A PHYSICO-CHEMICAL STUDY OF THE MECHANICAL PROPERTIES OF LOW AND INTERMEDIATE MOISTURE FOODS

Area of Science:

• Food Science
• Materials Science
• Thermodynamics

Background:

• Precooked, freeze-dried beef is a common food product.
• Understanding its textural properties is crucial for quality assessment.
• Moisture content significantly impacts food texture.

Purpose of the Study:

• To investigate the textural properties of freeze-dried beef.
• To correlate textural changes with water activity (A_w).
• To interpret these changes using thermodynamic principles.

Main Methods:

• Cutting-extrusion tests (Allo Kramer Shear Press) for force measurements.
• Compression tests (Instron Universal Testing Apparatus) for seven textural properties.
• Analysis across the complete range of water activity (A_w).

Main Results:

• A maximum force was observed in cutting-extrusion tests around A_w = 0.85.
• Significant textural property changes occurred between A_w = 0.15-0.30 during compression.
• These mechanical changes correlated with alterations in thermodynamic functions, such as standard differential entropy.

Conclusions:

• Textural properties of freeze-dried beef are highly dependent on water activity.
• Observed textural changes can be explained by increased crystallinity and swelling of the food structure.
• Integrating mechanical testing with thermodynamic analysis provides insight into food material behavior.