TRANSGLUTAMINASE MODIFICATION OF SUNFLOWER PROTEINS
PETYA IVANOVA*, VESELA CHALOVA, GEORGI DOBREV, LIDIA KOLEVA, IVAN PISHTIYSKI
University of Food Technologies, Plovdiv
*Corresponding author: petia_ivanova_georgieva@abv.bg
Keywords: sunflower protein isolates, transglutaminase, OPA, SDS-PAGE, gel-filtration chromatography
Abstract: Transglutaminase modification of proteins is used in the food industry to improve their functional properties. The enzyme catalyses cross-linking of proteins by formation of ε-(γ-glutamyl) -lysine bonds, which leads to the formation of protein aggregates with net structure and altered functional properties.
In this research, the potential of microbial transglutaminase to modify proteins isolated from industrially produced sunflower meal was explored. The influence of pH and the longevity of reaction at two temperatures (40°C and 60°C) were studied. Cross-linking process was monitored via the amount of free amino groups and electrophoretic mass distribution of proteins by using ortho-phtalaldehyde analysis (OPA) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) respectively. Results demonstrated that the amount of free amino groups during the polymerization reaction decreased as indicated by decreased absorption at 340 nm when using OPA analysis. The formation of high-molecular weight proteins (MW > 150kDa) gradually increased at the expense of low-molecular weight protein fractions (MW < 50 kDa). The formation of protein fractions with molecular weight between 50 and 150 kDa increased at the beginning of enzymatic reaction followed by a gradual decrease. Molecular aggregates with molecular weights of approximately 400 kDa appeared 2 h after the beginning of cross-linking at 40°C and pH 7-8 and after 4h at pH 9. At 60°C, they were observed 10 to 60 min after the start of the reaction depending on pH values.