## 3 Results
### Organic Acids and Sugars
The predominant sugar in black current berries is fructose with a content of 25.667 mg/100 g, while in sea buckthorn berries, the predominant sugar is glucose with a content of 2.1533 mg/100 g.  
Similarly, to organic acids, depending on the increase in the freeze-drying time, a decrease in the carbohydrate content was also observed. In black current berries, the decrease in glucose and fructose depending on the freeze-drying time was about 17.1-17.8%, while the decrease in sucrose was 21-24%. For sea buckthorn berries, a slightly different picture was observed, the decrease in fructose and glucose at 18 h was 17% and 18%, while at 22 h sublimation, the decrease was 22% and 25%, respectively. Sucrose proved to be more sensitive to freeze-drying; at 18 h of sublimation, its content decreased by 11%, at 20 h by 23%, and at 22 h of sublimation by 55%. A similar downward trend in the content of all three carbohydrates during the drying of lemon juice was observed in the study of [PERSON] et. al. [65]. Pearson correlation analysis was used to investigate the correlation coefficients of the observed changes in different organic compound pairs during freeze-drying. The correlation coefficients are shown in Figure 3.  
Blue and red colors indicate stronger and weaker positive correlations. The analysis revealed no negative correlations among the pairs studied, suggesting that all changes in the quantities of organic compounds during freeze-drying occur in a similar manner. The correlation coefficients between pairs of organic compounds in sea buckthorn were 0.8500 or higher, while in black current, they were 0.8020 or higher. These correlation coefficients signify a significant relationship in the processes of organic compound changes during drying. Hence, the studies unveiled that the duration of freeze-drying for black currant and sea buckthorn berries directly influences the levels of organic acids and sugars, with a freeze-drying duration of 22 h being deemed undesirable. The Table 4 shows the effect of freeze-drying on the content of organic acids in black currant and sea buckthorn berries. The quantification of organic acids post freeze-drying revealed a differential stability across the compounds. Notably, Lactate and Malate demonstrated considerable resilience during the freeze-drying process. Lactate displayed a high re  
Figure 3: Pearson correlation analysis based on the content of vitamins, organic acids, and sugars in the samples during freeze-drying. Heat map of Pearson correlation analysis ((**a**)—black currant samples, (**b**)—sea buckthorn samples). 93.94% at 18 h, which gradually reduced to 88.73% at 20 h, and slightly further to 85.71% at 22 h. Malate followed a similar pattern with an initial recovery of 80% at 18 h, declining to 75% at 20 h and subsequently to 70% at 22 h.  
In contrast, Acetate and Pyruvate showed more substantial losses. The recovery of Acetate after 18 h was 80%, which diminished to 70% at 20 h, and further to 60% at 22 h. Pyrruvate experienced a pronounced decrease from 76% at 18 h to 62.57% at 20 h, and a sharp drop to 50% at 22 h.  
Propionate and Formate demonstrated intermediate stability. The recovery of Propionate was 76.67% at 18 h, decreasing to 60% at 20 h, and halving to 50% by the 22 h mark. Formate exhibited a somewhat gradual decline from 85% at 18 h to 80% at 20 h and 70% at 22 h.  
Of the more abundant organic acids, Oxalate exhibited moderate stability throughout the freeze-drying process. Oxalate maintained a recovery rate above 78% throughout the tested durations, with a marginal decrease from 80.05% at 18 h to 78.43% at 22 h.  
The observed decreases in the recovery percentages with the extended freeze-drying duration suggest that the process affects the stability of organic acids to varying degrees. Lactate and Malate proved to be the most stable, whereas Pyrruvate showed the highest sensitivity to the freeze-drying conditions.