# Effects of Different Pretreatments on the GABA Content of
## 3 Results and Discussion
### Effect of HPP and Ultrasonic Treatment on GABA and Antioxidants of Germinated Brown Rice  
Table 4 shows the effect of various soaking solutions combined with HPP or ultrasonic treatment on the GABA content of germinated brown rice. GABA contents in the HPP group reached 83.10 mg/100 g after HPP treatment (100 MPa, holding 10 min) with 0.1% CaCl\({}_{2}\) soaking solution. Similarly, when treated with 0.1% Glu soaking solution, the GABA content was 64.29 mg/100 g. However, increasing the soaking solution concentration to 0.2% CaCl\({}_{2}\) and Glu, reduced the GABA content to around 62 mg/100 g. Therefore, 0.1% CaCl\({}_{2}\) combined with HPP processing was more effective in increasing GABA content. In the ultrasonic group, soaking with 0.1% CaCl\({}_{2}\) for 20 min resulted in a higher GABA content of 102.38 mg/100 g. In general, the ultrasonic group obtained higher GABA contents than the HPP group, and these two physical treatments after soaking various solutions enhanced GABA contents in germinated brown rice. [PERSON] et al. [14] integrated mechanisms of HPP to promote GABA, including (1) changing enzyme conformation; (2) promoting H\({}^{+}\) release in plants; (3) disrupting cell structure, accelerating mass transfer between substrate and cells, and promoting enzyme reactions; and (4) altering the structure of Ca\({}^{2+}\) channels, promoting calcium ion release [36]. [PERSON] et al. [35] investigated the effect of ultrasonic treatment combined with CaCl\({}_{2}\) soaking on brown rice to stimulate brown rice for the first 9 h before germination. Although 0.2% Glu contained more GABA content, there was no significant difference between them, and CaCl\({}_{2}\) is cheaper than that of L-Glu, making CaCl\({}_{2}\) a more cost-effective option for increasing GABA content. When comparing the equipment cost and convenient operation of HPP and ultrasonic treatments, ultrasonic treatment was significantly less expensive to operate [37]. Considering production costs, subsequent research recommended \begin{table}
\begin{tabular}{c c c c} \hline \hline \begin{tabular}{c} **Germination** \\ **Treatment** \\ \end{tabular} & \begin{tabular}{c} **Total Polyphenols** \\ **(mg Gallic Acid** \\ **Equivalent/g)** \\ \end{tabular} & \begin{tabular}{c} **Flavonoids** \\ **(ug Quercetin** \\ **Equivalent/g)** \\ \end{tabular} & \begin{tabular}{c} **Scavenging DPPH** \\ **Free Radicals (\%)** \\ \end{tabular} \\ \hline \begin{tabular}{c} Ungermination \\ Water \\ \end{tabular} & 0.91 \(\pm\) 0.01 \({}^{\text{ab}}\) & 3.68 \(\pm\) 0.00 \({}^{\text{a}}\) & 87.01 \(\pm\) 0.11 \({}^{\text{d}}\) \\ \
\begin{tabular}{c} 0.84 \(\pm\) 0.01 \({}^{\text{b}}\) \\ \end{tabular} & 4.41 \(\pm\) 0.00 \({}^{\text{a}}\) & 84.61 \(\pm\) 2.61 \({}^{\text{e}}\) \\ \hline \hline
\begin{tabular}{c} Soaking \\ 0.1\% CaCl\({}_{2}\) \\ \end{tabular} & 0.90 \(\pm\) 0.03 \({}^{\text{ab}}\) & 4.17 \(\pm\) 0.42 \({}^{\text{a}}\) & 89.98 \(\pm\) 0.24 \({}^{\text{abc}}\) \\ 0.1\% Glu & 0.85 \(\pm\) 0.02 \({}^{\text{b}}\) & 3.68 \(\pm\) 0.00 \({}^{\text{a}}\) & 89.39 \(\pm\) 0.17 \({}^{\text{bc}}\) \\ 0.2\% CaCl\({}_{2}\) & 0.90 \(\pm\) 0.07 \({}^{\text{ab}}\) & 4.17 \(\pm\) 0.85 \({}^{\text{a}}\) & 88.94 \(\pm\) 1.83 \({}^{\text{c}}\) \\ 0.2\% Glu & 0.93 \(\pm\) 0.01 \({}^{\text{a}}\) & 3.68 \(\pm\) 0.00 \({}^{\text{a}}\) & 88.69 \(\pm\) 0.25 \({}^{\text{cd}}\) \\ \hline \hline \multicolumn{2}{c}{Vitamin C} & 91.72 \(\pm\) 0.00 \({}^{\text{a}}\) \\ \multicolumn{2}{c}{BHA} & 91.06 \(\pm\) 0.00 \({}^{\text{ab}}\) \\ \hline \end{tabular} Data were expressed as mean and error bars of \(\pm\) S.D. (\(n\) = 3). Means with different superscript letters in the same column are significantly different (\(p<0.05\)). The concentrations of the sample, vitamin C, and BHA for the DPPH assay were 20 mg/mL.  
\end{table} 
Table 3: Analyses of antioxidant active components and DPPH free radical scavenging ability in germinated brown rice by various soaking solutions.