Chemical composition as an indicator for evaluating heated whey protein isolate (WPI) and sugar beet pectin (SBP) systems to stabilize O/W emulsions

Authors: Qi, Phoebe; Wickham, Edward; XIAO, YINPING - Academy Of Agricultural Science

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2020
Publication Date: 6/9/2020
Publication URL: https://handle.nal.usda.gov/10113/6983600
Citation: Qi, P.X., Wickham, E.D., Xiao, Y. 2020. Chemical composition as an indicator for evaluating heated whey protein isolate (WPI) and sugar beet pectin (SBP) systems to stabilize O/W emulsions. Food Chemistry. 330: 1-9. https://doi.org/10.1016/j.foodchem.2020.127280.
DOI: https://doi.org/10.1016/j.foodchem.2020.127280

Interpretive Summary: Whey proteins have been widely used in many food products including the ready-to-drink protein beverages. However, they are known to be affected by standard processing treatment such as heating, which can lead to undesirable traits such as cloudiness, the formation of sediment, and gelation. Research has demonstrated that mixing whey proteins with pectin, a gelatinous, naturally occurring substance from fruits used to make jellies and jams, and then heating, an example of the Maillard browning reaction, can significantly alleviate these problems. We used this reaction in our research, in this case, by combining whey proteins and sugar beet pectin, one of the most versatile yet underutilized pectin sources, in water, to determine if SBP can be utilized. The results provided an understanding of the physical and chemical changes that occurred during the reaction and correlated them with the observed improvement in the functional properties, i.e., the emulsion stability and the cloudiness of the end products. This work will help design new protein-enriched beverage formulations that contain high levels of protein and are also resistant to heat treatment, and to increase the economic values of both the protein and pectin.

Technical Abstract: We investigated changes in the physical properties, chemical compositions and O/W emulsion stability of an interacting and reacting system formed between whey proteins isolate (WPI) and sugar beet pectin (SBP) through heating (60 °C) in aqueous solution. The concentration of WPI was maintained at a constant (3%) while the concentration of SBP was varied at 1%, 1.5 and 3%. The resulting complexes were examined using chemical assays and spectroscopic techniques. It has been shown that the free sulfhydryl (SH) and the primary (NH2) and secondary amine (NH) contents of WPI were considerably mitigated by the presence of SBP, demonstrating that the impediment of the Maillard-type reactions occurred in solution compared to the dry-state in similar conditions. Analyses from the UV-VIS spectroscopic measurements showed that less pronounced changes occurred in the molecular electronic states of both WPI and the feruloyl moieties of SBP upon heat-induced interaction and conjugation reactions in solution than that in the dry-state. The reacted mixtures of WPI and SBP, particularly at higher levels of SBP, 1.5 and 3%, saw a significantly improved stability than WPI alone for an O/W emulsion system at pH 3.2. On the other hand, only reactions at a lower concentration of SBP (1%) produced conjugates with greater stability for the O/W emulsion at neutral pH, contrary to the conjugates formed in the dry-state reaction. These results attested that the Maillard-type reaction in solution was less efficient and productive than that in the dry-state for the purpose of fabricating WPI-SBP interacting systems with enhanced O/W emulsion stability.