ESAV - DIA - Artigo em revista científica, não indexada ao WoS/Scopus
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Browsing ESAV - DIA - Artigo em revista científica, não indexada ao WoS/Scopus by Author "Alves, Mariana"
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- 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, 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.
- 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.