Effects of exogenous proteins on retrogradation properties of rice starch, gel properties of raw rice flour and eating quality of fresh wet rice noodles.

INTRODUCTION

Starch retrogradation severely deteriorates texture and shelf life of fresh wet rice noodles, while the distinct regulatory mechanisms of wheat gluten (WG) and soy protein isolate (SPI) on rice starch gel structure and noodle quality remain insufficiently clarified.

METHODS

Indica rice flour was supplemented with 0-6% WG or SPI. Multi-scale characterizations including pasting, thermal, gel texture, water distribution, microstructure and starch lamellar structure and noodle cooking qualities were performed to compare their anti-retrogradation effects and fresh wet rice noodle quality characteristics.

RESULTS

Both WG and SPI inhibited gelatinization and retrogradation of rice starch, restricted water migration, restrained gel structural rearrangement and slowed the growth of gel hardness during storage. However, WG and SPI regulated noodle quality through different pathways. WG optimized noodle texture by consolidating gel networks, whereas SPI inhibited starch retrogradation and water movement to slow noodle hardening. SPI performed better in alleviating rice noodle stiffness, and samples containing 6% SPI presented a hardness increase rate as low as 1.44 g·d-1 after 14 days of storage. Within the WG addition range of 1-6%, increasing WG dosage elevated noodle hardness while reducing adhesiveness and cooking loss. Supplementation of SPI over 3% negatively affected noodle quality, which could be attributed to its strong inhibition against starch retrogradation.

DISCUSSION: This study systematically distinguishes the differential regulation modes of WG and SPI on multi-scale starch structural rearrangement and fresh wet rice noodle quality, offering theoretical support and technical reference for delaying rice noodle retrogradation and extending shelf life via exogenous protein fortification.