Abstract
The aim of this study was to investigate and compare the effects of different extraction techniques (high hydrostatic pressure-assisted extraction (HHPE), ultrasound-assisted extraction (UAE), and classical solvent extraction (CSE)) on phenolic compounds from spent coffee grounds (SCG). Different HHPE parameters (300, 400 and 500 MPa at 25 °C for 5, 10 and 15 min) and UAE parameters (40%, 50%, and 60% amplitude at 25 °C for 5, 10 and 15 min) were used. These techniques were compared with CSE (at 50 °C for 30 min) according to total phenolic content (TPC), antioxidant activity (AA), high-performance liquid chromatography (HPLC), scanning electron microscopy (SEM), and infrared (IR) spectroscopy. The results showed that eco-friendly techniques increased the TPC and AA compared to CSE and morphological changes were verified by SEM results. Furthermore, chlorogenic and caffeic acid were also quantified by using HPLC. Chlorogenic acid was found as the main phenolic compound in spent coffee grounds (SCG). The highest chlorogenic acid was detected as 85.0 ± 0.6 mg/kg FW with UAE at 60% amplitude for 15 min. In brief, for the extraction of phenolic compounds from waste SCG eco-friendly techniques such as HHPE and/or UAE were more convenient than CSE.
Highlights
Food waste is defined as any food industry outputs that are neither used for defining end-products nor for alternative purposes such as recycling [1]
There has been many studies related to the presence of phytochemicals in spent coffee grounds (SCG), SCG might be a source of valuable waste products because of the presence of mainly phenolic compounds such as caffeic and chlorogenic acids which might be used as natural antioxidants, in different industries such as food, cosmetics and pharmaceuticals [4,5,6,7,8]
As seen in the figure, high hydrostatic pressure-assisted extraction (HHPE) and ultrasound-assisted extraction (UAE) treatments increased the total phenolic content (TPC) content compared to conventional solvent extraction (CSE)
Summary
Food waste is defined as any food industry outputs that are neither used for defining end-products nor for alternative purposes such as recycling [1]. A huge amount of food waste is generated every day and it is assumed that up to one-third of the food produced is wasted around the world. Food waste valorization is important and it is in the core of many studies [2]. There has been many studies related to the presence of phytochemicals in SCG, SCG might be a source of valuable waste products because of the presence of mainly phenolic compounds such as caffeic and chlorogenic acids which might be used as natural antioxidants, in different industries such as food, cosmetics and pharmaceuticals [4,5,6,7,8]
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