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- Advances in extraction methods to recover added-value compounds from seaweeds: sustainability and functionalityPublication . Matos, Gabriela S.; Pereira, Sara G.; Genisheva, Zlatina A.; Gomes, Ana Maria; Teixeira, José A.; Rocha, Cristina M. R.Seaweeds are a renewable natural source of valuable macro and micronutrients that have attracted the attention of the scientists in the last years. Their medicinal properties were already recognized in the ancient traditional Chinese medicine, but only recently there has been a considerable increase in the study of these organisms in attempts to demonstrate their health benefits. The extraction process and conditions to be used for the obtention of value-added compounds from seaweeds depends mainly on the desired final product. Thermochemical conversion of seaweeds, using high temperatures and solvents (including water), to obtain high-value products with more potential applications continues to be an industrial practice, frequently with adverse impact on the environment and products’ functionality. However more recently, alternative methods and approaches have been suggested, searching not only to improve the process performance, but also to be less harmful for the environment. A biorefinery approach display a valuable idea of solving economic and environmental drawbacks, enabling less residues production close to the much recommended zero waste system. The aim of this work is to report about the new developed methods of seaweeds extractions and the potential application of the components extracted.
- Using ohmic heating effect on grape skins as a pretreatment for anthocyanins extractionPublication . Pereira, Ricardo N.; Coelho, Marta; Genisheva, Zlatina; Fernandes, Jean Michel; Vicente, António A.; Pintado, Manuela E.; Teixeira, José A.This study aims to obtain aqueous extracts of valuable phytochemicals, in particular anthocyanin’s, from winemaking residues by using grape skins as natural electrical conductors allowing internal heat dissipation through Ohmic Heating (OH) effect. Two different electric pretreatments were evaluated: i) using mild temperatures at 40 °C during 20 min; ii) flash heating from 40 to 100 °C in less than 20 s (no holding time). These pretreatments were followed by aqueous extraction in water at room temperature. Independently of the temperature applied, OH allowed to boost extraction levels increasing concentration of total phenolic compounds, as well as conductivity, soluble solids and red color intensity of the obtained extracts, as shown through principal component analysis (PCA). OH pretreatments at high-temperature short-time (HTST) due to the fast internal heating of grape skin structure allowed increase total concentration of anthocyanins from 756 to 1349 μg/g, with malvidin-3-O-glucoside being the main compound identified and quantified in the aqueous extracts through HPLC analysis (corresponding to about 60% of the total). These results showed that OH bring potential to be an efficient and environmentally friendly technology towards sustainable food processes.