Oxidation of whey protein isolate after thermal convection and microwave heating and freeze-drying: Correlation among physicochemical and NIR spectroscopy analyses

Juliany Cristiny Sonda Bordignon; Amanda Teixeira Badaró; Douglas Fernandes Barbin; Lilian Regina Barros Mariutti; Flavia Maria Netto

doi:10.1016/j.heliyon.2023.e17981

Oxidation of whey protein isolate after thermal convection and microwave heating and freeze-drying: Correlation among physicochemical and NIR spectroscopy analyses

Heliyon. 2023 Jul 6;9(7):e17981. doi: 10.1016/j.heliyon.2023.e17981. eCollection 2023 Jul.

Authors

Juliany Cristiny Sonda Bordignon¹, Amanda Teixeira Badaró¹, Douglas Fernandes Barbin¹, Lilian Regina Barros Mariutti¹, Flavia Maria Netto¹

Affiliation

¹ School of Food Engineering, State University of Campinas, Street Monteiro Lobato, 80, 13082-862, Campinas, SP, Brazil.

Abstract

This study investigated the oxidative susceptibility of whey protein isolate (WPI) dispersions treated by microwave or thermal convection before freeze-drying. WPI (20 mg protein/mL) in distilled water (DW) was heated at 63 ± 2 °C for 30 min by microwave (WPI-MW) or convection heating (WPI-CH) and freeze-dried. Untreated WPI (WPI-C), WPI solubilized in DW and freeze-dried (WPI-FD), and WPI solubilized in DW, heated at 98 ± 2 °C for 2 min and freeze-dried (WPI-B) were also evaluated. Structural changes (turbidity, ζ potential, SDS-PAGE, and near-infrared spectroscopy (NIR)) and protein oxidation (dityrosine, protein carbonylation, and SH groups) were investigated. WPI-FD showed alterations compared to WPI-C, mainly concerning carbonyl groups. Microwave heating increased carbonyl groups and dityrosine formation compared to conventional heating. NIR spectrum indicated changes related to the formation of carbonyl groups and PCA analysis allowed us to distinguish the samples according to carbonyl group content. The results suggest that NIR may contribute to monitoring oxidative changes in proteins resulting from processing.

Keywords: Carbonylated protein; Dityrosine; Protein oxidation.