Desirability Function-Based Optimization of Apple Pomace Extraction to Produce a Fermentable Must Using Central Composite Design Methodology (CCD) for the Development of Non- or Low-Alcohol Beverages

The cider industry generates substantial amounts of apple pomace (AP), a by-product rich in fermentable sugars, organic acids, and bioactive compounds. This study aimed to optimize the extraction of fermentable must from AP using a central composite design (CCD) and to evaluate its potential for producing non- or low-alcohol (NoLo) beverages through fermentation. The extraction process was optimized using a desirability function targeting maximum sugar (26.69 g/L), malic acid (1.30 g/L), and nitrogen content (29.60 mg/L). The model revealed that extraction time and agitation had significant effects on sugar and malic acid, while an enzyme was less influential. The selected optimal condition was 4.6 h of maceration without enzyme addition providing an efficient must composition. Must was then fermented using combinations of Saccharomyces cerevisiae, Lactobacillus plantarum, and Pichia kluyveri. Physicochemical, microbiological, and volatile compound analyses were conducted throughout fermentation. Results showed that fermentation time and microbial composition significantly influenced sugar degradation, ethanol and lactic acid production and malic acid conversion, while mixed fermentation S. cerevisiae + L. plantarum and L. plantarum + P. kluyveri demonstrated the most promising aromatic profiles. Principal component analysis (PCA) confirmed distinct fermentation trajectories based on microbial consortia, highlighting the potential of AP as a sustainable substrate for developing innovative NoLo beverages.