Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- Effect of Drying Temperature on the Physical-chemical and Sensorial Properties of Eggplant (Solanum melongena L.)Publication . Guiné, Raquel; Correia, Paula; Correia, Ana Cristina; Gonçalves, Fernando; Brito, Mariana; Ribeiro, JéssicaBackground: Eggplant is an important crop, being cultivated and consumed in many countries. However, like other vegetables, is highly perishable and has a short shelf life. Objective: The objective of this study was to evaluate the effect of hot air drying on some physical, chemical and sensorial properties of eggplant. Methods: Eggplant samples were dried in convective chambers at constant temperatures of 50, 60, 70 and 80°C. The fresh and dried samples were evaluated for moisture, water activity, vitamin C, total phenolic compounds, antioxidant activity, colour and texture. To complement the study, a sensorial evaluation was made by a consumer panel. Results: The results showed that drying decreased importantly the contents of vitamin C and phenolic compounds as well as antioxidant activity. Moreover, the negative impact was higher for higher drying temperatures. Drying also altered the colour, turning the samples darker. The textural properties were similarly considerably altered by drying, although the temperature did not show significant influence. Regarding the sensorial evaluation, even though it allowed establishing the sensory profiles of the dried samples, it was not possible to clearly distinguish among them, particularly the global appreciation. Conclusion: It was concluded that the drying operation substantially changed the physical, chemical and sensory properties of eggplant. Furthermore, the drying temperature had higher effect on the chemical components and colour and nor so much on the texture.
- Extraction of Phenolic Compounds with Antioxidant Activity from Beetroot (Beta Vulgaris L.)Publication . Guiné, Raquel; Gonçalves, Fernando; Lerat, C.; Idrissi, T.E.; Rodrigo, E.; Gonçalves, João Carlos; Correia, PaulaBACKGROUND: Beetroot is reported as an important source of polyphenols as well as betalains, which are compounds that possess high antioxidant effect and radical scavenging capacity. OBJECTIVE: The present study aimed at identifying the most suitable extracting parameters to attempt maximizing the recovery of phenolic compounds with antioxidant activity in beetroot. METHODS: Grounded beetroot was used to perform extractions with different aqueous solutions (ethanol at 50% and acetone at 60%), for different times (15 and 60 min), using different volumes of the extraction solution (25 and 50 ml). For each of the combinations three successive extraction steps were performed and in each extract were quantified the total phenolic compounds (TPC), the anthocyanins (ANT) and the antioxidant activity (AOA), all by spectrophotometric techniques. RESULTS: The results indicated the usefulness of using three successive extraction steps over the same sample besides clearly indicating clearly that an extraction time of 15 min was sufficient. It was further observed that 50 ml of extraction solvent were preferable than 25 ml and the best solution was acetone at 60%. The TPC in the fresh beetroot varied from 1.45 to 2.70 mg GAE/g, the ANT from 0.23 to 0.77 mg Mv3G/g and the AOA from 13.9 to 19.9 µmol TE/g. CONCLUSION: It was concluded that the method of using three successive extraction steps of 15 minutes each was appropriate to increase the recovery of phenolics with antioxidant activity from beetroot.
- Evaluation of phenolic and antioxidant properties of strawberry as a function of extraction conditionsPublication . Guiné, Raquel; Correia, Paula; Ferrão, Ana Cristina; Gonçalves, Fernando; Lerat, Clémence; El-Idrissi, T; Rodrigo, EWe studied the extraction of antioxidant phenolic compounds, anthocyanins and the evaluation of antioxidant activity of strawberries in different extraction conditions, varying the type of solvent (ethanol:water (50%) and acetone:water (60%), the extraction time (15 and 60 min) and the solvent volume to sample mass ratio (5 mL/g and 20 mL/g). In addition, we performed principal component analysis and cluster analysis. The results showed that, although the two solvents tested had similar influence on total phenolic compounds extraction and antioxidant activity, the 60 minutes of extraction and the use of the solvent volume/sample mass ratio of 20 mL/g were the best extraction conditions, both for the 1 st and 2 nd recovered extracts. However, the solvent had a marked effect on anthocyanins’ extraction, so that acetone/water extracted almost the double as compared to ethanol/water, for the same extraction conditions. Finally, factor analysis allowed identifying a grouping structure of two components, which was confirmed by the dendogram obtained from cluster analysis.
- Influence of extracting variables in the phenolic and antioxidant properties of strawberryPublication . Ferrão, Ana Cristina; Gonçalves, Fernando; Correia, Paula; Guiné, Raquel
- 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.