Investigation of rheological and some physical chemicalproperties of sour lemon juice concentrate

ABSTRACT INVESTIGATION OF RHEOLOGICAL AND SOME PHYSICAL CHEMICAL PROPERTIES OF SOUR LEMON JUICE CONCENTRATE Esra ÇAVDIR M.Sc., Department of Food Engineering Supervisor: Assist. Prof. Dr. Adnan BOZDOĞAN November 2019, pages 48 In this study, rheological and chemical characteristics of sour lemon juice concentrate were examined. For this purpose, enterdonat types of lemons were squeezed and lemon juices were obtained. Sour lemon juice concentrate was produced from lemon juice by two methods: atmospheric and vacuum conditions. Rheological characteristics of sour lemon juice concentrate were examined under the temperatures of 10, 20, 30, 40, 50 °C and by using rheometer in the 31, 36, 41, 46, 51 ºBrix concentrations. It was determined that sour lemon juice concentrate showed the behavior of Newtonian flow under the measured concentrations and temperatures. The viscosity of the sour lemon juice concentrate produced by vacuum condition was higher than the sour lemon juice concentrate produced by atmospheric condition and this difference was found to be statistically significant(p<0.05). Arrhenius equation was used to determine the effect of temperature on the viscosity of the sour lemon juice concentrate. The activation energy values of sour lemon juice concentrate produced by atmospheric and vacuum condition ranged between 13.6-24.0 kj / mol and 9.0-17.9 kj / mol, respectively. Power law and Exponential models were used to explain the effect of concentration on viscosity. The effect of concentration was better expressed by the Power law model with the sour lemon juice concentrate produced by atmospheric condition while the Exponential model with the sour lemon juice concentrate produced by vacuum condition. Key words: Sour lemon Juice concentrate, rheological behavior, concentration, temperature.