Silvia Cristina Sobottka Rolim de Moura

Estudo da vida-de-prateleira de fruta estruturada e desidratada obtida de polpa concentrada de mamão

The restructured fruit made with concentrated papaya pulp (700 g/kg), sugar (340 g/kg), sodium alginate (7 g/kg), low methoxy pectin (7 g/kg) and glycerol (50 g/kg), cut in a solid cylindrical form (volume approx. 2 cm3), dehydrated (12% humidity) and covered with icing sugar, was chosen for the shelf life studies. The physical, chemical, sensory and microbiological analyses were made on the product packaged in a multi layer film and stored at 0, 25 and 35 °C, for 120 days to check for quality loss. The results showed that the firmness (TA.XT2 Texturometer) and the subjective evaluations of texture and overall quality were the evaluation that best explained the quality loss of the restructured fruit during storage. Under accelerated conditions (35 °C) the product was considered adequate for consumption for up to 56 days, when it reached 4.5 (neither liked nor disliked) from the overall quality scale of the sensorial test. The kinetic values, Ea= 19,89 kcal/mol and Q10= 3, established using accelerated shelf life testing, allowed for the estimation of a shelf life of 168 days for the product at 25 °C. Under normal storage conditions, the shelf life of the product being estimated as 154 days based on the overall quality using the sensory results.

Cinética da degradação da cor de solução hidrossolúvel comercial de urucum, submetida a tratamentos térmicos

Commercial water-soluble annatto solutions were submitted to different time/temperature treatments to investigate the stability of the color in these conditions. The color was measured in a COMCOR 1500 Plus spectrophotometer in the Hunter Lab System and the results are discussed, as well as the changes in the norbixin salt concentration and L, a, b color parameters. Data were analised for order reaction and the temperature dependence being well explained by the Arrhenius model, with activation energy values between 11 and 25 kcal/mol. The changes in color showed increase on lightness and yellow color and decrease on red color. Norbixin salt degradation reaction follows the second order and for other color parameters, the first order.

Propriedades termofísicas de soluções modelo similares a sucos - Parte I

Thermophysical properties, thermal diffusivity and specific heat of model solutions similar to juices were experimentally determined and the values obtained compared to those predicted by mathematical models (STATISTIC 6.0) and to values mentioned in the literature, according to the chemical composition. It was adopted a star planning to define the composition of the model solutions fixing the acid amount in 1.5% and varying water (82-98.5%), carboydrate (0-15%) and fat (0-1.5%). The specific heat was determined by Hwang & Hayakawa method and the thermal diffusivity was determined by Dickerson method. The results of each property were analysed by the response surface method. The results were significative, indicating that the models represented considerably the changes of thermal properties of juices according to their composition and temperature variations.

Thermophysical properties of model solutions similar to juice: part II

Thermophysical properties, density and viscosity of model solutions similar to juices were experimentally determined. The results were compared to those predicted by mathematical models (STATISTIC 6.0) and to values mentioned in the literature, according to the chemical composition. A star planning was adopted to define model solutions composition; fixing the acid amount in 1.5% and varying water (82-98.5%), carbohydrate (0-15%) and fat (0-1.5%). The density was determined by picnometer. The viscosity was determined by Brookfield LVF model viscosimeter. The thermal conductivity was calculated based on thermal diffusivity and specific heat values (presented at the 1st . Part of this paper - MOURA [7]) and density. The results of each property were analyzed by the response surface method. The found results were significant, indicating that the models represent the changes of thermal and physical juices properties, according to their composition and temperature variations.

Encapsulating anthocyanins from Hibiscus sabdariffa L. calyces by ionic gelation: Pigment stability during storage of microparticles

Hibiscus extract (HE) has a strong antioxidant activity and high anthocyanin content; it can be used as a natural pigment, also adding potential health benefits. The objective of this work was the microencapsulation of HE anthocyanin by ionic gelation (IG) using two techniques: dripping-extrusion and atomization, both by means of a double emulsion (HE/rapseed oil/pectin) and a cross-linked solution (CaCl2). Particles (77-83% moisture content) were conditioned in acidified solution at 5, 15 and 25°C, absence of light, and evaluated for anthocyanins and color for 50-days. The median diameter (D50) of the particles ranged from 78 to 1100μm and encapsulation efficiency ranged from 67.9 to 93.9%. The encapsulation caused higher temperature stability compared with the free extract. The half-life (t1/2) values of the particles ranged from 7 (25°C) to 180days (5°C) for anthocyanins and from 25 (25°C) to 462days (5°C) for Chroma value. The IG increased the stability of HE anthocyanin. Both the dripping-extrusion and the atomization have shown to be feasible techniques.

