Aplicação de revestimento comestível em abacaxis processados por métodos combinados: isoterma de sorção e cinética de desidratação osmótica

A desidratação osmótica é uma etapa essencial na elaboração de produtos de fruta através da Tecnologia dos Métodos Combinados ou de Obstáculos (Hurdle Technology), pois reduz a atividade de água para níveis que, combinando um ou mais obstáculos, aumentam a estabilidade do produto. Neste processo há uma perda de água da fruta para a solução e incorporação de sólidos solúveis pelo produto. Este último fluxo é considerado uma desvantagem do processo pois pode alterar o sabor do produto. Neste trabalho estudou-se a ação de revestimentos comestíveis a base de alginato e gelatina aplicados em abacaxis, previamente à desidratação osmótica, como barreira à incorporação de sólidos solúveis. Os abacaxis com e sem revestimento (controle) foram desidratados em solução de sacarose sob condições isotérmicas. Foram determinadas as isotermas de dessorção de abacaxis revestidos com gelatina, alginato e sem revestimento e os parâmetros cinéticos do processo de desidratação osmótica. Abacaxis revestidos com alginato apresentaram menor velocidade de ganho de sólidos, sem alterar a velocidade de perda de água, quando comparado ao controle.

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

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Abundance and composition of Rotifera in an abandoned meander lake (Lago Amapá) in Rio Branco, Acre, Brazil

A comunidade de rotíferos do Lago Amapá (meandro abandonado da planície de inundação do Rio Acre) foi investigada sazonalmente. As amostragens foram realizadas semanalmente em três estações de coletas, em dois períodos: estação seca entre 08/V/1997 e 31/X/1997 e estação chuvosa, entre 02/I/1998 e 24/II/1998. A densidade e composição de rotíferos (48 táxons de rotíferos) foram determinadas. A diversidade e abundância foram caracterizadas por serem maiores, respectivamente, nas águas altas e águas baixas. Anova e teste F foram usados, visando observar diferenças sazonais nas variáveis ambientais e rotíferos. Transparência e pH foram estatisticamente altamente significativos (p < 0,01). As análises de correlações de Pearson revelaram que a condutividade elétrica foi negativamente correlacionada com a densidade de rotíferos (r = -0,8824; p < 0,05), na fase de águas baixas, bem como, profundidade, na fase de águas altas (r = -0,7513; p < 0,05). Mudanças sazonais, causadas pelas flutuações do nível da água, e baixa diversificação dos nichos influenciaram a composição e abundância do grupo estudado.

COMPORTAMENTO DAS SEMENTES DE SOJA DURANTE A FASE INICIAL do PROCESSO DE GERMINAÇÃO

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

PHYTOCHROME CONTROLLED SEED-GERMINATION IN LIGHT INSENSITIVE SEEDS OF RAPHANUS-SATIVUS L CV REDONDO GIGANTE

Seed germination of Raphanus sativus is inhibited by light only under low water potential of the medium. Curves of fluence response to white, red and far-red lights demonstrated that the inhibition of seed germination is dependent on light irradiance being far-red light the more effective than the formers and the germination being inhibited by intermitent light indicates phytochrome involvement through the high irradiance reactions in the control of seed germination in radish seeds under water stress conditions.

Glass transitions and state diagram for freeze-dried pineapple

Glass transition temperature of freeze-dried pineapple conditioned by adsorption at various water activities at 25 degreesC was determined by differential scanning calorimetry (DSC). High moisture content samples corresponding to water activities higher than 0.9, obtained by liquid water addition, were also analysed. The DSC traces showed a well-visible shift in baseline at the glass transition temperature (T(g)). Besides, no ice formation was observed until water activity was equal to 0.75. For water activities lower than 0.88, the glass transition curve showed that T(g) decreased with increasing moisture content and the experimental data could be well-correlated by the Gordon-Taylor equation. For higher water activities, this curve exhibited a discontinuity, with suddenly increasing glass transition temperatures approaching a constant value that corresponds to the T(g) of the maximally freeze-concentrated amorphous matrix. The unfreezable water content was determined through melting enthalpy dependence on the sample moisture content.

Influence of different drying methods on tbe rheological properties of raisins

The rheological parameters of raisins were obtained after three different drying methods: convective, osmo-convective and solar drying. Compression tests were applied to rehydrated samples by using a Texture Analyzer TAXT2i. A mathematical trick was used to determine the stress and area was calculated along the deformation. A power law model could adequately fit stress-true strain curves and parameters; K (measure of stiffness) and n (solid behavior index) were obtained as a function of water activity between 0.755 to 0.432. Results showed that these parameters were strongly dependent on water activity for all drying methods. The constant K, which indicates the resistance against deformation, increased with decreasing water activity. on the other hand, increasing water activity resulted in higher solid behavior indexes, showing a large deviation from the Hookean behavior.

Thermodynamic and quality properties of lemon juice powder as affected by maltodextrin and Arabic gum

Sorption isotherms of lemon juice (LE) powders with and without additives-18% maltodextrin (MA) or 18% gum Arabic (GA) were determined at 20-50 degrees C. Addition of additives was shown to affect the isotherms in such a way that, at the same water activity, samples LE + GA and LE + MA presented lower equilibrium moisture content and were not so affected by varying temperature. The net isosteric heats of sorption of juice powders with additives were higher (less negative) than those of lemon juice powders, suggesting that there are more active polar sites in the product without addition of GA or MA. In general, the quality properties decreased with the addition of maltodextrin and gum arabic and it was obtained similar values for LE + GA and LE + MA.

