## 3 Results and Discussion
### Physicochemical Properties of Powder and Reconstituted Kefir Samples  
According to ANOVA, there is a significant effect (\(p<0.05\)) on moisture content among the samples. As can be seen in Figure 1, the kefir powder samples subjected to low-temperature storage (4.4-7 and 5.2-7) had the highest moisture content (\(p<0.05\)) and  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **Moisture (\%)** & **pH** \\ \hline CONTROL & 89.01 \(\pm\) 0.03 \({}^{\text{a}\ast}\) & 4.43 \(\pm\) 0.01 \({}^{\text{a}}\) \\
4.4-0 & 89.06 \(\pm\) 0.03 \({}^{\text{a}}\) & 4.44 \(\pm\) 0.01 \({}^{\text{a}}\) \\
4.4-7 & 89.08  
the kefir powder samples from kefir grains without storage (4.4-0 and 5.2-0) exhibited the lowest. The moisture content of powdered food products is crucial to determining their shelf life and ensuring microbial stability. Especially with regard to fatty milk powders, the requirement for the water content is below the limit of 5% \(w\)/\(w\)[16]. The CONTROL, 4.4-0, and 5.2-0 samples without low-temperature storage meet the aforementioned legal requirements for such products with regard to moisture. Conversely, the moisture content of the kefir powders produced following 7 day storage at 4 \({}^{\circ}\)C, 4.4-7 and 5.2-7, was 6.69% and 6.73%, respectively. Similar values, higher when compared to the limit of 5% (6.92-8.5 and 7.75%) [10; 16], or below 5% [12; 13; 15] were reported in the literature for kefir powders. Based on our understanding, the samples subjected to refrigeration temperatures for prolonged periods (4.4-7 and 5.2-7) display an increased moisture content that can be attributed to the enhanced hydrophilic interactions between protein molecules [31] and kefiran, which could result in the entrapment of more water molecules compared to the non-treated samples (CONTROL, 4.4-0, 5.2-0). Hydrophobic interactions of protein molecules, that are favored at high temperatures, weaken when subjected to refrigeration temperatures, resulting in the domination of the hydrophilic interactions (favored at low temperatures) that are increased in number and strength. The pH values of the reconstituted kefir samples exhibited statistically significant differences among them (\(p\) < 0.05). According to Figure 2, the samples subjected to low-temperature storage (4.4-7 and 5.2-7) displayed the lowest pH values, while the sample of the fermentation discontinued at pH 5.2 (5.2-0), without any prior drying storage, showed the highest, as was expected. The low and similar pH values of the two samples subjected to 7 day low-temperature storage were attributed to the slow, but existing, metabolic activity of the kefir microflora during refrigeration, which, although the initial pH values were different, when initially refrigerated and after 7 days, they ended up almost the same. Figure 1: Moisture content of kefir powders as affected by fermentation pH and low-temperature treatment (CONTROL: sample prepared with commercial starter culture, without storage prior to drying; 4.4-0 and 5.2-0: samples prepared with kefir grains to final fermentation pH of 4.4 and 5.2, respectively, without storage prior to drying; and 4.4-7 and 5.2-7: samples prepared with kefir grains to final fermentation pH of 4.4 and 5.2, respectively, subjected to storage at 4 \({}^{\circ}\)C for 7 days). Vertical bars with no overlaps differ significantly. Concerning the comparison between the fresh kefir (Table 1) and its respective reconstituted kefir powder (Figure 2), it seems that the original fresh product displayed the highest pH values. This could be attributed either to an alteration to the ionized groups in kefir or to an evaporation or dissociation of its organic acids that occurs during the high-temperature drying process. Since most consumers do not prefer products with a strong acidic taste, increasing the pH of the reconstituted kefir samples could lead to less acidic and more acceptable products.