Abstract 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.

中文翻译：

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在葡萄皮上使用欧姆加热效应作为花青素提取的预处理

摘要 本研究旨在通过使用葡萄皮作为天然电导体，通过欧姆加热 (OH) 效应实现内部散热，从酿酒残渣中提取有价值的植物化学物质，特别是花青素的水提取物。评估了两种不同的电预处理：i) 在 20 分钟内使用 40 °C 的温和温度；ii) 在不到 20 秒的时间内从 40°C 快速加热到 100°C（无保温时间）。这些预处理之后是在室温下在水中的水萃取。与施加的温度无关，OH 可以提高提取水平，从而增加总酚类化合物的浓度，以及所获得提取物的电导率、可溶性固体和红色强度，如主成分分析 (PCA) 所示。由于葡萄皮结构的快速内部加热，在高温短时 (HTST) 下进行 OH 预处理使花青素的总浓度从 756 微克/克增加到 1349 微克/克，其中，malvidin-3-O-葡萄糖苷是鉴定的主要化合物，通过 HPLC 分析（相当于总量的约 60%）在水提取物中定量。这些结果表明，OH 具有成为实现可持续食品加工的高效和环保技术的潜力。