# Analysis of Sushi Rice: Preparation Techniques, Physicochemical Properties and Quality Attributes
## 3 Results and Discussion
### Shelf-Life Study of Cooked Sushi Rice  
#### 3.3.1 TPA  
In Table 4, data are provided on TPA parameters for different storage times. These parameters are influenced by the washing time which, in turn, affects the quality and characteristics of the samples. Hardness generally significantly increases (\(p<0.05\)) with storage time for all samples. For example, in W1, hardness increases from 59.44 N on day 1 to 132 N on day six. This indicates that over time, the samples become harder, which could be due to the re-crystallization of starch over time [19]. Shorter washing durations (W1) may leave more surface starch, initially contributing to higher cohesiveness and hardness, while prolonged washing (W2-W5) removes excess starch, resulting in softer textures. However, with extended washing (W6), the rice exhibits the highest initial hardness at 72.48 N, suggesting a complex relationship between washing duration and textural properties. Figure 4: Impact of temperature on nigiri weight and repeatability during formation. Values are presented as means with standard error bars. Bars labelled with the same superscript letters indicate no significant differences between treatments (\(p<0.05\)). The adhesiveness shows a marked decrease with increased storage time, although with minor fluctuations, as observed in sample W2. For example, in W4, it increases (\(p<0.05\)) from \(-645.32\) on day one to \(-21.06\) on day six. The observed decrease in adhesiveness value (less sticky) may be attributed to the progressive retrogradation of starch molecules, particularly the reassociation of amylose and amylopectin chains [41]. Springiness remains relatively constant but exhibits slight fluctuations (\(p<0.05\)). For example, in W2, it starts at 0.93 on day one, drops to 0.50 on day four, and then to 0.81 on day six. The stability of springiness suggests that the rice maintains its elastic properties even as other textural attributes change. This is crucial for the structural integrity of sushi rice, ensuring it can recover its shape after compression during handling or consumption. Cohesiveness does not change significantly across storage times, maintaining values within a small range. For W5, it stays around 0.56 to 0.52 (\(p<0.05\)) over the storage period. Cohesiveness, indicating the internal bonding strength of the rice grains, appears unaffected by washing duration or storage time. This stability ensures that the rice maintains its compact form, an essential characteristic for sushi preparation. Chewiness exhibits a general increase (\(p<0.05\)) with storage time, as evidenced in sample W3, for which values rise from 16.19 on day one to 46.73 on day six. This trend indicates progressive textural changes in the rice, likely due to starch retrogradation and molecular restructuring. The increased chewiness suggests that samples become firmer and require more masticatory effort over time, reflecting changes in the rice's textural properties during storage. Resilience remains relatively stable across the storage times, with slight fluctuations (\(p<0.05\)). For example, the resilience of W6 ranges from 0.18 to 0.24. The uniformity in resilience across treatments indicates that this property is not significantly influenced by washing duration or storage. As storage duration increases, the TPA parameters generally indicate that the samples become harder, adhesive, and chewier. This is a typical behaviour for products that lose moisture and become denser over time [42]. The washing time, although not explicitly stated, can be inferred to have a role in the initial texture of the rice [43]. If washing time affects the removal of certain components, it could influence the initial hardness and adhesiveness [11]. However, the data suggests that storage time has a more pronounced effect on the TPA parameters than the initial washing duration. The trends are consistent across all samples, suggesting that the washing processes affecting texture are similar across different sample groups.