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Structural changes in apple rings during convection air-drying with controlled temperature and humidity
Yan Bai1, M Shafiur Rahman, Conrad O Perera
1Horticulture and Food Research Institute of New Zealand, Private Bag 92 169, Auckland, New Zealand.
Journal of Agricultural and Food Chemistry
|May 16, 2002
Summary
Heat pump drying of apple slices causes cellular collapse and case hardening. Porosity increases with moisture loss, potentially leading to surface cracks at higher temperatures.
Area of Science:
- Food Science
- Materials Science
Background:
- Understanding the structural changes in dehydrated foods is crucial for quality assessment.
- Heat pump drying is an energy-efficient dehydration method with potential impacts on food microstructure.
Purpose of the Study:
- To investigate the structural evolution of heat pump dried apple slices.
- To correlate structural changes with drying parameters like temperature and moisture content.
Main Methods:
- Heat pump drying of apple slices at varying air temperatures.
- Measurement of porosity.
- Scanning electron microscopy (SEM) for cellular structure analysis.
Main Results:
- Porosity increased linearly with decreasing moisture content, eventually plateauing.
- Cellular collapse was observed in all dried samples.
- Case hardening occurred at 40-45°C and 60-65°C.
- Surface cracking was noted at the extreme temperature of 60-65°C.
Conclusions:
- Heat pump drying significantly alters apple slice microstructure.
- Temperature is a critical factor influencing case hardening and cracking.
- Optimizing drying conditions is necessary to mitigate undesirable structural changes.