Optimization of Bioactive Compound Extraction from Eggplant Peel by Response Surface Methodology: Ultrasound-Assisted Solvent Qualitative and Quantitative Effect

Abstract

Anthocyanin pigments, which the peel of eggplant is rich in, contribute to food quality because of their function in color, appearance, and nutritional advantages. For the first time, this study aimed to optimize the composition of the extracting solvent as three factors: factor A (ratio of ethanol to methanol 0–100% v/v), factor B (ratio of water to alcohol 0–100% v/v), and factor C (citric acid in the final solvent 0–1% w/v) using response surface methodology (RSM), central composite design (CCD) with α 2, and two repeats in axial and factorial points and four central points, for maximum total phenolic content, total anthocyanin content, extraction yield, antioxidant activity in terms of DPPH radical scavenging activity and ferric reducing antioxidant power (FRAP) assay of the eggplant peel dry extract assisted by ultrasound (200 watts power, frequency of 28 kHz) in 60 °C for 45 min has been investigated. The best optimal formulas determined using RSM for the final solvent comprised optimal formula 1 (i.e., ethanol-to-methanol ratio 59% and water-to-alcohol ratio 0%, and citric acid in final solvent 0.47%), and optimal formula 2 (i.e., ethanol-to-methanol ratio 67% and water-to-alcohol ratio 0%, and citric acid in final solvent 0.56%). In general, an alcoholic–acidic extract of eggplant peel made with an ethanol–methanol solvent including citric acid can be used in the food industry as a natural source of antioxidants and pigment.

Establishment of a Sonotrode Ultrasound-Assisted Extraction of Phenolic Compounds from Apple Pomace

“…Although there is little research about the use of ultrasound technology for extracting phenolic compounds [ 27 , 28 ], it has been applied previously to apple pomace with other aims such as isolating xyloglucans [ 29 ], or extracting pectin [ 30 ]. Further, ultrasound technology for optimizing the extraction of bioactive compounds has been performed by other authors in other matrices such as eggplant [ 31 ], orange peel [ 32 ], tangerine [ 33 ], cashew apple bagasse [ 34 ] or onion leaves [ 35 ].…”

Optimization of Bioactive Compound Extraction from Saffron Petals Using Ultrasound-Assisted Acidified Ethanol Solvent: Adding Value to Food Waste

“…The sonication was accomplished with an ultrasonic transducer and a power supply (HAMEG 8150, Mainhausen, Germany). Sonication enhances bioactive compound extraction by facilitating mass transfer from pomace to solvent and improving fluid dynamics along the extraction column [13]. Subsequently, the liquid part of the extract was evaporated under vacuum at 40 • C using an evaporator.…”

“…At 517 nm, the absorbance was determined spectrophotometrically. The scavenging ability of the plant extract was calculated as the following [13][14][15][16].…”

“…The results were reported in terms of FeSO 4 levels determined using the established standard curves. Each sample was analyzed three times [13][14][15][16].…”

Effect of Ultrasound Combined with Glycerol-Mediated Low-Sodium Curing on the Quality and Protein Structure of Pork Tenderloin

“…Compared with traditional techniques, it has the advantages of being highly efficient, instantaneous, safe, environment-friendly, and having low economic cost. Studies have shown that ultrasound treatment (UT) accelerates the diffusion process, shortens the curing time, positively affects mass transfer during the curing process [ 17 , 18 ], reduces the salt content, and improves the quality of low-salt cured meat products [ 19 ]. Moreover, UT can improve protein properties by reducing particle size and promoting the de-folding of secondary structures, thus improving product characteristics [ 20 ].…”