2010 - 19th Annual NC State Undergraduate Research Spring Symposium

Session Time : 4/22/10 10:30 AM - 4/22/10 11:45 AM

Content Area : Honors Teaching Students

Student Presenters :
Marjorie Ronan Griffiths Food Science

Mentors and/or Co-Authors :
Edward Foegeding Food, Bioprocessing & Nutrition Sciences
Bongkosh Vardhanabhuti Food, Bioprocessing and Nutrtion Sciences ;
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Abstract Title : Formation of Amyloid Fibrils in Heat Aggregation of Beta-Lactoglobulin as Directed by Charged Polysaccharide and Chaperone Protein

Abstract :
The objectives of this study were to investigate the presence of amyloid fibrils formed during heat aggregation of β-lactoglobulin (BLG) as directed by charged polysaccharide and chaperone protein, and how fibril formation correlates with heat stability of proteins. Samples containing 2-6 % w/w BLG and 2% w/w Dextran Sulfate (DS, MW = 5-500 kDa) or 5% w/w β-casein (BCN), pH (5.8-6.5) were heated at 85 °C for 15 minutes. Thermal stability was evaluated by measuring the optical density at 400 nm. Formation of fibrils was observed using the Thioflavin T (ThT) assay. Results showed that the presence of DS and BCN at appropriate biopolymer ratios and pH significantly lowered the turbidity of heated BLG as previously reported. It was determined for 2% protein at a pH range of 5.8- 6.5 that the fluorescence intensity increased until 0.1 BLG: DS then the fluorescence intensity plateaued. Therefore, the heat stability of 2% BLG increased in the presence of DS and the structure of BLG aggregates were more like amyloid fibrils. While BCN decreased the turbidity of heated BLG, the aggregates did not form fibrils as there was no change in fluorescence intensity, suggesting that the stabilization mechanisms from DS and BCN were different. The ability to control the amyloid formation by charged polysaccharide or chaperone protein will allow the creation of protein aggregates with desirable texture for food applications. This knowledge can be applied to improve heat stability of protein beverages by reducing cloudiness.