Valéria Paula Rodrigues Minim

Estresse oxidativo: conceito, implicações e fatores modulatórios

There is evidence that oxidative stress, defined as a persistent imbalance between the production of highly oxidative compounds and antioxidant defenses, leads to tissue damage. Oxygen metabolism generates free radicals and/or non-radical reactive oxygen species. The mitochondria, through the electron transport chain, are the main generator of these species. The antioxidant defense system has the function of inhibiting and/or reducing the damage caused by the deleterious free radicals and/or non-radical reactive oxygen species. This system is divided into enzymatic (superoxide dismutase, catalase and glutathione peroxidase), and nonenzymatic. The nonenzymatic system consists of a variety of antioxidant substances, which may be endogenous or dietary. This study proposed to review the main mechanisms of reactive oxygen species generation and the role of the most relevant agents of the antioxidant defense system on the biomarkers of oxidative stress. The main exogenous factors that modulate oxidative stress will also be discussed.O estresse oxidativo decorre de um desequilibrio entre a geracao de compostos oxidantes e a atuacao dos sistemas de defesa antioxidante. A geracao de radicais livres e/ou especies reativas nao radicais e resultante do metabolismo de oxigenio. A mitocondria, por meio da cadeia transportadora de eletrons, e a principal fonte geradora. O sistema de defesa antioxidante tem a funcao de inibir e/ou reduzir os danos causados pela acao deleteria dos radicais livres e/ou especies reativas nao radicais. Esse sistema, usualmente, e dividido em enzimatico (superoxido dismutase, catalase e glutationa peroxidase) e nao-enzimatico. No ultimo caso, e constituido por grande variedade de substâncias antioxidantes, que podem ter origem endogena ou dietetica. Objetivou-se revisar os principais mecanismos de geracao de radicais livres, bem como a acao dos agentes mais relevantes do sistema de defesa antioxidante, ressaltando suas implicacoes sobre os marcadores do estresse oxidativo. Tambem serao abordados os principais fatores exogenos moduladores do estresse oxidativo.

Capacidade dos biomarcadores inflamatórios em predizer a síndrome metabólica: Inflammation biomarkers capacity in predicting the metabolic syndrome

The inflammatory process is the link between metabolic syndrome and cardiovascular diseases. To measure the degree of subclinical inflammation some inflammatory biomarkers have been considered. This work reviews the recent researches of the associations between inflammatory biomarkers and metabolic syndrome, as well as the capacity in predicting the metabolic syndrome. These biomarkers include pro-inflammatory cytokines, anti-inflammatory cytokines, adipokines, chemokines, inflammation markers derived from hepatocites, the consequence markers of inflammation and enzymes. This review integrates the new knowledge of inflammatory mediators interactions with metabolic syndrome, since these biomarkers play different roles and follow diverse metabolic ways.

Application of the response surface methodology for optimization of whey protein partitioning in PEG/phosphate aqueous two-phase system.

In order to develop a new strategy for β-lactoglobulin (β-lg) removal from whey protein, partitioning of α-lactalbumin (α-la), β-lg and glycomacropeptide (Gmp) was studied using aqueous two phase systems (ATPS). A system composed of 13% (w/w) polyethylene glycol (PEG, average molar mass 2000 g/mol) and 13% (w/w) potassium phosphate was used at 25°C. A central composite rotatable design (CCRD) associated to the response surface methodology (RSM) was applied to investigate the effects of NaCl concentration and pH on the partition of these proteins. It was found that α-la and Gmp partitioned to the top phase rich in PEG, whereas β-lg partitioned to the bottom phase rich in salt. According to the RSM, optimal conditions for β-lg removal where found where pH was equal to 6.7 and salt concentration was 0.35 mol/L. Under these conditions, the partition coefficient K(α) was 0.48 and K(Gmp) was 0.92. On the other hand, the partition coefficient K(β) was only 0.01. In such conditions β-lg preferentially concentrates in the bottom phase, while the top phase exclusively contains the proteins α-la and Gmp. Fractionation of the proteins from fresh whey was performed in a three stage cross-flow extraction system. The extraction yield for β-lg in the bottom phase was 97.3%, while the yields for α-la and Gmp in the top phase were 81.1% and 97.8%, respectively.

Índices dietéticos para avaliação da qualidade de dietas

The relation between diet and health can be evaluated by the level of some food components (nutrients), kinds of food, group or food groups and eating patterns. The association between these parameters and some chronic diseases can be examined by dietary instruments of global diet assessments and some indices have been considered for this end. The aim of this work was to describe the different indices for assessing diet quality, including the Index of Nutrients, Dietary Variety Score, Dietary Diversity Score, Diet Quality Index, Healthy Eating Index, Diet Quality Index Revised, Alternative Healthy Eating Index, Recommended Food Score, Alternative Mediterranean Diet Score, as well as their derivations. These indices show an improvement in the concept of quality, emphasizing the functional properties of food components related to risk reduction of the most prevalent diseases nowadays.

Cryogel Poly(acrylamide): Synthesis, Structure and Applications

This review focuses on the description of macromolecular gels formed as a result of polymerization, under freezing conditions, from monomer solutions. Materials resulting from this polymerization are known as cryogels and have particular properties, such as porosity of a specific nature. They are attractive in terms of biotechnological applications. The cryogels have interconnected macropores, and their preparation method from aqueous solutions in freezing conditions is a process that combines the crystallization of a solvent with the copolymerization of monomers. Cryogels have recently been used as adsorbents for the efficient separation and purification of biomacromolecules, such as proteins, DNA, cell organelles, viruses and enzymes that are present in solutions. Despite the wide application of cryogels, improvements in their preparation are necessary to minimize problems, such as the formation of hydrogels, instead of cryogels. Hydrogels form due to immediate polymerization after addition of the redox initiator before solvent freezing. The synthesis and use of cryogels as chromatographic supports are also discussed.

