Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to observe the microstructure of rice grains and rice grains with similar amylose content but large differences in protein content, and study the relationship between protein and cooking and eating quality. The results show that: through sensory evaluation and rapid viscosity analysis (RVA) characteristic spectrum measurement, it was determined that the eating quality of Koshihikari, m90, and m119 gradually decreases with the increase in protein content; SEM and CLSM observed brown rice cross-sections, and m119 with high protein content A large number of protein bodies surround the composite starch grains in an approximate honeycomb shape; CLSM observes the broken cross-sections of water-soaked grains. The roughness of the broken cross-sections of varieties with different protein contents is also different. The higher the protein content, the rougher the broken cross-sections, that is, absorption The low water content reflects the influence of protein on rice’s water absorption; SEM and CLSM observed the microstructure of rice and found that a large number of protein bodies in the high-protein variety m119 are surrounded by complex starch granules, which limits the water absorption and gelatinization of starch, resulting in cooking taste. Reduction in quality

Introduction to the Study on Protein Content and Rice Quality

The intricate relationship between protein content and the cooking and eating quality of rice grains has been a subject of considerable interest within the food science domain. A recent study employing Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) techniques offers new insights into the microstructural differences in rice grains, particularly focusing on those with similar amylose content but varied protein levels. This research not only elucidates the impact of protein content on rice’s sensory attributes and cooking quality but also advances our understanding of how protein interacts with starch within the grain’s architecture.

Methodology: Analyzing Rice Grain Microstructure with SEM and CLSM

The study meticulously examined the microstructure of different rice grain varieties, namely Koshihikari, m90, and m119, through SEM and CLSM. These varieties were selected based on their amylose content being similar, yet showcasing substantial differences in their protein levels. The primary objective was to discern how these protein variations influence the rice’s overall cooking and eating quality.

Observations: Protein’s Influence on Starch Granules and Water Absorption

Observations from SEM and CLSM revealed distinct microstructural characteristics among the varieties. Notably, in the high-protein variety m119, a significant number of protein bodies were found surrounding the starch granules, forming an arrangement reminiscent of a honeycomb. This unique formation was speculated to hinder the water absorption capacity of the starch granules, thereby impacting the gelatinization process—a critical factor in determining the cooked rice’s texture and overall eating quality.

Sensory and RVA Analysis: Linking Protein Content to Eating Quality

The research further utilized sensory evaluation techniques alongside Rapid Viscosity Analysis (RVA) to quantitatively assess the eating quality of the rice varieties in question. The findings from these analyses were telling; as the protein content increased from Koshihikari to m90, and then to m119, there was a noticeable decline in the rice’s eating quality. This decline was attributed to the protein’s interference with water absorption, as evidenced by the rougher texture of the broken cross-sections of water-soaked grains observed under CLSM in varieties with higher protein content.

Insights from Microscopic Observations on Rice Grain Texture

Moreover, the study’s use of SEM and CLSM to examine the brown rice cross-sections and the broken cross-sections of water-soaked grains provided unprecedented insights into the micro-level interactions between protein bodies and starch granules. The roughness of the broken cross-sections, varying with the protein content, served as a proxy for assessing the grains’ water absorption capabilities. The higher the protein content, the rougher the texture, indicating a lower water absorption capacity. This phenomenon underscores the crucial role of protein in influencing the physical properties of rice grains, which in turn affects their cooking behavior and sensory attributes.

Conclusion: The Impact of Protein on Rice Breeding and Culinary Quality

In conclusion, the study leverages advanced microscopic techniques to unravel the complex relationship between protein content and rice quality. The findings underscore the importance of considering protein content as a key factor in breeding and selecting rice varieties for specific culinary purposes. By providing a deeper understanding of the microstructural effects of protein on rice grains, this research paves the way for optimizing rice breeding strategies to enhance both cooking and eating quality, catering to diverse consumer preferences and culinary traditions.

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Original research was done by Ding Yi, Hua Zetian, Wang Lei, Wang Fang, Cai Zhuo, Guo Danxiao

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