Physicochemical properties of cassava starch oxidized by sodium hypochlorite

In this work, cassava starch was modified by treatment with sodium hypochlorite (NaClO) at different concentrations (0.8, 2.0 and 5.0 % of active chlorine) and selected physicochemical properties of the oxidized starches were investigated. The native and modified samples were evaluated considering moisture, carboxyl content, apparent viscosity, susceptibility to syneresis, mid-infrared spectroscopy and crystallinity index. The treatment with NaClO resulted in alterations in carboxyl content of the oxidized starches that increased with increasing concentration of the oxidant. Oxidized starches also showed higher susceptibility to syneresis, as assessed by the release of liquid during freezing and thawing. Apparent viscosity analysis showed decrease in peak viscosity of the oxidized starches. X-ray diffractograms showed that the oxidation influenced the extent of cassava starch relative crystallinity found to lie between 34.4 % (native) and 39.9 % (2.0 % active chlorine). The infrared spectra are sensitive to structural changes on starch macromolecules and presented characteristic peaks as C-O-C of the six carbon glucose ring absorbs at 1,150-1,085 cm -1 and due to axial deformation these bands changed with the crystal structure of the starch samples. © 2012 Association of Food Scientists & Technologists (India).

Influence of the concentration of polyols on the rheological and spectral characteristics of guar gum

Polyols are widely used as sugar substitutes and provide texture to foods. Guar gum has many applications in food industry such as increasing product viscosity and improving texture. Knowledge of rheological properties of gum/polyol systems is important to permit replacing sugar while maintaining product texture. In this work, rheological properties of 0.1, 0.5 and 1 g/100 g guar solutions containing 10 and 40 g/100 g of maltitol, sorbitol, or xylitol were studied. The behavior of these mixtures was evaluated by steady and oscillatory shear measurements, and after a freezing/thawing cycle. Apparent viscosity of guar solutions increased with addition of polyols and with the increase in their concentrations, except for 40 g/100 g sorbitol addition to 1 g/100 g guar gum, in which the apparent viscosity decreased. Addition of polyols also increased the dynamic moduli of the systems. In mixtures of guar with 40 g/100 g polyol, the phase angle (δ) was below unity, but was dependent on frequency, which is characteristic of concentrated solutions with a certain degree of structuring. FTIR spectroscopy was studied to provide information on possible interactions between guar gum and polyols. Analyses carried out after freezing/thawing showed no changes in the viscoelastic behavior of the solutions. © 2013 Elsevier Ltd.

Comportamento reológico de gomas guar e xantana na presença de polióis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comportamento reológico de géis de amido de mandioquinha salsa (Arracacia xanthorrhiza B.)

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

Obtenção e avaliação de mutantes exoZ- e phbAB- envolvidos no metabolismo de polímeros de carbono em Rhizobium tropici SEMIA 4080 com potencial biotecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Rheological behavior of Peruvian carrot starch gels as affected by temperature and concentration

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

Análise da influência do agente umectante na estabilidade reológica e avaliação de cristais líquidos em formulações cosméticas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A Simple maxwell Based Model in Order to Represent the frequency-dependent viscosity measured by ultrasound

A previous work showed that viscosity values measured high frequency by ultrasound agreed with the values at low frequency by the rotational viscometer when conditions are met, such as relatively low frequency viscosity. However, these conditions strongly reduce the range of the measurement cell. In order to obtain a measurement range and sensitivity high frequency must used, but it causes a frequency-dependent decrease on the viscosity values. This work introduces a new simple in order to represent this frequency-dependent behavior.model is based on the Maxwell model for viscoelastic , but using a variable parameter. This parameter has physical meaning because it represents the linear behavior the apparent elasticity measured along with the viscosity by .Automotive oils SAE 90 and SAE 250 at 22.5±0.5oC viscosities at low frequency of 0.6 and 6.7 Pa.s, respectively,tested in the range of 1-5 MHz. The model was used in to fit the obtained data using an algorithm of non-linear in Matlab. By including the viscosity at low frequency an unknown fitting parameter, it is possible to extrapolate its . Relative deviations between the values measured by the and extrapolated using the model for the SAE 90 and SAE 250 oils were 5.0% and 15.7%, respectively.©2008 IEEE.

Effects of different sampling intervals on apparent protein and energy digestibility of common feed ingredients by juvenile oscar fish (Astronotus ocellatus)

O presente estudo avaliou a digestibilidade aparente da proteína e da energia de ingredientes (farelo de soja, farinha de peixe, farelo de trigo e milho) por juvenis de apaiari (Astronotus ocellatus) usando dois diferentes intervalos de coleta (30 min. e 12h). Os 160 juvenis de apaiari utilizados (22,37 ± 3,06 g de peso corporal) foram divididos em quatro tanques rede plásticos e cilíndricos, cada um colocado em um tanque de alimentação de 1.000 L. O experimento foi inteiramente casualizado em esquema fatorial 2 x 4 (2 intervalos de coleta de fezes e 4 ingredientes foram) com quatro repetições. Os testes estatísticos não detectaram efeito da interação entre o intervalo de coleta e tipo de ingrediente nos coeficientes de digestibilidade. O intervalo de coleta não afetou a digestibilidade da proteína e da energia. As características físicas das fezes dos juvenis de apaiari aparentemente as tornam menos sensíveis à perda de nutrientes por lixiviação, permitindo intervalos de coleta maiores. A digestibilidade da proteína dos ingredientes avaliados foi semelhante, mostrando que a digestibilidade aparente de ingredientes animais e vegetais por juvenis de apaiari é eficiente. Os coeficientes de digestibilidade da energia foram maiores para a farinha de peixe e o farelo de soja comparado a farelo de trigo e milho. Ingredientes ricos em carboidratos (farelo de trigo e milho) apresentaram os piores coeficientes de digestibilidade da energia e, portanto, não são usados eficientemente pelos juvenis de apaiari.

