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- Sensory evaluation of virgin olive oils from organic agriculture and integrated productionPublication . Peres, Maria de Fátima; Gouveia, Cecília; Anjos, O.; Vitorino, Conceição; Henriques, LuísIn the present work four olive groves were selected: two in organic agriculture and two in integrated production. Olives were handpicked at two ripening stages and processed by a low-scale mill with a working capacity of 0.05 tons h-1. Differences between olive oils were evaluated through a sensory quantitative descriptive analysis (QDA) for positive attributes; moreover, some chemical parameters that could be related with bitterness, like phenol content and the specific absorbance at 225 nm (K225), were determined as well. Some analyses were also conducted with an Alpha MOS electronic nose system, FOX 2000.
- Is cork a good closure for virgin olive oil?Publication . Anjos, O.; Coutinho, Luís; Gouveia, Cecília; Peres, Maria de FátimaMost of the studies on olive oil preservation during storage are focused on the type of conditioning rather than on the most efficient type of bottle seal to be used. However, the bottle closure is also an important issue because of the negative impact that oxygen has on olive oil quality and flavor. The aim of this study was to assess the performance of a natural cork stopper as a closing system of glass bottles for olive oil. To evaluate the effect of a bottle closure, a storage trial over 24 months, after harvest, was performed comparing the effect of three types of glass bottle closure on virgin olive oil quality: screw cap, natural cork and bar top cork stopper. The bottle neck of those with a natural cork stopper was covered with bee's wax. The results for quality criteria showed that all three types of bottle closure acted in a very similar way for most of the studied parameters. However, based on FTIR-ATR spectral information it was possible to separate the samples with different closure systems at the end of the storage period. These differences could be given by the retention of some volatile compounds detected by sensory evaluation. The olive oil oxidation parameters were not highly affected by the cork stopper. However, for olive oil quality characterization with a cork stopper, more studies are needed for the volatile composition.
- Olive oil extraction optimization of ‘Galega Vulgar’ fruits by response surface methodologyPublication . Peres, Maria de Fátima; Gouveia, Cecília; Vitorino, Conceição; Dias, Suzana FerreiraNew strategies to attain better yields, without compromising olive oil quality, are necessary in olive oil extraction. To improve virgin olive oil yield, several processing aids (talc, calcium carbonate, salt, enzymes) have already been tested. ‘Galega Vulgar’, one of the most abundant Portuguese cultivar for olive oil, usually gives difficult pastes in the malaxation step, which represents a loss of income. The present work aimed to optimize olive oil extraction, at laboratory-scale, from fruits of ‘Galega Vulgar’ cultivar in 2016 (ripening index=4; moisture content=62 % and fat content (FW) =15.8 %) with the addition of processing aids (ProZym® and natural microtalc FC8-AW), using response surface methodologies (RSM). The combined effects of the concentrations of natural microtalc (MT) and of the enzyme preparation (E) on the oil extraction yield (Y), extractability index (IE), the concentration of total phenols (TPH), chlorophyll pigments (CP), as well as on chemical quality criteria parameters of the extracted olive oil, were investigated by RSM. A Central Composite Rotatable Design (CCRD) was followed, as a function of the contents of enzyme preparation (0-0.12 %, v/w) and of natural microtalc (0-0.46 %, w/w). For ‘Galega Vulgar’ olives, the highest extractability was obtained with simultaneous addition of enzymes between 0.02 and 0.08 % (v/w) and of microtalc (0.45-0.50 %, w/w).