IMPROVING THE RECOVERY OF PHENOLIC COMPOUNDS FROM DIFFERENT FOOD WASTES BY NOVEL FOOD TECHNOLOGIES

2022-11-23
Okur, İlhami
The main scope of this dissertation was to investigate the effects of High Hydrostatic Pressure-Assisted Extraction (HHPE) on phenolic compounds from different food wastes. The other aim of this study was to compare HHPE with conventional solvent extraction (CSE). At this study, three different food wastes namely spent coffee ground (SCG), olive leaves and olive pomace were used. In the first part of the study, the effect of HHPE on the spent coffee ground was examined. Three different pressure levels (300,400 and 500 MPa) for 5,10 and 15 min at 25 ºC was used. HHPE treatment at 500 MPa for 15 min gave the highest TPC (11.96±0.11 mg GAE/g DW). Also, it was observed that pressure and time had a significant effect on TPC (p≤0.05). In the second part of the study, the optimum HHPE condition for the recovery of bioactive compounds from olive leaves was investigated. For the optimization study, a Box–Behnken design (BBD) with 3 variables was used. The independent HHPE parameters were chosen as the pressure (X1), time (X2) and solid to solvent ratio (X3). Like spent coffee ground, the pressure parameter was selected as 300 and 500 MPa. The treatment time was between 5 and 15 min. Solid to solvent ratio was chosen as 0.1-0.3 (w/v). Extraction temperature and ethanol-water solution were constant in this research and they were 25°C and 70% respectively. Optimum HHPE condition was selected as 433.33 MPa for 15 min with 0.1 w/v solid-solvent ratio to obtain maximum total phenolic (57.5 mg GAE/g DW) and oleuropein content (18.45 mg/g DW). In the third part of the study, like olive leaves, an optimization study was conducted for olive pomace. a Box–Behnken design (BBD) with 3 variables was used. The independent HHPE parameters were chosen as the pressure (X1), time (X2) and solvent concentration (X3). The pressure and time parameters were the same with spent coffee ground and olive leaves. The solvent concentration was chosen as 50-90%. The best HHPE condition for recovery phenolic compounds from olive pomace with the highest total phenolic (16.39 g GAE/ g DW) oleuropein content (45.90 mg/ 100 g DW) was found as 409 MPa for 11.16 min with 63.74% v/v ethanol concentration. In all three studies, it was observed that HHPE increased the phenolic content significantly compared to CSE (p≤0.05). In addition, based on FTIR results, there was no significant difference on the chemical structure of phenolic compounds by HHPE. HHPE increased individual phenolic compounds identified by HPLC significantly and this result was also supported by FTIR results according to bands corresponding to oleuropein, chlorogenic acid and caffeic acids. According to SEM results, HHPE treatment increased the contact area between sample and solvent compared to CSE. As a result, it could be said that the mass transfer rate of phenolic compounds was raised when HHPE treatment was performed. Overall, HHPE has a good potential to be used as a recovery method of phenolic compounds from waste material such as spent coffee ground, olive leaves and pomace based on reduction of treatment time temperature.

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Citation Formats
İ. Okur, “IMPROVING THE RECOVERY OF PHENOLIC COMPOUNDS FROM DIFFERENT FOOD WASTES BY NOVEL FOOD TECHNOLOGIES,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.