## 2 Results and Discussion
### pH, TSS, TA, and TSS/TA Ratio  
Figure 4 shows the changes in the pH, TSS, TA, and TSS/TA ratio of the drinking jelly made with different concentrations of GF seaweed gelling agent. Overall, the pH values of the tested drinking jelly samples ranged from 3.4 to 4.0 (Figure 4A). [PERSON] et al. [32] reported that a pH below 5 is generally effective for preserving jellies as it inhibits the growth of common spoilage organisms. If the pH is increased, the chance of microbial growth will increase, resulting in a shorter shelf life of the drinking jelly. The S1 samples had the lowest pH value, while the S5 samples had the highest (\(p<0.05\)). The results showed that the pH values of the S1 and S2 samples were significantly lower than those of the S4 and S5 samples. Furthermore, the S3 samples exhibited intermediate pH values. This variation in pH levels indicates a range of acidity among the samples, with S1 being the most acidic and S5 being the least acidic. [PERSON] et al. [33] reported that an increased concentration of gelling agent from seaweed in drinking jelly increases the pH levels, leading to a less acidic environment in the jelly matrix. [PERSON] et al. [34] reported that gelling agents derived from seaweed are alkaline because they contain sulfate groups, which can ionize in solution. This ionization increases the pH and alters the charge interactions between the gelling agent molecules and water. The TSS values in the drinking jelly ranged from 12.5 to 15.1 (Figure 4B). The addition of the GF gelling agent in the drinking jelly significantly affected the TSS level (\(p<0.05\)). The S1 sample had the lowest TSS value, whereas the S5 sample had the highest. The S2-S4 samples showed a gradual increase in TSS levels as the GF concentration in the drinking jelly composition increased. However, the difference in the TSS increment between the S2 and S3 samples was minimal. [PERSON] et al. [33] and [PERSON] [35] reportedthat an increased concentration of seaweed-based gelling agent in the drinking jelly could influence the TSS levels by altering the water retention and solution distribution within the gel. Acidity plays a key role in determining the taste and stability of the jelly, as more acidic products tend to have a tangier taste and potentially longer shelf life [36]. The TA value of the drinking jelly samples is shown in Figure 4C. The TA values were consistent across all samples (\(p\geq 0.05\)), ensuring the jelly maintained a uniform acid level. Presumably, the TA values in the drinking jelly were primarily contributed by the strawberry concentrate, as strawberries contain a moderate level of organic acids, ranging from 0.8% to 2.0% [37]. The stable levels of TA are due to the unchanged proportion of strawberry concentrate in the drinking jelly compositions. Generally, the consistent TA values suggest that the differences in pH and TSS are not due to variations in citric acid content. The TSS/TA ratio is an important indicator and a critical parameter in jelly production, influencing the final product's taste and texture. The TSS/TA ratio ranged from approximately 13 to 16 (Figure 4D). Increasing the GF concentration in the drinking jelly composition effectively increased the TSS/TA ratio. The S1 samples exhibited the lowest TSS/TA ratio, while the S5 samples had the highest ratio. A higher TSS/TA ratio generally indicates a sweeter, more palatable product [38].  
Figure 3: Microscopical observation of drinking jelly made with strawberry fruit concentrate and different concentrations of GF gelling agent. Note: S1–S5 represent the drinking jelly samples prepared with varying concentrations of GF gelling agent: S1 (0.2%), S2 (0.4%), S3 (0.6%), S4 (0.8%), and S5 (1.0%).