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Histological structures of cooked rice grain
Yukiharu Ogawa1, Gregory M Glenn, William J Orts
1USDA, ARS, Western Regional Research Center, 800 Buchanan Street, Albany, California 94710, USA.
Journal of Agricultural and Food Chemistry
|November 13, 2003
Summary
Comparing raw and cooked rice reveals cooking creates wider cracks, facilitating water entry and causing grain expansion through void formation. This study visualizes rice microstructure changes during cooking.
Area of Science:
- Food science
- Materials science
- Microscopy
Background:
- Understanding the physical and chemical changes in rice during cooking is crucial for food processing and quality control.
- Microstructural analysis provides insights into the mechanisms of water absorption and structural modification in grains.
Purpose of the Study:
- To compare the histological and morphological features of raw and cooked whole grain rice.
- To investigate the role of cracks and voids in water migration and grain expansion during cooking using advanced microscopy techniques.
Main Methods:
- Utilized fluorescence microscopy and scanning electron microscopy (SEM) to examine milled, medium grain California rice.
- Assessed differences between raw and cooked grains by analyzing cell wall autofluorescence and correlating it with SEM images.
Main Results:
- Raw rice grains exhibit fine cracks in the endosperm, while cooked grains show wider, more defined cracks.
- These cracks act as channels for water penetration, leading to unequal water distribution within the grain.
- High water penetration results in large, transversely oriented voids, which are the primary cause of grain expansion during cooking.
Conclusions:
- The microstructural changes, specifically the formation and expansion of voids, are key to understanding rice grain expansion during cooking.
- Autofluorescence and SEM provide complementary information for visualizing these cooking-induced transformations in rice microstructure.