Arthrospira platensis ou Spirulina é uma microalga com alto valor nutricional. Foram preparados extratos de Spirulina, caracterizados e aplicados como estabilizadores de emulsão de óleo de girassol comercial em água (O/A) (10% v/v) na ausência e na presença de quatro tipos de hidroxipropil metilcelulose (HPMC). Os extratos brutos de Spirulina foram preparados em tampões a pH 6 (EB6) e pH 8 (EB8) por sonicação para promover a lise celular e a libertação de proteínas e fosfolípides; Parte dos extratos foi centrifugada (EC6 ou EC8). Independentemente das condições de extração, todos os extratos apresentados apresentaram valores de potencial-&#950 médio variando de - (16 ± 2) mV a - (20 ± 2) mV, tamanho médio variando de (108 ± 52) nm a (306 ± 68) nm e atividade interfacial. As emulsões O/A preparadas com extratos de Spirulina (10 g / L) exibiram partículas com potencial- médio variando de - (16 ± 2) mV a - (27 ± 4) mV, tamanho médio variando de ~ 70 nm (EB6 ou EB8) a ~ 700 nm (EC6 ou EC8). No entanto, o EB6 levou a emulsões ligeiramente mais estáveis do que as outras. A combinação de EB6 (10 g / L) e HPMC (1,0 % m/m) levou a um aumento substancial na estabilidade da emulsão, embora os valores de potencial- diminuíram uma ordem de grandeza. Em particular, a HPMC com a maior massa molar e o maior grau de substituição de grupos metila conduziu a i) camada interfacial mais robusta resultante da formação de complexos entre cadeias HPMC e proteínas EB6 e (ii) meio contínuo mais viscoso. / Arthrospira platensis or Spirulina is a microalga with a high nutritional value. Extracts of Spirulina were prepared, characterized and applied as oil in water (O/W) (10 % v/v) emulsion stabilizers in the absence and presence of four types of hydroxypropyl methylcellulose (HPMC). The emulsions were prepared with edible sunflower oil. Crude extracts of Spirulina were prepared in buffers at pH 6 (CE6-Crude extract pH6) and pH 8 (CE8-Crude extract pH8) by sonication to promote cell lysis and protein and phospholipids release; part of the extracts was centrifuged (CCE6 or CCE8). Regardless of the extraction conditions, all extracts presented mean -potential ranging from (16 ± 2) mV to (20 ± 2) mV, mean diameter ranging from (108 ± 52) nm to (306 ± 68) nm and interfacial activity. The emulsions prepared with Spirulina extracts (10 g/L) displayed particles with mean -potential ranging from (16 ± 2) mV to (27 ± 4) mV, mean diameter ranging from ~ 70 nm (CCE6 or CCE8) to ~ 700 nm (CE6 or CE8). However, CE6 led to emulsions slightly more stable than the others did. The combination of CE6 (10 g/L) HPMC (1.0 wt %) led to substantial increase in the emulsion stability, although the -potential values decreased one order of magnitude. Particularly, the HPMC with the highest molecular weight and highest methyl substitution degree led to the most (i) robust interfacial layer resulting from the complex formation between HPMC chains and CE6 proteins and (ii) viscous continuous medium.

