Buttermilk and Whey Powders: Microstructural Characteristics and Functional Properties
This study characterizes the microstructural and functional properties of various dairy powders, revealing that rennet whey powder exhibits the poorest flowability and highest fractal dimension while skim milk powder shows the best wettability, demonstrating that image analysis combined with fractal dimension calculations is a valuable tool for evaluating powder microstructures to guide product formulation.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the modern food industry, turning liquid milk into a stable, transportable powder is a feat of engineering that has reshaped how we eat. By removing water through a process called spray drying, manufacturers create products that can sit on shelves for months without spoiling, bypassing the need for refrigeration during long journeys. However, not all milk powders are created equal. The raw material used—whether it is skim milk, the liquid byproduct of cheese making, or the residue left after butter is churned—determines the final powder's behavior. These powders must do more than just sit in a bag; they must dissolve quickly in water, flow smoothly through machinery, and sometimes even create foam. Understanding the tiny physical details of these particles is crucial for food scientists who need to select the right powder for specific products, from ice cream mixes to protein supplements.
A team of researchers from the University of Warmia and Mazury in Olsztyn, Poland, set out to examine the hidden physical world of four different dairy powders: skim milk powder, acid whey powder, rennet whey powder, and buttermilk powder. Their goal was to see how the microscopic shape and size of the particles influenced how the powders behaved in the real world. They looked at everything from how heavy the powder was for its size to how easily it dissolved and how well it could form bubbles when whipped. To get a clear picture of the particles, the scientists used a powerful microscope to take high-resolution images, then analyzed the outlines of hundreds of individual particles to measure their irregularity. They found that the most complex, jagged shapes belonged to the rennet whey powder, which had the most intricate surface contours. In contrast, the skim milk powder particles were smoother and more uniform, while the acid whey and buttermilk powders tended to clump together in larger, wrinkled agglomerates.
The study revealed that these microscopic differences had a direct and measurable impact on how the powders functioned. The rennet whey powder, with its highly irregular and complex surface, turned out to be the most soluble, dissolving more completely than the others, as indicated by the lowest insolubility index. However, this same complexity made the rennet whey powder difficult to handle in bulk; it was the most cohesive, meaning the particles stuck together tightly, resulting in the poorest flowability. It was also the densest when packed down. On the other end of the spectrum, the skim milk powder flowed very easily and demonstrated the best wettability, taking only 12.5 seconds to wet completely, whereas the rennet whey and buttermilk powders took more than 180 seconds to even begin absorbing water.
The researchers also tested how well these powders could create and hold foam, a property vital for products like ice cream and whipped toppings. Here, the composition of the powder played a major role. The buttermilk powder produced the largest volume of foam when whipped, creating a capacity of 181 percent, yet the foam it created was less stable over time. The skim milk powder, despite producing a smaller initial volume of foam, created the most stable bubbles that held their shape for the full 30-minute observation period. The rennet whey powder failed to hold any foam at all, collapsing completely within the half-hour window. These results highlight a clear trade-off: the powder that made the biggest bubbles was not the one that kept them stable, and the powder that dissolved the most completely was not the one that flowed the best.
Ultimately, the study demonstrates that the functional performance of a dairy powder is not just about its chemical ingredients but is deeply rooted in its physical structure. The researchers found that using image analysis to measure the complexity of particle shapes provided a useful way to predict how a powder would behave. By linking the jaggedness of a particle's edge to its ability to dissolve or flow, food manufacturers can make more informed choices about which powder to use for a specific application. The work suggests that if a product requires rapid dissolution, a powder with a more complex surface might be ideal, while a product needing smooth flow through a machine would benefit from a powder with a simpler, more uniform shape. This connection between the tiny, invisible geometry of a particle and the large-scale behavior of the final product offers a practical tool for improving the quality of dairy-based foods.
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