# Gelatinization and Pasting Property of Small Granular Starch from Chlamydomonas reinhardtii and Its Structural Basis

## TL;DR

This study explores the unique gelatinization and pasting properties of starch from the microalga Chlamydomonas reinhardtii, revealing its potential as a sustainable food ingredient.

## Contribution

The study reveals the unique structural and functional properties of Chlamydomonas reinhardtii starch, including its high branching and thermostability.

## Key findings

- CRS has a high degree of branching (18.6%) and thin crystalline lamellae (9.29 nm).
- CRS exhibits low viscosity and high shear resistance during pasting.
- Cooked CRS has lower hydrolysis and higher resistant starch content than terrestrial starches.

## Abstract

The gelatinization and pasting behavior of starch play a critical role in governing its suitability for various food and non-food applications. Although Chlamydomonas reinhardtii is the most-studied microalga, its starch gelatinization and pasting properties have remained elusive. In this study, we applied nitrogen limitation to promote the starch accumulation of C. reinhardtii and recovered the starch using high-pressure homogenization. The multiscale structure and properties of C. reinhardtii starch (CRS) were comprehensively analyzed and compared with those of commonly used terrestrial plant starch. Results showed that CRS possesses a unique multiscale structure characterized by an exceptionally high degree of branching (18.6%) and a thinner crystalline lamellae (9.29 nm). While maintaining an A-type crystalline pattern, CRS granules exhibited higher crystallinity compared with other microalgal starches. CRS had an irregular red blood cell-like morphology with a small size (~1 μm diameter). Physicochemical analysis revealed that CRS has an intermediate gelatinization temperature and a pasting profile defined by low viscosity and remarkable shear resistance, suggesting high stability during hydrothermal processing. Significantly, cooked CRS demonstrated a lower hydrolysis rate and higher resistant starch content than several common terrestrial starches. It is attributed to its higher degree of branching and superior thermostability. This study extends the fundamental knowledge of CRS and provides a critical scientific basis for its application as a novel, sustainable ingredient with special gel properties in the future food industry.