Thermal and Structural Behavior of Milk Fat

Area of Science:

• Food science and technology
• Materials science
• Physical chemistry

Background:

• Milk fat crystallization is crucial for dairy product texture and stability.
• Understanding the polymorphic forms of triacylglycerols (TGs) is key to controlling milk fat properties.

Purpose of the Study:

• To investigate the crystalline structures formed during slow cooling of milk fat globules in cream.
• To analyze the melting behavior of these crystals using X-ray diffraction and differential scanning calorimetry.
• To compare milk fat crystallization in an emulsion versus bulk form.

Main Methods:

• X-ray diffraction as a function of temperature (XRDT) was used to identify crystalline structures.
• Differential scanning calorimetry (DSC) was employed to analyze thermal transitions.
• Slow cooling (0.15 °C/min) and heating (2 °C/min) protocols were applied to cream samples.

Main Results:

• During cooling, specific double-chain-length (2L) and triple-chain-length (3L) organizations of TGs formed.
• Alpha and alpha+beta' polymorphic forms were observed during cooling.
• The 40-Å crystalline structure exhibited growth during the melting of other species.
• Crystallization patterns differed between milk fat in emulsion (cream) and anhydrous (bulk) forms.

Conclusions:

• Milk fat crystallization in cream involves distinct TG organizations and polymorphic transitions.
• The melting behavior is complex, with some structures growing as others melt.
• Emulsion state significantly influences milk fat crystallization compared to bulk fat.