## 3 Results and Discussion
### Titratable Acidity, Synereis and Water Holding Capacity (WHC) Measurements  
Lactic acid is the main component of yogurt that imparts a characteristic flavor and is produced by the action of the starter bacteria during the formation of the casein network and storage of yogurt at low temperatures [31; 32]. In this research, titratable acidity (TA) of yogurt samples enriched with extracts of LSB 0%, 0.5%, 1%, 2%, and 3% \(w/w\) is expressed in mg/L of lactic acid and presented in Figure 1. All samples had a similar TA, for example, the yogurt with 0% \(w/w\) LBS had 1.00 \(\pm\) 0.03%, that with 1% \(w/w\) LBS had 1.01 \(\pm\) 0.02%, and that with 3% \(w/w\) LSB had 1.01 \(\pm\) 0.04% and no significant differences were found between the samples (\(p\) > 0.05) So, the extracts of LSB did not influence lactic acid production.  
This is in contrast with other research where the enrichment of yogurt with aqua guarana extracts showed a differentiation of TA values of the lowest concentration of guarana extract compared to the rest of the samples [16] and for yogurt with flaxseed powder and pineapple peel powder [33; 34]. On the other hand, our results agree with the TA values of yogurt with 0.5% \(w/w\) SB in the form of mousse which had no significant differences with the control sample [35].  
Synereis and WHC in a milk protein network are critical quality parameters that could affect the physicochemical stability of the set-type yogurt. The liquid phase of serum could not be kept from the yogurt gel network and thus separation of whey proteins takes place giving a negative appearance in the final yogurt product. In this research, both syneresis and WHC were measured and the effects of the extracts of LSB are presented in Figure 2. The highest value of syneresis was found for the sample with 0% \(w/w\) LSB and the lowest for the sample of yogurt enriched with 3% \(w/w\) extract of LSB with values of 65.03 \(\pm\) 1.89% and 51.83 \(\pm\) 1.80%, respectively. The opposite was found for WHC, and specifically the yogurt without LSB had the smallest value and the yogurt with 3% \(w/w\) extracts of LSB showed the highest WHC compared to the rest of the samples, 29.25 \(\pm\) 1.25% and 36.00 \(\pm\) 0.09%, respectively.  
Figure 1: Titratable acidity (%) of set-type yogurts containing 0, 0.5, 1, 2, and 3% \(w/w\) extracts of lyophilized sea buckthorn. Different letters within the columns indicate significant differences (\(p\) < 0.05) among the different treatments. All measurements were conducted in triplicate.  
Our results showed that when the extract concentration of LSB increases, the water retention also increases and the yogurt gel network exhibits greater stability concerning serum elimination. Probably the polysaccharides that are present in extracts of LSB stabilize the casein network. Also, the sort fermentation time is a factor that increases syneresis. In this study, the addition of extracts of LSB drives the formation of molecular structures that retain moisture more effectively compared to the control yogurt [20]. Our results differ from our previous research which showed that guarana aqua extracts added to yogurt samples increase syneresis and decrease WHC [16]. The addition of edible rose extract [20] and moringa [26] in yogurt showed similar results on WHC and syneresis with the enriched set-type yogurt with the extracts of LSB.