selection of the adequate operational conditions (time, pH and temperature) also determines the composition of the resulting hydrolysate. Hig-,er reaction times lead obviously to higher degrees of hydrolysis and smaller peptides (usually more hydrophobic) and pH and temperature determine the resistance of whey proteins to the hydrolysis as well as the activity of the enzyme. Considering the enzyme immobilization procedures, the activity recovery was 100 with ali carriers except for trypsin crosslinked on zeolites, where it was satisfactory However, when a more purified enzyme from bovine pancreas was used with glyoxyl-spent grain or POS-PVA wilh glutaraldehyde, the activity retention was of 46 % and 73 % against 11 % and 9 % with crude enzyme. Thus it can be stated that trypsin was successfully immobilized on spent ~ains by multipoint covalent attachment using glycidol and on POS-PVA functionalized with glutaraldehyde Even so, the immobilized trypsin with the hi~est actillity was achieved with covalent binding through glutaraldehyde to silanized zeolite followed by crosslinking with glutaraldehyde, probably due to a positive effect of the zeolite on the enzyme activity Only trypsin immobilized on spent grain showed significant activity towards whey proteins Allhou~ trypsln immobilized on cross-Iinked zeolite NaY and trypsin covalently immobilized m POS-PVA and glutaraldehyde have shown a high activity towards a small substrate (eg BAPNA), this did not happen when whey proteins were used as substrate. Peptide profile of hydrolysates trom whey protein isolate wilh both free and immobilized on spent grain enzymes were similar, which indicates lhat spent grains can be used as carriers for trypsin to produce hydrolysates similar to those obtained with the free enzyme The contrai of the extent of the hydrolytic reaction is extremely important to ensure that a hydrolysate wilh the intended properties is obtained. The immobilizatlon allows such control by simplywithdrawing the enzyme trom the reaction medium, without the need of using high temperatures or considerable pH shifts. Furlher, immobilization also allows the reuse of the enzyme, with obllious advantages trom the economical point of view. The gelling ability of whey proteins can be changed by limited hydrolysis Depending on the environmental conditions it can either be improved or impaired. At WPC concentrations close to lhe gelling point, stronger gels with lower gelation temperatures can be achieved with limited hydrolysis ofwhey proteins. However, at hl~er protein concentrations this effect Is Impaired There is an increase of the gel strength with the increase of the protein concentration, as expected, but lhis increase is smaller for the hydrolysates than for the intact proteins. In fact, a similar increase in the protein concentration corresponds to a lower increase in the amount of protein with effective gelation ability in the case of the hydrolysates The relative importance of non-covalent interactions in the structure of whey protein gels seems to increase with the de~ee of hydroslysis. LBG alters the microstructure of whey protein gels by modifying the equilibrium between aggregation and se~egation The gelation time is aiso decreased. The volume of the protein-enriched phase decreases with the increase of the LBG concentration and the protein concentratlon probably increases within that phase The final structure of the gels is a result of the equilibrium between aggregation and se~egation and of the increase of the protein concentration on the protein-enriched phase. The behaviour of gels from whey proteins ar whey protein hydrolysates towards the presence of LBG is very similar. For whey proteins and for whey protein hydrolysates a small amount of LBG in the presence of salt leads to a big enhancement In the gel strength. The gelation process is very sensible to environmental conditions and to processing and often leads to quite coarse data. The factorial planning used in this work ailowed validating conclusions using fewer experiments lhan those needed if no planning had been used, while still getting statistical siE1J1ificance out of the results. However, as many factors are involved, the modelling of the process was not strai~tforward. A simple linear or quadratic function was generally not enou~ to accurately describe lhe system behaviour. In short, hydrolysates with many different functional, nutritional and biologlcal properties can be produced by manipulating the hydrolysis conditions and lhe source of the enzyme (alone or in combination; free or immobilized; pure or Impure; H). The introduction of a pOlyssacharide allows an even bigger range of functional properties and can be used to ad]ust the desired property to the desired appIication., União Europeia. Fundo Social Europeu - Formação Avançada de Docentes do Ensino Superior

Neste trabalho utilizou-se um sub-produto da indústria cervejeira proveniente do malte com um teor elevado em celulose, a drêche, como suporte de imobilização para tripsina. Efectuaram-se hidrólises de concentrado proteico de soro de queijo com tripsina imobilizada com diferentes condições de pH e temperatura de forma a determinar os valores óptimos de operação. O perfil dos hidrolisados resultantes foi posteriormente analisado por cromatografia líquida de alta performance em fase reversa. O valor óptimo de operação com tripsina imobilizada ocorreu a 60 ºC, superior à temperatura correspondente com enzima livre. A actividade da enzima imobilizada em drêche foi bastante inferior à da enzima livre. O perfil de péptidos obtido com os dois tipos de enzima foi semelhante., Fundação para a Ciência e a Tecnologia (FCT); Fundo Social Europeu.

