Effect of ultrasound on lactoperoxidase and alkaline phosphatase enzymes

ABSTRACT Master Thesis EFFECT OF ULTRASOUND ON LACTOPEROXIDASE AND ALKALINE PHOSPHATASE ENZYMES Yavuz YÜKSEL Atatürk University Institute of Pure and Applied Sciences Department of Food Science and Technology Supervisor: Assoc. Prof. Dr. M. Fatih ERTUGAY In this study, ultrasound process, a kind of cold preservation methods, was applied to lactoperoxidase (LPO) and alkaline phosphatase (AP) enzymes which have an significant function in milk technology and the changes in their activities were determined. For this purpose, 4 different amplitudes (20, 40, 60 and % 80) addition to untreatment (control), 2 different temperatures (20 and 40 °C) and 4 different exposure times (30, 60, 90 and 120 s) were applied to these enzymes and the effects of these factors were tried to determine on LPO and AP enzymes. In the study, a certain amount of LPO enzyme was added in 0. 1 M Na2HP04.7H20 solution (pH: 6.0) and than this solution was exposed to ultrasound treatment. An increase in a minute at 412 nm absorbance in spectrophotometer was recorded as enzyme unit by means of ovidation reaction of 2,2-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) with together H202. AP enzyme was also subjected to ultrasound after added in certain amount to 2-amino-2- methyl-1-propanol (AMP) (pH: 10.45, 35°C). It was observed that colourful solution (p- nitrophenolate), occurred by reaction of p-nitrophenyl phosphate (nNPP) substrat with water in spectrophotometer, has absorbance increase to occure by accomplishment with AP enzyme. Absorbance increase in a minute was determined as an enzyme unit. A decrease was determined in activities of LPO and AP enzymes by ultrasound process depend on level of amplitude, temperature and exposure time. Furthermore, we observed that activities of these enzymes decreased dramatically depending on temperature and exposure time in % 80 amplitude. Finally, we can say that the usage of ultrasound process with other treatments (temperature, ultraviolet, high pressure... etc.) would be more effective. 2002, 40 pages Keywords: Ultrasound, lactoperoxidase, alkaline phosphatase 11