ESAV - DIA - Documentos de congressos (comunicações, posters, actas)
Permanent URI for this collection
Browse
Browsing ESAV - DIA - Documentos de congressos (comunicações, posters, actas) by Subject "acidity"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Evaluation of the physical-chemical properties of blueberries from diferente geographic originPublication . Matos, Susana; Guiné, Raquel; Gonçalves, Fernando; Costa, DanielaBlueberries are very popular for their potential health benefits around the world, from USA to Asia and to the Mediterranean. In the present work blueberries from cultivar Bluecrop harvested in different regions of Portugal (Estarreja-ES, Vouzela-VZ, Vila Verde-VV, Sever do Vouga-SV and Oliveira do Hospital-OH) were analysed to evaluate their physical-chemical properties: moisture content, total soluble solids (ºBrix) acidity, calibre, colour and texture. Moisture was evaluated by drying until constant weight, sugar content by refractometry and acidity by titration. Calibre was evaluated with a caliper rule, colour with a colorimeter in the CIELab colour space, and texture with a texturometer by measuring force in compression with a 2 mm probe P/2. The results showed that the sample VV had the highest moisture content as compared to all other varieties (83%), whereas the sample OH showed the highest acidity (0.79 mg citric acid/100g) and the sample ES the highest total soluble solids content (14,65 ºBrix). The average calibre ranged from 0.90 cm for sample SV to 1.17 cm for sample OH. Regarding the colour parameters it was observed that lightness (L*) was under 50, thus indicating that the samples are dark, whereas a* was around 0, so neither red nor green and b* was negative in all cases, so the colour is blue instead of yellow. The values of L* ranged from 31.07 to 36.79, respectively for samples VV and VZ; a* ranged from -0.02 to 0.62, respectively for samples VZ and VV; b* ranged from -7.76 to -5.02, respectively for samples ES and OH. The skin firmness varied from 11.0 N to 15.1 N, respectively for samples VZ and SV, while elasticity varied from 2.18 mm in the sample ES to 2.54 mm in the sample SV.
- Influence of drying treatments on the colour of green bell peppers.Publication . Guiné, Raquel; Lopes, Pedro; Barroca, Maria João; Ferreira, DulcineiaPears of the variety S. Bartolomeu have been used over the years in Portugal to produce a traditional dried pear known as “pera passa”. The processing comprehends a solar drying performed at open air, with obvious disadvantages, either concerning the drying efficiency or the sanitary quality of the final product, taking into account that the products are exposed to multiple contamination agents. For these reasons, attempts have been made to study alternative production methodologies, including the use of solar stoves, among others. In the present work pears of the variety S. Bartolomeu which were harvested at three different moments, and therefore correspond to three different ripening stages, were dried in a solar stove and the evolution of some properties was monitored along the drying process. From the results obtained was possible to conclude that the pears harvested in the two first dates show quite similar trends through drying, while the pears harvested at the last date reveal a clear distinct behavior, allowing to infer that the ripening stage at harvest plays an important role in the subsequent drying operation.
- Study of chemical and physical properties of apples dried in a convective drier.Publication . Cruz, AC; Guiné, Raquel; Gonçalves, JC; Correia, ACThe present study evaluates the effects of drying on apple slices from two varieties, Golden Delicious and Granny Smith, which were analyzed in terms of physical and chemical properties. The tests involved the determination of moisture, acidity, soluble solids, colour and texture. Trials were performed in a convective hot air dryer for different temperatures of 30, 40, 50 and 60 ° C. The results showed that the final moisture of the two varieties of apples was around 3 % (wet basis). With regards to acidity, the variety Granny Smith was found to be more acid than the Golden Delicious. The soluble solids are present, in general, in greater amounts in the variety Granny Smith. As to the colour, this varied very considerably from the fresh apples to the dried ones. Apples of the variety Golden Delicious presented a higher intensity of yellow (b* > 0) and red (a* > 0). However, in comparison to the variety Granny Smith the Golden Delicious presents, in general, smaller total colour differences. The textural attributes evaluated were hardness, adhesiveness, elasticity, cohesiveness and chewiness. However, the results for adhesiveness were very close to zero showing that these products do not have adhesiveness, as it happens with other fruits. It was also found that the fresh apples have a much higher hardness, when compared to the dried samples. Elasticity, on the other hand, was kept approximately constant regardless of the variety or state. Cohesiveness was higher in the fresh apples, and for the dried ones was higher for variety Golden. Finally, chewiness was higher for the fresh apples in comparison to the dried ones, and was higher for Golden Delicious when compared with Granny Smith.