Arthrospira platensis ou Spirulina é uma microalga com alto valor nutricional. Foram preparados extratos de Spirulina, caracterizados e aplicados como estabilizadores de emulsão de óleo de girassol comercial em água (O/A) (10% v/v) na ausência e na presença de quatro tipos de hidroxipropil metilcelulose (HPMC). Os extratos brutos de Spirulina foram preparados em tampões a pH 6 (EB6) e pH 8 (EB8) por sonicação para promover a lise celular e a libertação de proteínas e fosfolípides; Parte dos extratos foi centrifugada (EC6 ou EC8). Independentemente das condições de extração, todos os extratos apresentados apresentaram valores de potencial-&#950 médio variando de - (16 ± 2) mV a - (20 ± 2) mV, tamanho médio variando de (108 ± 52) nm a (306 ± 68) nm e atividade interfacial. As emulsões O/A preparadas com extratos de Spirulina (10 g / L) exibiram partículas com potencial- médio variando de - (16 ± 2) mV a - (27 ± 4) mV, tamanho médio variando de ~ 70 nm (EB6 ou EB8) a ~ 700 nm (EC6 ou EC8). No entanto, o EB6 levou a emulsões ligeiramente mais estáveis do que as outras. A combinação de EB6 (10 g / L) e HPMC (1,0 % m/m) levou a um aumento substancial na estabilidade da emulsão, embora os valores de potencial- diminuíram uma ordem de grandeza. Em particular, a HPMC com a maior massa molar e o maior grau de substituição de grupos metila conduziu a i) camada interfacial mais robusta resultante da formação de complexos entre cadeias HPMC e proteínas EB6 e (ii) meio contínuo mais viscoso. / Arthrospira platensis or Spirulina is a microalga with a high nutritional value. Extracts of Spirulina were prepared, characterized and applied as oil in water (O/W) (10 % v/v) emulsion stabilizers in the absence and presence of four types of hydroxypropyl methylcellulose (HPMC). The emulsions were prepared with edible sunflower oil. Crude extracts of Spirulina were prepared in buffers at pH 6 (CE6-Crude extract pH6) and pH 8 (CE8-Crude extract pH8) by sonication to promote cell lysis and protein and phospholipids release; part of the extracts was centrifuged (CCE6 or CCE8). Regardless of the extraction conditions, all extracts presented mean -potential ranging from (16 ± 2) mV to (20 ± 2) mV, mean diameter ranging from (108 ± 52) nm to (306 ± 68) nm and interfacial activity. The emulsions prepared with Spirulina extracts (10 g/L) displayed particles with mean -potential ranging from (16 ± 2) mV to (27 ± 4) mV, mean diameter ranging from ~ 70 nm (CCE6 or CCE8) to ~ 700 nm (CE6 or CE8). However, CE6 led to emulsions slightly more stable than the others did. The combination of CE6 (10 g/L) HPMC (1.0 wt %) led to substantial increase in the emulsion stability, although the -potential values decreased one order of magnitude. Particularly, the HPMC with the highest molecular weight and highest methyl substitution degree led to the most (i) robust interfacial layer resulting from the complex formation between HPMC chains and CE6 proteins and (ii) viscous continuous medium.

<p>Seme tikve (Cucurbita pepo) obiluje kako uljem tako i proteinima. Nakon izdvajanja ulja, proteini se koncentri&scaron;u u uljanoj pogači, sekundarnom proizvodu procesa proizvodnje ulja, gde njihov sadrţaj dostiţe do 65%. Proteini semena tikve su primamljiv sastojak za prehrambenu, farmaceutsku i kozmetičku industriju zbog svoje farmakolo&scaron;ke aktivnosti i visoke biolo&scaron;ke vrednosti. Pored toga, budući da su mnogi proizvodi ovih industrija po svojoj koloidnoj prirodi emulzije, proteini semena tikve bi se u njima mogli naći i kao prirodne povr&scaron;inski aktivne materije. Međutim, koloidna funkcionalnost proteina semena tikve se jo&scaron; uvek potcenjuje zbog globularne strukture za koju se vezuju slabija funkcionalna svojstva u odnosu na proteine sa fleksibilnijom strukturom. Prema tome, cilj ove disertacije je ispitivanje funkcionalnih osobina proteinskog izolata semena tikve, pre svega njegovih adsorpcionih i emulgujućih svojstava, kao i ispitivanje uticaja promene proteinske strukture putem enzimske hidrolize na ispitivana svojstva.<br />Pripremljeni su izolat proteina semena tikve (IPST) i dva enzimska hidrolizata, H1 i H2. IPST, H1 i H2 su okarakterisani određivanjem sadržaja vlage, proteina i pepela, zatim, određivanjem prinosa, molekulske mase i zeta potencijala. Ispitan je uticaj koncentracije proteina/peptida (0,0001&ndash;1 g/100 cm³), pH (3&ndash;8) i jonske jačine (0&ndash;1 mol/dm³ NaCl) na rastvorljivost i adsorpciona svojstva: dinamički međupovr&scaron;inski pritisak (ulje/voda), statički povr&scaron;inski (vazduh/voda) i međupovr&scaron;inski (ulje/voda) pritisak, kinetiku adsorpcije i dilatacionu reologiju proteinskih adsorpcionih filmova. Nakon toga, ispitan je i uticaj pomenutih parametara na emulziona svojstva IPST, H1 i H2. Emulgujuća svojstva IPST, H1 i H2 su okarakterisana na osnovu prosečnog prečnika kapljica emulzija, raspodele veličina kapljica i stabilnosti emulzija.