Casein-maltodextrin Conjugates as Emulsifiers for Preparation of Structured Calcium Carbonate Particles as Fat Globule Mimetics

Removing fat globules to produce reduced-fat dairy products faces several quality defects such as flavor, mouth feel, viscosity, and appearance. Conversely, dairy products are important sources of calcium, but the addition of ionic calcium can cause protein aggregation, especially during thermal pasteurization and sterilization of milk, that deteriorates quality and shelf-life. To solve these issues, the first objective of the present study was to fabricate a group of dispersible fat globule mimetics (FGMs) that have calcium carbonate particles (CCPs) as the core, coated with two sequential layers of anhydrous milk fat (AMF) and milk protein. The second objective was to study impacts of addition of spray-dried FGMs on fat content, color, turbidity, and viscosity of skim milk. To fabricate FGMs, CCPs were suspended at 20-33.3% w/w in melted AMF at 80 °C that was then emulsified at 5% w/v into a neutral aqueous phase with 5% w/v sodium caseinate (NaCas), 10% w/v casein–maltodextrin (MD) conjugates, or NaCas-MD mixture with 5% w/v each. Span^® 80 was used at different ratios to AMF to facilitate the encapsulation of CCPs. Smaller particles were observed when a higher amount of Span^® 80 was used, which was concluded to have resulted from the greater reduction in interfacial tensions. The particle dimension followed the increasing order of casein-MD conjugate < casein-MD mixture < NaCas treatments, resulting from balances of surface activity and viscosity. The conjugate treatment had better encapsulation performance after spray drying. In addition, spray-dried FGMs prepared from the conjugate had better stability than the other two emulsifiers after hydration in skim milk, with the absence of visible precipitation and only 30.5% increase in particle dimension after 10 day storage at 5 °C. The inclusion of spray-dried FGMs in skim milk increased the viscosity, redness and yellowness, and turbidity. Skim milk with 10% FGMs had a viscosity higher than and turbidity similar to full fat (3.8%) milk, while the overall fat content was only 2%. Therefore, casein-MD conjugates are appropriate emulsifiers to prepare dispersible FGMs that may be used to simultaneously improve sensory properties and increase calcium content of reduced-fat products.