Czech J. Food Sci., 2014, 32(1):82-89 | DOI: 10.17221/326/2012-CJFS

Changes of secondary structure and surface tension of whey protein isolate dispersions upon pH and temperatureOriginal Paper

Marta TOMCZYŃSKA-MLEKO¹, Elżbieta KAMYSZ², Emilia SIKORSKA², Czesław PUCHALSKI³, Stanisław MLEKO⁴, Lech OZIMEK⁵, Grzegorz KOWALUK 6, Waldemar GUSTAW 7, Marta WESOŁOWSKA-TROJANOWSKA⁴

¹ Institute of Plant Genetics, Breeding and Biotechnology, 4Department of Biotechnology, Human Nutrition and Food Commodity Science, and 7Department of Technology of Fruits, Vegetables and Mushrooms, University of Life Sciences in Lublin, Lublin, Poland

² Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland

³ Department of Bioenergetic Technologies, Faculty of Biology and Agriculture, University of Rzeszów, Rzeszów, Poland$2

⁵ Department of Agricultural, Food &

Nutritional Science, University of Alberta, Edmonton, Canada

⁶ Faculty of Physical Education in Biala Podlaska, Josef Pilsudski University of Physical Education in Warsaw, Biała Podlaska, Poland$5

The secondary structure of proteins in unheated and heated whey protein isolate dispersions and the surface tension of the solutions were investigated at different pH. Heating protein solutions at 80°C results in an increase of unordered structure. Nevertheless, the difference between the contents of unordered structure in the unheated and heated samples increases with increasing pH of the solution. At low protein concentrations the surface tension decreased with increasing protein concentration to about 5 mg/ml. For the heated solution, a similar trend was observed in the decrease in the surface tension with increasing concentrations of protein. In both cases, the curves depicting the surface tension as a function of protein concentration could be fitted to the exponential function with a negative exponent, but with the heated solutions lower values of surface tension were observed. Studies on the surface tension of whey protein isolate solutions prove that the unfolding of whey proteins, revealed by changes in the secondary structure, causes a decrease in the surface tension.

Keywords: circular dichroism; globular protein; protein concentration

Published: February 28, 2014  Show citation