Interacciones de la glicina en soluciones acuosas de tetrafluoroborato de 1-butil, 3-metilimidazolio a diferentes temperaturas

Densities of glycine in aqueous solutions of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate were determined at temperatures ranging from 283.15 to 313.15 K. The apparent molar volume, infinite dilution apparent molar volume, second derivative of the infinite dilution partial molar volume with respect to temperature, partial molar volume of transfer at infinite dilution, and the number of hydration were determined. It was found that the apparent molar volume at infinite dilution was positive, but decreased with increasing ionic liquid concentration and increased with increasing temperature. On the other hand, the partial molar volume of transfer at infinite dilution behaved in a similar manner, but was negative.

Obtenção de nanocelulose da fibra de coco verde e incorporação em filmes biodegradáveis de amido plastificados com glicerol

Composites strengthened with nanocellulose have been developed with the aim of improving mechanical, barrier, and thermal properties of materials. This improvement is primarily due to the nanometric size and the high crystallinity of the incorporated cellulose. Cassava starch films plasticized with glycerol and incorporated with nanocellulose from coconut fibers were developed in this study. The effect of this incorporation was studied with respect to the water activity, solubility, mechanical properties, thermal analysis, and biodegradability. The study demonstrated that the film properties can be significantly altered through the incorporation of small concentrations of nanocellulose.

Determination of Alkalinity and dissociation constants of high salinity waters: use of F5BC titration function

Measurements of parameters expressed in terms of carbonic species such as Alkalinity and Acidity of saline waters do not analyze the influence of external parameters to the titration such as Total free and associated Carbonic Species Concentration, activity coefficient, ion pairing formation and Residual Liquid Junction Potential in pH measurements. This paper shows the development of F5BC titration function based on the titrations developed by Gran (1952) for the carbonate system of natural waters. For practical use, samples of saline waters from Pocinhos reservoir in Paraiba were submitted to titration and linear regression analysis. Results showed that F5BC involves F1x and F2x Gran functions determination, respectively, for Alkalinity and Acidity calculations without knowing "a priori" the endpoint of the titration. F5BC also allows the determination of the First and Second Apparent Dissociation Constant of the carbonate system of saline and high ionic strength waters.

Microencapsulation of pequi pulp by spray drying: use of modified starches as encapsulating agent

The aim of this study was to evaluate the microencapsulation of pequi pulp by spray drying. A central composite rotational design was used in order to evaluate the effect of the independent variables: inlet air temperature, surfactant concentration and modified starch concentration. The dependent variables were assumed as yield of the process and the product features microencapsulated. A selection of the best process condition was performed to obtain the best condition of a product with the highest vitamin C and carotenoids content. Powders showed moisture content below 2%. The experimental values of hygroscopicity, yield, water activity, total carotenoids and vitamin C powders ranged from 7.96 to 10.67 g of adsorbed water/100g of solids, 24.34 to 49.80%, 0.13 to 0.30, 145.78 to 292.11 mg of ascorbic acid/g of pequi solids and 15.51 to 123.42 mg of carotenoids/g of pequi solids, respectively. The inlet air temperature 140°C, the surfactant concentration of 2.5% and the modified starch concentration of 22.5% was recommended as the selected condition. By the scanning electron microscopy, it was observed that most of the particles had spherical shape and smooth surface.

