Browsing by Author "Alves, Mariana"
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- 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.
- Contribuition for the physical characterization of carolino ricePublication . Correia, Paula; Alves, Mariana; Lemos, Diogo; Guiné, RaquelMost of the rice produced in Portugal is of the Carolino type, botanically classified as Oryza sativa ssp. Japonica. Nowadays, this rice is playing a vital role in Portuguese rice trading, and therefore the aim of this work was to evaluate some cultivars as to biometric characteristics, water uptake ratio, cooking time and textural properties. Five types of Carolino rice were collected for analysis. Biometric characteristics (length, width, length/width ratio) were evaluated using an automatic biometric equipment. Other morphological characteristics were evaluated: white vitreous, total whiteness, vitreous percentage, percentage of chalky area and kett (using a colorimeter). Texture was evaluated on compression by texture profile analysis with a texturometer. The samples studied showed biometric characteristics to be commercially classified as long grains type-A. The results indicated that one of the samples was quite different from the others, presenting less adhesiveness, and lower hardness, springiness and cohesiveness. Also some differences were found between different rice samples regarding colour characteristics, cooking time and water absorption.
- Contribution for physical characterization of aromatic ricePublication . Correia, Paula; Alves, Mariana; Lemos, Diogo; Guiné, RaquelIntroduction: Rice is consumed mainly as whole grain, and quality considerations are much more important than for any other food crop. Rice grain quality preference varies from country to country and among regions. Nowadays, aromatic rice varieties are playing a vital role in global rice trading, and also in Portugal. The economic value of rice depends on its cooking and processing quality, such us water uptake ratio, cooking time and texture properties. Materials and methods: Three types of aromatic rice were collected and analysed for biometry characteristics, cooking time, water absorption, and texture properties.The rice grains were collected from the Portuguese trade market. Biometric characteristics of all rice grains were evaluated by S21 (LKL) and C-300 (Kett) colorimeter. The rice flour texture was performed by a TPA (texture profile analysis), giving information about adhesiveness, chewiness, gumminess, hardness, resilience and cohesiveness. The extrusion force was also determined according to ISO 11747:2012. Results: Rice samples are commercially classified as long grains B type, because they presented a length higher than 6 mm and the ratio length/width higher than 3. The samples presented a high degree of whiteness, with a strictly relationship between the total and vitrea whiteness (r2=0.95). The cooking time varied from 12 to 17 minutes and this properties was strongly related with water uptake (from 155.7 – 209.1 g). Generally, aromatic rice cultivars presented different textural properties. Aromatic rice samples are different for hardness, adhesiveness, gumminess, resilience and extrusion force. Conclusions: From the results obtained it was concluded that the studiedc aromatic rice cultivars presented different physical properties, mainly the cooking time, water uptake and texture. These differences could be a commercial advantage considering the consumer point of view, because the enterprise could provide a specific aromatic rice in order to attend different consumer targets.
- Contribution for physical characterization of aromatic ricePublication . Correia, Paula; Alves, Mariana; Lemos, Diogo; Guiné, RaquelRice is consumed mainly as whole grain, and quali- ty considerations are much more important than for any other food crop. Rice grain quality preference varies from country to country and among regions. Nowadays, aromatic rice varieties are playing a vital role in global rice trading, and also in Portugal. The economic value of rice depends on its cooking and processing quality, such us water uptake ratio, cooking time and texture properties. Three types of aromatic rice were collected and ana- lyzed for biometry characteristics, cooking time, wa- ter absorption, and texture properties. The rice grains were collected from the Portuguese trade market. Biometric characteristics of all rice grains were eval- uated by S21 (LKL) and C-300 (Kett) colorimeter. The rice flour gels texture was performed by a TPA (texture profile analysis), giving information about adhesive- ness, chewiness, gumminess, hardness, resilience and cohesiveness. The extrusion force was also determined according to ISO 11747:2012. Rice samples are commercially classified as long grains B type, because they presented a length higher than 6 mm and the ratio length/ width higher than 3. The samples presented a high degree of whiteness, with a strictly relationship between the total and vitrea white- ness (r 2 = 0.95). The cooking time varied from 12 to 17 minutes and these properties was strongly related with water uptake (from 155.7 - 209.1 g). Generally, aromat- ic rice cultivars presented different textural properties. Aromatic rice samples are different for hardness, adhe- siveness, gumminess, resilience, and extrusion force. From the results obtained it was concluded that the studied aromatic rice cultivars presented different physical properties, mainly the cooking time, water uptake and texture. These differences could be a com- mercial advantage considering the consumer point of view, because the enterprise could provide specif- ic aromatic rice in order to attend different consumer targets.
- Contribution for physical characterization of carolino ricePublication . Correia, Paula; Alves, Mariana; Lemos, Diogo; Guiné, RaquelMost of the rice produced in Portugal is of the Carolino type, botanically classified as Oryza sativa ssp. Japonica. Nowadays, this rice is playing a vital role in Portuguese rice trading. Five types of Carolino rice were collected and analysed for biometry characteristics, cooking time, water absorption, and texture properties. The Carolino rices studued are commercially classified as long grains type-A, because they present a length higher than 6 mm and the ratio length/width lower than 3 mm. This type of rice showed a high level of plastered area, meaning low vitrea aspect, with a negative strong correlation (r2=-0.99), and it was observed a great discrepancy for the study cultivars. The cooking time varied from 17 to 22 minutes, with a water uptake between 143.9 and 182.5 g after achieving the cooking point. To compare the differences between the cultivars, the cooking time was also determined after 13 minutes of cooking, and the results showed that the water absorption veried from 101.9 to 139.6 g. Carolino rice flours were quite different considering the results of TPA (texture profile analysis). One of the samples was quite different from the others, presenting less adhesiveness, chewiness, gumminess, hardness, resilience and cohesiveness. The extrusion force (kg/cm2) was similar between the five cultivars. In general, it could be concluded that in spite of the samples belonging to the same species, the different cultivars showed quite different biometric, cooking and texture characteristics.
- 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 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.