Browsing by Author "Pinho, M.N."
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- Membrane processing of grape must for control of the alcohol content in fermented beveragesPublication . Mira, Helena; Guiomar, A.; Geraldes, V.; Pinho, M.N.The great demand of beverages, both alcohol-free and with low alcohol content, is a great challenge for the production of beverages with controlled alcohol content through the use of sustainable enological practices. The present work addresses this challenge with the processing of grape must by reverse osmosis (RO) for must reconstitution with different sugar contents prior to the alcoholic fermentation. The original must came from grapes grown in Quinta do Quinto, in Santarém, collected after destemming and mechanic crushing, and preserved in a refrigerated chamber at -1.6 °C until processing by RO. The RO processing was carried out in Escola Superior Agrária de Santarém, with a pilot plant equipped with RO spiral wound modules, M38RO, from Alfa Laval, Denmark. The total membrane permeation area is 15 m2. The work pressure was 55 bar. The original must had 23.7 oBrix, a density of 1108 g.L-1, 15.2% (v/v) of probable alcohol, and a conductivity of 2.01 mS.cm-1. The must reconstitution was carried out, by mixing the concentrated grape must with the vegetal water produced by RO (permeate) to obtain beverages with a nominal alcohol content of 5%, 7%, 10% and 13% (v/v). The fermentation average temperature was between 18.2 and 19.7 °C, and the final density rounded about 993 g.cm-3. The beverages were analysed by different parameters, including total polyphenols, total anthocyanins, colour intensity and hue, the coordinates CIELab, alcohol content, total acidity, volatile acidity, pH, free SO2 and total SO2. The attributes of the beverage, corresponding to the visual appearance, aroma and taste senses, as well as the overall judgment were evaluated by the tasters. The proposed method can produce beverages with controlled low alcohol content. The decrease of the alcohol content led to lower content of polyphenols compounds which influenced the sensory evaluation.
- Ultrafiltration based process for the recovery of polysaccharides and polyphenols from winery effluentsPublication . Giacobbo, A.; Oliveira, Margarida; Duarte, E.; Mira, Helena; Bernardes, A.; Pinho, M.N.Winery effluents have a high pollution potential, especially those effluents that are obtained from the second racking. However, these effluents are rich in phenolic compounds and polysaccharides and can be potential sources for the recovery of these compounds. Therefore, a process was developed in this study to reduce the pollution potential of the winery effluents from the second racking and to recover the polyphenols and polysaccharides from the effluents by utilizing ultrafiltration (UF) and sedimentation operations. The sedimentation was optimized by varying the pH from 3.8 to 8.0, while the UF experiments were optimized by varying the transmembrane pressure from 0.5 to 4.0 bar and the feed circulation velocity from 0.44 to 0.87 ms−1. This process provided a permeate stream with a reduction in the TOC content by 56.6%, while the polyphenols and the polysaccharides in the concentrate stream were concentrated by 6 times and 5 times, respectively.