A Comparative Quality Evaluation of Whey Powder Using Spray and Freeze Drying Methods

Background: Whey powder production from whey, a dairy by-product, remains a significant challenge. This study aimed to evaluate how spray drying and freeze drying methods influence the quality of whey powder by comparing their physical, chemical, and functional characteristics. Methods: Six whey samples were collected from a local manufacturer in September 2024 with three processed by spray drying and three by freeze drying. Spray drying was performed at an inlet temperature of 160 °C and freeze drying at -41 to -65 °C under vacuum pressure (0.05 mbar), both with 5% maltodextrin added. The powders were analyzed for physical (color, solubility, hygroscopicity, and wettability), chemical (moisture content, protein content, and titratable acidity), and functional (bulk density, tapped density, Carr’s index, Hausner ratio, foaming capacity, and foaming stability) properties following AOAC and standard methods. Statistical analysis employed one-way ANOVA and Duncan's Multiple Range Test using SPSS (version 22.0, SPSS Inc., Chicago, IL) at a 5% significance level (p<0.05). Results: Spray dried powder had significantly lower moisture (3.26%) and higher titratable acidity than freeze dried powder (p<0.05); nevertheless, there was no apparent difference in the protein content (20-21.01%). Spray dried powder appeared lighter and less greenish in color, whereas freeze dried powder exhibited more yellowish and greenish tones. Solubility (98.76-98.87%) and hygroscopicity (49.06-49.26%) were not significantly different. However, spray dried powder showed lower wettability (154 s). No significant differences were observed in bulk and tapped densities. Flowability was poor in spray dried powder and very poor in freeze dried powder. Freeze dried powder showed significantly higher foaming capacity and stability (p<0.05). Conclusion: Both drying techniques are suitable for large-scale production, depending on their specific uses within the food and pharmaceutical sectors. However, considering factors such as stability, flowability, and economic viability, spray dried powder demonstrated higher efficacy than freeze dried powder.