This work compares different types of zeolites (NaA, NaX and NaY) as potential carriers for trypsin immobilisation. Silica was also used as a traditional carrier. Covalent attachment to the carriers was tested using glutaraldehyde. The efficiency of immobilisation and activity, operation and storage stability of free and immobilised enzyme on the three supports were studied. Optimum value of operation temperature was determined for trypsin immobilised on the best zeolite. Trypsin was most successfully immobilised on NaY by covalent attachment using glutaraldehyde. Though the best efficiencies were still obtained with silica, promising results were achieved with zeolite NaY. The ratio of immobilised protein achieved was very high, especially with silica, NaX and NaY. However there was a significant loss of enzyme activity with the immobilisation of trypsin. Optimal temperature obtained with immobilised enzyme was ca. 60 ºC, higher than the correspondent temperature for free enzyme (50 ºC)., Fundação para a Ciência e a Tecnologia (FCT) - POCTI/2000/QUI/36452., European Social Fund (ESF).

Trypsin is a widely used enzyme for protein hydrolysis and can be used to improve functional and nutritional properties of foods. The immobilization of enzymes on solid supports can offer several advantages over free enzymes including easy handling, recovery from the reaction medium, reuse and operation in continuous reactors. Traditional carriers include porous silica, porous glass and cellulose derivatives. Zeolites are porous alumino-silicates available in a wide range of particle size and porosity and can also be used as carriers. Spent grains are a brewing by-product with a high content in cellulose and can also be interesting as carriers for enzyme immobilization because, besides having the necessary conditions (as stability, rigidity, low mass transfer limitations, for instance), they are cheap and food grade. This work proposes the use of spent grains and zeolites as alternative carriers for trypsin immobilization and compares them with a traditional support (silica). Physical adsorption, ionic attachment and covalent attachment to the supports were tested. The efficiency of immobilization and activity, as well as the operation and storage stability of free and immobilized enzyme on the three supports were studied. Trypsin was most successfully immobilized on the supports by covalent attachment using glutaraldehyde. Though the best efficiencies were still obtained with silica, promising results were achieved with both spent grains and zeolite., Fundação para a Ciência e a Tecnologia (FCT) - project POCTI/2000/QUI/36452., European Social Fund (ESF).

Dissertação de mestrado em Engenharia Biológica, Esta tese teve como objectivos principais a elaboração e implementação de soluções para a planificação óptima de experiências de modo a resolver o problema da identificação na estimação de coeficientes de rendimento num modelo de fermento de padeiro. O objectivo final foi programar trajectórias de alimentação de substrato. As metodologias apresentadas para a identificação de coeficientes de rendimento envolvem medições completas do estado e visam a optimização da riqueza informativa da experiência, quantificada por índices relativos à matriz de informação de FISHER. Procurou projectar-se experiências que conduzissem a um máximo de informação através da programação do caudal de alimentação em glucose. O procedimento utilizado necessita de um conhecimento a priori dos coeficientes de rendimento e é independente das cinéticas de reacção. Foram, depois, realizadas experiências com o perfil de alimentação de glucose optimizado para determinação dos coeficientes de rendimento., The main objectives of this thesis were the development and implementation of solutions to achieve an optimum experimental design in order to solve the problem of identification in the estimation of yield coefficients af a baker’s yeast model. The final objective has been to program substrate feeding profiles. The methodologies developed in order to identify yield coefficients involve complete state measurements and aim at the optimisation of the informative richness of the experiment, quantified by indexes related to the concept of FISHER’s information matrix. An effort has been made to design experiments that would lead to a maximum of information by programming the glucose feeding rate. The procedure needs a priori knowledge of the yield coefficient values and it is independent of the growth kinetics. Finally, experiments were performed with the optimised glucose feeding profile in order to determine the yield coefficients., Cette thése a pour objectif l’élaboration et l’implémentation de solutions pour la planification optimale d’essais, pour résoudre le problème de l’identification dans l’éstimation de coefficients de rendement dans un modèle de levure de boulangerie. Le but es programmer trajectoires d’alimentation en substrat. Les méthodologies developpées pour l’identification des coefficients de rendement enveloppent la mesure de l’état complet et ont pour but d’optimiser la consistance informative de l’expérience, quantifiée par des indexes relatifs à la matrice de l’information de FISHER. La planification expérimentale est faite pour obtenir un maximum d’information à travers de la programmation du débit d’alimentation en glucose. Le procédé a besoin d’une connaissance a priori de coefficients de rendement et est idépendant des taux de croissance. Finalement, expériences sont realisées avec le profil d’alimentation de glucose optimisé pour déterminer les coefficients de rendement., Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI.

The main objective of this work is to elaborate methodologies that allow the identification of yield coefficients through complete measurements of the state. Experimental design strategies are proposed in order to optimize the richness of data coming out from the experiments, quantified by indexes related to the Fisher information matrix. The objectives of the experimental planning have been addressed in terms of the programming of input trajectories. The experimental planning is envisaged for baker’s yeast aiming at the computation of the substrate feed trajectories.