Optimizing the solvent extraction process for high-value compounds from sweet cherry press cake treated with pulsed electric fields using response surface methodology

Abstract

Introduction: Cherry juice production generates substantial cherry processing by-products, presenting a significant environmental challenge. The valorization of these by-products can not only reduce management costs but also enhance profitability by recovering valuable intracellular compounds.Methods: This study aimed at the extraction of bioactive compounds with potent antioxidant activity from sweet cherry press cake using Pulsed Electric Fields (PEF)-assisted extraction. PEF pre-treatment, carried out using a predetermined field strength (E = 3 kV/cm) and total specific energy input (WT = 10 kJ/kg), was applied to the cherry press cake prior to the subsequent solid-liquid extraction (SLE) stage. To optimize the SLE process for both untreated and PEF-treated samples, Response Surface Methodology (RSM) was employed to determine the most effective extraction parameters, including extraction temperature (20–50°C), solvent concentration (0–50% ethanol in water), solid-liquid ratio (0.05–0.2 g/mL), and diffusion time (30–360 min). The objective was to maximize key response variables: total phenolic content (TPC), flavonoid content (FC), total anthocyanin content (TAC), and antioxidant activity (FRAP). The extracts obtained from both untreated and PEF-treated samples under optimal conditions underwent HPLC-DAD analysis.Results and discussion: The results revealed that, under optimized SLE conditions (50°C, 50% ethanol-water mixture, 0.2 g/mL solid-liquid ratio, and 360 min extraction time), PEF pre-treatment significantly enhanced the extractability of high-value compounds. This resulted in notable increases in TPC (+26%), FC (+27%), TAC (+42%), and antioxidant activity (+44%) compared to conventional SLE. Additionally, the application of PEF reduced extraction time (by 5–18 min) and solvent usage (by 2%). HPLC analysis identified cyanidin-3-O-rutinoside as the predominant phenolic compound in both untreated and PEF-treated extracts, with a remarkable increase (+2.3-fold) after PEF application. These findings underscore the potential of PEF-assisted extraction as a promising approach to maximize the recovery of valuable compounds from sweet cherry press cake, contributing to food waste reduction and enhanced value generation from by-products.

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

“…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.…”

“…main contributors to the overall antioxidant activity of cherry pomace extracts, consistent with findings from prior research [12,33,49].…”

“…In the first step, approximately 80 g of industrial fresh cherry pomace underwent PEF pre-treatment under established optimal conditions (E = 3 kV/cm, W T = 10 kJ/kg) as defined by Rrucaj et al [12]. Following the electropermeabilization treatment, the cherry pomace underwent solid-liquid extraction (SLE) according to the protocol outlined in previous studies [12,34]. The combination of PEF pre-treatment and SLE will be referred to as PEF-assisted extraction in the following.…”

“…Cherry pomace, or press cake, accounts for 15-28% of the initial fruit weight [10] and is typically produced during mechanical pressing operations [11]. Rich in lignin, cellulose, dietary fiber, and phenolic compounds such as neochlorogenic acid, chlorogenic acid, 4-p-coumaroylquinic acid, and rutin, cherry pomace also serves as a valuable source of anthocyanins like cyanidin-3-O-rutinoside and cyanidin-3-O-glucoside [11,12]. These compounds contribute to various biological activities, including antioxidant, anti-inflammatory, anticancer, α-glucosidase inhibiting, and antihypertensive properties [13][14][15][16].…”

“…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].…”