# Effects of Organic Acid Coagulants on the Textural and Physical-Chemical Properties of Tofu
## 3 Results and Discussion
### Color Measurement  
The evaluated samples show significant differences in the luminosity and the evaluated chromaticity components (a* and b*), thus showing that the T6C3 treatment had a higher trend toward luminosity L*, for a brilliant tofu with a tendency toward white; the T1C5 treatment showed higher values in b*, for a tofu with a tendency toward yellow; the T3C3 treatment showed tendencies for L* and B*, where the tofu obtained showed a tendency toward white and yellow. Regarding the values obtained in a*, it is observed that the highest tendency was shown by the T5C5 treatment, for which this tofu tended toward green/red; nevertheless, its values in L* and b* increased, showing a tendency toward white and yellow, for which it can be mentioned that the tofu obtained in this treatment showed an opaque tonality. For such reasons, Table 4 shows that each one of the coagulants applied in obtaining the tofu interfered with the tonalities of the final product, but comprised the tonalities of tofu, which were from white to yellow. The color changes in the tofu were due to non-enzymatic browning, specifically the Maillard reaction [31]; thus, the color tendencies will depend on the variation in the soybean, germination time, and thermal treatment. Because of the presence of chlorophyll, all of the soybean varieties were green in the first maturity stages. As they matured, the chlorophyll was lost and flavonoid pigments appeared [32].  
The observed differences in the tofu color might result from variations in the soybean varieties and the specific processes used in the production. Previous studies have shown that different soybean varieties and processing conditions, such as heating and agitation, significantly affect the tofu color and texture [24].  
The type and concentration of coagulant, and the pH during coagulation, play crucial roles in determining the tofu color. Coagulants with different acidities and buffering capacities can cause variations in the final product's appearance. For instance, apple vinegar and rice vinegar have different pH levels and buffering capacities, which can influence the Maillard reaction and resulting color [33]. The Maillard reaction, responsible for browning, can vary based on the specific amino acids and sugars present in the soybeans, the processing temperature, and the duration of heating. Different coagulants might accelerate or decelerate this reaction, leading to color differences [31].  
Concerning the results obtained in the colorimetry by the CIEL*A*B scale, the tofu samples showed luminosity (L*) values from 88.55 to 91.63, with a tendency toward white, while, in the chromatic values of a* (tendencies from green to red), values from 0.09 to 1.23 were obtained, referring to the fact that certain tofu types can be white but with opaque tonalities. Regarding the chromatic values of b* (a tendency from blue to yellow), values from 13.56 to 14.85 were obtained, specifying that the obtained tofu samples showed the tendency toward yellow, for which it is mentioned that the tofu obtained in this research fulfills the indications made by other authors who mentioned that color is an indicator of tofu quality, showing variations from white to yellow that usually appear in cream-white blocks [33].