Physicochemical characterization of soluble proteins of whole camel milk powders produced by spray drying treatment at high temperatures

Abstract

Objective. Camel milk is highly nutritious food with numerous health benefits proposed. Demand for 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 we characterized 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 six different inlet temperatures (190°C - 250°C) or by freeze drying. The soluble protein fractions upon the treatments were analysed by combination of electrophoretic and spectroscopic techniques. Functional properties, such as antioxidant activity and protein solubility were assessed. Results. SDS-PAGE revealed non-uniform increase in Mw of major protein bands, while native electrophoresis revealed non-uniform decrease in pI values with increased inlet temperature of spray drying. That indicated attachement of lactose moieties to NH2- group of proteins via non-enzymatic Maillard reaction. Spectrophotometric analysis showed formation of intermediate Maillard reaction products (increased absorbance at 294 nm) and no detectable late Maillard reaction products formation. Far-UV circular dichroism spectra showed no differences in secondary structures between freeze and spray dried samples. Antioxidant activity and protein solubility were increased with increase in inlet temperature. Conclusions. Our results showed that spray drying treatment promoted non-enzymatic glycation of camel milk proteins. Glycation of food proteins affects their technofunctional properties, shelf-life and nutritional value. Thus, optimization of spray drying parametars is essential for production of high quality camel milk powders. Acknowledgements: This research work was funded the Ministry of Education and Science of the Republic of Serbia, GA No. OI172024, Ghent University Global Campus, Belgian Special Research Fund BOF StG No. 01N01718, Serbian Academy of Sciences and Arts Project F-26. The project leading to this application has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 810752.