Apparent thermal and UHT stability of native, homogenized and recombined creams with different average fat globule sizes.

Abstract

Milk fat globule size plays a significant role in stability, microstructure and nutritional functionalities of dairy-based products. Understanding of thermal stability of differentiated-size fat globules in dairy creams can provide intervention opportunities for improving functionalities and shelf-life of dairy-based products. This study focused on apparent thermal and UHT stability of native, homogenized (from native cream) and recombined creams (sodium caseinate-stabilized anhydrous milk fat) as a function of their fat globule sizes at 18 and 36% fat contents. Native creams were fractionated by the two-stage centrifugal method into five sizes (~1.45, ~2.45-3.65, ~3.85 and ~4.5 μm) whereas homogenized and recombined creams (~1.45, ~2.45, ~3.85 and ~4.5 μm) were obtained by microfluidisation. All cream samples were tested for thermal stability at 140 °C following a test similar to Heat Coagulation Time. Some selected creams were also studied for UHT stability at 140 °C for 4 s. Native creams exhibited diverse thermal stability depending upon fat content and size; however, native creams (~2.45-3.65 and ~4.5 μm) were UHT stable. Native creams of all sizes were also significantly more thermal stable than homogenized creams. Homogenized creams of all sizes at both fat contents showed poor apparent thermal and UHT stability. It appeared that small fat globules of native creams were more heat stable than larger fat globules at 18% fat content. Recombined creams made with sodium caseinate as emulsifier (without the presence of other milk components) were the most stable among all. However, dilution of recombined cream with skim milk or lactose significantly reduced their apparent thermal stability, but they were UHT stable.