Abstract
In this paper we demonstrate that the denaturation behavior, i.e. Tden, of egg white proteins in sugar and sugar replacer solutions is explained by the volumetric density of hydrogen bonds in the solutions, i.e. nOH,eff. The validity of the presented approach is demonstrated using 18 solutions comprising single compounds as well as 7 ternary/quaternary mixtures. Different classes of plasticizers are used at various concentrations and at various ratio with proteins. Sweet amino acids such as l-proline and glycine are included as novel alternatives to polyols. The experimental data are modelled with the Flory-Huggins (FH) theory for biopolymer melting. For such purpose, solutions are treated as a single solvent, which is described by the effective volume fraction of the solvent Φw,eff (⁓nOH,eff). Overall, the FH model can well describe the denaturation behavior of egg white proteins in sugar and sugar replacer solutions up to 30% concentration. Deviations from the model become particularly evident at high sugar concentrations (i.e. 50%), which relate to conditions of phase separation in a protein-rich and sugar-rich domain. In such conditions, Φw,eff does not reflect the composition of the solvent around the proteins. An elevation in Tden is observed due to a reduction in hydrogen bond density in the protein-rich domain. The results indicate that phase separation is driven by both the concentration and the molar volume density of effective hydroxyl groups NOH,s/vs of the plasticizers or plasticizer mixtures. Finally, the proposed approach can predict key phase-transitions which result in protein network formation in pound cake baking.
Highlights
In many bakery products, sugar is a major ingredient with a contri bution of up to 30–40% depending on product
The hypothesis of this study was that the denaturation profile, i.e. The onset of protein dena turation (Tonset) and Tpeak, of egg white proteins is controlled by the volumetric density of hydrogen bonds Φw;eff and that it can be predicted for various sugars and sugar replacers solutions in water, following on its applica tion in the FH theory
We have shown that the volumetric density of effective hydrogen bonds nOH;eff available for intermolecular interactions governs the denaturation behavior of egg white proteins in mixtures of water with polyhydroxy compounds
Summary
Sugar is a major ingredient with a contri bution of up to 30–40% depending on product (van der Sman & Renzetti, 2019). The reformulation of sweet bakery products with a substantial reduction in sugars has proven to be difficult due to the multiple func tionalities that sugars exert in bakery products, next to providing sweetness (Pareyt & Delcour, 2008); (Wilderjans, Luyts, Brijs, & Del cour, 2013), (Mariotti & Lucisano, 2014 ) (van der Sman & Renzetti, 2019). In bakery products such as cakes, sugars play important functional ities throughout the different process stages, from mixing to baking and cooling of the final cake product (Wilderjans et al, 2013). Understanding the functionality of sugars and sugar replacers with respect to biopolymers phase transitions is key for defining optimal reformulation strategies
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