Fermentative activity of Saccharomycodes ludwigii and evaluation of the synthesis of compounds of sensory importance during fermentation of apple juice

Abstract

The fermentative activity of Saccharomycodes ludwigii RIVE 16-1-5 was studied in order to evaluate its importance in fermentation processes. The results demonstrated that the strain ferments monosaccharides very well, and also sucrose and maltose. Its fermentative activity was not inhibited even at sodium metabisulphite concentrations of 200 mg/L in the culture medium. Furthermore, it was able to produce ethanol up to 6.88±0.1% (v/v). Agitation of the culture medium enhances the production of higher alcohols (843.7mg/L), but diminishes the production of glycerol (0.18±0.2 g/L) and acetic acid (56.0±8.5 mg/L). In addition, synthesis of ethyl acetate in shaken culture (130.0±8.0 mg/L) was higher compared to that in static culture (without agitation). During batch cultivation carried out under aerated conditions, the growth rate µ reached a value of 0.11 h-1. The oxygen concentration in the medium would affect the yeast metabolism, thus insufficient amounts of oxygen would provoke a respiro-fermentative metabolism with production of ethanol, higher alcohols, esters and acetic acid. Aeration control during fermentation is an important tool to control the balance between the respiratory and fermentative activity. Finally, the best results of sensory quality related to aroma, flavor and smell were obtained in static culture.