2.9.1. Total Viable Bacterial Count (TVBC) and Acidity

Probiotic products have proved to have at least 10<sup>8</sup> colony forming unit (cfu) of prebiotic strains/mL juice [15]. Probiotic LA-5 and ABT-5 strains were used in this study to produce a probiotic beetroot-milk fermented beverage. The total viable cells of LA-5 and ABT-5 in addition to the beverage's pH and acidity % during the fermentation were illustrated in Table 3. The milk was added to the beet juice to enhance the bacterial growth, as the LA-5 and ABT-5 numbers declined significantly after 6, 24, and 48 h of the fermentation of beet juice according to the preliminary studies. As noticed from the obtained results, pH value was reduced significantly at the end of the fermentation process from 6.6 in both LA-5 and ABT-5 fermented juices to 5.14 and 5.16, respectively (*p* < 0.05). The reduction of the pH was due to the production of lactic acid [35], which was confirmed by the % acidity of the juices. The acidity significantly increased from 0.41% of both samples at (zero time) to 1.84% and 1.94% at 6 h of fermentation for LA-5 and ABT-5 beverages, respectively (*p* < 0.05). *L. acidophilus* was increased significantly in LA-5 fermented beet-milk beverage after six hours of fermentation from 1.75 <sup>×</sup> <sup>10</sup><sup>7</sup> to 1.25 <sup>×</sup> <sup>10</sup><sup>10</sup> (*<sup>p</sup>* <sup>&</sup>lt; 0.05). Similarly, the ABT-5 probiotic strain raised significantly from 2.37 <sup>×</sup> <sup>10</sup><sup>7</sup> to 3.7 <sup>×</sup> <sup>10</sup><sup>9</sup> after six hours of fermentation (*<sup>p</sup>* <sup>&</sup>lt; 0.05). The obtained viable bacterial count in the present study was higher than 27.8 <sup>×</sup> <sup>10</sup><sup>8</sup> resulted in beetroot juice after 72 h of fermentation with LA-5 strain as mentioned by Yoon et al. [35], and 7 <sup>×</sup> <sup>10</sup><sup>8</sup> resulted from the fermentation of beet juice by LA-5 for 8 h [13]. Thus, adding 40% full-fat milk to the beetroot enhanced the bacterial growth and reduced the fermentation period.


**Table 3.** PH, acidity, and viable cell count of LA-5 and ABT-5 beet-milk beverage.

Different superscripts are significantly different at (*p* ≤ 0.05); \* Acidity expressed as % of lactic acid; \*\* CFU/mL: colony forming unit of probiotic culture/mL of beet-milk beverage.
