Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2014
Publication Date: 7/8/2014
Publication URL: http://handle.nal.usda.gov/10113/59570
Citation: Qi, P.X., Wickham, E.D., Garcia, R.A. 2014. Structural and thermal stability of beta-lactoglobulin as a result of interacting with sugar beet pectin. Journal of Agricultural and Food Chemistry. 62(30):7567-7576. DOI: 10.1021/jf502699g.
Interpretive Summary: Ingredients containing proteins and polysaccharides (chains of carbohydrates) are especially useful for improving the nutritional value, textural properties and stability of foods. In a variety of food products ranging from mayonnaise to ice cream, milk proteins are often used as emulsifiers (agents that can help prevent oil and water from separating) whereas polysaccharides are used as thickeners and gelling agents. However, keeping these valuable components stable in a complex food formulation remains a challenge to the food industry. Research on studying changes in the interacting system containing a whey protein, one of the major milk proteins, and sugar beet pectin, one of the most versatile polysaccharides, caused by environmental change such as temperature demonstrated, on the molecular level, that even though a short period of heating changed the protein significantly, binding with pectin helped to stabilize and preserve some of its properties. This study added knowledge on finding new ways to keep foods and beverages containing protein and pectin stable.
Technical Abstract: The effect of interaction on the structure and stability of beta-lactoglobulin (beta-LG) with beta-sugar beet pectin (beta-SBP) has been studied by circular dichroism (CD), infrared spectroscopy (FT-IR) and steady-state as well as time-resolved fluorescence spectroscopy at pH 6.75, and low ionic strength (I=50 mM). It was demonstrated that not only untreated beta-SBP is capable of binding to native beta-LG, it also reduced both the secondary structure content, notably the amount of intermolecular beta-sheet (by ~8%), and disrupted the environment of Phe, and to a lesser degree that of Trp residues. However, when both interacting partners were subjected to thermal treatment, a limited level of protection and restoration effect on heat-denatured beta-LG on its secondary (4% beta-sheet) and tertiary structural elements was observed upon binding to beta-SBP. The feruloyl groups of beta-SBP proved to be both a sensitive fluorescent probe for diagnosing the degree of interaction with beta-LG as well as an effective energy acceptor transferred from the protein.