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Abstract
This research has studied the effects of using different types of whey protein isolate (WPI) powders with different fat concentrations on the surface concentrations and morphology of spray-dried powders and on the yields of powders from spray drying. Three different whey protein isolate (WPI) sources with three different trademarks, giving powders with different protein levels and fats concentrations, have been investigated in the present work by XPS (X-ray photoelectron spectroscopy) and SEM (scanning electron microscopy). The results showed that the WPI powders (NHS and Dr. Earth) with a high percentage of fats (1.5% and 10%, respectively) showed the greatest fat surface coverage of spray-dried WPI powders (inlet temperature 190°C, outlet temperature 95°C), with relatively low yields, 66% and 58%, respectively. The trademark (Fitlife) with the smallest amount of fats (0.5%) showed the maximum yield of 80%, with the greatest protein coverage on the outer surface. Furthermore, the XPS analysis of the spray-dried powders (inlet temperature 190°C, outlet temperature 95°C) also showed the maximum atomic percentage 18.6% N (from proteins) on the surface, in the case of the Fitlife source, followed by 0.2% and 2.4% for the other trademarks (Dr. Earth and NHS, respectively). Higher drying outlet temperatures (95°C) increased the yields but gave lower protein surface coverages due to rapid skin formation in the particles.