Carla Rosane Barboza Mendonça

Role of the co-surfactant nature in soybean w/o microemulsions.

The influence of the co-surfactant on physicochemical properties of w/o soybean oil microemulsions (MEs) has been studied. In spite of the similarity in phase diagrams, the MEs display remarkable differences when examined by electrical conductivity, dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and linear voltammetry. When different short-chain alcohols were employed as co-surfactants, together with sodium dodecyl sulfate (SDS) as surfactant, the DLS results indicated the systems to be monodisperse. Both the electrical conductivity of the MEs and the hydrodynamic radii of the droplets (R(H)) increased with water content while R(H) diminished as temperature increased, no aggregation or percolation of the droplets being observed. In comparison to w/o MEs prepared with 3-methyl-1-butanol, those prepared with 1-pentanol presented higher electrical conductivity and larger limiting currents at a Pt ultramicroelectrode for oxidation of the water occluded into the particles. Finally, from the electrochemical viewpoint the use of 1-pentanol is recommended, no advantage being gained by using any of the other tested alcohols.

Water in soybean oil microemulsions as medium for electrochemical measurements

Microemulsions of water in soybean oil (w/o ME) were prepared with sodium dodecyl sulfate (SDS) as surfactant and amyl or isoamyl alcohol, as co-surfactants. Microemulsions containing 40.0% oil, 43.2% alcohol, 10.8% SDS and 6.0% water in weight, in the ratio 1:4 [SDS]:[alcohol] showed the highest thermodynamic stability. The aqueous droplet size and its diffusion coefficient Dw/o in the ME were determined through dynamic light scattering (DLS). Voltammetric measurements in the ME at a Pt disk ultramicroelectrode (ume) evidenced the oxidation of both water and ferrocene (Fc), and the reduction of oleic acid. The Dw/o values calculated from the limiting current being lower than the ones obtained from DLS indicate that water oxidation probably requires diffusion towards the electrode of both the droplets and the water molecules from inside the droplets. The results show that electroanalytical determinations can be carried out in w/o ME.

Caracterização física, química, microbiológica e sensorial de geléias light de abacaxi

O trabalho objetivou elaborar geleias com reduzido teor calorico, utilizando como agentes de corpo diferentes combinacoes dos hidrocoloides xantana, carragena e locusta. Como comparativo utilizou-se uma formulacao padrao de geleia de abacaxi (controle), elaborada com sacarose e xarope de glicose na proporcao de 4:1 (p/p), e com teor final de solidos soluveis de 65oBrix. As quatro formulacoes light foram preparadas pela substituicao de 50% da quantidade de acucar da formulacao controle, sendo que para equiparar a docura, adicionou-se o edulcorante sucralose. Foram avaliadas as caracteristicas quimicas, fisicas, microbiologicas e sensoriais, alem do valor calorico total das geleias. Os resultados mostraram que as geleias apresentaram caracteristicas quimicas e fisicas semelhantes as descritas na literatura e enquadraram-se na categoria de produtos light, segundo a legislacao vigente. Quanto as caracteristicas microbiologicas, todas as formulacoes enquadraram-se nos padroes microbiologicos estabelecidos pela legislacao brasileira. Em termos sensoriais a formulacao com a combinacao das gomas carragena:xantana:locusta (1:1:1, p/p/p) foi a que apresentou melhores caracteristicas de geleia.

Características sensoriais de compotas de pêssego light elaboradas com sucralose e acesulfame-K

The objective of this work was carried out as a sensory characterization of low calorie peach compote. The products were adjusted with the partial substitution of sugar by sucralose, acesulfame-K and sucralose+acesulfame-K. The shelf life of these products during a period of 90 days was also evaluated. The attributes of appearance, colour, shiny, softness, flavour and acidity were also evaluated soon after processing and after 30, 60 and 90 days of storage. A preference test at the end of the storage period was also performed. According to the sensory evaluation of the attributes significant differences were detected among the four formulations of peach compote, especially in relation to the attributes of flavour and acidity. The formulations with acesulfame-K and sucralose+acesulfame-K showed lower values than the others. During the storage period expressive changes in the compote sensory characteristics were not observed. The results of the preference test showed that there was no difference in the consumers preference for any of the formulations.

