# Analysis of Sushi Rice: Preparation Techniques, Physicochemical Properties and Quality Attributes
## 3 Results and Discussion
### Investigating the Sushi Rice Production Process
#### 3.2.2 Seasoning  
The addition of vinegar mix serves several functions in the case of sushi rice. It is responsible for the specific sensory qualities of the product, giving it the proper taste and aroma. In addition, by lowering the pH of rice, it extends its shelf-life during storage. The addition of sugar and salt to the vinegar mix serves primarily to balance the acidity of the vinegar while enhancing the overall flavour of the rice [36]. Sucrose inhibits retrogradation at low concentrations (<40%), but at higher concentrations (>40%) it acts as a retrogradation promoter. Additionally, the co-crystallization of an NaCl solution with amylopectin leads to a change in the molecular structure of amylopectin, thus inhibiting retrogradation [6]. The findings obtained by [37] demonstrated that reducing the pH to 4 significantly slows down the process of retrogradation compared to higher pH levels. Also, [PERSON] et al. [38] reported that acidic conditions disrupt starch's crystalline structure and inhibit retrogradation, while alkaline environments (pH > 7) increase crystallinity. Similarly, [PERSON] et al. [39] confirmed that low pH (<4) inhibits starch retrogradation. This reduction in retrogradation preserves the desired softness and stickiness of the rice, essential for maintaining its textural qualities during storage. The addition of vinegar mix with a large amount of sucrose also increases the stickiness of the rice after it has been cooled and may inhibit the retrogradation process [40]. The addition of a properly configured vinegar mix is therefore a key parameter in obtaining rice of the right quality during storage. In addition, vinegar mix can be a good source of introducing thermolabile additive ingredients that cannot be used at the cooking stage.  
The pH of cooked rice, without the addition of vinegar mix, ranges from 7.1 to 7.3, depending on the amount of water added during cooking. The initial pH values of mix 1, mix 2, mix 3, and mix 4 are 2.43, 2.37, 2.31, and 2.61, respectively. The addition of vinegar mix lowered the pH to below 4.5 relatively quickly. A greater reduction in pH, however, requires a significant increase in the amount of vinegar mix or vinegar concentration in the mix. For example, the addition of more mix 3, with the highest amount of vinegar, lowered  
Figure 3: Rice weight gain after soaking in water at different temperatures. 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 pH to only 4.08, while the addition of the same amount of vinegar mix with a smaller amount of vinegar (mix 2) reduced the pH to 4.09 (Table 3). In the case of adding 180 g/kg of the seasoning, it was difficult to evenly distribute the mix in the product and leakage accumulated at the bottom of the container, regardless of mixing duration. This explains the small difference in pH between rice with mixes 2 and 3. Based on the sensory evaluation, mix 1 was selected as the optimal formulation for use in our subsequent experiments.