# Effects of Organic Acid Coagulants on the Textural and Physical-Chemical Properties of Tofu
## 2 Materials and Methods
### Experimental Design  
The soybean milk was elaborated with some modifications according to the indications made in [15]. Firstly, 35 kg of soybean grains were soaked for 10 h. The swollen grains were drained and then hulled. Afterward, they were scaled at 90 \({}^{\circ}\)C for 10 min. The grains were drained and poured in an industrial blender (Metvisa LQL811, Bimg Brazil Machinery Industry for Gastronomy, Santa Catarina, Brazil) to be crushed using a 1:1 (_w/w_) ratio with water; the obtained mixture was filtered with an ultrafine 120-\(\upmu\)m nylon mesh sieve (Merck Millipore from Burlington, MA, USA), and the resulting soymilk was pasteurized at 100-110 \({}^{\circ}\)C during 10 min. Later, the coagulation process was carried out, where the treatments were applied according to Table 1: T1C5 = tofu coagulated with apple vinegar at a 5% concentration; T2C3 = tofu coagulated with rice vinegar at a 3% concentration; T3C3 = tofu coagulated with white vinegar at a 3% concentration; T4C5 = tofu coagulated with apple vinegar + rice vinegar at a 5% concentration; T5C5 = tofu coagulated with apple vinegar + white vinegar at a 5% concentration; T6C3 = tofu coagulated with rice vinegar + white vinegar at a 3% concentration. The analysis of the physical-chemical characteristics, the texture profile analysis, and the color analysis were performed on all of the treatments.  
The tofu was elaborated with soymilk (72 L) with 3.54% protein, which was taken to a temperature of 38 \({}^{\circ}\)C to be divided into 1-L samples, which were placed in transparent recipients; the coagulants were then added at concentrations of 1%, 3%, and 5%, taking readings of the coagulation times with the aid of a digital clock with chronometers (AL-613A, Takshun Electronic Co., Ltd., Puttian, China) until visible curd formation. After the curd was formed, perforated recipients eliminated the residual whey. The curd yield was expressed as g of the obtained tofu per 1 L of soymilk, which was later expressed as a percentage. The treatments that achieved a shorter clotting time had all of the analyses performed. The tofu varieties obtained per treatment were labeled as follows: T1, apple vinegar; T2, rice vinegar; T3, white vinegar; T4, apple vinegar + rice vinegar; T5, apple vinegar + white vinegar; T6, rice vinegar + white vinegar, accompanied by C1, C3, and C5, which corresponded to the used concentrations (1%, 3%, and 5%).  
\begin{table}
\begin{tabular}{c c c c} \hline
**Treatment/Vinegar** & **Denomination** & **Dose \%** & **Coagulation Time** \\
**and Combinations** & **(Nomenclature)** & **(Concentration)** & **Means** \\ \hline T1 & T1C1 & 1 & 6.5 \({}^{\text{a}}\)\(\pm\) 0.51 \\ T1 Apple & T1C3 & 3 & 3.99 \({}^{\text{c}}\)\(\pm\) 0.03 \\  & T1C5 & 5 & 2.85 \({}^{\text{d}}\)\(\pm\) 0.21 \\ T2C1 & 1 & 4.73 \({}^{\text{b}}\)\(\pm\) 0.31 \\ T2 Rice & T2C3 & 3 & 0.99 \({}^{\text{i}}\)\(\pm\) 0.33 \\ T2C5 & 5 & 1.43 \({}^{\text{g}}\)\(\pm\) 0.14 \\ T3C1 & 1 & 2.08 \({}^{\text{g}}\)\(\pm\) 0.17 \\ T3 White & T3C3 & 3 & 1.30 \({}^{\text{gh}}\)\(\pm\) 0.16 \\ T3C5 & 5 & 1.58 \({}^{\text{g}}\)\(\pm\) 0.11 \\ T4C1 & 1 & 3.78 \({}^{\text{c}}\)\(\pm\) 0.10 \\ T4 Apple + Rice & T4C3 & 3 & 1.63 \({}^{\text{fg}}\)\(\pm\) 0.13 \\ T4C5 & 5 & 1.55 \({}^{\text{fg}}\)\(\pm\) 0.07 \\ T5C1 & 1 & 1.65 \({}^{\text{fg}}\)\(\pm\) 0.08 \\ T5 Apple + White & T5C3 & 3 & 1.21 \({}^{\text{h}}\)\(\pm\) 0.13 \\ T5C5 & 5 & 0.89 \({}^{\text{i}}\)\(\pm\) 0.13 \\ T6C1 & 1 & 1.73 \({}^{\text{f}}\)\(\pm\) 0.11 \\ T6 Rice + White & T6C3 & 3 & 0.78 \({}^{\text{i}}\)\(\pm\)0.09 \\ T6C5 & 5 & 0.93 \({}^{\text{i}}\)\(\pm\) 0.08 \\ \hline \end{tabular} Note: \({}^{\text{a+}}\) means in the same column with different superscripts significantly differ (_p_ \(<\) 0.05).  
\end{table}
Table 1: Experimental design, mean values, and standard errors of the coagulation time.