Percorrer por autor "Borges, Barbara Lopes"
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- Assessment of bioactive compounds and antioxidant activity of wine residues submitted to intermittent drying processPublication . Borges, Barbara Lopes; Amaral, Joana S.; Defendi, Rafael Oliveira; Barros, LillianDuring wine production a large amount of waste (grape pomace) is generated. This material is considered a rich source of bioactive compounds, thus being of interest for cosmetics, pharmaceutical and food industries. However, it is susceptible to microbial degradation due to its high moisture content, and therefore drying is frequently considered an essential process for grape pomace conservation and stabilization. Nevertheless, drying conditions such as temperature and time may affect grape pomace bioactive potential. Because drying represents a high energy consumption, an alternative for reducing the energy costs is the use of intermittent operation, which operates with transient inputs of air conditions, such as the supply temperature. Intermittent drying, in addition to promoting lower energy consumption, also enables less damage to heat-sensitive materials. In the present work, modeling of the drying process of grape skins and seeds from red wine grape pomace was performed at temperatures of 40 °C, 55 °C and 70 °C, both for drying in the conventional and in the intermittent mode, with intermittences of 5 and 10 minutes. Moreover, total phenolics content (TPC), total flavonoids content (TFC) and antioxidant activity (DPPH and reducing power assays) were determined by spectrophotometric methods before and after the drying process at the proposed conditions. The identification and quantification of phenolic compounds (non-anthocyanins and anthocyanins) was carried out through LC-DAD-ESI-MS/MS analysis. Modeling results showed that, among the 8 models tested for the conventional drying, the one that best suited the experimental data, for both skin and seeds, was the Approximation of diffusion model and therefore can be used in following studies to optimize drying parameters. For the intermittent drying, experimental data could be predicted by the intermittent drying model with a global maximum deviation of 10%. Results of TPC, TFC and antioxidant activity assays showed that conventional drying had the highest impact on lowering the content of bioactive compounds both on grape skins and seeds. By the contrary, the present work showed that intermittent drying can provide grape pomace samples with higher content of bioactive compounds and higher antioxidant activity, with 10 minutes intermittence in general performing best when compared to 5 minutes intermittent period, particularly for grape seeds pomace samples.