Starch-protein interplay varies the multi-scale structures of starch undergoing thermal processing

Area of Science:

• Food Science
• Materials Science
• Biochemistry

Background:

• Starch pasting is crucial in food processing, influenced by various factors.
• Understanding starch-protein interactions is key to controlling food texture and structure.
• Previous research has explored starch modification but detailed multi-scale structural impacts of specific proteins are less understood.

Purpose of the Study:

• To investigate the effects of different proteins on the multi-scale structure of indica rice starch (IRS) during thermal processing (pasting).
• To elucidate the molecular interactions between IRS and whey protein isolate (WPI), soy protein isolate (SPI), and casein (CS).
• To correlate rheological changes with structural modifications at nanoscale and microscale levels.

Main Methods:

• Rheological analysis (viscosity, pasting profiles) using Rapid Visco-Analyser (RVA).
• Investigation of molecular interactions (hydrophobic, hydrogen bonding, electrostatic) between starch and proteins.
• Microscopy and other techniques to assess multi-scale structural changes (short/long-range order, nanoscale morphology, gel network formation).

Main Results:

• IRS-WPI and IRS-CS interactions were primarily hydrophobic; IRS-SPI involved hydrophobic, hydrogen bonding, and electrostatic interactions.
• Globular proteins (WPI, SPI) accelerated starch swelling and reduced paste stability (higher breakdown and setback).
• Starch-casein interactions showed opposing effects on pasting properties. Protein interactions altered starch chain reassembly, leading to reduced short/long-range order, larger nanoscale clusters, and modified microscale gel networks.

Conclusions:

• Starch-protein interactions profoundly influence starch pasting behavior and multi-scale structural organization.
• The type of protein dictates the nature of interaction and the resulting structural modifications.
• Findings provide insights into controlling starch-based food structures through protein addition.