Steroidien selektiivinen erottaminen sähköavusteisesti mikroemulsioita käyttäen

Mikroemulsiosähkökineettinen kromatografia on sähköavusteinen erotusmenetelmä. Yhdisteiden erottuminen tapahtuu mikroemulsiopisaroiden vaikutuksesta, kun nanometrien kokoiset öljypisarat ovat dispergoituneena veteen valmistettuun puskuriliuokseen. Yleensä mikroemulsiot valmistetaan raakaöljynkin sisältämistä hiilivedyistä, joita ovat esimerkiksi oktaani ja heptaani. Työn kokeellisessa osassa perehdyttiin seitsemän hydrofobisen ja varauksettoman steroidihormonin erottamiseen mikroemulsioliuoksessa kapillaarielektroforeesitekniikalla. Työssä valmistettiin öljyistä koostuvia mikroemulsioita, joista osan koostumus valittiin kirjallisuuden perusteella. Työssä kokeiltiin myös uusia mikroemulsiokoostumuksia, joissa käytettiin luonnosta peräisin olevia öljyjä: rypsi-, oliivi-, pellavansiemen- ja saksanpähkinäöljyä. Seitsemästä steroidihormonista viisi yhdistettä saatiin erottumaan optimoiduilla menetelmillä. Steroidien erotus perustuu niiden oktanoli-vesi jakautumiskertoimien avulla saatavaan migraatiojärjestykseen. Mikroemulsiossa, jossa käytettiin 1-oktanolia, steroidihormonit erottuivat nopeammin, kuin saksanpähkinäöljyä käytettäessä. Lyhyimmät migraatioajat saatiin mikroemulsiolla, jossa öljyfaasina käytettiin 1-heksanolia ja viidentenä yhdisteenä asetonitriiliä. Selektiivisimmillään menetelmä on, kun erotus tapahtuu liuoksessa, joka koostuu etyyliasetaatista, natriumdodekyylisulfaatista, butanolista, asetonitriilistä ja natriumtetraboraatista. Toteamisrajat tutkituille steroidihormoneille olivat 0,20–0,43 mg/L mikroemulsioissa.

Inhibitory effect of high [Mg2+] on the vasopressin-stimulated hydroosmotic permeability of the isolated perfused cortical collecting duct

High magnesium concentration inhibits the effect of arginine vasopressin (AVP) on smooth muscle contraction and platelet aggregation and also influences hepatocyte AVP receptor binding. The aim of this study was to determine the role of magnesium concentration [Mg2+] in AVP-stimulated water transport in the kidney collecting duct. The effect of low and high peritubular [Mg2+] on the AVP-stimulated osmotic water permeability coefficient (Pf) was evaluated in the isolated perfused rabbit cortical collecting duct (CCD). Control tubules bathed and perfused with standard Ringer bicarbonate solution containing 1 mM Mg2+ presented a Pf of 223.9 ± 27.2 µm/s. When Mg2+ was not added to the bathing solution, an increase in the AVP-stimulated Pf to 363.1 ± 57.2 µm/s (P<0.05) was observed. An elevation of Mg2+ to 5 mM resulted in a decrease in Pf to 202.9 ± 12.6 µm/s (P<0.05). This decrease in the AVP-stimulated Pf at 5 mM Mg2+ persisted when the CCDs were returned to 1 mM Mg2+, Pf = 130.2 ± 20.3 µm/s, and was not normalized by the addition of 8-[4-chlorophenylthio]-adenosine 3',5'-cyclic monophosphate, a cAMP analogue, to the preparation. These data indicate that magnesium may play a modulatory role in the action of AVP on CCD osmotic water permeability, as observed in other tissues.

Effect of osmotic predehydration on drying characteristics of banana fruits

Osmotic dehydration is considered to be a suitable preprocessing step to reduce the water content of foods. Such products can be dried further by conventional drying processes to lower their water activity and thus extend their shelf life. In this work, banana (Musa sapientum) fruits were initially treated by osmosis by varying several parameters of the processing conditions which included, besides the cutting format (longitudinal and round slices) of the fruit, temperature (28 and 49 ºC), syrup concentration (50, 60 and 67 ºBrix), treatment time (2, 4, 6, 10, 14, 16 and 18 hours), fruit and syrup ratio (1:1, 1:2, 1:3 and 1:4) and agitation effects. The best quality products were obtained by the use of the 67 ºBrix syrup, for 60 minutes of osmotic treatment, at 28 ºC, having a fruit and syrup ratio of 1:1 and agitation. The experimental data obtained on reduction in moisture content during the osmotic treatment were correlated with the experimental equation of M/Mo = Ae(-Kt), where A and K are the constants which represent the geometry and effective diffusivity of the drying process. This simplified mathematical model correlated well with the experimental results.

