High pressure leads to denatured proteins with optimal surface activity.

The development of improved functional ingredients requires us to understand the importance of an ingredient's structural-functional relationship. The primary protein in whey, b-lactoglobulin, is usually denatured by environmental factors such as pH, temperature and high hydrostatic pressure (HHP) to increase protein functionality.

However, the desired effect is often diminished because of the aggregation of the denatured protein. The objective of scientists at Oregon State University was to denature b-lactoglobulin using an optimized HHP treatment. They wanted to increase its functionality while minimizing protein aggregation.

In experiments, b-lactoglobulin was treated with HHP at 420 MPa, 510 MPa and 600 MPa for 10 minutes at pH 5.2, pH 6, pH 7 and pH 7.5, and at concentrations of 0.2 mg per ml, 0.5 mg per ml, 1.0 mg per ml and 1.5 mg per ml. Temperatures used were 5 C and 21 C. The researchers used native gel electrophoresis to monitor the aggregation.

Changes in the surface tension of protein-buffer model solutions were measured and used as an indication of changes in surface activity. Circular dichroism (CD) spectrophotometry analyzed changes in secondary structure. Scientists stored samples under frozen and freeze-dried conditions and monitored them for surface activity and structural changes.

The b-lactoglobulin, 0.5 mg per ml, pH 7.5, treated by HHP at 5 C for 10 minutes at 510 MPa and 600 Mpa, had the lowest surface tension. At these conditions, protein aggregation was minimized. Surface tension measurements on stored samples were consistent with this trend. CD data indicated secondary structural changes, with the primary changes occurring in the a-helix. Freeze-drying the samples minimized structural changes during their storage.

The results show that HHP treatment at low temperatures has the potential to develop denatured proteins with optimal surface activity. This is especially important when the proteins are used as an ingredient in food systems consisting of emulsions or foams. The researchers have just completed their work and will soon submit it for publication review. They tell us that they have optimized the treatment conditions and have obtained good results.

Further information. Lisbeth Goddik, Department of Food Science and Technology, Oregon State University, 100 Wiegand Hall, Corvallis, OR 97331; phone: [phone]; fax: [phone]; email: [e-mail].