Background: Whey is the most abundant by-product of the cheese industry. It is estimated that it contains up to 55% of all nutrients of milk and therefore, it is considered a starting material for obtaining valuable products.

Results: The response surface methodology was used to find the combination of temperature (between 20 and 36°C), and the content of whey powder (37.5–77% (m/m)) to maximize the concentration of kefiran, the concentration of lactic acid bacteria (LAB) and yeast in the supernatant. After validating the quadratic models of each transformed response variable, it underwent a maximization procedure to find the optimal condition obtaining two maximum spaces at the temperature range of 28.5–29.7°C and 43.3% (m/m) of whey-powder content, or 28.0–28.3°C and 71.2% (m/m) of whey-powder content. The validation experiments were carried out for the first suggested optimal solution, through three repetitions under the same optimal conditions, and it was confirmed that there is no significant difference with the values provided by the model.

Conclusions: Physicochemical characteristics (protein, fat, acidity, lactose, viscosity, alcoholic content) under optimal conditions were evaluated and proved its compliance with the Ecuadorian and Andean community regulations. These results suggest that we are in the presence of a functional beverage candidate in which the contents of LAB and yeast (probiotics) and kefiran (prebiotic) were simultaneously maximized.