Charles Windson Isidoro Haminiuk

Rheological Properties of Butia Pulp

Rheological parameters of Butia pulp were determined at different temperatures using a concentric cylinder Haake Rotovisco rheometer, model RV-20, with measurement system ZA-30. Butia pulp was found to exhibit non-Newtonian, pseudoplastic behavior at all temperatures and the rheological parameters were adequately described by the Herschel-Bulkley model. Yield stress, flow behavior index, and consistency coefficient were significantly affected by temperature. The yield stress decreased exponentially with process temperature and ranged between 36.60 and 21.70 Pa. Apparent viscosity calculated through the Herschel-Bulkley model decreased with an increase in temperature. The Arrhenius model gave a good description of temperature effect on apparent viscosity of the pulp.

Propriedades reológicas da polpa de manga (Mangifera indica L. cv. Keitt) centrifugada

Objetivou-se com este trabalho estudar experimentalmente o comportamento reologico da polpa de manga centrifugada na faixa de temperatura de 10°C a 60°C. As medidas reologicas foram feitas no reometro Haake Rotovisco modelo RV 20, utilizando o sistema de medida de cilindros concentricos. A polpa integral foi produzida em uma despolpadeira com tela de 1,6 mm, congelada em um congelador de placas e armazenada a -15oC e centrifugada a 15000 rpm (29000 G), durante 40 minutos. O comportamento reologico da polpa de manga centrifugada (reogramas) foi ajustado pelo modelo de Ostwald de Waelle (Lei da Potencia) e as curvas de viscosidade aparente ajustadas pelo modelo de Mizrahi-Berk. Observou-se um comportamento pseudoplastico para a polpa de manga centriguda (n<1) e uma diminuicao na viscosidade aparente com o aumento da taxa de deformacao e temperatura, sendo que a viscosidade aparente da polpa de manga centrifugada tendeu a ficar constante a partir 200s-1.

Physicochemical properties of modified citrus pectins extracted from orange pomace

Modified pectin is a polysaccharide rich in galacturonic acid altered by pH adjustment and thermal treatment used especially as an anti-cancer agent. The aim of this work was to study the physical and chemical properties of modified pectins extracted from orange pomace with citric and nitric acids. The galacturonic acid content, degree of esterification, Fourier Transform Infrared Spectroscopy profile, molecular weight, intrinsic viscosity, rheological properties and antioxidant activity of the pectins were evaluated. The modification process caused the de-esterification of pectins and a decrease of molecular weight due to removal of neutral sugars, maintaining the linear chain of galacturonic acid. Such changes also caused a significant increase in the in vitro antioxidant activity (p ≤ 0.05) and influenced the rheological properties of pectin, reducing its viscosity. This work showed that the modification of pectin from orange pomace with citric and nitric acids altered its structural and physical characteristics as well as its biological activity toward a free-radical.

Modelling the extraction of phenolic compounds and in vitro antioxidant activity of mixtures of green, white and black teas (Camellia sinensis L. Kuntze)

AbstractThe aim of this study was to model the extraction of phenolic compounds and antioxidant activity from mixtures of green, white and black teas (Camellia sinensis) using a simplex-centroid design coupled with multiple regression analysis. White tea showed the highest content of phenolic compounds and in vitro antioxidant activity, while black tea presented the opposite behaviour. The lowest values found in black tea are due to the oxidation of phenolic antioxidants during the fermentation. Gallic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, epigallocatechin, and epicatechin gallate showed a significant correlation (P < 0.05) between all the antioxidant assays. All the mathematical models proposed were significant (P < 0.05) and showed high determination coefficients (R2adj > 0.80). A simultaneous optimization was performed using the desirability function and the optimum condition to maximize the extraction of epicatechin, epigallocatechin gallate, epicatechin gallate, as well as the antioxidant activity (DPPH and FRAP). The results showed that pure white tea was the best solution for obtaining a higher content of antioxidants. Graphical abstractExtraction process of phenolic compounds using response surface methodology

Antioxidant and rheological properties of guava jam with added concentrated grape juice

BACKGROUND Guava jam enriched by the addition of concentrated grape juice in the proportion of 30% (w/w) (ENR) was studied for its antioxidant potential and rheological behavior. Total phenolics content, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH(•)) scavenging activity and β-carotene-linoleic acid coupled oxidation assays were used to evaluate the antioxidant properties of the samples during storage for 90 days at room temperature (25°C). RESULTS The ENR showed a total phenolic content of 11.09 g GAE kg(-1) of jam at production, more than two-fold the phenolic content presented by the standard formulation (STA). For the ENR formulation the antioxidant capacity increased in almost 20% (P ≤ 0.05) with time on the β-carotene assay and decreased with time on the DPPH assay. The enriched guava jam exhibited a non-Newtonian shear-thinning behavior at temperatures ranging from 25 to 55°C, and, moreover, presented higher stability than the standard formulation when exposed to temperature variation. CONCLUSION ENR constitutes an original food product with a notable antioxidant potential, even greater than the potential presented by the standard guava jam, worldwide appreciated delicacy.

