Free fat, surface fat and dairy powders: interactions between process and product. A review

Nowadays, fat-filled spray-dried dairy powders have acquired an economic importance. Increasing the fat content leads to further quality implications such as off-flavors, and poor rehydration and flowing properties. However, the control of the drying operation and of the powder properties is still rather empirical in this case and few studies have focused on the whole issue up to now. This review aims at giving an overview of research work on fat-filled powders. The so-called “free fat” is often related to fat-filled powders, but the review also highlights the relevance of “surface fat” to powder physical properties. Quantitative and qualitative analytical techniques, mainly referring to free fat, are described here. This review focuses on the specific and combined influence of composition constituents (fat, protein, lactose and mineral elements) and process steps (such as heat treatments, homogenization, drying and storage) on physical properties of fat-filled powders (oxidation, wettability, dispersibility, solubility and flowing properties).