Use of response surface methodology to evaluate the extraction of Debaryomyces hansenii xylose reductase by aqueous two-phase system

Xylose reductase (XR) from Debaryomyces hansenii was extracted by partitioning in aqueous two-phase systems (ATPS) composed of polyethylene glycol (PEG) 4000 in the presence of different salts, specifically sodium sulfate, lithium sulfate and potassium phosphate. Batch extractions were carried out under different conditions of temperature (25-45 degrees C) and tie-line length (TLL) for each system, according to a central composite design face-centered of 36 tests, and the response surface methodology was used to evaluate the results. Quadratic polynomial models were adjusted to the data to predict the behavior of four responses, namely the XR partition coefficient (K(XR)), the selectivity (S), the purification factor (PF(T)) and the activity yield (Y(T)) in the top phase. The optimal extraction conditions were found using the PEG 4000/sodium sulfate system at 45 degrees C and TLL=25.1, which ensured PF(T)=3.1 and Y(T)=131%. The ATPS proved effective for partial purification of D. hansenii xylose reductase in cell-free crude extract, and the response surface methodology revealed to be an appropriate and powerful tool to determine the best dominion of temperature and ATPS composition.

Estudo de mercado de iogurte da cidade de Belo Horizonte/MG

O estudo do perfil dos consumidores e dos fatores envolvidos no processo de compra do iogurte e uma ferramenta importante na identificacao dos diferentes segmentos desse mercado e de suas potencialidades. Assim, neste trabalho entrevistaram-se 387 consumidores de iogurte, residentes em Belo Horizonte - MG, que responderam os questionarios estruturados. Os resultados foram analisados de forma descritiva, e para verificar a correlacao entre caracteristicas sociodemograficas com o perfil de consumo aplicou-se a analise de correlacao de Pearson. Os resultados indicaram que o iogurte sabor morango apresenta maior aceitacao pelos consumidores, que a categoria light/diet possui grande parte do seu publico consumidor (54%). Segundo a pesquisa, 39,9% dos respondentes que nao consomem iogurte light/diet disseram nao consumi-lo por nao gostar desse produto. Isto revela a importância de pesquisas para desenvolvimento de iogurte light/diet visando a melhoria da qualidade sensorial. O fato de nao ver necessidade de consumir o produto foi apontado como um dos principais motivos por nao consumir iogurte da categoria light/diet. A qualidade, a marca e o preco apresentaram grande importância na conquista de mercado, sendo os tres principais atributos observados no momento da compra de iogurte na cidade estudada. Analisando a correlacao entre consumo e fator sociodemografico, observou-se que a renda e a idade influenciam tanto na frequencia de consumo de iogurte quanto no consumo do produto na versao light/diet.

Perfil sensorial e aceitabilidade de diferentes formulações de pão de queijo

Bread cheese is a traditional product of Minas Gerais-Brazil Its production comes growing a lot, expanding besides for the external market. Despite of this expansion, a trading quality standard was not yet developed. In this work, Quantitative Descriptive analysis was applied to select sensory attributes which best define the changes in appearance, aroma, flavour and texture when different ingredients were used. Seven formulations were evaluated by a selected panel and eighteen attributes best describing similarities and differences between then were defined. After a training period panellist evaluated the samples in an incomplete block design using a 9 cm unstructured scale. The developed formulations were also appraised in relation to acceptability through the hedonic scale of 9 points, for 70 consumers of cheese breads. ANOVA and Tukey test (p 0,05) was observed between the samples.

Development and validation of the high performance liquid chromatography-ion exclusion method for detection of lactic acid in milk

The present work reports the development and validation of an analytical method for lactic acid quantification in milk by ion exclusion-HPLC with UV detection. This method showed good precision (variation coefficient <7.0%) and good accuracy (97.6-99.6%). Calibration curves were linear (R(2)>0.996) at the tested range of 5.0-25.0mmolL(-1); and the detection and quantification limits were 0.5 and 1.0mmolL(-1), respectively. Analysis of lactic acid in fermented milk (FM) or NaOH neutralised fermented milk (FNM) was performed using samples obtained during 9h of fermentation. An ANOVA analysis combined with the Tukey test was used to show that the method was insensitive to the differences between FM and FNM. The proposed method therefore proved to be a useful quality control tool in laboratories because it was able to determine milk acidity even in adulterated samples.

Modeling Thermal Conductivity, Specific Heat, and Density of Milk: A Neural Network Approach

Abstract The accurate determination of thermophysical properties of milk is very important for design, simulation, optimization, and control of food processing such as evaporation, heat exchanging, spray drying, and so forth. Generally, polynomial methods are used for prediction of these properties based on empirical correlation to experimental data. Artificial neural networks are better suited for processing noisy and extensive knowledge indexing. This article proposed the application of neural networks for prediction of specific heat, thermal conductivity, and density of milk with temperature ranged from 2.0 to 71.0°C, 72.0 to 92.0% of water content (w/w), and 1.350 to 7.822% of fat content (w/w). Artificial neural networks presented a better prediction capability of specific heat, thermal conductivity, and density of milk than polynomial modeling. It showed a reasonable alternative to empirical modeling for thermophysical properties of foods.