# Analysis of Sushi Rice: Preparation Techniques, Physicochemical Properties and Quality Attributes
## 3 Results and Discussion
### Investigating the Sushi Rice Production Process
#### 3.2.3 Nigiri Ball Weight at Different Temperatures  
The global popularity of sushi products, especially nigiri sushi, makes this research particularly timely and significant. Nigiri sushi quality depends critically on the characteristics of the sushi rice, which are influenced by multiple factors including preparation methods, washing, soaking, water-to-rice ratio, seasoning, and nigiri-forming temperature. Therefore, it is important to investigate the effect on various production processes and their parameters on the quality of the final product. Improper temperature and water-to-rice ratios adversely affect nigiri formation and quality. At temperatures above 38 \({}^{\circ}\)C, rice becomes overly soft and mushy, compromising its structural integrity. Conversely, temperatures below 30 \({}^{\circ}\)C reduce the rice's natural stickiness, hindering its ability to form cohesive shapes. Similarly, a high water-to-rice ratio (>1.8:1) results in overly soft rice with compromised grain integrity, producing dense and compact nigiri, while excess surface stickiness combined with internal mushiness negatively influences texture and presentation. A low water-to-rice ratio (<1.3:1) yields rice that is too firm and prone to crumbling, making moulding difficult. Maintaining optimal temperature and hydration levels ensures consistent, high-quality nigiri with desirable taste and texture. A soft texture in rice often means excessive moisture, causing the grains to stick excessively to hands or equipment and fall apart easily. A mushy texture suggests that the grains have lost their structure, becoming overly sticky and pasty, which can make the nigiri appear clumped and lacking in definition. In contrast, a firm texture means the grains retain their shape; however, if the rice is not sticky enough, it may not hold together well, making it difficult to form properly. Therefore, we carefully optimize both the rice temperature prior to forming and the water-to-rice ratio, as these factors greatly influence the texture and ultimately the quality of the nigiri. In Figure 4, it is illustrated how different temperatures affect the weight of nigiri when shaping cooked rice. There appears to be a slight increase in weight as temperature increases from 10 \({}^{\circ}\)C to 50 \({}^{\circ}\)C, followed by a small decrease at 60 \({}^{\circ}\)C. The error bars increase in size at higher temperatures, indicating greater variability in weight measurements at these temperatures. The total change in weight across the temperature range is relatively small, with the difference between the lowest and highest mean weights being approximately 11 g.  
During nigiri formation, the temperature of sushi rice plays a crucial role in determining how well it can be shaped and maintain its form. Temperature affects both the handling characteristics and final weight of the nigiri in distinct ways: when the rice is warmer (30-40 \({}^{\circ}\)C), it becomes more malleable and easier to shape. Under these conditions, less compression force is needed, typically resulting in a lighter final weight of nigiri pieces. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Amount (g/kg)** & **Seasoned Rice 1** & **Seasoned Rice 2** & **Seasoned Rice 3** & **Seasoned Rice 4** \\ \hline
120 & 4.28 \(\pm\) 0.01 & 4.22 \(\pm\) 0.01 & 4.18 \(\pm\) 0.01 & 4.46 \(\pm\) 0.10 \\
180 & 4.16 \(\pm\) 0.02 & 4.09 \(\pm\) 0.01 & 4.08 \(\pm\) 0.01 & 4.33 \(\pm\) 0.02 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: pH of rice with addition of various vinegar mixes. Conversely, when the rice is cooler (20-29 \({}^{\circ}\)C), it becomes firmer and more resistant to shaping. More pressure is required during formation to get the grains to stick together. The increased compression typically results in denser, slightly heavier nigiri. The relationship between temperature and weight is largely due to how much compression is required at different temperatures to achieve proper formation.