Production and characterization of aroma compounds from apple pomace by solid-state fermentation with selected yeasts

Volatile aroma profiles generated during apple pomace fermentation were characterized. The apple pomace was fermented with 4 yeast strains, using three strains of indigenous cider yeasts ( Saccharomyces cerevisiae, Hanseniaspora valbyensis and Hanseniaspora uvarum ) and a commercial S. cerevisiae combined with an enzymatic preparation as inocula. In all cases, the initial sugar content decreased until depletion within 21 days or less, yielding similar ethanol contents at the end of the alcoholic fermentation. Chromatographic analysis of the apple pomaces allowed the identification of 132 volatile compounds belonging to different chemical families. Quantitatively, the production of aromas was strongly strain-dependent. The apple pomaces inoculated with Saccharomyces strains accumulated higher levels of fatty acids and their corresponding ethyl esters, increasing throughout the period of study (28 days). On the other hand, the volatile profiles from experimental units fermented with Hanseniaspora genus yeasts were characterized by higher levels of acetic acid esters with a maximum at 7–14 days of fermentation. A significant decrease in the concentration of unsaturated carbonyls was also detected between 21 and 28 days in apple pomaces fermented with Hanseniaspora strains.