Food protein network formation and gelation induced by conductive or microwave heating: A focus on hen egg white. (December 2020)

• Record Type: Journal Article
• Authors: Rombouts, Ine; Wouters, Arno G.B.; Lambrecht, Marlies A.; Uten, Lien; Van Den Bosch, Wouter; Vercruysse, Sabine A.R.; Delcour, Jan A.
• Is Part Of: Innovative food science & emerging technologies. Volume 66(2020)
• Publication Date: 2020-12
• Subjects: Conductive heating -- Dielectric heating -- Ovalbumin -- Denaturation - protein network; Food -- Biotechnology -- Periodicals; Food industry and trade -- Technological innovations -- Periodicals; Aliments -- Biotechnologie -- Périodiques; Food -- Biotechnology; Periodicals; Electronic journals; 664.005
• DOI: 10.1016/j.ifset.2020.102484
• Languages: English
• ISSNs: 1466-8564

Abstract

Abstract: Heat-induced protein polymerization, gelation and the associated molecular scale changes were investigated during conductive and microwave heating (CH and MH, respectively). Given identical temperature-time profiles, polymerization of bovine serum albumin, ovalbumin, egg white (EW) and wheat gluten protein occurred faster and to a greater extent with CH than with MH. Moreover, lanthionine cross-links were present in some MH but in none of the CH samples. Gelation of EW protein by CH or MH was studied in more detail. Differential scanning calorimetry and fluorescence spectroscopy indicated that EW proteins initially denatured to a larger extent with CH than with MH. Size exclusion high performance liquid chromatography demonstrated that CH resulted in more heavily cross-linked EW protein networks than MH. Homogeneous EW gels were obtained by 15 min CH at 80 °C while 120 min MH at this temperature still resulted in inhomogeneous (with liquid and solid zones) gels. This was affirmed by low resolution 1 H nuclear magnetic resonance measurements which indicated more mobile water in MH than in CH samples. However, MH gels had higher firmness than the corresponding CH gels. Thus, MH here led to less covalent cross-linking than CH, but still resulted in firmer gels most likely because its protein network relied heavily on non-covalent interactions. Industrial relevance: This study highlighted differences between microwave and conventional, conductive, heating of different protein materials. While literature is divided about the origin of differences noted between these different heating modes, it is clear from our data that heating mode, given identical temperature-time profiles, impacts the changes that proteins undergo during heating. The knowledge that microwave heating favors protein unfolding, aggregation and cross-linking to a lower extent than conductive heating can likely be exploited in industrial applications. Highlights: Protein gelation by microwave (MH) and conductive (CH) heating was researched. Egg white protein was subjected to identical temperature-time profiles by MH and CH. MH resulted in less pronounced protein denaturation and polymerization than CH. Gels obtained by MH were firmer than those obtained by CH. Non-covalent interactions are likely more important in MH than in CH gels.