Antimicrobial activity and overall sensory acceptance of fermented goat whey beverage: Process conditions optimization using response surface approach

Even though it contains high levels of many important nutritive compounds, whey has not been widely accepted by consumers due to its unappealing taste and texture. Whey fermentation could improve its sensory properties and result in a functional beverage with appealing characteristics and a clear potential to replace traditional functional milk-based beverages. Therefore, this work aimed to develop a goat whey-based functional beverage fermented with kefir grains and to examine the influence of fermentation temperature and inoculum size on the overall sensorial acceptability of the product and its antimicrobial activity. Response surface methodology along with the central composite design was used to estimate the individual and combined effect of temperature and inoculum size on lactic and acetic acid, ethanol, antimicrobial activity and overall sensory acceptability of the obtained beverage. The experimental data for lactic and acetic acid, antimicrobial activity and overall sensory acceptance of beverage were fitted to a quadratic model, while a linear 2FI model was proposed for the ethanol content. Temperature and inoculum size have been found to affect the quality of the obtained beverage. Multi-response optimization provided an optimum solution for the production of the most acceptable beverage with the highest antimicrobial activity. According to desirability criteria, with overall desirability of 0.79, the following fermentation conditions were proposed for the fermentation of goat whey using kefir: temperature of 27.5 ° C and inoculum size of 7.36%. Proposed values were validated confirming the minimum deviation of experimental and predicted values.