Electrophoretic and mass spectrometry-based characterization of soluble fraction of camel milk proteins upon freeze and spray drying treatment

Abstract

Objective: Camel milk is highly nutritious food with numerous health benefits proposed. Demandfor camel milk has increased worldwide.Production of camel milk powders facilitate its transport,prolonge shelf-life, and also offer an attractive additive for various food products. In this study wecharacterized proteins of soluble fraction of freeze/spray dried camel milk powders.Material and Methods: Whole camel milk powders were prepared by spray drying treatment at sixdifferent inlet temperatures (190°C - 250°C) or by freeze drying. The soluble protein fractions uponthe treatments were analysed by combination of electrophoretic techniques and circular dichroism.Freeze dried camel milk and spray dried at 250°C were analysed by mass spectrometry.Results: SDS-PAGE revealed non-uniform increase in Mw of major protein bands, while nativeelectrophoresis revealed non-uniform decrease in pI values with increased inlet temperature ofspray drying. That indicated occurence of the Maillard reaction. Far-UV circular dichroism spectrashowed no differences in secondary structures between freeze and spray dried samples. Massspectrometry identified α-lactalbumin, glycosylation-dependant cell adhesion molecule 1(GLYCAM1), immunoglobulin heavy chain, peptidoglycan recognition protein and camel serumalbumin as dominant proteins in soluble fraction of camel milk powders. Carboxymethyl-lisyne(CML), well known marker of Maillard reaction in food analysis, was detected on GLYCAM1 and onimmunoglobulin heavy chain.Conclusions: Our results indicate glycation of camel milk proteins via Maillard reaction upon spraydrying treatment which further may affect techno-functional properties of camel milk powders,their shelf-life and nutritional value.Acknowledgments: This work was supported by the Ministry of Education, Science andTechnological Development of the Republic of Serbia, grant number 172024. The project leading tothis application has received funding from the European Union's Horizon 2020 research andinnovation programme under grant agreement No 810752.