ESR/spin probe study of ice cream

Area of Science:

• Food science and physical chemistry
• Application of spin probe techniques
• Material characterization of frozen foods

Background:

• Understanding the physical state of ice cream during freezing and melting is crucial for texture and quality.
• Traditional methods may not fully capture the dynamic changes in different phases.
• Spin probes offer a sensitive method to probe molecular dynamics in complex food systems.

Purpose of the Study:

• To investigate the physical transformations of the fat and aqueous phases of ice cream during thermal cycling.
• To determine the freezing and melting behavior of ice cream using electron spin resonance (ESR) spectroscopy.
• To characterize the molecular dynamics of ice cream's components using spin probes.

Main Methods:

• Utilized electron spin resonance (ESR) spectroscopy.
• Employed two spin probes: 1,1,3,3-tetramethylisoindolin-2-yl (TMIO) for the fat phase and sodium salt of 1,1,3,3-tetramethylisoindolin-2-yloxyl-5-sulfonate (NaTMIOS) for the aqueous phase.
• Measured rotational correlation times (tau(B)) to assess phase transitions and molecular mobility.

Main Results:

• The fat phase remained a mixture of solid and liquid until approximately -60°C.
• The aqueous phase transitioned completely from liquid to solid within 1°C of -18°C.
• Slow recovery of NaTMIOS rotational correlation times after thermal cycling indicated changes in the aqueous phase structure.

Conclusions:

• Spin probes provide valuable insights into the distinct freezing behaviors of the fat and aqueous phases in ice cream.
• The study quantifies phase transitions and molecular dynamics, contributing to a deeper understanding of ice cream microstructure.
• ESR spectroscopy with spin probes is a powerful tool for analyzing physical changes in frozen dairy products.