Comparison of textural properties and structure of gels prepared from cooked rice grain under different conditions.

Tomoko Sasaki,Hideo Maeda,Ken Tokuyasu,Junichi Sugiyama,Junko Matsuki,Akiko Shigemune,Koichi Yoza

doi:10.1002/fsn3.916

Abstract

The objective of this study was to investigate the effects of rice variety, water content, and preparation temperature on the textural properties of gels processed from cooked rice grains via high‐speed shear homogenization. Rice gels were prepared from seven high‐amylose rice varieties. The results demonstrated the significant differences in rice gel hardness and hardening rates during storage based on the rice variety used. The proportion of short chains of amylopectin was negatively correlated with the hardness of the rice gel. The sample temperature before shear treatment also influenced the rice gel hardness. Rice gels prepared from cooked rice maintained at 75°C prior to homogenization showed a higher breaking force than those from cooked rice at 25°C. Observation using scanning electron microscopy demonstrated the tendency of the cooked rice sample maintained at 75°C to form a finer gel network after homogenization than those at 25°C from the same rice variety.

Highlights

Gels derived from various cereals are prominent in solid foods
The softer texture of the cooked rice surface at 75°C may allow the grains to be homogenized more which may contribute to a finer gel network, resulting in the reinforcement and rigidity of the gel structure
A new material with an expected potential to modify the texture of rice products, were prepared from seven high-amylose rice varieties by homogenizing cooked rice grains

Summary

Introduction

Gels derived from various cereals are prominent in solid foods. The rheological properties of rice flour gel contribute to the texture and palatability of rice flour products such as noodles. Starch is the primary component of rice and an important ingredient in processed foods made from rice. Retrograded starch is common in the human diet, because it is formed by cooking or food processing. The physical properties of starch, such as gelatinization, retrogradation, and gelation, play an important role in determining the quality of rice products. The short-term development of retrogradation in starch gels is attributed to the gelation of the solubilized amylose fraction (Miles, Morris, & Ring, 1985), and the long-term changes in starch granules are attributed to the recrystallization of the amylopectin fraction (Abd Karim, Norziah, & Seow, 2000). The quality of rice noodles, one of the primary rice gel products, is greatly dependent on the amylose content of rice (Cham & Suwannaporn, 2010)

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