# Analysis of Sushi Rice: Preparation Techniques, Physicochemical Properties and Quality Attributes
## 3 Results and Discussion  
### Initial Characterization of Sushi Rice  
The rice sample displayed a proximate composition to that declared by the manufacturer (Table 1). An analysis of rice samples from consecutive harvest seasons revealed significant variations in their initial compositional characteristics. The amylose content, a crucial parameter influencing sushi rice functionality and quality, exhibited marked differences between harvests. Samples from the 2020 harvest yielded an amylose content of 20.20 \(\pm\) 0.8%, whereas those from the 2019 harvest demonstrated a notably lower amylose content of 15.10 \(\pm\) 0.2%. This inter-annual variation in amylose content suggests potential influences of environmental factors or agricultural practices on rice starch composition [25]. Such differences in amylose-to-amyloectin ratio are known to have significant impact on the physicochemical properties, cooking behaviour, and textural attributes of rice [26]. In a study conducted by [PERSON] and [PERSON] [14], it was revealed that cooking and textural properties depend more on the cultivars' chemical composition than physical characteristics. They found that high-amylose rice cooks faster than low-amylose varieties. [PERSON] et al. [27] reported that amylose content in _Japonica_ rice contributes to heterogeneity and can reduce starch product quality by increasing gelatinisation temperature and promoting retrogradation. In Figure 1, the Brabender viscosity profiles are illustrated for two rice samples from different harvest years, alongside the applied temperature regime. The temperature profile, depicted by the purple curve, demonstrates the standardized heating and cooling cycles employed for both samples, ensuring comparable experimental conditions. The green curves represent the viscosity profiles of the rice starch suspensions during thermal processing. Sample A (20% amylose, 2020 harvest) exhibits a gradual viscosity increase with temperature elevation, reaching a peak (approximately 0.55 Pa*) at the point of starch gelatinisation. Subsequently, a decrease in viscosity (approximately 0.13 Pa*) is observed, indicative of starch granule disruption under prolonged thermal exposure. Upon cooling, a modest viscosity increase (approximately 1.35 Pa*) is noted. In contrast, Sample B (15% amylose, 2019 harvest) displays a higher peak viscosity (approximately 2.9 Pa*), followed by a more pronounced viscosity reduction (approximately 1.8 Pa*) post peak, suggesting enhanced granule breakdown. Both samples show viscosity increases during the cooling phase, with Sample B demonstrating a more significant rise (approximately 5.1 Pa*). The cooling phase for this sample is characterized by a more substantial viscosity increase, resulting in a higher terminal viscosity compared to Sample A. The observed variations in viscosity profiles can be attributed to the differential amylose content between the samples. The higher amylose content (20%) in the 2020 sample restricts granule swelling  
Figure 1: Gelatinisation profiles for rice harvested in 2019 (**A**) and 2020 (**B**). and promotes the formation of a more rigid gel structure upon cooling. Conversely, the lower amylose content (15%) in the 2019 sample facilitates extensive granule swelling, manifesting as higher peak viscosity and more significant breakdown during continued heating. The final viscosity disparities further reflect the influence of amylose-amyloiden ratios. The 2019 sample's higher terminal viscosity is consistent with its elevated amylopectin content, which forms a more viscous gel. In contrast, the 2020 sample shows a more stable viscosity profile during cooling, aligning with the characteristic behaviour of higher amylose content in forming a more rigid gel structure. A study conducted by [PERSON] et al. [28] examined changes in starch fine structure and physicochemical properties in japonica, indica, and indica-japonica hybrid rice varieties after one year of storage.