Recovery of polyphenols from distillery stillage by microwave-assisted, ultrasound-assisted and conventional solid–liquid extraction

Abstract

Recovery of bioactive compounds from distillery waste could be an option for valorizing this waste. This study investigated how the extraction of polyphenols (which have antioxidant activity) from distillery stillage was affected by solvent type and concentration, extraction time, and method of extraction (conventional solid–liquid extraction, CSLE; ultrasound-assisted extraction, UAE; microwave-assisted extraction, MAE). Although recovery was similar with UAE and MAE, 3 min MAE with 80% ethanol and 80% methanol produced the highest yields of total phenolic content (TPC), total flavonoid content (TFC) and phenolic acids. With CSLE, TPC was 2.1–1.8-times lower than with MAE and 1.7–1.4-times lower than with UAE. Increasing the solvent concentration to 100% significantly decreased recovery. Six phenolic acids were recovered (ferulic and p-coumaric acid predominated), which were present mainly in the free form. There was a significant positive correlation between antioxidant activity, as measured with three methods (one based on the hydrogen atom transfer and two based on single electron transfer mechanisms), and phenolic acid content. With MAE and UAE, polyphenols were recovered more efficiently, with 2.1 times and 1.5 times higher antioxidant activity, and with 15 times and 9 times shorter extraction times, respectively, than with CSLE; thus, they can be considered "green" alternatives to CSLE.

Optimization of bioactives extraction from grape marc via a medium scale ambient temperature system and stability study

“…The bioactivity of natural extracts is strongly conditioned by the type of extractant solvent and its capacity for the extraction of bioactive compounds with different polarities ( 32 ). Ethanolic-based solvents have been widely used demonstrating a high antioxidant potential.…”

Ultrasound assisted extraction of phytochemicals from Piper betel L.

“…This approach proved to be efficient in isolating bioactive compounds with higher extraction yields compared to conventional methods, while also maintaining the desired biological properties of the extracts [10] and [11] . UAE has been widely used for the retrieval of polyphenols, flavonoids, and antioxidants owing to its exceptional capability in terms of recovery efficiency and extraction speed [12] .…”

Optimization of accelerated aqueous ethanol extraction to obtain a polyphenol-rich crude extract from rambutan (Nephelium lappaceum L.) peel as natural antioxidant

“…Various extraction techniques for recovery of polyphenols from by-products or agro-industrial wastes have been studied including maceration 10 , heat-assisted extraction 11 , ultrasound assisted extraction (UAE) 12 , 13 , microwave assisted extraction (MAE) 12 , 14 , enzyme-assisted extraction 15 , subcritical water extraction (SWE) 16 , and accelerated solvent extraction (ASE) 17 , 18 . Most of the mentioned extraction processes have been applied to recover the polyphenols and other bioactive compounds from rambutan peel.…”

“…Accordingly, the influences of process variables including extraction temperature, time and ethanol concentration for extraction of polyphenol-rich extract from rambutan peel using ASE were investigated in this work. Aqueous ethanol is considered for use as an extraction solvent in this work because of its polarity feature, which would demonstrate a high recovery, it is also safe and environmentally friendly 12 , 17 . The response variables were extraction yield, total phenolic content (TPC), total anthocyanin content (TAC), and ABTS activity.…”