Understanding surface free fat extraction of cheese powder: Solvent comparison and lipidomic characterization

Caking during production and transport is a challenge in dairy powders with high fat content. Powder cake formation mechanisms are linked to high levels of fat on the powder surface, termed surface free fat. Multiple factors influence the surface free fat content of cheese powders, such as fat content and additives. This study aimed to understand the surface free fat extraction of cheese powder by examining how different solvents and numbers of washings affect the removal of surface or inner free fat in powders. The lipid composition of the stepwise removed fat from cheese powder was further characterized using an untargeted lipidomic approach. The results showed that both heptane and petroleum ether could be used for free fat extraction. Depending on the type of cheese powder, 55–67% of the total fat content was identified as surface free fat, while 15–20% was characterized as inner free fat. Confocal laser scanning microscopy (CLSM) confirmed the removal of surface free fat, and inner free fat extraction reduced fat patches inside the particles. With lipidomics, it was possible to detect 92 triacylglycerols (TAG) and 14 diacylglycerols (DAG). No difference was observed in the lipid composition based on the solvent used to extract the fat or between surface free and inner free fat. However, the cheese powder type influences the lipid composition. In conclusion, four washes with either heptane or petroleum ether are sufficient to extract surface free fat from multiple cheese powder.