<br />Utvrđeno je da je prinos IPST veći od prinosa oba hidrolizata za oko 65 %. IPST ima najniţu rastvorljivost na pH=5, &scaron;to ujedno predstavlja i njegovu izoelektričnu tačku. Enzimskom hidrolizom IPST značajno se povećava rastvorljivost, posebno na pI=5. Povećanje jonske jačine je izazvalo salting&ndash;in ili salting&ndash;out efekat rastvorljivosti kod svih uzoraka u zavisnosti od pH. IPST, H1 i H2 poseduju povr&scaron;insku aktivnost pri čemu je povr&scaron;inski/međupovr&scaron;inski pritisak H1 i H2 manje zavistan od promene pH i jonske jačine u poređenju sa povr&scaron;inskim/međupovr&scaron;inskim pritiskom IPST. Adsorpcijom na granicu faza IPST i oba hidrolizata obrazuju adsorpcione filmove sa dominantnom elastičnom komponentom. Emulgujuća svojstva IPST, H1 i H2 zavise od koncentracije uzorka, pH vrednosti i jonske jačine kontinualne faze. Pri koncentraciji od 1 g/100 cm³ i Ic=0 mol/dm³ pripremljene emulzije su stabilne na svim pH osim emulzije IPST na pH 5. Sve emulzije podležu gravitacionoj nestabilnosti.</p> / <p>Pumpkin (Cucurbita pepo) seed is rich source of both, oil and proteins. Once the oil has been extracted, proteins concentrate in oil cake, a by&ndash;product of the oil<br />extraction process, where their content can reach up to 65%. Pumpkin seed proteins are desirable ingredient in food, pharmaceutical and cosmetic industry due to their pharmacological activities and high biological value. Moreover, since many of products of these industries are, in colloidal terms, emulsions, pumpkin seed proteins could serve as surface active materies. However, colloidal functionality of pumpkin seed proteins is still underestimated for their globular structure which entails inferior functional properties to functional properties of proteins with more flexible structure. Based on that, the aim of this dissertation is to investigate functional properties of pumpkin seed protein isolate, adsorption and emulsifying properties, in the first place, and then to investigate the influence of modification of the protein structure, by means of enzymatic hydrolysis, on the aforementioned properties.<br />Pumpkin seed protein isolate, IPST, and two enzymatic hydrolysates, H1 and H2, were prepared. IPST, H1 and H2 were characterized by determination of moisture, ash and protein content, then, by determination of protein recovery, molecular mass and zeta potential. Influence of the protein/peptide concentration (0.0001&ndash;1 g/100 cm³), pH (3&ndash;8) i ionic strength (0&ndash;1 mol/dm³ NaCl) on the solubility and adsorption properties: dynamic interfacial (oil/water) pressure, static surface (air/water) and interfacial (oil/water) pressure, adsorption kinetics and interfacial dilatational properties, was<br />investigated next. In the end, influence of the aforementioned pharameters on the emulsifying properties of IPST, H1 and H2 was investigated. Emulsifying properties of IPST, H1 and H2 were discussed in terms of mean droplet diameter, droplet size distribution and emulsion stability.<br />Protein recovery of IPST was determined to be 65 % higher than recovery of H1 and H2. Solubility of IPST was the lowest at pH 5, what presents the isoelectric point. The enzymatic hydrolysis of IPST significantly increased solubility, especialy at the isoelectric point. Increase in the ionic strenght led to salting&ndash;in or salting&ndash;out effect depending on pH of the sample. Three investigated samples, IPST, H1 and H2 exhibited surface activity, however, sufrace/interfacial pressure of H1 and H2 were found to be less influenced by change in pH or ionic strenght of the solution in comparison to the IPST. Once adsorbed to the interface IPST and both hydrolysates form interfacial film with dominant elastic component. Emulsifying properties of IPST, H1 and H2 depend on the concentration, pH and ionic strength of the continuous phase. Stabile emulsions were formed at concentration of 1 g/100 cm3 and Ic=0 mol/dm³ regardless of pH, with the exception of the IPST at pH 5. All emulsions were susceptibile to gravitational separation.</p>