Browsing by Author "Oliveira, Solange"
Now showing 1 - 10 of 12
Results Per Page
Sort Options
- Analysis of some chemical components, phenolic compounds and antioxidant activity in physalisPublication . Correia, Paula; Guiné, Raquel; Gonçalves, Fernando; Oliveira, SolangePhysalis peruviana L. is appreciated for its organoleptic characteristics, besides being rich in many beneficial compounds. Because its characteristics are yet not fully understood, the present work aimed at studying some of its chemical properties and bioactive phenols and the corresponding antioxidant activity. For obtaining the phenolic extracts three methods with different combinations of extracting solvents were essayed and the evaluation of total phenols, ortho-diphenols, flavonoids and antioxidant activity by DPPH and ABTS were done following established methodologies. The results showed that P. peruviana had important amounts of fibre, vitamin C and carotenoids. Regarding the methods for extraction of phenolic compounds, the most efficient were those in which a combination of the solutions methanol:water and acetone:methanol were used. The phenolic compounds contents were quantified as being p to 59.9 mg GAE/100 g, flavonoids up to 0.340 mg QE/100 g and ortho-diphenols up to 94.6 mg GAE/100 g. The antioxidant activity ranged between 7.7 and 9.6 µmol TE/g for method DPPH and between 12.3 and 13.7 µmol TE/g for method ABTS.
- Aplicação da modelização por redes neuronais ao teor de compostos fenólicos e atividade antioxidante em bananas de diferentes cultivares secadas sob condições distintasPublication . Guiné, Raquel; Barroca, Maria João; Gonçalves, Fernando; Alves, Mariana; Oliveira, Solange; Mendes, MateusOs compostos fenólicos estão amplamente presentes no reino vegetal, sendo essenciais para o crescimento e reprodução das plantas, além de serem responsáveis pela cor, adstringência e aroma em vários alimentos [1]. Estes compostos, sendo antioxidantes, combatem os radicais livres, previnem doenças cardíacas, doenças neurodegenerativas, problemas do aparelho circulatório, cancro, inflamação e inibem a oxidação lipídica [1-2]. Porém, o processamento térmico pode destruir a quantidade ou a biodisponibilidade destes compostos, reduzindo assim os efeitos benéficos para a saúde [3]. As redes neurais artificiais (ANN: Artificial Neural Networks) têm sido utilizadas nos últimos anos para a modelização de muitos processos em engenharia de alimentos, como por exemplo: modelização e controlo do processo de secagem das uvas, previsão do desempenho energético do processo de secagem por atomização para óleo de peixe e leite em pó desnatado, previsão do encolhimento e reidratação de cenouras desidratadas [4-5]. O presente estudo foi realizado com o objetivo de investigar o impacto das condições de secagem sobre o teor em compostos fenólicos totais e atividade antioxidante em bananas de duas cultivares, bem como modelizar as variáveis do processo por meio de redes neurais artificiais. Bananas (cv. Musa nana e Musa cavendishii) em fresco, secadas por ar a 50 e 70 ºC e liofilizadas foram analisados quanto ao seu conteúdo em compostos fenólicos (FT) utilizando o reagente de Folin-Ciocalteu e atividade antioxidante (AA) utilizando o radical ABTS. Todas as amostras foram sujeitas a seis extrações sucessivas (três com metanol e três com uma solução de acetona). Os dados experimentais serviram para treinar uma rede neural usada para análise de dados e previsão das variáveis de saída (FT e AA). Os resultados indicam que as bananas das duas cultivares apresentam resultados semelhantes e que a secagem ao ar provocou um decréscimo do conteúdo de fenóis e na atividade antioxidante para ambas as temperaturas. A liofilização também diminuiu o teor de compostos fenólicos, porém em menor grau. Os testes feitos com as redes neurais mostraram que as variáveis FT e AA podem ser previstas com uma precisão elevada a partir das variáveis de entrada (Figura 1): variedade, estado de secagem, tipo de extrato e ordem do extracto, sendo que de entre estas as que assumem maior importância são o estado de secagem e a ordem do extrato.
