Pulsed electric fields-assisted extraction of valuable compounds from red grape pomace: Process optimization using response surface methodology

Abstract

BackgroundThe application of Pulsed electric fields as a mild and easily scalable electrotechnology represents an effective approach to selectively intensify the extractability of bioactive compounds from grape pomace, one of the most abundant residues generated during the winemaking process.ObjectiveThis study addressed the optimization of the pulsed electric fields (PEF)-assisted extraction to enhance the extraction yields of bioactive compounds from red grape pomace using response surface methodology (RSM).MethodsThe cell disintegration index (Zp) was identified as response variable to determine the optimal PEF processing conditions in terms of field strength (E = 0.5–5 kV/cm) and energy input (WT = 1–20 kJ/kg). For the solid-liquid extraction (SLE) process the effects of temperature (20–50°C), time (30–300min), and solvent concentration (0–50% ethanol in water) on total phenolic content (TPC), flavonoid content (FC), total anthocyanin content (TAC), tannin content (TC), and antioxidant activity (FRAP) of the extracts from untreated and PEF-treated plant tissues were assessed. The phenolic composition of the obtained extracts was determined via HPLC-PDA.ResultsResults demonstrated that the application of PEF at the optimal processing conditions (E = 4.6 kV/cm, WT = 20 kJ/kg) significantly enhanced the permeabilization degree of cell membrane of grape pomace tissues, thus intensifying the subsequent extractability of TPC (15%), FC (60%), TAC (23%), TC (42%), and FRAP values (31%) concerning the control extraction. HPLC-PDA analyses showed that, regardless of the application of PEF, the most abundant phenolic compounds were epicatechin, p-coumaric acid, and peonidin 3-O-glucoside, and no degradation of the specific compounds occurred upon PEF application.ConclusionThe optimization of the PEF-assisted extraction process allowed to significantly enhance the extraction yields of high-value-added compounds from red grape pomace, supporting further investigations of this process at a larger scale.

Sustainable Valorization of Industrial Cherry Pomace: A Novel Cascade Approach Using Pulsed Electric Fields and Ultrasound Assisted-Extraction

“…Maximum phenolic compound content was detected after approx-imately 60 min of extraction for TPC (41.6 ± 0.02 mgGAE/gDW) and 45 min for both FC (48.6 ± 0.24 mgGAE/gDW) and TAC (0.59 ± 0.01 mgGAE/gDW). This trend aligns with previous studies that indicate a slight decrease in FC and TAC values with prolonged extraction time, which is likely due to oxidation reactions or degradation phenomena accelerated at higher temperatures [30,32,45].…”

“…The results from Figure 2a-c indicate that the profiles of the extracts from untreated and PEF-pre-treated samples were similar, regardless of the type of phenolic compounds. Both showed a significant dependence of TPC, FC, and TAC on extraction time, in line with previous findings [12,30]. Initially, the phenolic compound content increased rapidly during conventional extraction (SLE (I) ), driven by a high concentration gradient between the solid and liquid phases.…”

“…Initially, the phenolic compound content increased rapidly during conventional extraction (SLE (I) ), driven by a high concentration gradient between the solid and liquid phases. Additionally, the influence of ethanol and moderate temperature on cell membrane barrier properties likely contributed to improved compound solubility and diffusivity, thereby enhancing extractability [22,30,43,44]. However, extraction in a hydroalcoholic solvent was relatively slow, with limited yield even after prolonged diffusion times.…”

“…The TAC of the extracts was quantified using the pH differential method according to the method described by Carpentieri et al [30]. Briefly, each extract was used to prepare two mixtures.…”

“…Several studies have demonstrated the effectiveness of PEF-assisted extraction and ultrasound-assisted extraction (UAE), applied individually, in recovering natural pigments and phenolic compounds from various food and food byproducts [22,[27][28][29][30][31][32], including cherry fruit and pomace [12,28,[33][34][35][36], while reducing energy consumption and extraction time [22,32,37]. Moreover, the combination of PEF and UAE has shown enhanced extraction efficiency of phenolic compounds from different matrices, such as fresh rosemary and thyme byproducts [38] almonds [39], and grapefruit [40].…”