Molecular characterization of interacting complexes and conjugates induced by the dry-state heating of beta-lactoglobulin and sugar beet pectin (SBP)

Authors: Qi, Phoebe; Chau, Hoa - Rose; Hotchkiss, Arland

Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2019
Publication Date: 1/8/2019
Citation: Qi, P.X., Chau, H.K., Hotchkiss, A.T. 2019. Molecular characterization of interacting complexes and conjugates induced by the dry-state heating of beta-lactoglobulin and sugar beet pectin (SBP). Food Hydrocolloids. 91:10-18. https://doi.org/10.1016/j.foodhyd.2019.01.010.
DOI: https://doi.org/10.1016/j.foodhyd.2019.01.010

Interpretive Summary: Whey proteins are often used as natural emulsifiers in a variety of food products ranging from nutritional beverages to weight-management supplements. Despite their superior nutrition and exceptional functional properties, whey proteins suffer some shortcomings such as inferior heat stability and low solubility, when used alone in a formulation requiring heating. To look for new ways to improve and diversify the properties of whey proteins, we carried out research on combining and heating whey proteins and sugar beet pectin, one of the most versatile yet under-utilized polysaccharides, under mild and controlled conditions. The results provided a detailed understanding of the molecules involved in the food-grade modification reaction that contributed to the enhanced quality of the end products containing whey proteins as the main ingredient, and pectin, the minor additive. This study not only helps advance our knowledge on the Maillard browning reaction that occurred between whey proteins and pectin, but it also offers opportunities for designing new food formulations that contain these two biopolymers and meet the global market demand for whey proteins and consumers’ preferences for healthier foods.

Technical Abstract: To gain an understanding of the improved emulsion stability, exhibited by the Maillard-type reaction products consisted of whey protein isolate (WPI) and sugar beet pectin (SBP), we investigated the molecular properties of interacting complexes and conjugates formed between beta-lactoglobulin (beta-LG), the main protein of whey, and SBP. The reaction was carried out at varying mass ratios, '-LG:SBP = 1:0, 5:1, 3:1, 2:1, 1:1, and 0:1 through dry heating (60 ºC, 79% RH, 72 h). The physiochemical properties of the resulting products from the reaction were characterized by an online multi-detection (UV, dRI, MALLS, and DPV) High-Performance Size Exclusion Chromatography (HPSEC) system. The results showed that although the molecular weight distribution and the shape of the SBP in each fraction was significantly transformed by dry heating alone, the overall apparent average weight molar mass ([Mw]av) and intrinsic viscosity ([hw]av) were not affected. Detailed analyses revealed about 29, 34, 44 and 56% of total beta-LG participated in the reactions and interactions with SBP for the mixture of 5:1, 3:1, 2:1, and 1:1 respectively. Furthermore, it was demonstrated that the group of SBP molecules with higher [Mw] (~ 800 kDa) and medium (~ 120 kDa) and formed interacting complexes with beta-LG through local electrostatic and hydrophobic interactions and maintained the shapes of SBP, a mixture of compact spheres, random coils, and rigid rods. The conjugates were likely developed by the chemical reactions between the group of SBP with low [Mw] (~ 100 kDa) and beta-LG, leading to the products with altered molecular structures and increased chemical bond stiffness compared to that of SBP.