- Artificial neural network modelling of the antioxidant activity and phenolic compounds of bananas submitted to different drying treatmentsPublication . Guiné, Raquel; Barroca, Maria João; Gonçalves, Fernando; Alves, Mariana; Oliveira, Solange; Mendes, MateusBananas (cv. Musa nana and Musa cavendishii) fresh and dried by hot air at 50 and 70 C and lyophilisation were analysed for phenolic contents and antioxidant activity. All samples were subject to six extractions (three with methanol followed by three with acetone/water solution). The experimental data served to train a neural network adequate to describe the experimental observations for both output variables studied: total phenols and antioxidant activity. The results show that both bananas are similar and air drying decreased total phenols and antioxidant activity for both temperatures, whereas lyophilisation decreased the phenolic content in a lesser extent. Neural network experiments showed that antioxidant activity and phenolic compounds can be pre- dicted accurately from the input variables: banana variety, dryness state and type and order of extract. Drying state and extract order were found to have larger impact in the values of antioxidant activity and phenolic compounds.
- Determination of Some Chemical Properties of Uncommon FloursPublication . Andrade, Sónia; Oliveira, Solange; Guiné, Raquel; Correia, PaulaFlours of wheat, chestnut, acorn and lupin were evaluated in relation to phenolic compounds, antioxidant activity, and oxalate content.At the chemical level the results show some variability between samples by type of flour, and the sample of chestnut flour presented the higher value of oxalate (0.00348 mg/100g) when compared to the other samples in the study. Considering the content of phenolic compounds, the sample that stood out was the acorn flour, having a high value of 0.812 g AGE/100 g. All the samples presented intermediate content of antioxidant activity and the sample that showed a slightly higher value was the wheat flour with a value of 0.746 mM TRE/g sample.
- Determination of Some Chemical Properties of Uncommon FloursPublication . Andrade, Sónia; Oliveira, Solange; Guiné, Raquel; Correia, PaulaFlours of wheat, chestnut, acorn and lupin were evaluated in relation to phenolic compounds, antioxidant activity, and oxalate content. At the chemical level the results show some variability between samples by type of flour, and the sample of chestnut flour presented the higher value of oxalate (0.00348 mg/100g) when compared to the other samples in the study. Considering the content of phenolic compounds, the sample that stood out was the acorn flour, having a high value of 0.812 g AGE/100 g. All the samples presented intermediate content of antioxidant activity and the sample that showed a slightly higher value was the wheat flour with a value of 0.746 mM TRE/g sample.
- Effect of drying on the properties of pears cv. D. JoaquinaPublication . Barroca, Maria João; Guiné, Raquel; Alves, Mariana; Oliveira, Solange; Gonçalves, Fernando; Correia, PaulaIn the present work, pears of the Portuguese cultivar, cv. D. Joaquina, were dehydrated by hot air drying at temperatures of 60 ºC and 70 ºC. Drying properties such as moisture, color, antioxidant activity, and total phenols content were evaluated. The drying temperature induced the increase of a* and b* colorimetric parameters, due to non-enzimatic browning reaction which turns the dried fruits more reddish and yellow. The obtained results lead to the conclusion that total phenols content decreased with drying, but the observed values were similar to the pears dried at 60 ºC and 70 ºC. Furthermore, the results also indicate that antioxidant compounds might be degraded or modified during the drying process. In addition, a decrease of more of 50 % was observed in the fruits dried at 60 ºC and 70 ºC.
- Effect of Drying on Total Phenolic Compounds, Antioxidant Activity, and Kinetics Decay in PearsPublication . Guiné, Raquel; Barroca, Maria João; Gonçalves, Fernando; Alves, Mariana; Oliveira, Solange; Correia, PaulaThe polyphenols have been identified as food components sensitive to high temperatures; therefore, the application of heat treatments can lead to a significant reduction in the phenolic content and also on antioxidant capacity. The objectives of the present work were to investigate the decrease in total phenolic compounds and antioxidant activity in pears during air drying at different tem- peratures and to model the kinetics of those variations. The pears (cv. D. Joaquina) were dried at 60 ◦ C and 70 ◦ C in an electrical drying chamber with hot air at 0.5 m / s. Along drying several samples were collected for analysis, being submitted to multiple extractions with methanol and acetone solutions. The phenolic compounds were determined by the Folin-Ciocalteu method and the antioxidant activity was determined by the ABTS method. The results showed that three successive extractions with methanol fol- lowed by three extractions with acetone solution was necessary for an efficient quantification of the total phenolic compounds and antioxidant activity. The decrease along drying was found to be of about 40% for both parameters and for the two temperatures studied. Furthermore, a relatively strong relation was observed between total phenols and antioxidant activity. The mathematical modeling of the kinetics showed that a 3-parameter exponential decay function was the best function to describe the experimental data, and the kinetic constants were found to vary in the range 0.0136–0.0444 min− 1.
