Unveiling lotus root processing under vacuum microwave: starch-malic acid interactions based on moisture, structure,...

Area of Science:

• Food Science
• Material Science
• Agricultural Science

Background:

• Lotus root (LR) is a valuable food source with complex carbohydrate structures.
• Understanding preconditioning effects on LR starch is crucial for food processing and functional ingredient development.
• Malic acid vacuum microwave preconditioning (MVMP) is an emerging technique with potential applications in food modification.

Purpose of the Study:

• To investigate the impact of malic acid vacuum microwave preconditioning (MVMP) on lotus root (LR) characteristics.
• To analyze changes in moisture content, dielectric properties, microstructure, and starch composition.
• To evaluate the effects on phenolic compounds, flavonoids, and resistant starch (RS) formation.

Main Methods:

• Evaluation of moisture content and dielectric properties (dielectric constant ε', dielectric loss factor ε″).
• Microstructural analysis using LF-NMR and FT-IR spectroscopy.
• Assessment of starch characteristics: crystallinity, resistant starch (RS) content, amylose content, solubility, swelling power, and thermal enthalpy.

Main Results:

• Dielectric properties correlated with moisture content and water migration influenced by microwave power.
• Increased microwave power and malic acid concentration caused starch granule damage and hydrolysis.
• MVMP treatment preserved higher levels of phenolic and flavonoid compounds.
• MVMP-treated LR starch showed increased crystallinity and a maximum resistant starch (RS) content of 68.3%.

Conclusions:

• MVMP effectively modifies lotus root (LR) starch structure, enhancing resistant starch (RS) content and crystallinity.
• The process preserves valuable phenolic and flavonoid compounds.
• MVMP offers a promising method for functionalizing lotus root (LR) starch for food applications.