Deep eutectic solvent-assisted starch acetylation within stale bread particles to improve water resistance

Area of Science:

• Food Chemistry
• Materials Science
• Biotechnology

Background:

• Deep eutectic solvents (DES) have shown promise as reaction promoters for starch modification.
• Previous studies focused on pure wheat starch acetylation using DES.

Purpose of the Study:

• To investigate the acetylation of macromolecules within bread particles using DES.
• To optimize reaction conditions (time, temperature, reagent ratios) for efficient starch modification in a complex matrix.

Main Methods:

• Acetylation of bread macromolecules using DES as a solvent and promoter.
• Quantification of acyl substitution degree (DS_acyl) via ¹H NMR, ¹³C NMR, and FTIR.
• Analysis of molecular weight changes (M_w) and side products using spectroscopy.
• Thermogravimetric analysis (TGA) coupled with FTIR to assess thermal properties and hydrophobicity.

Main Results:

• High DS_acyl (0.73-1.09) achieved rapidly (<36 min, <16 molar ratio).
• Minimal side-reaction products (carbamates, acetyl urea) detected.
• Starch degradation observed (M_w reduction), with partial wash-off of polysaccharides and increased gluten content.
• Enhanced hydrophobicity and glass transition temperature (T_g) correlated with DS_acyl.

Conclusions:

• DES are effective promoters for esterification reactions in complex starchy matrices like bread.
• DES-mediated acetylation offers a controlled method for modifying bread components, potentially improving material properties.
• The study highlights the potential of DES in food processing and material science applications.