## 4 Conclusions  
This study delved into both sensory evaluation and variations in the content of vitamins, organic acids, and sugars during the freeze-drying process of black currant and sea buckthorn berries, comparing them with fresh berries. The sensory evaluation yielded the determination of an optimal moisture content for black currant and sea buckthorn berries, which was achieved at 16.27% and 17.2%, respectively, under a shelf temperature of 50 \({}^{\circ}\)C and a sublimation time of 20 h.  
After comparing the freeze-dried berry samples to their fresh counterparts, it can be seen that those subjected to drying durations of 18 and 20 h exhibited minimal reductions in the content of vitamins, organic acids, and sugars. Extending the freeze-drying time to 22 h resulted in a significant decrease in the levels of both organic acids and sugars for black currant and sea buckthorn berries.  
Thus, based on the sensory evaluation data and analyses of the chemical composition of freeze-dried black currant and sea buckthorn berries, the optimal freeze-drying parameters were identified as a shelf temperature of 50 \({}^{\circ}\)C and a freeze-drying duration of 20 h. Further research may explore the kinetics of degradation for each acid to refine the understanding of their stability profiles during freeze-drying.  
Conceptualization, G.O.; methodology, S.K., D.T. and L.M.; software, Y.Y. and D.K.; validation, B.B.; formal analysis, Y.Y. and M.M.; investigation, S.K., D.T., I.T., L.M. and A.A.; resources, T.T.; data curation, D.K. and I.T.; writing--original draft preparation, S.K.; writing--review and editing, G.O.; visualization, A.A. and I.T.; supervision, G.O.; project administration, G.O.; funding acquisition, T.T. All authors have read and agreed to the published version of the manuscript.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Name**} & \multirow{2}{*}{**Fresh (per 100 g)**} & **18 h** & **20 h** & **20 h** & **20 h** & **Freeze-dried** & **22 h** & **22 h Recovery** \\  & & **(per 100 g)** & **(5x)** & **(per 100 g)** & **(\%)** & **(per 100 g)** & **(\%)** \\ \hline Lactate & 0.07 & 0.066 & 93.94 & 0.002 & 88.73 & 0.06 & 88.71 \\ Acetate & 0.05 & 0.04 & 80.00 & 0.005 & 70.00 & 0.03 & 60.00 \\ Proplicate & 0.03 & 0.023 & 76.67 & 0.018 & 60.00 & 0.015 & 50.00 \\ Formate & 0.34 & 0.289 & 85.00 & 0.272 & 80.00 & 0.238 & 70.00 \\ Pyruvate & 0.35 & 0.266 & 76.00 & 0.219 & 62.57 & 0.175 & 50.00 \\ Scotate & 0.10 & 0.085 & 85.00 & 0.08 & 80.00 & 0.075 & 75.00 \\ Malate & 0.25 & 0.20 & 80.00 & 0.1875 & 75.00 & 0.175 & 70.00 \\ Oxalate & 204.00 & 163.30 & 80.05 & 161.70 & 79.26 & 160.00 & 78.43 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Effect of freeze-drying on the content of organic acids in black currant and sea buckthorn berries, mg/100 g dry matter.  
**Funding:** This research was funded by the Ministry of Agriculture of the Republic of Kazakhstan, grant number BR10765062 \"Development of technology to ensure the safety of the quality of agricultural raw materials and processed products in order to reduce losses in various storage methods\".  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** All data generated or analyzed during this study are included in this published article.  
**Conflicts of Interest:** The authors declare no conflict of interest.