Filtration of grape juice was investigated. Effects of process parameters of filtration were examined. The usage of precoating material and filter aid were found to be necessary to prolong the filter life. Filter cake was found to be incompressible with the effect of increasing pressure. Increase in temperature caused increase in flow rate due to the reduction in viscosity. The influences of depectinization and clarification on filtration process were also examined. Depectinization and clarification decreased the resistance and increased the flow rate. Improvement in the quality of the grape juice was observed when these pretreatments were employed.
The effects of temperature and soluble solid concentration on physical properties of clarified fruit juices were investigated. High temperature and soluble solid content dependencies of density, viscosity and heat capacity were detected. Experimental data were fitted as a function of temperature and soluble solid content. Models being valid for studied clarified fruit juices were achieved for density and viscosity with the regression coefficients (R2) higher than 0.90.
Optimization of the solid-liquid extraction conditions for trans-resveratrol, trans-& / #949 / -viniferin, ferulic acid, and total phenolics from milled grape canes has been investigated. Temperature and ethanol concentration were found to be major process variables for all responses. Maximum yields of trans-resveratrol, trans-& / #949 / -viniferin, ferulic acid, and total phenolics were predicted as 4.25 mg/g dw, 2.03 mg/g dw, 1.05 mg/g dw, and 9.28 mg/g dw, respectively.
Optimization of extraction conditions for antioxidant activity of grape cane extracts measured by the Trolox equivalent antioxidant capacity (TEAC) and the oxygen radical absorbance capacity (ORACFL) assays was carried out using solid-liquid extraction and response surface methodology. Ethanol concentration and temperature employed for the extraction of antioxidant agents from grape cane samples were found to be statistically significant process variables affecting antioxidant activity measured by the TEAC and ORAC methods.
trans-Resveratrol and trans-& / #949 / -viniferin were extracted from milled grape canes using pressurized low polarity water (PLPW). The extraction temperature was significant for both compounds: extraction at 160oC resulted in a 40% loss of trans-resveratrol compared to 95oC while reduction of trans-& / #949 / -viniferin at both temperatures remained at 30%. Increasing ethanol concentration from 0 to 25% increased the extraction of total phenolics and trans-& / #949 / -viniferin by 44% and 489%, respectively. Solvent flow rate also influenced trans-& / #949 / -viniferin extraction. Effective diffusivities of trans-resveratrol increased by three times with increasing temperature. The modified Gompertz equation satisfactorily explained the extraction of the stilbenes investigated.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/2/12610989/index.pdf |
| Date | 01 September 2009 |
| Creators | Karacabey, Erkan |
| Contributors | Bayindirli, Levent |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for METU campus |
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