- Evaluation of Phenolic Compounds, Antioxidant Activity and Bioaccessibility in Physalis Peruviana LPublication . Guiné, Raquel P. F.; Gonçalves, Fernando Jorge; Oliveira, Solange; Correia, PaulaThis work evaluated phenolic compounds in Physalis peruviana as well as their antioxidant activity and bioaccessibility, using an in vitro model of the gastrointestinal system. Three combinations of solvents were evaluated for the extraction of phenolic com- pounds. All other chemical components, their antioxidant activity and bioaccessibility were evaluated using established methods. P. peruviana is rich in fiber (4.61 g/100 g), vitamin C (26.70 mg/ 100 g), carotenoids (5.95 µg/100 g), total phenolic compounds (59.9 mgGAE/100 g), flavonoids (0.340 mgQE/10 g) and ortho- diphenols (94.6 mgGAE/100 g). The antioxidant activity varied from 7.7 to 13.7 µmolTE/g. The simulation of the digestive tract showed that only about 40-50% of the phenolic compounds remained available for intestinal absorption, and only 23 – 34% of the antioxidant activity was preserved after passing through the gastrointestinal system. Hence, these ratios have to be taken into consideration regarding the ingestion of phenolic com- pounds in order to expect desired health benefits for the human body, namely in terms of antioxidant activity.
- Evaluation of some chemical properties of different flours.Publication . Andrade, Sónia; Oliveira, Solange; Guiné, Raquel; Correia, PaulaThe antinutritional factors in flours include phenol, tannin, oxalate, phytate and alkaloids. Wheat is one of the most important food for the world population, in which about 35% of the total world population regularly consume wheat-based foods.In recent times, there has been growing interest in using chestnut flour for use in bakery because its chemical composition is close to many cereals. The acorn is the fruit with an edible oval that grows on trees called by oaks, and contains in its composition a high starch content. There are available on the market a great variety of industrial products made from acorn flour or starch, including breads, cakes, soups, jelly, among others range. The lupine flour is of enormous importance, being widely used in the food industry to improve the nutritional value of other foods. In this work, five types of flours made were evaluated in relation to some chemical properties (oxalate, phenolic compounds and antioxidant activity). At the chemical level the results show some variability between samples by type of flour, and the sample of chestnut flour presented higher value of oxalate (3.48 g/100g) when compared to the other samples in the study. With respect to the content of phenolic compounds the sample that stood out was the acorn flour, having a value of 0.812 g EAG/100 g. Regarding the determination of antioxidant activity the sample that showed a slightly higher value than the other samples was the sample of wheat flour with a value of 0.746 mM TE/g sample.
- Evaluation of total phenolic compounds and antioxidant activity for the drying of bananas and pearsPublication . Guiné, Raquel; Gonçalves, Fernando; Alves, Mariana; Oliveira, Solange; Barroca, Maria João; Correia, PaulaChemically, the phenolic compounds are cyclic benzene compounds having one or more hydroxyl groups directly associated to the ring structure. While they contain alcohol groups, they do not show properties of alcohols. The phenols can be distinguished into two groups: non-flavonoids and flavonoids [1-4]. Bananas cv. nana and pears cv. D. Joaquina were subject to drying (at 70 ºC) for comparison of their properties with the corresponding fresh fruits. All samples were obtained from 5 g of product and 6 successive extractions were performed for each sample (three with methanol and three with acetone solution (40% v/v)), for 1 hour each in an ultrasonic bath. The phenolic content of the different extracts was determined by Folin-Ciocalteu reagent, and the results expressed as gallic acid equivalents. The antioxidant capacity was estimated using the ABTS method, and the results expressed as trolox equivalents. All results were expressed in dry basis, to allow a direct comparison. The results revealed that both fruits studied showed some degree of degradation of the phenolic compounds and consequently a decrease in the antioxidant activity when submitted to drying. Comparing the fresh fruits with those dried at 70 °C, it was found that the amount of reduction in total phenolic content was about 45% for bananas and 59% for pears, while the decrease in the antioxidant activity was around 33% for bananas and 53% for pears.