Changes in molecular size and shape of waxy maize starch during dextrinization

Area of Science:

• Food Chemistry
• Polymer Science
• Carbohydrate Chemistry

Background:

• Pyrodextrins are modified starches with diverse applications.
• Understanding their conformational properties is crucial for controlling functionality.
• Waxy maize starch offers unique properties due to its high amylopectin content.

Purpose of the Study:

• To investigate the conformational properties of pyrodextrins derived from waxy maize starch.
• To establish the relationships between molecular weight and intrinsic viscosity (Mark-Houwink equations).
• To determine how preparation conditions (pH, temperature, time) influence pyrodextrin conformation.

Main Methods:

• Preparation of pyrodextrins from waxy maize starch under varying pH (2, 3) and temperatures (150°C, 170°C).
• High-performance size exclusion chromatography (HPSEC) with multiple detectors.
• Determination of Mark-Houwink equations to characterize molecular conformation.

Main Results:

• Molecular size decreased with increased heating time.
• Preparation conditions significantly impacted molecular size and conformation.
• Pyrodextrins prepared at pH 3 and 170°C or 150°C showed a single compact spherical conformation (α = 0.27-0.31).
• Pyrodextrins prepared at pH 2 and 150°C exhibited a mixture of compact sphere (α = 0.26) and rigid coil (α = 0.89) conformations.

Conclusions:

• The conformational behavior of waxy maize starch pyrodextrins is highly dependent on dextrinization conditions.
• Specific pH and temperature combinations can yield pyrodextrins with distinct molecular architectures.
• These findings provide insights into controlling pyrodextrin structure for targeted applications.