## 3 Results and Discussion
### Microbiological Properties of Kefir and Reconstituted Kefir Samples
The increased survival of kefir microflora exhibited by the samples prepared with kefir grains, during spray drying, when compared to the CONTROL prepared with commercial starter cultures, is attributed to the unique symbiotic relationship that characterizes the variety of microorganisms present in the grains. Co-cultures of lactic acid bacteria with  
Figure 5: Microbial population of lactococci (**a**) lactobacilli (**b**) and yeasts (**c**) of kefir (K) and reconstituted (RK) kefir samples 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. ycasts were shown to make microorganisms more resilient to environmental changes, performing more complex metabolic activities through the culture combination of various strains and affecting consequently exopolysaccharideacharide biosynthesis [19]. Therefore, in the case of kefir grains, where an abundance of microorganisms exists, the metabolites produced including kefiran, might result in an amplified protective effect during drying and thus improved microbial survival. The protective effect of kefiran toward the microorganisms present in kefir, induced by its enhanced production that is favored under the applied low-temperature storage with the grains, regardless of the final fermentation pH, might be responsible for the increased survival of kefir microorganisms. Under environmental stress conditions, lactic acid bacteria react by synthesizing exopolsaccharides to form a protective barrier around the cells. The synthesis of exopolsaccharides in lactic acid bacteria under stress conditions depends on the type of stress and the bacterial species [19]. The results of the present study indicated that the survival of lactococci and lactobacilli was better when the fermentation ended at higher pH values (5.2). This might be attributed to the more favorable conditions occurring, due to the higher pH, before spray drying. The pH of the medium influences cell viability during drying [30] and according to the results of the presented study, this is further supported. In the case of stopping the fermentation at a pH of 5.2, low-temperature storage would result in increasing the population of lactobacilli in the fresh product without affecting negatively the population of lactococci and yeasts, which in turn results in the increased numbers of lactobacilli in the powder products. The improved survival of lactobacilli for sample 5.2-7 can be attributed to increased exopolsaccharide production during low-temperature storage. The optimum pH for exopolsaccharide biosynthesis was reported to vary depending on the lactic acid bacteria strain and the experimental conditions [18,19]. According to [PERSON] [37], the _L. plantarum_ T10 strain produced the highest exopolsaccharide concentrations at pH 5.5, which is almost similar to the present study. The effect of storage, for 15 and 45 days at ambient temperature, on the microbial populations of lactococci, lactobacilli, and yeasts in the kefir powder after its reconstitution is shown on Figure 6. According to the analysis, lactococci during storage were statistically affected by both final fermentation pH and low-temperature treatment. The low-temperature storage and the increased final fermentation pH exhibited the best results (Figure 6a). It is worth also mentioning is that the survival of lactococci observed was significantly higher, up to one logarithmic cycle, to the samples prepared with kefir grains when compared to the CONTROL. The population of lactobacilli (Figure 6b) was not significantly affected by storage time when an increased final fermentation pH was used (5.2).