Viscosity measuring cell using ultrasonic wave mode conversion

This work presents a cell to measure dynamic viscosity of liquids using ultrasonic wave mode conversion from longitudinal to shear wave. The strategy used to obtain the viscosity is based on the measurement of the complex reflection coefficient of shear waves at a solid-liquid interface. Viscosity measurements of automotive oils (SAE90 and SAE140) were obtained in the frequency range from 1 to 10 MHz. These results are compared with the Maxwell model with two relaxation times, showing the dependency of viscosity with frequency. Several parameters affecting viscosity measurements, including the solid material properties, liquid viscosity, and operating frequency are discussed.

Viscosity measurement of Newtonian liquids using the complex reflection coefficient

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

Long-term high-fat diet-induced obesity decreases the cardiac leptin receptor without apparent lipotoxicity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Determination of chromium by GFAAS in slurries of fish feces to estimate the apparent digestibility of nutrients in feed used in pisciculture

This paper presents a simple, fast and sensitive method to determine chromic oxide (used as a biological marker of fish feed) in samples of fish feces by GFAAS through the direct introduction of slurries of the samples into the spectrometer's graphite tube. The standard samples of feces and of fish feed containing 0.10-1.00 mg kg(-1) of Cr2O3 were pre-frozen for I min in liquid nitrogen and then ground a cryogenic mill for 2 min, which reduced the samples' grain size to less than 60 mu m. The standard slurries were prepared by mixing 20 mg of standard samples of fish feed or feces with I mL of a solution containing 0.05% (v/v) of Triton X-100 and 0.50% (v/v) of suprapure HNO3 directly in the spectrometer's automatic sampling glass. The final concentrations of Cr2O3 present in the standard slurries were 2, 4, 8, 16 and 20 mu g L-1. After sonicating the mixture for 20s, 10 mu L of standard slurries were injected into the graphite tube, whose internal wall was lined with a metallic palladium film that acted as a permanent chemical modifier. The limits of detection (LOD) and quantification (LOQ) calculated for 20 readings of the blank of the standard slurries (2%, m/v of feces or feed devoid of minerals) were 0.81 and 2.70 mu g L-1 of Cr2O3 for the standard feces slurries, 0.84 and 2.83 mu g L-1 of Cr2O3 for the standard feed slurries. The proposed method was applied in studies of nutrient digestibility of different fish feeds and its results proved compatible with the results obtained from samples pre-mineralized by acid digestion. (c) 2005 Elsevier B.V. All rights reserved.

Comparison of indigestible markers from in situ and in vivo incubation to predict apparent digestibility in hay- and corn-fed horses

Foram utilizados quatro cavalos castrados sem raça definida pelo delineamento em blocos casualizados. Objetivou-se viabilizar os indicadores internos indigestíveis, FDNi e FDAi, obtidas pelas técnicas in situ nos bovinos e in vivo nos equinos por meio do saco de náilon móvel (SNM). Os tratamentos consistiram de digestibilidade determinada por método direto com a coleta total de fezes (CT) e indireto pelo uso de FDNi e FDAi obtidos pelas técnicas in situ (IS) na cavidade ruminal de bovinos e in vivo (IV) nos equinos por meio do SNM. As FDNi-IV e FDAi-IV promoveram a melhor taxa de recuperação (TR) do indicador, igualando-se ao grupo CT, em 91,50%, enquanto a técnica in situ resultou nas piores taxas, na média 86,50%, para ambos os indicadores indigestíveis (p < 0,05). As estimativas dos CD dos nutrientes foram adequadamente preditos pela FDAi-IV, para equinos alimentados com feno, no qual os valores observados foram de 46,41; 48,16; 47,92 e 45,51% para MS, MO, FDN e EB, respectivamente. Concluiu-se que o SNM em equinos pode ser usado para obter a FDAi em equinos alimentados exclusivamente com feno de coast-cross e para cavalos consumindo dieta mista, as FDNi e FDAi foram eleitas para predizer CD de nutrientes.

Indigestible cellulose and lignin in determining feces production and apparent digestibility in horses

Foram utilizados quatro cavalos castrados sem raça definida, distribuídos em blocos casualizados. Objetivou-se estudar a viabilização dos indicadores internos, celulose (CELi) e lignina indigestíveis (LIGi), para predizer a digestibilidade em cavalos. Os tratamentos consistiram na determinação da digestibilidade por método direto com a coleta total de fezes (CT) e indireto pelo uso CELi e LIGi obtidos pelas técnicas in situ (IS) na cavidade ruminal de bovinos e in vivo (IV) nos equinos por meio do saco de náilon móvel (SNM). A produção fecal e taxa de recuperação (p > 0,05) médios encontrados foram de 2,80 kg na MS e 101%, respectivamente. As estimativas dos CD dos nutrientes (p > 0,05) foram adequadamente preditos pela CELi e LIGi, obtidos in situ e in vivo, no qual os valores médios observados foram de 52,63, 54,17, 64,90, 43,73 e 98,28% para MS, MO, PB, FDN e Amido, respectivamente. Concluiu-se que a CELi e LIGi podem ser obtidas in vivo por meio do SNM em equinos, para predizer os coeficientes de digestibilidade de nutrientes, consumindo dieta mista.