The Potential of Environmental Non-Saccharomyces Yeast to Valorise Apple Pomace During Low-Temperature Fermentation

It is estimated that approximately 25% of waste remains after the apple juice pressing process. Combining this waste biomass with valuable compounds creates the potential for reuse. To create a cost-efficient ecological process without any expensive steps, the aim of this research was to examine the potential of using non-Saccharomyces yeasts (Kazachstania barnettii D1, Hanseniaspora uvarum D9, and Wickerhamomyces anomalus D11) for the low-temperature valorisation of apple pomace. The scope encompassed characteristics of apple pomace and the evaluation of yeast growth and metabolic activity, including carbohydrate consumption, enzymatic activity, and the biosynthesis of volatile organic compounds. Moreover, the effect of inoculum size on biomass increases and the productivity of metabolites during the fermentation of apple pomace were evaluated. To investigate the potential intensification of the process, the experiment was performed on hydrolysed and untreated apple pomace. The obtained results indicate that yeast growth was satisfactory regardless of the inoculum size in both fermentation media. Various activities of peptidases, esterases, phosphatases, and glucosidases were observed. The yeast isolates presented metabolic activity during the process which was confirmed by the production of ethanol and acetic acid. Moreover, a significant amount of volatile organic compounds, especially esters, were synthesised, which have a positive impact on the sensory profile of fermented apple pomace. In general, the hydrolysis of apple pomace did not result in better yeast activity and the formation of aroma compounds.