Moisture adsorption characteristics of ginger slices

The moisture adsorption characteristics of dried ginger slices was studied to determine the effect of storage conditions on moisture adsorption for the purpose of shelf life prediction, selection of appropriate packaging materials, evaluate the goodness-of-fit of sorption models, and determine the thermodynamics of moisture adsorption for application in drying. There was a highly significant effect (p < 0.05) of water activity (a w), temperature, and pre-treatment on the equilibrium moisture content (EMC) of the dried ginger slices. At constant a w, the EMC decreased as temperature increased. The EMC of all samples increased as the a w increased at constant temperature. The sorbed moisture of the unpeeled ginger slices was higher than the peeled while those of unblanched samples were higher than the blanched. Henderson equation allows more accurate predictions about the isotherms with the lowest %RMS, and therefore, it describes best the adsorption data followed by GAB, Oswin, and Halsey models in that order. The monolayer moisture generally decreased with temperature for all samples. The isosteric heat decreased with moisture content approaching the asymptotic value or the latent heat of vaporization of pure water (∆Hst = 0) while the entropy of sorption was observed to increase with moisture content.

Almond and peanut flours suppelmented with iron as potential ingredients to develop gluten-free cookies

Brazil is the second biggest worldwide producer of cookies and there are many varieties in the market; however, only a few are gluten-free. The objectives of this work were to formulate two gluten-free cookies added with iron, peanut or almond, and analyze their physicochemical, chromatic and sensory properties. Moisture, instrumental color (L*, a*, b* and C*), ash, proteins, lipids, iron, carbohydrates (estimated by difference), and water activity were determined. The acceptance of the products was assessed by 115 untrained taste panelists using a five-point hedonic scale. The data collected from the physicochemical analyses were submitted to Levene's, ANOVA, and Tukey's tests, which showed statistical difference (p < 0.05) in all the attributes for centesimal composition, water activity, and color of the cookies. Peanut and almond cookies could be considered sources of iron once they presented at least 15% of the daily recommended value of intake. They also garnered acceptance indexes of 80 and 85%, respectively, concluding that both formulations developed in this study were source of iron and contained high concentration of lipids and proteins with great sensory acceptance, suggesting their potential consumption by gluten-intolerants.

Chemical and biochemical characterization of soybean produced under drought stress

Brazil is the second soybean (Glycine max L. Merrill) producer and exporter in the world. In 2005, soybean cultivated in the southeastern region of the country suffered drought stress imposed by adverse high temperatures and low humidity during its reproductive stage. Little information is available regarding the effect of drought stress on the quality of grains. In this study chemical and biochemical characteristics of five soybean samples belonging to three different cultivars grown under drought stress were evaluated. The samples did not meet standards for marketing and contained high amounts of green seeds. Grains were analyzed for appearance, 100 seed weight, humidity, water activity, proteins, lipids, lipoxygenase 1 activity, peroxides, and pigment contents after harvest and after 20 months of storage at room temperature. Acidity was measured also after 30 months of storage. The values of water activity and humidity were 0.6-0.7 and 8.7-11.9%, respectively, and they did not change during storage time, but there was an increase in acidity, which alludes to lipase activity. The activity of lipoxygenase 1 was greatly affected. Immediately after harvest, the green pigments were represented mainly by pheophytin a, followed by pheophytin b, small quantities of chlorophyll b and chlorophyll a, and traces of other chlorophyll derivatives. After 20 months of storage almost all green pigments had disappeared. Drought stress probably enhanced membrane permeability, which led to a lower pH and promoted transformation of chlorophylls to pheophytins.

Effect of drying method on the adsorption isotherms and isosteric heat of passion fruit pulp powder

The sorption behavior of dry products is generally affected by the drying method. The sorption isotherms are useful to determine and compare thermodynamic properties of passion fruit pulp powder processed by different drying methods. The objective of this study is to analyze the effects of different drying methods on the sorption properties of passion fruit pulp powder. Passion fruit pulp powder was dehydrated using different dryers: vacuum, spray dryer, vibro-fluidized, and freeze dryer. The moisture equilibrium data of Passion Fruit Pulp (PFP) powders with 55% of maltodextrin (MD) were determined at 20, 30, 40 and 50 ºC. The behavior of the curves was type III, according to Brunauer's classification, and the GAB model was fitted to the experimental equilibrium data. The equilibrium moisture contents of the samples were little affected by temperature variation. The spray dryer provides a dry product with higher adsorption capacity than that of the other methods. The vibro-fluidized bed drying showed higher adsorption capacity than that of vacuum and freeze drying. The vacuum and freeze drying presented the same adsorption capacity. The isosteric heats of sorption were found to decrease with increasing moisture content. Considering the effect of drying methods, the highest isosteric heat of sorption was observed for powders produced by spray drying, whereas powders obtained by vacuum and freeze drying showed the lowest isosteric heats of sorption.

