https://doi.org/10.15255/KUI.2022.023
Published: Kem. Ind. 71 (11-12) (2022) 699–709
Paper reference number: KUI-23/2022
Paper type: Original scientific paper
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Intensification of Polyphenols Extraction from Mandarin Peel by High Voltage Electric Discharge: Effect of Process Parameters and Optimisation
M. Banožić, S. Šafranko, D. Bogadi, K. Aladić and S. Jokić
Abstract
The peel of the Okitsu variety of mandarin is created as a by-product of the fruit’s growth and processing. The primary goal of this research was to use a unique nonthermal extraction method (high-voltage electric discharge assisted) with green solvent (water) to valorise citrus peel as a valuable raw material. In October 2020, samples (citrus peel) were collected from the farm of Mr. Dalibor Ujević (Opuzen, Hrvatska). Samples were washed, freeze-dried, and sieved before extraction. The effects of extraction process parameters, such as treatment duration (5–15 min), frequency (40–100 Hz), and liquid to solid ratio (200–400 ml g–1) on the extraction yield and content of hesperidin and narirutin were studied. Spectrophotometric methods were used to assess the antiradical activity and total phenolic content of the extracts. Individual phenolic components were identified and quantified using HPLC method. The extraction process parameters were optimised with a commercial softer tool (Design Expert®) using experimental data gathered using the Box-Behnken experimental design. Experiments were conducted as shown in Tables 1 and 2. The extraction yield was ranked from 359.23 to 463.20, the total phenol values ranged from 96.23 to 275.46 mg GAE l–1, DPPH values ranged from 87.08 to 94.93 %. Total phenol content and antiradical activity decreased with increasing extraction time, as shown in Fig. 1. Six phenolic compounds were identified and quantified, predominated by hesperidin and narirutin (Table 3). The regression models for all tested HVED extraction responses were significant (p-value under 0.05) based on the acquired data, and the quality of the models produced was evaluated based on the coefficients of determination (R2) and Lack of Fit value. The obtained R2 values for all models developed were 0.911; 0.844, and 0.845 with a nonsignificant lack of fit, indicating an adequate relationship between input parameters (extraction conditions) and observed variable, in this case, extraction efficiency, hesperidin and narirutin content (Table 4). The obtained data was utilised to create three-dimensional (3D) response surface graphs, as shown in Figs. 2–4. The regression models within this study were predicted by Eqs. (1)–(3). With response surface methodology (RSM), optimal parameters of HVED extraction process were defined, as follows: extraction yield (285.93 ml g–1, 73.38 Hz and 14.84 min), hesperidin content (366.19 ml g–1, 97.56 Hz, and 5.1 min), and narirutin content (200 ml g–1, 70 Hz, and 15 min), as presented in Table 5, together with predicted and experimentally verified values.
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Keywords
citrus peel, phenolic compounds, high-voltage electric discharge, optimisation