AÇÚCAR MASCAVO EM GELEIADAS DE MAÇÃ

The work had the objective to elaborate apple jellies by using brown sugar. The jellies were elaborated with apple pulp, water, lemon juice, pectin and 20, 35, 50 and 65% of brown sugar. It was verified the yield, cost and the consumers preference of the jelly formulations. The most favorite jellies, were reprocessed, and it was determined the physical, chemical and microbiological characteristics, soon after the processing, after 30, 60 and 90 days of storage. It was observed that the jellies elaborated with 35, 50 and 65% of brown sugar were equally acceptable by the consumers, overcoming that ones with 20%; the jelly with 65% of brown sugar presented advantages over the others, when considering the cost and yield; the products stability was superior to three months and there were a physical and chemical significative difference among the formulations.

Direct determination of oleic acid in soybean oil by capacitively coupled contactless conductivity detection capillary electrophoresis in an oil-miscible KOH/1-propanol/methanol medium

The aim of this work was to develop a quick direct analytical technique for the determination of oleic acid content in soybean oil by non-aqueous capillary electrophoresis with capacitively coupled contactless conductivity detection. The oil-miscible background electrolyte was a mixture of methanol/1-propanol (1:6 v/v) containing 4 × 10-2 mol L-1 KOH and 10% (v/v) ethylene glycol. Samples of 50 g L-1 soybean oil were prepared directly in the background electrolyte added with 1.33 × 10-3 g L-1 of salicylic acid as internal standard. Quantitative tests were performed by adding to the samples pure oleic acid in the range from 0.53 to 2.13 × 10-3 mol L-1. Under negative polarity anionic solutes moved faster than the electro-osmotic flow so that oleic acid was detected in 16 minutes. The limits of detection and quantification were, respectively, 24 and 81 µmol L-1. Such results demonstrate that, unlike required by other methods, low levels of oleic acid can be quantitatively determined in soybean oil without prior extraction.

Physical chemical properties and kinetics of redox processes in water/soybean oil microemulsions

Microemulsoes de agua em oleo (ME w/o) constituidas de agua, oleo de soja, SDS (dodecil sulfato de sodio) e diversos alcoois de cadeia curta foram caracterizadas sob o ponto de vista fisico-quimico e de propriedades eletroanaliticas. Foram testados diferentes co-surfactantes e razoes surfactante:cosurfactante, sendo a ME com a composicao mais favoravel utilizada para estudar a cinetica de processos redox. Para tanto, realizaram-se medidas de voltametria ciclica utilizando como eletrodo de trabalho um ultramicroeletrodo de disco de Pt e, como eletrodo de referencia e auxiliar, foram usados Ag/AgCl e Pt, respectivamente, e ferroceno como uma sonda. Verificou-se que a estabilidade termodinâmica das MEs aumenta com o conteudo de co-surfactante. A estrutura molecular e a solubilidade em agua do co-surfactante afetam a condutividade eletrica e o raio hidrodinâmico das MEs. Devido aos baixos coeficientes de difusao observados na ME, foi possivel a realizacao de medidas em estado transiente usando velocidades de varredura convencionais. A oxidacao do ferroceno na ME demonstrou ocorrer em condicoes de quasi-reversibilidade. Assim, foi demonstrada a possibilidade de realizar estudos por voltametria ciclica em oleos vegetais sob a forma de ME w/o. Water/oil microemulsions (w/o ME) constituted by water, soybean oil, SDS (sodium dodecyl sulfate) and several short-chain alcohols were characterized from the viewpoint of its physical-chemical and electroanalytical properties. Different co-surfactants and surfactant:co-surfactant ratios were used, and the ME with the most favourable composition was used to study the kinetics of redox processes. For this purpose, cyclic voltammetry measurements using a Pt disk working ultramicroelectrode, an Ag/AgCl reference electrode and a Pt auxiliary electrode, and ferrocene as a probe, were performed. It was verified that the thermodynamic stability of the MEs increases with the co-surfactant content. The molecular structure and water solubility of the co-surfactant affect the electrical conductivity and the hydrodynamic radio of the MEs. Owing to the low diffusion coefficients verified in the MEs, measurements in transient state using conventional sweeping rates could be performed. Ferrocene oxidation in the ME has been demonstrated to proceed in quasi-reversibility conditions. Thus, the possibility of carrying out studies of cyclic voltammetry in vegetable oils under the w/o ME form was demonstrated.

