Process optimization of polyphenol extraction from carob (Ceratonia siliqua) kibbles using microwave‐assisted technique

Abstract

Microwave‐assisted extraction (MAE) method was investigated to recover phenolic compounds from carob kibbles and validated using response surface methodology. The study parameters were microwave power (170–900 W), ethanol concentration (30–90%), and solvent‐to‐sample ratio (10–30 mL/g) in terms of total phenolic content (TPC) and condensed tannins. Among optimized parameters (340 W, 45%, 30 mL/g), microwave power and ethanol concentration were found more influential parameters to get higher yields of TPC and condensed tannins. Moreover, the results of TPC (70.11 mg GAE g−1 DM), condensed tannins (4.11 mg CE g−1 DM), free radical scavenging activity (94.42%), ferric ion reducing potential (22.67 mg Fe+3 100 g−1 DM), and gallic acid (1.576 mg/g DM) obtained from optimal MAE conditions were found comparable to ultrasound‐assisted extraction method. The newly developed MAE method illustrates its potential to recover phenolic compounds from plant sources in a short duration. Practical applications Based on the results presented in this work, it is proposed that carob kibble could be considered as interesting raw material to get extracts rich in antioxidant properties. This extract could be used as an alternative to synthetic antioxidants in bio‐food products as natural preservative. Therefore, carob kibbles could be recommended for production of extracts rich in antioxidants, instead of being discarded from gum factory as by‐product. In addition, microwave‐assisted extraction method could be employed to increase time efficiency of the process.

Technological Application of Tannin-Based Extracts

“…Intracellular content is heated and evaporated, producing strong pressure. This pressure breaks the cell wall and membranes, liberating intracellular content into the solvent [59,61]. Water, methanol, and ethanol are the solvents recommended for this extraction [39].…”

“…The frequency applied, ranging from 300 MHz to 300 GHz, and the microwave power, with ranges between 100 and 900 W, play a fundamental role in the extraction of tannins since their increment, usually, leads to a more efficient recovery [34,35,54]. The time needed for these extraction protocols is short, from 1 to 20 min, achieving a substantial amount of tannins (from 4.11 to 528.5 mg/g of dried extract, Table 2) [43,59,61].…”

Evaluation of the impact of chlorophyll removal techniques on polyphenols in rosemary and thyme by‐products

“…Traditionally, aqueous ethanol is utilized for the recovery of polyphenol‐rich food grade extracts from plant materials (Huma, Jayasena, Nasar‐Abbas, Imran, & Khan, ). However, the use of ethanol results in the co‐extraction of high chlorophyll concentrations (Yasuda, Oda, Ueda, & Tabata, ).…”

Optimisation of Sequential Microwave-Assisted Extraction of Essential Oil and Pigment from Lemon Peels Waste

“…Other authors have reported that high percentages of ethanol can break the hydrogen and hydrophobic bonds existing between phenolics–proteins and phenolics–cellulose in ethanol/water solutions, improving the extraction process [ 26 ]. However, some authors have demonstrated that the presence of small amounts of water in the solvent during MAE could favour a possible diffusion of water into the matrix cells, achieving a better heating and, thus, helping the transfer of compounds into the solvent at higher mass transfer rates [ 27 ].…”