Enhancing fat globule homogenisation in raw milk for functional dairy applications

This study evaluated the optimization of homogenization parameters in raw bovine milk to achieve desirable milk fat globule (MFG) size characteristics for functional dairy applications, with a focus on kefir production. Three batches of raw milk were subjected to varying shear rates, temperatures, and processing durations. The effects on MFG size, pH, creaming index (CI), and total fat and protein contents were monitored over seven days. MFG size was measured by laser diffraction, pH with calibrated meters, CI by visual assessment, fat content via the Gerber method, and protein content by Kjeldahl analysis. Higher shear rates, particularly when combined with elevated temperatures, significantly reduced MFG size (minimum D [3,2] of 1.8 ± 0.01 µm at day seven) compared with unhomogenized controls (3.4 ± 0.01 µm). Smaller globules were associated with lower CI values, indicating enhanced emulsion stability, and supported a more controlled pH decline during storage. Total fat and protein contents were largely unaffected, although protein concentration positively correlated with both pH and globule size. Selected homogenized samples were subsequently inoculated with kefir grains to evaluate fermentation performance. These samples exhibited consistent acidification and stable pH progression, whereas unhomogenized milk showed less uniform fermentation. Overall, homogenization at higher shear rates and temperatures improved emulsion stability and facilitated uniform fermentation without compromising milk composition. These findings underscore the importance of controlling MFG size to enhance both functional and processing characteristics of milk for fermented dairy products.