Carmen C. Tadini

Rheological Properties of Banana Puree at High Temperatures

Abstract The rheological behavior of banana puree was determined using a dynamic stress rheometer with a pressure couette fixture, which allowed experiments to be conducted at high temperature. The pressure couette was pressurized with compressed air to 206.8 kPa (gage pressure) and experiments were carried out at temperatures ranging from 30 to 120°C. The shear stress values ranged from 10 to 170 Pa and the shear rate values from 10−5 to 103 s−1. The model that best fitted the experimental data at all temperatures was the Herschel-Bulkley model. There was a usual tendency for the apparent viscosity to decrease with increasing temperature but an increase in apparent viscosity with increasing from 50 to 60°C and from 110 to 120°C was found. This could be due to interaction of polysaccharides present in banana puree. There was a slight difference between the apparent viscosity values for increasing shear stress sweeps and those for the decreasing shear stress sweeps suggesting time dependency of the rheological behavior. Models were proposed to correlate the parameters of the Herschel-Bulkley model and viscosity with temperature.

Impregnation of cinnamaldehyde into cassava starch biocomposite films using supercritical fluid technology for the development of food active packaging.

In this work, supercritical solvent impregnation (SSI) has been tested for the incorporation of natural compounds into biocomposite materials for food packaging. Cinnamaldehyde, with proved antimicrobial activity against fungi commonly found in bread products, was successfully impregnated on biocomposite cassava starch based materials using supercritical carbon dioxide as solvent. Different process experimental conditions were tested (pressure, impregnation time and depressurization rate) at a fixed temperature (35 °C) in order to study their influence on the amount of impregnated cinnamaldehyde as well as on the morphology of the films. Results showed that all conditions permitted to impregnate antimicrobial active amounts superior to those previously obtained using conventional incorporation methods. Moreover, a significant decrease of the equilibrium water vapor sorption capacity and water vapor permeability of the films was observed after SSI processing which is a clear advantage of the process, considering the envisaged applications.

Rheological Properties of Frozen Concentrated Orange Juice (FCOJ) as a Function of Concentration and Subzero Temperatures

Data on flow properties of Frozen Concentrated Orange Juice (FCOJ) produced from oranges cv. Pera-Rio (65.04 °Brix, 8.8% w/w pulp content, 2.5% w/w pectin, 3.84% citric acid, 1.293 g cm−3) from −18 to 0°C were fitted with appropriate predictive models. The power law model was found to be the most appropriate to fit the flow curves obtained for FCOJ between 46.56 and 65.04 °Brix. In higher concentrations, thixotropy was observed and showed more temperature dependence. A single equation combining Arrhenius and exponential relationships was applied to describe the temperature effect and shear rate on the quantity of breakdown of FCOJ.

Análise físico-química e microbiológica do suco de laranja minimamente processado armazenado em lata de alumínio

In this work, single-strength orange juice was pasteurized in a plate heat exchanger using three different temperatures: 82.5oC, 85.0oC and 87.0°C and holding times varying from 11 to 59s in order to obtain a minimally processed product. A comparison among orange juice samples stored in aluminium cans and in polyethylene bottles under refrigerated conditions for 21 days was carried out. Degree of Brix, acidity, pH, insoluble and total solids, and microbiological analyses were conducted soon after processing and during the storage period. The physico-chemical properties of the pasteurized orange juice showed differences due to variations in the raw material during the period of study. The most appropriate pasteurization temperature for orange juice was 87.0°C, with the holding time varying according to pH; pH 4.0 required longer holding times. According to the results, a shelf life of 15 days was determined for the processed orange juice, under the above conditions.

Perfil sensorial e aceitação de suco de laranja pasteurizado minimamente processado

Onze provadores selecionados e treinados avaliaram a aparencia, aroma e sabor de amostras de suco de laranja natural processado em nove diferentes condicoes de temperatura de pasteurizacao - tempo de retencao, e compararam com amostras do suco de laranja natural nao processado, utilizando a Analise Descritiva Quantitativa (ADQ). Teste de aceitacao pelo consumidor foi conduzido em laboratorio, com cinquenta provadores nao treinados, utilizando as escalas: hedonica, intensidade de odor e sabor natural, e intencao de compra. Tanto os provadores, como os consumidores, receberam as amostras em cabines individuais iluminadas com luz vermelha, exceto para os testes de aparencia, que foram conduzidos sob a luz branca do dia. As amostras foram apresentadas segundo delineamento experimental de blocos completos casualizados com duas repeticoes e os resultados foram analisados aplicando a Analise de Variância (ANOVA). A ADQ mostrou que houve diferencas significativas em relacao a presenca de particulas, aroma e sabor natural de laranja, diminuindo a intensidade com o aumento do tempo de retencao. Entretanto, nao houve diferencas significativas entre as amostras do suco nao processado e do suco processado, em relacao a cor amarela, viscosidade percebida visualmente, odor e sabor fermentado, e sabor de oleo essencial. O teste de consumidor indicou que o suco de laranja natural processado sob a condicao mais severa (87,0°C/58,55s) foi melhor aceito, apresentou maior intensidade de aroma e sabor de laranja natural e revelou maior intencao de compra em relacao a um suco de laranja pasteurizado de marca comercial.

