## 3 Results and Discussion
### Components and Properties of Goat's Milk with Permeate after Enzymatic Conversion of Lactose
Inhibition of Galactooligosaccharide (GOS) Degradation in Heated Gout's Milk and Gout's Milk with Permeate  
The GOS content in goat's milk depended on the temperature and time of heating (Table 4). Temperatures of 72 \({}^{\circ}\)C and 85 \({}^{\circ}\)C had no effect on the GOS content in total sugars in goat's milk (\(p>0.05\)). A reduction in GOS content was observed at 92 \({}^{\circ}\)C after 60 min. After heating at 92 \({}^{\circ}\)C for 60 min, the proportion of GOS in total sugars decreased from 6.3% to 5.3% (\(p<0.05\)). Greater GOS stability was observed in goat's milk with permeate as compared to goat's milk alone. The GOS content remained consistent in the mixture before and after heating (6.9%; \(p>0.05\)). Hence, goat's milk with permeate in terms of the GOS content was stable for 60 min at 72, 85, and 92 \({}^{\circ}\)C.  
[PERSON] and [PERSON] [38] reported the heat stability of GOS in goat's milk. Their results showed that at 85 \({}^{\circ}\)C and 121 \({}^{\circ}\)C for 60 min, the GOS content remained stable throughout the heating and storage period. The GOS content in goat's milk heated at 85 \({}^{\circ}\)C for 0, 15, 30, 45, and 60 min was 13.2%, 13.4%, 13.6%, 13.2%, and 12.6% of total sugars, respectively, which confirmed that GOS in goat's milk was stable at high temperatures. In contrast, after heat treatment at 121 \({}^{\circ}\)C for 60 min, the GOS content was 13.3% of total sugars. Thus, no significant changes were observed compared to the initial GOS content (13.2% GOS). These results inspired us to conduct this research. However, our research is enriched with the results of GOS stability in goat's milk with permeate. [PERSON] et al. [15] studied the thermal stability and decomposition of samples of different carbohydrate families, such as fructol oligosaccharides, cyclodext, and resistant starches at 150 \({}^{\circ}\)C, 170 \({}^{\circ}\)C, 190 \({}^{\circ}\)C, 210 \({}^{\circ}\)C, and 220 \({}^{\circ}\)C for 10 min. They showed that most samples retained their composition and structure up to 170 \({}^{\circ}\)C, and degradation began to occur at 190 \({}^{\circ}\)C. Intense degradation occurred at 210 \({}^{\circ}\)C and 220 \({}^{\circ}\)C. The degradation processes mainly involved chain degradation and the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Temperature (\({}^{\circ}\)C)** & **Time (min)** & **M/GOS** & **M + P/GOS** \\ \hline
72 & 0 & 6.3 \(\pm\) 0.1 \({}^{\mathrm{aB}}\) & 6.9 \(\pm\) 0.1 \({}^{\mathrm{bA}}\) \\  & 30 & 6.3 \(\pm\) 0.2 \({}^{\mathrm{aB}}\) & 6.9 \(\pm\) 0.3 \({}^{\mathrm{bA}}\) \\  & 60 & 6.3 \(\pm\) 0.1 \({}^{\mathrm{aB}}\) & 6.9 \(\pm\) 0.1 \({}^{\mathrm{bA}}\) \\  & 30 & 6.3 \(\pm\) 0.1 \({}^{\mathrm{aB}}\) & 6.9 \(\pm\) 0.0 \({}^{\mathrm{bA}}\) \\  & 60 & 6.0 \(\pm\) 0.2 \({}^{\mathrm{aB}}\) & 6.9 \(\pm\) 0.2 \({}^{\mathrm{bA}}\) \\
92 & 0 & 6.3 \(\pm\) 0.1 \({}^{\mathrm{aB}}\) & 6.9 \(\pm\) 0.1 \({}^{\mathrm{bA}}\) \\  & 30 & 6.0 \(\pm\) 0.5 \({}^{\mathrm{aB}}\) & 6.9 \(\pm\) 0.2 \({}^{\mathrm{bA}}\) \\  & 60 & 5.3 \(\pm\) 0.2 \({}^{\mathrm{aA}}\) & 6.9 \(\pm\) 0.1 \({}^{\mathrm{bA}}\) \\ \hline \hline \end{tabular} M/GOS—goat’s milk after enzymatic conversion of lactose; M + P/GOS—goat’s milk with permeate after enzymatic conversion of lactose. Values represent mean \(\pm\) SD (\(n=7\)); SD—standard deviation; \({}^{\mathrm{aB}}\); \({}^{\mathrm{bA}}\), different lowercase letters in the superscript in a row and capital letters in a column for each parameter indicate statistically significant differences at the level \(\alpha=0.05\).  
\end{table} 
Table 4: Galactooligosaccharide (GOS) content in total sugars (%) in goat’s milk and goat’s milk with permeate after permeate after enzymatic conversion of lactose.