Crystallization of bothropstoxin II isolated from the venom of Bothrops jararacussu

A myotoxic phospholipase A(2), bothropstoxin II, which exhibits low hydrolytic activity, was crystallized and X-ray diffraction data were collected to a resolution of 2.2 Angstrom. Preliminary analysis reveals the presence of three molecules in the asymmetric unit. Copyright (C) 1996 Elsevier B.V. Ltd.

Crystallization of piratoxin I, a myotoxic LYS49-phospholipase A(2) homologue isolated from the venom of Bothrops pirajai

Fernanda Canduri, Lit C. Mancuso, Andreimar M. Soares, Jose R. Giglio, Richard J. Ward and Raghuvir K. Arni. Crystallization of piratoxin I, a myotoxic Lys49-phospholipase A(2) homologue isolated from the venom of Bothrops pirajai. Toxicon 36, 547-551, 1998.-Large single crystals of piratoxin I, a Lys49-PLA(2) homologue with low enzymatic activity, have been obtained. The crystals belong to the orthorhombic system space group p2(1)2(1)2(1) and diffract X-raps to a resolution of 2.8 Angstrom. Preliminary analysis reveals the presence of two molecules in the crystallographic asymmetric unit. (C) 1998 Elsevier B.V. Ltd. All rights reserved.

Viscoelastic behavior of persimmons dried at constant air temperature

The viscoelastic behavior of dried persimmons at different air-drying temperatures and velocities was evaluated. Air temperatures and velocities were varied according to a second-order central composite design, with temperature ranging from 40degreesC to 70degreesC and air velocity from 0.8 to 2.0 m/s. After drying, persimmons were equilibrated at four different water activities: 0.432, 0.576, 0.625 and 0.751. The rheological behavior of dried and conditioned persimmons was studied under uniaxial compression-relaxation tests. Three different rheological models were fitted to the experimental relaxation curves: Maxwell, Generalized Maxwell and Peleg and Normand. Based on the root mean square of residuals, the Generalized Maxwell model showed the best fit and a regression analysis was applied to obtain response surfaces for the model parameters. The dependence of the rheological properties on water activity was also analysed. Results showed that only the linear effect of air temperature was significant at a 5% level on the equilibrium stress and relaxation times. In a general way, these parameters increased with increasing air temperature and decreasing water activity. (C) 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.

REEVALUATION OF CHLORIDES REGULATION OF HEMOGLOBIN OXYGEN-UPTAKE - THE NEGLECTED CONTRIBUTION OF PROTEIN HYDRATION IN ALLOSTERISM

We have measured hemoglobin oxygen uptake vs. The partial pressure of oxygen, with independently controlled activities of chloride and water. This control is effected by combining different concentrations of NaCl and sucrose in the bathing solution to achieve: (i) water activities were varied and CI- activity was fixed, (ii) both water and CI- activities were varied with a traditional NaCI titration, or (iii) CI- activities were varied and water activity was fixed by adding compensating sucrose. Within this analysis, the CI--regulated loading of four oxygens can be described by the reaction Hb.CI- + 4 O-2 + 65 H2O reversible arrow Hb.4O(2).65H(2)O + CI-. The dissociation of a neatly integral chloride, rather than the nonintegral 1.6 chlorides inferred earlier from simple salt titration, demonstrates the need to recognize the potentially large contribution from changes in water activity when titrating weakly binding solutes. The single-chloride result might simplify structural considerations of the action of CI- in hemoglobin regulation.

Effect of drying method on the sorption isotherms and isosteric heat of persimmon pulp powder

Moisture equilibrium data of persimmon pulp powders with 50% maltodextrin (dry basis) obtained with different drying methods were determined at 20, 30, 40 and 50 degrees C. The spray-dryer gave a dry product with a higher adsorption capacity than the other methods. The vacuum- and freeze-dried products had the same adsorption capacity. The highest isosteric heat of sorption was observed for powders produced by spray-drying. The isokinetic temperature (T(B)) calculated for persimmon pulp powder obtained by vacuum-, spray- and freeze-drying were 541.4 K, 616.3 K, 513.2 K, respectively. The sorption process was spontaneous and enthalpy controlled.

Efeito da porosidade do substrato casca de pínus no desenvolvimento de mudas de grumixameira

Aiming to evaluate the effect of the pine bark substrate porosity on the development of the grumixama plant (Eugenia brasiliensis Lam.), an experiment was conducted in a greenhouse of the Escola Superior de Agricultura "Luiz de Queiroz"/USP, Piracicaba, Brazil. The treatments were: 100% ground pine bark without separation of particles; 100% pine bark of <= 0,1mm; 75% pine bark of <= 0,1mm + 25% between 0,1-4,0 mm; 50% of pine bark <= 0,1mm + 50% between 0,1-4,0 mm; 25% pine bark of <= 0,1mm + 75% between 0,1-4,0 mm and 100% pine bark of 0,1-4,0 mm. The evaluations (stem diameter, length and average dry weight of seedlings) were performed on the 90, 120 and 150(th) days after sowing. The low water absorption in the early stages and the low aeration of the roots promoted by the substrate, affect the development of the grumixama plant seedlings, that grow best when the total pore space of the substrate is less than 90% (v / v).

Effects of pretreatment with rosemary (Rosmarinus officinalis L.) in the prevention of lipid oxidation in salted tilapia fillets

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)