Light-triggered and cysteine-mediated nitric oxide release from a biodegradable starch-based film

A new nitric oxide-releasing material produced with cassava starch is described. The ruthenium nitrosyl complex trans-[Ru(NH3)4(isn)NO](BF4)3 (RuNOisn; isn = isonicotinamide) is able to release NO upon either photolysis or chemical reduction. Impregnating this complex under mild conditions into cassava starch (CS) films produced a NO-delivery platform (CSx-RuNOisn). Spectroscopic analysis of CSx-RuNOisn indicates that the coordination sphere of RuNOisn remains intact during film production. Exposure of CSx-RuNOisn to long wave UV-light (λirr = 355 nm) leads to NO release and formation of the paramagnetic photoproduct trans-[RuIII(NH3)4isn(H2O)]3+ in the CS film. Reaction of this aquaruthenium(iii) complex with aqueous nitrite regenerates RuNOisn in the film. Delivery of NO upon photolysis of CSx-RuNOisn was verified by trapping with oxymyoglobin. Moreover, NO release upon chemical reduction was carried out using l-cysteine as a reductant. Cysteine-mediated NO delivery from CSx-RuNOisn persisted for more than 7 h, during which physiologically relevant NO concentrations were liberated. These results suggest that CSx-RuNOisn is a promising candidate for use in biological applications.

Preparation and characterization of bio-nanocomposite films based on cassava starch or chitosan, reinforced with montmorillonite or bamboo nanofibers

In this study, films based on two different polysaccharides (chitosan and cassava starch) were produced by casting technique and nanostructured by montmorillonite (MMTNPs) or bamboo nanofibers (BNFs) at two different concentrations: 0.5g/100g and 1.0g/100g of polymer, using glycerol as plasticizer at concentration of 30g/100g of polymer. The particle size and surface charge of the MMTNPs and BNFs nanoparticles were 315±14nm and 60±3nm and -31.78mV and -20.77mV, respectively. In relation to the mechanical properties, the nanofibers increased the tensile strength in 50% of starch films, while the elongation at break shows a similar increase (66%) for both types of nanoparticles at concentration of 1.0g/100g. Cassava starch films showed a better response to nanostructure process, noticed through by the mechanical properties. XRD analyses showed good interaction between the polymer matrix and bamboo nanofibers.

Use of alpha-amylase and amyloglucosidase combinations to minimize the bread quality problems caused by high levels of damaged starch

The objective of this work was to investigate the contribution of α-amylase and amyloglucosidase to dough fermentation process and bread quality, as an alternative to reduce the negative effects caused by high damaged starch in flour. The dough properties during the proofing process were modified by higher damaged starch content. Higher damaged starch in flour resulted into breads with darker crusts and firmer crumbs. The enzymes reduced the negative influence of damaged starch, producing a positive effect on the maximum carbon dioxide pressure reached during fermentation and the carbon dioxide volume retained by dough. Incorporation of alpha-amylase reduced dimension ratio and crumb firmness attributes; however, progressive additions of this additive produced lower bread volume and red intensity, and higher crumb firmness. The amyloglucosidase additions produced higher bread volume and red intensity of the crust, and lower brightness crust and gas cell diameter. Incorporation of amyloglucosidase was beneficial in the presence of a suitable quantity of damaged starch. The results confirmed that the α-amylase and amyloglucosidase additions significantly improved bread quality. Incorporation of α-amylase and amyloglucosidase led to higher bread loaves and lower crumb firmness throughout the storage period, promoting a longer life of the finished product.

Predicting the dielectric behavior of orange and other citrus fruit juices at 915 and 2450 MHz

ABSTRACT Dielectric properties (DP: relative permittivity and loss factor) and electrical conductivity are important parameters for evaluating the microwave penetration depth and designing applicators for pasteurization processes. In this context, generalized equations that can predict the DP of a group of food products as a function of their characteristics are useful. The dielectric behaviours of eight citrus fruit juices (Pera, Lima, and Navel oranges, Ponkan tangerine, Murcott tangor, Mediterranean mandarin, Sicilian lemon, and Persian lime) and three Pera/Lima blends (25, 50, 75%) for temperatures between 0 and 90 °C and frequency between 500 and 3000 MHz were studied. The results were correlated with temperature at frequencies of 915 and 2450 MHz. It was possible to quantify the ionic and dipolar contributions. DPs were modelled based on the behaviour of pure water in a semiempirical approach using correction factors, which were correlated with temperature and juice physicochemical characteristics (pH, Brix, conductivity). Polynomial regressions can successfully predict relative permittivity with mean absolute errors of 0.49±0.35% and 0.58±0.48% and the loss factor with errors of 4.1±3.9% and 2.8±2.3% at 915 and 2450 MHz, respectively, for juices with Brix/acid ratio between 1.26 and 29.9.

Torque Measurement in Real Time during Mixing and Kneading of Bread Dough with High Content of Resistant Maize Starch and Enzymes

Abstract In this work, a methodology to measure torque during dough mixing in large scale was developed and the baking performance of bread dough formulated with resistant starch (RS) and enzymes was evaluated. Dough was formulated with 12.5 g/100 g of RS and 4 mg/100 g of a mixture of enzymes, glucose-oxidase (Gox), tranglutaminase (TG) and xylanase (HE) in proportions according to a three-component mixture design of experiments. Dough was mixed in a large-scale dynamic rheometer measuring instant torque and speed in real time through a personal computer (PC) interface. Maximum torque during mixing and parameters of the dough development curves obtained from rheofermentometer were fit to mathematical models within 95 % of confidence. Gox and TG showed positive effects on the maximum height of dough, while HE showed a negative one. Also, it was found that Gox and TG in the presence of HE could be important for reducing dough weakening.