Stability of whey protein nanofibrils at different pH

Protein nanofibers are obtained through heating the globular proteins above their denaturation temperatures at acidic pH. These structures have a length of about 1 μm and a diameter of about 1 to 10 nm and are very anisotropic. The main objective of this study was to produce nanofibrils from whey protein isolates, evaluate their appearance and functional properties in order to use them as ingredients in food. The protein nanofibrils were prepared at 90 °C at the concentration of 20 mg mL-1 then their appearance and functional properties were evaluated at pH 2, 4, and 6. The results obtained by atomic force microscopy showed that by increasing pH, the stability and the content of the produced nanofibrils decreased. Moreover, stable nanofibrils at higher pH values showed higher emulsion capacity and stability and higher solubility percentages. Also by increasing pH, samples opacity and turbidity and color parameters were increased. Nanofibrils also showed better functional properties compared to the control sample (P <0.05). In this way, protein nanofibrils can be commercially suggested as an additive to improve functional properties of food products. Desirable functional characteristics of WPI nanofibrils compared to the unprocessed native whey protein isolate, provides the possibility of their application to improve the qualitative properties of food products and as ingredients in foods for patients and elderly people and dietary and low-calorie foods.