Conservation of minimally processed apples using edible coatings made of turnip extract and xanthan gum

The objective of this study was to evaluate the potential of turnip extract and xanthan gum in the conservation of minimally processed apples. The apples were washed, sanitized with sodium hypochlorite (200 ppm) for 15 minutes, peeled, and cut into eight pieces prior to being subjected to one of the following treatments in aqueous solution: A – water (control); B – turnip extract; C – turnip extract and CaCl2; D – xanthan gum, CaCl2 and glycerol; E – turnip extract, xanthan gum, CaCl2, and glycerol. Subsequently, the freshly cut apples were dried under ventilation on nylon screens to ensure drying of the coatings, and then packed in polystyrene trays, covered with polyvinylchloride films and stored at 4 ± 1 ° C for 13 days. The following parameters were evaluated: mass loss, firmness, colouration, pH value, soluble solids, and peroxidase/polyphenoloxidase activities. The edible coatings were found to be ineffective with respect to controlling mass loss, but the minimally processed apples coated with turnip extract maintained their initial levels of colouration, firmness and pH value. A considerable increase in peroxidase activity was registered for apples treated with turnip extract, suggesting that this effect may also be responsible for the reduction in browning. No advantage could be observed for the simultaneous presence of turnip extract and xanthan gum or calcium chloride. The turnip extract may represent an interesting alternative for applications to minimally processed apples, especially as it is a natural product, easily obtained, cost effective and contributes to the nutritional quality (e.g. as a source of calcium ions).

Características físico-químicas de cebolinhas comum e europeia

Chives are a leafy vegetable widely used as a condiment in Brazil, where the most used species are popularly known as common and European. The aim of this study was to evaluate the physicochemical quality of in natura Allium fistulosum (common) and Allium schoenoprasum(European) chives. The samples of the different species were harvested and analysed for colour (brightness, hue angle and chromaticity); soluble solids (SS); titratable acidity (TA); SS/TA; pH; moisture; chlorophylla; chlorophyll b; total chlorophyll and total carotenoids. Regarding the colour parameters, the species showed similar results, with the characteristic colour of chives, expressed by the colour green with a tendency to yellow. The pH values were also similar, both fitting into the low acid range. However for SS and acidity, the European variety showed higher levels. The values found for the pigments evaluated were also similar, the average ratio of chlorophyll a:b being 2.3:1. The physicochemical data also showed similarities, both species presenting low acidity, high moisture and chlorophyll contents, and reasonable levels of soluble solids and carotenoids. This information about the chives grown in Brazil, still scarce in the literature, contributes to the production of data about this plant and could motivate its consumption and the expansion of its marketing in diverse ways.

Adjuncts used for beer production: Features and applications

Among the raw materials used for beer production, barley malt is the most widely used to provide the necessary carbohydrates to yeasts during fermentation, in which alcohol and carbon dioxide are produced. Must supplementation with adjuncts is recommended to correct properties that were not reached but this should not affect beer quality. Thus, the aim of this review is to present the main raw materials used to replace barley malt. Cereals and starchy materials can be used as starchy adjuncts, such as corn gritz , rice, wheat. Another group of adjuncts, known as sugary adjuncts, also has wide applications. They do not need to suffer enzymatic hydrolysis, because their sugars are readily fermentable. The adjuncts, in general, are used to decrease production costs since they allow the use of reduced energy during processing. Key words: beer, adjuncts, fermentation.