Evaluation of the quality of a molded sweet biscuit enriched with okara flour

The objective of this research was to test the addition of soymilk residue, also known as okara, to a molded sweet biscuit (MSB). The okara was provided by two soymilk producing companies whose production systems are based on hot disintegration of decorticated (company B) or non-decorticated (company A) soybeans and separation of the soymilk. Okaras A and B were dehydrated in a flash dryer and then ground to a flour (< 200 mesh). The okara flours showed high protein (35 g.100 g-1 dwb), lipid (17 g.100 g-1 dwb), and fiber (17 to 21 g.100 g-1 dwb) contents. The water holding capacity, protein solubility, emulsifying capacity, emulsion stability and isoflavone contents found in flour A were significantly higher (p < 0.05) than in flour B. The formulation of MSB, replacing 30% (w/w) of the wheat flour with okara flour was tested. The results of the physical measurements, brittleness and water activity of the MSB with flours A and B did not differ significantly (p < 0.05) from those of the standard. The color, flavor and overall quality of the MSB with 30% of okara flour B did not differ significantly from those of the standard biscuit, demonstrating its potential for application in confectionery products.

The influence of achyrocline satureioides ("Marcela") extract on the lipid oxidation of salami

The effect of two levels (0.5 and 1%) of hydroalcoholic extract of Achyrocline satureioides on the safety (TBARS values) and quality (pH, water activity, colour, weight loss, and sensorial attributes) of salami was evaluated. The addition of Achyrocline satureioides extract decreased TBARS values significantly during the storage of salami when compared to the control, which was elaborated without Achyrocline satureioides extract. The treatment with 1% of "Marcela" extract showed larger lipid stability than that of the lot with 0.5%, However, it presented a decrease (p < 0.05) in the sensorial acceptance. The two levels of "Marcela" extract did not influence pH, water activity, colour, and weight loss significantly. This study indicates that the hydroalcoholic extract of "Marcela" was effective in decreasing the lipid oxidation and at 0.5% it did not alter the sensorial features; therefore, it may be used in salami to provide safer products for the consumers.

Restructuring Passiflora cincinnata fruit pulp: influence of hydrocolloids

This study evaluated the effect of mixtures of alginate, low methoxy pectin and gelatin on characteristics of P. cincinnata fruit gels, containing pulp with high soluble solids content (50 °Brix). The results of a central composite design showed that the models obtained, except for water activity and pH, were predictive. Gelatin was an important factor affecting firmness and colour parameters since higher concentrations of this hydrocolloid, combined with alginate concentrations greater than 1.3% and pectin quantity up to 1.26%, could be used to obtain clear yellow products with firmness greater that 1.2 kg.

Influence of packaging and potassium sorbate on the physical, physicochemical and microbiological alterations of guava preserves

The elaboration of preserves through fruit processing is a promising alternative for their conservation. Such processing provides pleasant flavor due to the increase of sweetness and allows good conservation of the product for a prolonged time. Seeking quality and higher durability of fruit preserves, the purpose of this work was to evaluate the interference of potassium sorbate addition, and polypropylene, metallic and cellophane film packaging on the quality of guava (Psidium guajava L.) preserves during storage, through the physical, physiochemical and microbiological characteristics. The physical, physiochemical and microbiological analyses showed that the different types of packaging did not interfere in the stability of the guava preserves until the 5th month of storage - time being the factor that most influences the quality of the preserves when stored under temperature and humidity of 19.6 °C and 76.2%, respectively. The potassium sorbate caused an increase of the soluble solid levels and a decrease of the water activity. Regardless of the treatment, the preserves remained microbiologically stable during storage.