|Clare, D - NCSU|
|Catignani, G - NCSU|
|Swaisgood, H - NCSU|
Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: July 12, 2003
Publication Date: July 16, 2003
Citation: TRUONG, V., CLARE, D.A., CATIGNANI, G.L., SWAISGOOD, H.E. CROSSLINKING AND RHEOLOGICAL CHANGES OF WHEY PROTEINS TREATED WITH MICROBIAL TRANSLUTAMINASE. ANNUAL MEETING OF THE INSTITUTE OF FOOD TECHNOLOGISTS. BOOK OF ABSTRACTS 2003:50, 2003. Technical Abstract: In order to be competitive in the food ingredient markets, the functionality of whey proteins must be continuously improved and designed for specific uses. Heat and acid treatments are commonly used for modifying whey proteins. Enzymes, including microbial transglutaminase (TG), have recently been applied. However, changes in rheological properties of whey proteins, as affected by extensive TG crosslinking, are not well studied. This study examined the factors affecting crosslinking of whey protein isolates (WPI) by TG and characterized their rheological properties. Both soluble and immobilized TG were used. The enzyme was immobilized on amino-propyl glass beads (CPG-3000) following the biotin-avidin procedure developed in our laboratory. TG, 0.12-10 units/g proteins, was added to 4-8% w/w WPI in sodium phosphate buffer, pH 7.5 containing 10 mM dithiothreitol. The reaction was carried out in a jacketed bioreactor for 8 h at 40 deg C with continuous circulation. Aliquots were taken at time intervals for SDS-PAGE, Western blots and rheological characterization using a stress controlled rheometer. Gel point temperature of WPI solutions treated with 0.12 units of immobilized TG was slightly decreased, but gel strength was unaffected. Ten units of soluble TG resulted in extensive crosslinking of alpha-lactalbumin and beta-lactoglobulin in WPI as evident in SDS-PAGE and Western blotting results. Crosslinking of WPI was manifested with increases in apparent viscosity and changes in gelation properties. Interestingly, the gelling point of WPI solutions increased from 68 deg C at 0 min to 94 deg C after 4 h of reaction, and the gel strength was drastically decreased (lower storage modulus, G'). Thus, extensive intra- and inter-chain crosslinking probably caused formation of polymers that were too large for effective network development. Modified WPI having a wide range of gelling properties can be obtained with TG crosslinking reactions. The process can be applied to produce heat-stable whey proteins for various food applications.