Starch Properties of Roasting Rice from Naturally High-Resistant Starch Rice Varieties

Area of Science:

• Food Science and Technology
• Nutritional Biochemistry
• Agricultural Science

Background:

• Resistant starch (RS) offers health benefits but its application in food products can be limited by processing.
• Natural high-RS rice varieties possess potential for developing functional food ingredients.
• Roasting is a common food processing technique that can alter rice properties.

Purpose of the Study:

• To investigate the impact of moisture content during roasting on the characteristics of high-RS rice.
• To evaluate the effects of roasting on resistant starch content, physical properties, and in vitro starch digestibility.
• To explore the potential of processed high-RS rice for the food industry.

Main Methods:

• High-resistant starch (RS) rice varieties were subjected to roasting after controlled moisture addition (various levels).
• Analysis included resistant starch (RS) content, thermal stability, chain length distribution, volatile flavor compounds, and scanning electron microscopy.
• In vitro starch digestion assays were performed to determine starch hydrolysis index.

Main Results:

• Optimal moisture content (15% water) before roasting maximized RS content to 22.61%.
• Roasting significantly increased volatile flavor compounds and thermal stability while altering chain length distribution.
• High-RS roasted rice exhibited lower water absorption, expansion, and a significantly reduced in vitro starch digestion rate.

Conclusions:

• Roasting natural high-RS rice, particularly with optimized moisture control, enhances its resistant starch content and flavor profile.
• The process leads to improved thermal stability and reduced starch digestibility, indicating a lower starch hydrolysis index.
• This study supports the use of high-RS rice varieties (e.g., Youtangdao2 with SBEIIb gene mutation) in functional food development.