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    Optimization of pectin extraction from orange pulp and characterization of compositional and steady shear properties
    (Namik Kemal University - Agricultural Faculty, 2017) Yilmaz M.T.; Muslu A.; Karasu S.; Bozkurt F.; Dertli E.
    Pectin, which is one of the most important wastes of fruit juice industry, was extracted from orange pulp at optimum conditions (pH, time and temperature) and modified using pectinase. The effect of modification on the structural properties of pectin was monitored using Fourier transformed infrared spectroscopy (FTIR) and high performance liquid chromatography (HPLC) analyses. The bands at 1600-1800 cm-1 which indicate the specific region and quality of pectin were detected using FTIR while galacturonic acid content was determined using HPLC. The results showed that the galacturonic acid content of pectin from orange pulp was determined to be 406.44 mg/g powder pectin while that of the modified pectin from the orange pulp was determined to be 465,34 mg/g powder pectin. In addition, flow properties of the pectin samples were determined using rheological analysis. The viscosity and viscoelastic properties of the modified pectin samples were revealed to be different from those of non-modified pectin samples. The consistency index values of unmodified and modified pectin samples were determined to be 0.0559 Pa.sn and 0.0046 Pa.sn, respectively. © 2017 Namik Kemal University - Agricultural Faculty. All Rights Reserved.
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    Thermal loop test to determine structural changes and thermal stability of creamed honey: Rheological characterization
    (Elsevier Ltd, 2015) Karasu S.; Toker O.S.; Yilmaz M.T.; Karaman S.; Dertli E.
    This study was the first attempt to understand if thermal stability of any food product during storage could be determined. In this respect, a novel method, namely, the thermal loop test was used to determine structural changes and thermal stability of creamed honey in this study. The novelty of this method was that thermal stability of a product is tested within a number of thermal cycles over a determined range of temperature. Creamed honey was characterized in terms of physicochemical, thermomechanical and rheological properties. It showed non-Newtonian thixotropic behavior at all temperature levels (10, 25 and 40 °C). Time-dependent flow behavior was successfully defined by Weltman and second order structural models. Hysteresis loop area depended on temperature and decreased with increase in temperature. Creamed honey had liquid-like structure, showing that it had more pronounced viscous nature than elastic nature (G? > G?). Temperature sweep tests were conducted to determine temperature dependency of ?50, G? and G? values using Arrhenius equation. These test results confirmed the thermal stability test results, revealing that thermal loop test can be an accurate method to determine thermal stability of similar food products, as a new information. Relative structural index value (?) increased with number of thermal loop, suggesting that creamed honey had low thermal stability and showed a great structural change by the thermal stress applied between 5 °C and 50 °C. These results suggest that crystallized honey be abstained from large temperature fluctuations to avoid from irreversible changes in rheological characters; thus, to maintain spreadability. © 2014 Elsevier Ltd.