Comportamento reológico de sistemas pécticos de polpas de frutas vermelhas

In this work, the rheological behavior of pectic systems formulated with pectins extracted from strawberry, blackberry, and raspberry pulps was investigated by means of oscillatory rheological tests. In addition, the chemical properties of these pectins were studied. The pectic systems from those red fruit pulps showed a strong gel character according to the rheological tests showing that the strawberry pectin presented the strongest gel character, which was confirmed by the Cox-Merz experiment, degree of esterification, and average molecular weight data. The galacturonic acid is directly related to the formation of the pectin network. Besides, the difference between the strength of the three pectic gels can be attributed to the esterification degree values and the average molecular weight of these biopolymers. The pectins extracted from the red fruits studied in this work can be classified as high methoxy pectins with a degree of esterification higher than 50%. The pectic gels exhibit good stability with an increase in temperature and in the shear-oscillatory constant time.

Granules morphology and rheological behavior of green banana (Musa cavendishii) and corn (Zea mays) starch gels

No presente trabalho foi utilizado amido obtido de banana verde (Musa cavendishii) e amido de milho (Zea mays) comercial, com o objetivo de comparar a morfologia dos grânulos e o comportamento reologico dos geis. As imagens da morfologia dos grânulos foram obtidas por microscopia eletronica de varredura. Os grânulos de amido da banana apresentaram forma oval e elipsoidal com diâmetros irregulares, todavia, os grânulos do amido de milho mostraram forma poliedrica e diferentes tamanhos. As analises reologicas dos geis das solucoes de amido mostraram carater nao-newtoniano, pseudoplastico. O modelo de Herschel-Bulkley foi o que melhor representou comportamento reologico dos geis. O gel de amido de banana verde obteve maiores valores de tensao de cisalhamento e viscosidade aparente quando comparada ao gel de amido de milho. Ocorreu um decrescimo progressivo na tensao de cisalhamento e na viscosidade com a adicao de cloreto de sodio e sacarose aos geis.

Efeito de pré-tratamentos no escurecimento das cultivares de maçã fuji e gala após o congelamento

Objetivou-se com este trabalho avaliar os efeitos de pre-tratamentos para a reducao do escurecimento nas cultivares de maca Fuji e Gala apos um periodo de congelamento de 12 dias. Aplicou-se quatro pre-tratamentos: imersao em agua fervente por dois minutos (IAF), imersao em solucao de bissulfito 0,25% por dois minutos (ISB), imersao em solucao de sacarose 35% por dois minutos (ISS) e um sem pre-tratamento para comparacao (SPT). Procedeu-se a analise, em que avaliou-se a cor, atraves de medidas colorimetricas empregando a escala universal L*, a* e b* nas amostras tratadas antes e depois do congelamento. Para avaliacao sensorial do atributo cor utilizou-se a analise descritiva quantitativa (ADQ) com escala estruturada de 9 pontos. O melhor pre-tratamento na prevencao do escurecimento foi o IAF e o pior foi o tratamento SPT, no qual se observou uma alta oxidacao dos compostos fenolicos. O pre-tratamento ISB apresentou a maior aceitacao no teste ADQ para as macas Fuji e Gala, nao obtendo-se relacao entre a analise fisica colorimetrica e a analise afetiva sensorial.

Polissacarídeos extraídos da gabiroba (Campomanesia xanthocarpa Berg): propriedades químicas e perfil reológico

The Campomanesia xanthocarpa Berg (Myrtaceae) is a Brazilian native fruit, widely abundant in the Southern region. Despite their large fructification, in addition to nutritional and attractive sensory characteristics, these fruits are not collected, being lost in the fields. In this work, the fruit pulp without seed (1500 g) was crushed in ethanol/water at a ratio of 1:4 (v/v), refluxed for 15 minutes at boiling temperature. The residue obtained was subjected to sequential extractions. The extractions were optimized using a factorial design 22, with the concentration of citric acid (0.5 and 5%) and temperature (50 and 100 oC) as variables. The polysaccharides were characterized according to their chemical composition and rheological profile. The high concentrations of uronic acids, arabinose and galactose, detected in all fractions, indicate that they consist of pectin. The results showed that the extraction method was efficient for fractionation of pectin from different areas of the cell wall. The polysaccharides extracted from the fruit pulp of gabiroba showed a pseudoplastic behavior. All the fractions were resistant to temperature variations. When these gels are heated up and cooled down, they adopt their original structure.

Study of the Rheological Parameters of Honey Using the Mitschka Method

In this work the rheological behavior of two varieties of honey were evaluated using a Brookfield viscometer R.V.T in a temperature range of 5-20°C. In order to interpret the experimental results in terms of viscosity, the torque-speed data and scale readings were converted into shear stress-shear rate relations using numerical conversion values proposed by Mitschka. This method offers excellent potential for quality control testing in the food industry. Samples exhibited Newtonian behavior and the temperature effect on the viscosity followed an Arrhenius-type relationship.