Location: Dairy and Functional Foods ResearchTitle: Molecular characterization of the interacting and reacting systems formed by alpha-lactalbumin and sugar beet pectin
Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2020
Publication Date: 11/26/2020
Citation: Qi, P.X., Chau, H.K., Hotchkiss, A.T. 2020. Molecular characterization of the interacting and reacting systems formed by alpha-lactalbumin and sugar beet pectin. Food Hydrocolloids. (2020) PP. 1-14. https://doi.org/10.1016/j.foodhyd.2020.106490.
Interpretive Summary: Sugar beet pectin (SBP) from sugar beet pulp is a low-value waste material from sugar manufacture. It was previously found to contain a reasonable amount of ferulic acid, a natural antioxidant and abundant in plant cell walls. However, its low water solubility makes its bioavailability poor. To increase its efficacy for food uses, we researched using whey proteins as a carrier system. Whey proteins, a co-product of cheese manufacture, are a mixture of several proteins, including beta-lactoglobulin (beta-LG, ~65% of the total whey proteins) and alpha-lactalbumin (alpha-LA, ~25% of the total whey proteins). Whey proteins are often used as natural emulsifiers in various food products ranging from infant formula to sports nutrition supplements. We combined and heated alpha-LA and SBP under mild and controlled conditions. We found that the food-grade alpha-LA could be used to bind ferulic acid effectively. We further demonstrated that this binding was dominated by physical interactions. Results from this work can lead to not only the development of new delivery systems for natural micronutrients such as ferulic acid but also increased uses of whey proteins.
Technical Abstract: We investigated the molecular properties of interacting complexes and conjugates formed between a-lactalbumin (aLA) and SBP using a multi-detection (UV, dRI, MALLS, and DPV) HPSEC. Dry-heating reactions were conducted at the mass ratios 1:0, 5:1, 3:1, 2:1, 1:1, and 0:1 aLA:SBP under controlled conditions (60 ºC, 79% RH, 72 h). The in-depth physicochemical analysis showed that the association levels were 32, 37, 47, and 61% aLA and 18, 24, 30, and 42% SBP for 5:1, 3:1, 2:1, and 1:1 aLA:SBP, respectively. The stoichiometry was estimated to be 233, 121, 90, and 45 aLA per SBP. Studies of the solution mixtures (3:1) demonstrated that aLA formed complexes with all sized SBP at pH ~ 6.50 through local charge-charge and hydrophobic interactions with stoichiometry ~110:1. Furthermore, the complexes and conjugates did not change the conformation of SBP considerably, i.e., compact spheres, random coils, and rigid rods but increased the molecular chains' stiffness.