Influence of heat and pH on structure and conformation of whey proteins

Abstract

Please cite this article as: Dissanayake, M., Ramchandran, L., Piyadasa, C., Vasiljevic, T., Influence of heat and pH on structure and conformation of whey proteins, International Dairy Journal (2012), doi: 10.1016/j.idairyj.2012.08.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The aim of this study was to understand the fundamental interactions responsible for 24 aggregation of whey proteins (WPs) at pH 6 and 3 during heating at 140 ºC for 30 s in the 25 presence of different acidulants. The conformational changes in the various heat-treated WP 26 dispersions were studied using chemical bond blockers and analysed using differential 27 scanning calorimeter thermograms, polyacrylamide gel electrophoresis and turbidity 28 measurements. Overall, the results indicated that WPs were denatured mainly by disruption 29 of hydrophobic interactions, and that the extent of WP denaturation at pH 3 was affected by 30 the type of acidulant used. The type of acidulant affected the extent of formation of additional 31 high or medium molecular weight aggregates during heating at pH 3, while the types of 32 interactions involved in the formation of such aggregates were affected by the pH at heating. 33Introduction 36 37Whey proteins (WPs) have distinctive nutritional and functional properties that make 38 them unique food ingredients. Different attractive and repulsive molecular forces, involved in 39 the stability of unique three-dimensional structure of proteins (Damodaran, 2008), affect their 40 functionality. These include intrinsic van der Waals and steric forces, as well as electrostatic, 41 hydrogen bonding and hydrophobic interactions that arise from the influence of the 42 surrounding environment. The physico-chemical properties that govern the overall 43 functionality of WPs are a result of intrinsic factors native to the proteins, mainly their 44 structure and conformation, as well as extrinsic factors, such as environmental conditions 45 including pH and temperature. Any processing condition that influences the intrinsic or 46 extrinsic factors will affect protein conformation and thereby influence the functionality of 47WPs. Therefore, the inclusion of WPs into food systems is dependent on processing 48 conditions applied and their influence on protein structure that, due to the heat sensitivity of 49 WPs, may even result in complete denaturation and thus limit their application. Recently a 50 novel approach to stabilization of WPs through microparticulation was proposed 51 (Dissanayake & Vasiljevic, 2009;Dissanayake, Liyanaarachchi, & Vasiljevic, 2012) to 52 alleviate this problem. 53Heating, a commo...

Heat stability improvement of antimicrobial whey proteins fromyak milk and colostrum at various acidic conditions

“…The results obtained are in agreement with other previous observations on thermal denaturation of whey proteins either in isolated, admixture form or in skimmed milk (Mainer et al 1997;Dissanayake, Ramchandran, Donkor et al 2013;Dissanayake, Ramchandran, Piyadasa et al 2013). Different methods have been applied to study heat stability of bovine IgG in different matrices.…”

Effects of Encapsulated Fish Oil by Polymerized Whey Protein on the Textural and Sensory Characteristics of Low-Fat Yogurt

“…Figure 2 showed DSC curve recorded (at a heating rate of 1.0 o C/min) for PWP at pH 8.5. The physicochemical pr operties of whey proteins present as well as intrinsic (structure and conformation) including Van der Waals and steric forces, different attractive or repulsive molecular forces, and extrinsic (environment) conditions including pH, temperature, ionic strength, solvent polarity and type, govern the whey protein functionality [Dissanayake et al, 2013].…”

Whey Protein-Pullulan (WP/Pullulan) Polymer Blend for Preservation of Viability ofLactobacillus acidophilus

“…During heat treatment, whey protein undergoes denaturation and some structural changes. [15,16] Studies have revealed that, due to unfolding by preheating treatment of whey protein, improved functional and encapsulation properties such as gelation and adsorption at the interface have been reported. [17][18][19][20] Whey protein has also proved to be an effective encapsulating agent because of its ability to form microcapsules easily under mild conditions using different techniques.…”