Characterization of the polymorphism of milk fat within processed cheese products

- The polymorphism of milk fat within processed cheese products is presented.
- A higher ratio of β to βʹ polymorph is present in processed cheese than in bulk fat.
- X-ray diffraction can be used to determine the thermal stability of processed cheese.
- Polymorphism does not seem to affect the rheological properties of processed cheese.

Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to characterize the polymorphism of milk fat within commercial processed cheese products. Using anhydrous milk fat (AMF) as control, we show that the dispersion of milk fat as cream and the embedding of milk fat globules into the casein matrix results in the formation of a higher proportion of the β polymorph of milk fat. Furthermore, the effects of other cheese ingredients on the polymorphic stability of milk fat were determined. By storing and determining the polymorphism of the cheese samples at the final melting temperature of AMF, we found similar amorphous XRD diffraction patterns which confirmed that the characteristic diffraction peaks observed at refrigeration temperatures are from milk fat crystals. Upon fast cooling of molten cheese sample, milk fat crystallized into the βʹ polymorph. No correlations were found between the polymorphism of fat and small deformation dynamic shear rheological parameters of processed cheese products. Characterization of the polymorphism of milk fat within processed cheese provides better understanding of the crystallization behavior of fats as affected by the food matrix. Furthermore, the results of the study could provide insights into the functionality of milk fat within food at the nano- or molecular scale.

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