Optimizing a sustainable ultrasound-assisted extraction method for the recovery of polyphenols from lemon by-products: comparison with hot water and organic solvent extractions

Abstract

Response surface methodology (RSM) based on a three-factor and three-level Box-Behnken design was employed for optimizing the aqueous ultrasound-assisted extraction (AUAE) conditions, including extraction time (35-45 min), extraction temperature (45-55 °C) and ultrasonic power (150-250W), for the recovery of total phenolic content (TPC) and rutin from lemon by-products. The independent variables and their values were selected on the basis of preliminary experiments, where the effects of five extraction parameters (particle size, extraction time and temperature, ultrasonic power and sample-to-solvent ratio) on TPC and rutin extraction yields were investigated. The yields of TPC and rutin were studied using a second-order polynomial equation. The optimum AUAE conditions for TPC were extraction time of 45min, extraction temperature of 50°C and ultrasonic power of 250W with a predicted value of 18.10±0.24 mg GAE/g dw, while the optimum AUAE conditions for rutin were extraction time of 35min, extraction temperature of 48°C and ultrasonic power of 150W with a predicted value of 3.20±0.12 mg/g dw. The extracts obtained at the optimum AUAE conditions were compared with those obtained by a hot water and an organic solvent conventional extraction in terms of TPC, total flavonoid content (TF) and antioxidant capacity. The extracts obtained by AUAE had the same TPC, TF and ferric reducing antioxidant power as those achieved by organic solvent conventional extraction. However, hot water extraction led to extracts with the highest flavonoid content and antioxidant capacity. Scanning electron microscopy analysis showed that all the extraction methods led to a cell damage to varying extents.

Effects of ultrasound‐assisted blanching on the processing and quality parameters of freeze‐dried guava slices

“…The TPC results are displayed in Figure 6. applied an US bath to fruit pieces to extract polyphenols by water immersion and found that this extraction reduced the polyphenol content (Papoutsis et al, 2018). Nunes et al (2016) reported that freeze-drying reduced the TPC of guava (Nunes et al, 2016), as was observed in the present study ( Figure 6).…”

“…The effect of sonication only became significant, with increased polyphenol losses, after long US exposure times (90 min) (Mieszczakowska‐Frąc et al, ). Papoutsis et al () applied an US bath to fruit pieces to extract polyphenols by water immersion and found that this extraction reduced the polyphenol content (Papoutsis et al, ). Nunes et al () reported that freeze‐drying reduced the TPC of guava (Nunes et al, ), as was observed in the present study (Figure ).…”

“…The effect of sonication only became significant, with increased polyphenol losses, after long US exposure times F I G U R E 3 Freeze-drying time of guava slices without and with ultrasonic assisted blanching (UAB; n = 3) F I G U R E 4 Macrostructure of guava slices before and after freeze-drying F I G U R E 5 Final moisture content of the freeze-dried guava slices. n = 3(90 min)(Mieszczakowska-Frąc et al, 2016) Papoutsis et al (2018).…”

Comparative Evaluation of Soxhlet and Ultrasonics on the Structural Morphology and Extraction of Bioactive Compounds of Lemon (Citrus limon L.) Peel

“…The process is distinguished by a more effective extraction and use of moderate temperatures of extraction especially beneficial for heat-labile compounds. Several process variables, like applied ultrasonic power, frequency, extraction temperature, reactor characteristics, solvent-sample interaction are considered crucial during USAE [14] and the most amounts of bioactives are reported to be extracted in the initial few minutes of the process. Ultrasound-assisted extraction has been shown to reduce significantly the extraction times, thereby limiting power consumption, as well as enhancing extraction yields in case of many materials [15].…”

Ultrasound-Assisted Extraction as a First Step in a Biorefinery Strategy for Valorisation of Extracted Olive Pomace

“…Other by-products from agro-industrial processes have been studied in terms of obtaining phenolic compounds while also using UAE. For example, waste from sunflower oil production, e.g., sunflower seed cake, reached 17.96 mg GAE/g dry TPC biomass in optimised UAE conditions, 43% ethanol, 70 • C and 86 µm amplitude [20], and the residue from lemon juice production produced 17.97 mg GAE/g dry TPC biomass and an antioxidant activity of 9.4 mg TE/g dry biomass in a FRAP assay of extracts that were obtained with UAE at 50 • C, 45 min and 250 W [21]. In both cases, the reported phenolic compound concentrations are lower than those that were obtained with EOP extracts in this work.…”