Crystallisation behaviour of buffalo milk fat

Milk fat is one of the key natural fats. It is used widely in the food industry such as in butter, cheese, ice cream, whipped cream and confectionary products. The quality attributes of those products are greatly influenced by the crystallisation behaviour of milk fat.
Buffalo milk has gained increasing popularity for the last few decades and has become the second most consumed milk globally. Its high fat content (6-15%) is particularly suitable for fat-based food products with buffalo mozzarella being the most popular one. However, the crystallisation behaviour of buffalo milk fat, which may explain the unique characteristics of buffalo milk-based products, is poorly understood. Therefore, this thesis aims to evaluate the key compositional differences of buffalo milk fat, as compared to the globally leading cow milk fat, and examines the compositional effects on the crystallisation behaviour. Further, the role of different triacylglycerols (TAGs) in milk fat crystallisation is analysed in great detail using a new proposed method using a chemical grouping approach.
The TAGs composition of cow and buffalo milk fat was measured using liquid chromatography and mass spectrophotometry. Whereas, the crystallisation behaviour of milk fat was investigated using small and wide-angle X-ray scattering, differential scanning calorimetry and polarised light microscopy techniques.
The results show that buffalo milk fat has similar TAGs species, but in significantly different proportions as compared to cow milk fat. This leads to a different crystallisation behaviour, where buffalo milk fat showed a higher melting point, but with slower α to β’ polymorphic transformation kinetics. In-depth analysis of the crystallisation of pure asymmetrical TAGs, which are abundantly present in milk fat, revealed a possible crystallisation inhibiting mechanism, which slows the polymorphic transformation and most-likely is also responsible for the dominant β’-polymorph appearance in milk fat crystals.
A new approach in the analysis of the TAG’s role in milk fat classified the complex milk fat TAGs into four different groups based on their chemical properties. This way, a direct association of two main crystal structures in milk fat - the high melting double-layered and the low melting triple-layered crystals - with fully saturated TAGs and TAGs containing unsaturated fatty acid(s), respectively, was demonstrated. This approach can be universally applied to other complex mixture of TAGs, and will be useful for future crystallisation studies involving modified TAGs compositions.