Microwave-assisted extraction of pectin from orange peel using deep eutectic solvents

Pectin is a polysaccharide which is utilized in food, pharmaceutical and other industries. The commercial production of pectin involves mineral acids with high environmental impacts. Non-conventional green solvents such as deep eutectic solvents could potentially reduce the environmental threats of the traditional method and make the pectin extraction more sustainable and eco-friendly. In this study, pectin is extracted using maceration and microwave-assisted deep eutectic solvent (MW-DES) methods from orange peel under variable operating conditions. Process conditions had positive impact on pectin containing extract yields. The best conditions consisted of choline chloride:formic acid concentration of 8 % (v/v), an extraction time of 15 min and microwave power of 360 W for MW-DES. The maximum yields were 46 and 40% for maceration and MW-DES extraction, respectively. Microwave assistance decreased the extraction time by 75% compared to maceration method. The pectin samples extracted using DES were high methoxyl type with a degree of esterification of 85.6 and 74.4% for Maceration-DES and MW-DES, respectively. The galacturonic acid and total sugar contents were found statistically same for both methods. In addition, a significantly lower galacturonic acid content was observed in DES extracts compared to that of commercial and conventional pectin, indicating the need for advanced purification steps after DES extraction. MW-DES pectin had better water holding capacity and higher viscosity compared to that of Maceration-DES. Moreover, total phenolic content of the pectin samples were found as 8.19 and 7.14 mg Gallic acid equivalent/g of sample for maceration and MW-DES methods, respectively. The findings suggest that MW-DES could be an effective and fast extraction method for pectin from orange peels. However, further research is required to determine the energy consumption and to optimize extraction conditions.