## 3 Results and Discussion
### Effect of Puree Addition on Gelation Temperature
#### 3.2.2 Soy Protein Isolate Solutions with Pumpkin Puree  
Figure 3A shows the gelation curves of the 4% soy protein isolate solution (SPI_4) with and without pumpkin puree. A composite solution of soy protein isolates at a concentration of 4% (SPI_4) with the addition of pumpkin puree is characterized by an initial decrease in the value of the viscosity modulus G\({}^{\prime\prime}\), which then stabilizes at the third minute of measurement and begins to increase at the 6 th minute. It was found that the composite solution of soy protein isolates at a concentration of 4% (SPI_4) with the addition of pumpkin puree was characterized by lower instability of measurements compared to the solution without the addition of pumpkin puree. It can also be seen that the measurements are most stable during the last 5 min of measurement at a constant temperature of 0 \({}^{\circ}\)C. When testing soy protein isolate solutions at a concentration of 4% (SPI_4), with and without the addition of pumpkin puree, no elastic modulus G\({}^{\prime}\) was observed, and the solutions did not form a gel.  
In the case of the 8% soy protein isolate solution (Figure 3B), it is also seen that the viscosity modulus G\({}^{\prime\prime}\) decreases at the start of the test, but the time over which the decrease in the G\({}^{\prime\prime}\) value is observed is much shorter for the soybean isolate solution 8% (SPI_8) soy protein isolate than 4% (SPI_4) soy protein solution. Similar to soy protein isolate solutions without puree, solutions with pumpkin puree have less measurement variation and are more stable as the concentration of soy protein isolate increases.  
When testing a solution of 12% soy protein isolate (SPI_12) with the addition of pumpkin puree (Figure 3C), the elastic modulus G\({}^{\prime}\) appears. However, the intersection of the modulus of elasticity G\({}^{\prime}\) and viscosity G\({}^{\prime\prime}\) is not possible because the values of both modulus increase linearly and the curves run parallel to each other, and additionally, reducing the temperature below 0 \({}^{\circ}\)C would result in freezing the solution.  
[PERSON] and [PERSON] [35] studied tomato juice prepared by heat treatment of tomatoes with the addition of 1% soy protein isolate. The test was carried out at 25 \({}^{\circ}\)C with a variable frequency of 0.1-10 Hz. In the case of a tomato juice solution with the addition of 1% soy protein isolate, they obtained results indicating that the tested solution showed the characteristics of a weak gel. It was suggested that such behaviour of the tested tomato juice solution with the addition of 1% soy protein isolate might result from the interaction of van der Waals forces, electrostatic interactions between solution molecules, or hydrogen bonds in the solution.  
[PERSON] et al. [36] studied the rheological properties of soy protein isolate solutions with the addition of CaSO\({}_{4}\) of different sizes of protein aggregates--small, medium, and large. Soy protein isolate solutions with three sizes of protein aggregates and concentrations of 60 mg/mL were heated from an initial temperature of 25 \({}^{\circ}\)C to 80 \({}^{\circ}\)C at a heating rate of 5 \({}^{\circ}\)C/min and held for 30 min, then cooled at a rate of 5 \({}^{\circ}\)C/min to 25 \({}^{\circ}\)C. The gelling of the soy protein isolate solution occurred already when the solution was heated to 80 \({}^{\circ}\)C. The gel formation temperatures depended on the size of the soy protein aggregates in the solution and were: 52.0 \({}^{\circ}\)C for the soy protein isolate solution with small protein aggregates, 43.1 \({}^{\circ}\)C for the solution with medium protein aggregates, and 36.5 \({}^{\circ}\)C for the solution with large protein aggregates. Gelation in the study by [PERSON] et al. [17; 37] of the solution was possible due to the presence of CaSO\({}_{4}\) in the soy protein isolate solution. In addition, due to the centrifugation of the samples to remove insoluble aggregates, the gelation curves had a more stable course.