Kinetic modelling for polyphenol extraction from onion (Allium cepa) solid wastes using acidified water/ethanol mixture

Abstract

Previous reports highlighted the onion solid wastes as abundant, residual material that might contain a signifi cant load of antioxidant polyphenols. Although there have been studies pertaining to polyphenol recovery from onion wastes, the effect of temperature has not been adequately addressed. In this line, this study was undertaken with the aim of establishing a correlation between the extraction yield in total polyphenols and the extraction temperature, using acidifi ed aqueous ethanol as the solvent system. Extraction of polyphenols from onion solid wastes was found to obey 2 nd -order kinetics. On such a basis, the yield in total polyphenols at saturation could be very effectively determined and correlated with temperature using non-linear regression. The results indicated that the extraction yield at saturation is highly correlated with temperature, following a quadratic function. The extract obtained at optimal temperature (40 °C) had a total polyphenol yield of 21.10 mg gallic acid equivalents per gram of dry weight, and it was further analysed by liquid chromatography-mass spectroscopy to characterise its major constituents. The polyphenols detected were quercetin glucosides, as well as quercetin oxidation derivatives, including certain degradation products and dimers. The outcome of this study outlined that temperatures above 40 °C are rather not favourable for polyphenol extraction from onion solid wastes, as suggested by the model established through kinetics. The extract obtained under optimal conditions contained peculiar polyphenolic composition, not encountered in any other food processing residue.

High-Performance Green Extraction of Polyphenolic Antioxidants from Salvia fruticosa Using Cyclodextrins: Optimization, Kinetics, and Composition

“…To appraise the temperature effects on polyphenol recovery, kinetics was traced using all three CDs over a range of 40 to 80 • C (Figure 4). The model that could effectively describe the patterns recorded was second-order kinetics [26]:…”

Optimization of methanol extraction parameters for total flavonoids from onion processing waste

“…The calculated rate constant (k, dm 3 s -1 ) of the reaction varied from 0.02 to 0.25 (Table 4). Makris and Kefalas also reported second-order kinetics for the extraction of polyphenols from onion solid waste [14].…”

“…Many studies related to modelling and optimization of the extraction process of phytochemicals from onion waste, including Box-Behnken design (BBD) in response surface methodology (RSM) as a statistical tool, have been reported recently [2,5,8,[11][12][13]. Moreover, the kinetic modelling of the extraction of polyphenols from OPW was used also for assessing the extraction efficiency [14].…”

Onion (Allium cepa L.) bioactives: Chemistry, pharmacotherapeutic functions, and industrial applications

“…Solid‐liquid extraction (SLE) has been used as a conventional method for decades to extract flavonoids from plant samples. SLE utilizes organic solvents such as methanol, ethanol, hexane, acetone, and ethyl acetate in pure or mixed forms for achieving bioactive rich extract (Makris & Kefalas, 2015). However, the utilization of organic solvents for extraction is harmful to the working person and a source of pollution for the environment.…”