Extraction of Phenolic Compounds from Fresh Apple Pomace by Different Non-Conventional Techniques

Abstract

Red Delicious apple pomace was produced at laboratory scale with a domestic blender and different non-conventional extraction techniques were performed to isolate phenolic compounds, such as ultrasound-assisted extraction (UAE), ultraturrax extraction (UTE), accelerated solvent extraction (ASE) and pulsed electric field (PEF) extraction pre-treatment. Total phenolic content (TPC) was determined by Folin–Ciocalteu assay. Phloridzin, the main phenolic compound in apples, was determined by chromatographic analysis Q-TOF-LC/MS. The results obtained with these techniques were compared in order to identify the most efficient method to recover polyphenols. The highest value of TPC (1062.92 ± 59.80 µg GAE/g fresh apple pomace) was obtained when UAE was performed with EtOH:H2O (50:50, v/v), while ASE with EtOH:H2O (30:70, v/v) at 40 °C and 50% of flush was the most efficient technique in the recovery of phloridzin. The concentration of the main phenolic compounds ranged from 385.84 to 650.56 µg/g fresh apple pomace. The obtained results confirm that apple pomace represents an interesti-ng by-product, due to the presence of phenolic compounds. In particular, phloridzin could be considered a biomarker to determine the quality of numerous apple products. Therefore, this research could be a good starting point to develop a value-added product such as a functional food or nutraceutical.

Ultrasound-Assisted Extraction and Characterization of Polyphenols from Apple Pomace, Functional Ingredients for Beef Burger Fortification

“…The ultrasound assisted extraction was carried out according to a previous paper with slight modifications [ 4 ]. The fresh sample of apple pomace was added with EtOH:H 2 O (50:50, v / v ) in a solid/liquid ratio of 1:10 ( w / v ) at 45 °C for 45 min in an ultrasonic bath.…”

“…The recovery of bioactive compounds involves extraction as the key step, which is achieved through traditional methods or innovative methods [ 4 ]. Among the latter, ultrasound assisted extraction (UAE) has advantages such as less time and energy requirement, extraction at low temperature, and retention of the quality of the extract.…”

Sustainable Use of Apple Pomace (AP) in Different Industrial Sectors

“…The UAE technique is often combined with other extraction methods, e.g., the Sono–Soxhlet approach involves the combination of UAE with Soxhlet extraction; other approaches include UAE being combined with microwave-assisted extraction, and the combination of UAE and SFE [ 81 , 82 ]. There are several reports in the literature from recent years on the use of the UAE technique to recover active substances from apple pomace [ 83 , 84 , 85 , 86 ]. For example, in the work of Pollini et al [ 86 ], the effect of the solvent on the TPC of apple pomace extract was investigated.…”

“…There are several reports in the literature from recent years on the use of the UAE technique to recover active substances from apple pomace [ 83 , 84 , 85 , 86 ]. For example, in the work of Pollini et al [ 86 ], the effect of the solvent on the TPC of apple pomace extract was investigated. In their research, the extract obtained through UAE, using the mixture of ethanol and water (50:50, vv) as a solvent, had the highest TPC value (1062.9 ± 59.80 µg GAE/g of fresh AP) compared to other solvents used (ethanol:water, 70:30 and 30:70, vv) [ 86 ].…”

“…For example, in the work of Pollini et al [ 86 ], the effect of the solvent on the TPC of apple pomace extract was investigated. In their research, the extract obtained through UAE, using the mixture of ethanol and water (50:50, vv) as a solvent, had the highest TPC value (1062.9 ± 59.80 µg GAE/g of fresh AP) compared to other solvents used (ethanol:water, 70:30 and 30:70, vv) [ 86 ]. Malinowska et al [ 84 ], compared the effect of the solvent used (water and ethanol) and the source of AP on the efficiency of the UAE process.…”