PROPRIEDADES TERMOFÍSICAS DE SOLUÇÕES MODELO SIMILARES A CREME DE LEITE

The requirement of UHT cream has been increased considerably. Several industries varied and increased their production, since consumers, more and more exigent, are demanding creams with a wide range of fat content. The objective of the present research was to determine the density, viscosity and thermal diffusivity of model solutions similar to cream. The range of temperature varied from 30°C to 70°C in order to study the influence of fat content and temperature in the physical properties of cream. The statistic method applied was the factorial 3X5 planning, with levels of fat content and temperature fixed in 15%, 25% and 35%; 30°C, 40°C, 50°C, 60°C and 70°C, respectively (STATISTICA 6.0). Both carbohydrates and proteins content were fixed at 3%. The density was determined by a method based on the displacement of fluids in a picnometer; the thermal diffusivity by Dickerson method and the viscosity by Rheotest 2.1 rheometer. The results of each property were analysed by the response surface method. For all the properties the results were significant, indicating that this model represented considerably the changes of thermal and physical properties of cream according to fat content and temperature variations.

PREDIÇÃO DA ATIVIDADE DE ÁGUA E RELAÇÃO ENTRE A ATIVIDADE DE ÁGUA E A DEPRESSÃO DO PONTO DE CONGELAMENTO DE SUCOS DE FRUTAS

This work proposes to determine the water activity and the freezing point depression of tangerine, pineapple and lemon juices at various concentrations (10-55oBrix) and to achieve a correlation between these properties. The freezing point depression was determined with a LAKTRON cryoscope and common laboratory materials. The water activity was determined with a DECAGON CX-2 hygrometer in the temperature range of 15 to 30oC. With the results, the adjustment to CHEN (1987) water activity prediction equation to non-electrolyte mixtures was verified, through the calculation of the variation coefficient (CV). Being CV smaller than 3% for the proposed model, it can be said that the experimental data have adjusted well to the prediction equation. The water activity and the freezing point depression was correlated for tangerine, pineapple and lemon juices and r2 values were higher than 99%. Therefore, it is possible to obtain the water activity by knowing the freezing point depression of studied juices.

Processamento e qualidade de compotas de figo diet e convencional

The objective of this research was to evaluate the physicochemical quality characteristics of diet and conventional fig jams. The fig variety used in this experiment was the cv. purple variety and different formulations with sweeteners were evaluated. The tests were carried out with nine treatments and three repetitions, giving a total of 27 samples. The syrup formulations were: sucrose (TA); sorbitol (TS); erythritol (TE); sorbitol and erythritol (TSE); stevioside (TST); sodium cyclamate, sucralose and sodium saccharin (TCSuSa); sodium cyclamate and sodium saccharin (TSC); acesulfame-K and sucralose (TAcSu); stevioside, sodium saccharin and sodium cyclamate (TSSC). In accordance with the literature and legislation for this type of product the physical and chemical attributes evaluated were pH, soluble solids, titratable acidity, reducing sugars, total reducing sugars, protein, lipid, ash and moisture contents, and the results obtained complied with the values found in the literature and the legislation for this type of product. With respect to the quality parameters, all the treatments showed satisfactory results, with the pH values ranging from 3.98 to 4.47, the presence of vacuum from 11 to 13 inches Hg and soluble solids contents ranging from 9.43 to 3.90 for the treatments with sweeteners. According to its characteristics, the product developed fitted into the category of diet products.

Propriedades físicas e reológicas de produtos à base de frutas

Em vista da crescente demanda da populacao por questoes relacionadas a saude, nutricao e bem-estar, o mercado alimenticio tem se preocupado em aumentar a insercao de ingredientes mais saudaveis como as frutas, por exemplo, visando atender a nova demanda do consumidor. A otimizacao de um processo e dependente da presenca de dados precisos que permitam o dimensionamento correto dos equipamentos. O objetivo deste trabalho foi caracterizar amostras comerciais de produtos a base de frutas e avaliar as propriedades termofisicas (densidade, calor especifico, difusividade termica e condutividade termica) e reologicas (viscosidade aparente e energia de ativacao), visando a adequacao a modelos teoricos. Os resultados foram ajustados a modelos matematicos apresentando erros relativos entre 0,2% e 50%, sendo o modelo de ajuste da densidade o mais preciso (erro maximo de 1,7%). O comportamento reologico das amostras teve melhor ajuste ao modelo Lei da Potencia (R2 > 0,96) e a viscosidade relacionou-se bem com a temperatura, segundo a equacao de Arrhenius (R2 > 0,90).