Influence of ethanol/water ratio in ultrasound and high‐pressure/high‐temperature phenolic compound extraction from agri‐food waste

Abstract

The valorisation and management of agri-food waste are currently hot investigation topics which probe the recovery of valuable compounds, such as polyphenols. In this study, high-pressure/high-temperature extraction (HPTE) and ultrasound-assisted extraction (UAE) have been used to study the recovery of phenolic compounds from grape marc and olive pomace in hydroalcoholic solutions. The main phenolic compounds in both extracts were identified by HPLC-DAD. Besides extraction yield (total polyphenol and flavonoid content) and the antiradical power, polyphenol degradation under HPTE and UAE has also been studied. HPTE with ethanol 75% gave higher phenolic extraction yields: 73.8 ± 1.4 mg of gallic acid equivalents per gram of dried matter and 60.0 mg of caffeic acid equivalents per gram of dried matter for grape marc and olive pomace, respectively. In this study, the efficient combination of ethanol/water mixture with HPTE or UAE has been used to enhance the recovery of phenolic compounds from grape marc and olive pomace. HPLC-DAD showed that UAE prevents phenolic species degradation damage because of its milder operative conditions. High-pressure/high-temperature extraction (HPTE) and ultrasound-assisted extraction (UAE) have been used to enhance the recovery of phenolic compounds from grape marc and olive pomace

Natural extracts from fresh and oven‐dried winemaking by‐products as valuable source of antioxidant compounds

“…UAE process is affected by numerous parameters such as solvent nature, output amplitude, extraction time, solid‐liquid ratio, etc. For this reason, different trials were performed according to the experience of the research group and to the UAE conditions of the bibliography (Carrera, Ruiz‐Rodriguez, Palma, & Barroso, ; Drosou et al., ; Paini et al., ). for optimize the extraction process.…”

The effect of particle size and solvent type on the gallic acid yield obtained from Labisia pumila by ultrasonic extraction

“…Consequently, the implosion cause less effective solid material disruption which is vital for gallic acid release from the plant material. Earlier, Paini et al [30] also obtained lower total phenolic content from agri-food waste with high percentage of ethanol via UAE. Similarly, Fecka and Turek [31] also reported a higher yield of polyphenol with solvent containing higher water content from maceration of thyme and marjoram.…”

“…The distribution was characterized by the volume weighted mean. Prior to analysis of the distribution, the refractive index of the powder were determined by calibration curve at different concentration (5,10,20,30,40 and 50%) of powder in water suspension. The curve was extrapolated to 100% to obtain the refractive index value of the dry powder.…”

“…Thus explaining why the GA yield is higher when water is used instead of aqueous ethanol. Paini et al [30] explained that the higher vapour pressure and viscosity of ethanol with respect to water can decrease the force of the implosion of the cavitation bubbles. Consequently, the implosion cause less effective solid material disruption which is vital for gallic acid release from the plant material.…”

Processing, Valorization and Application of Bio-Waste Derived Compounds from Potato, Tomato, Olive and Cereals: A Review

“…Most commonly, solid/liquid extraction is used for plant materials whereby the extraction yield is dependent on the applied parameters. For example, the addition of water enhanced the polyphenol yield during extraction with ethanol [374][375][376]. Furthermore, an adjustment of the pH value to an alkaline milieu increased the extraction due to an improved solubility of the phenolic substances [377].…”