Mead Fermentation Process Monitoring by Using Analytical Semiobjective Techniques

Mead is a wine-type alcoholic beverage obtained from honey fermentation, traditionally consumed in Eastern Europe and Africa. In this work mead was obtained by alcoholic fermentation over 21 d at 25 degrees C by using honey, pollen, and Saccharomyces cerevisiae subsp. bayanus, from a must of 24 degrees Brix. During the fermentation, different physicochemical indexes of the process were assessed, namely pH, titrable acidity, degrees Brix, density, and sugars' profile and ethanol concentration. The variation of these indexes, which allowed for determining productivity, conversion rate, yield, and other important variables of the process, did not show a clear relationship with the variation of sensory characteristics that the product undergoes as the fermentation process occurs. A new methodology to determine how organoleptic properties vary over time is proposed, considering their importance for the overall quality of this type of beverages. Conventionally, these determinations are made by sensory panels of trained people. In this work an electronic nose and an electronic tongue were used to evaluate the behaviour of sensory characteristics during fermentation. Such instrumental tools relate electrical signals obtained through different sensors, having different values of selectivity and sensitivity, to the presence of various chemicals responsible of the sensory profile of the samples. The dynamic electronic responses from these devices were recorded at different stages of the fermentation process and related to the physicochemical indexes. Multivariate statistical analysis permitted to find a clear correlation between the responses of electronic nose and tongue with fermentation time. These results confirm that such semiobjective techniques are adequate tools for online process monitoring, facilitating the sampling and data collection, and would eventually enable sensory-accurate online monitoring of mead fermentation processes.