Effect of Sequential Inoculation with Metschnikowia pulcherrima and Saccharomyces cerevisiae on the Chemical Composition of American Pale Ale (APA) Beer

Recent studies have shown that the use of non-Saccharomyces yeasts, either alone or in co-fermentation with Saccharomyces cerevisiae, can enhance the development of specialty beers with distinctive compositional characteristics. This study aimed to evaluate the main compositional and sensory differences between American Pale Ale (APA) beers produced using the commercial strain S. cerevisiae US-05 as a single starter (Test 1), and those produced through sequential inoculation with Metschnikowia pulcherrima 62 followed by S. cerevisiae US-05 (Test 2). Analyses focused on key chemical parameters and volatile compounds at the end of primary fermentation (F1) and after 20 days of refermentation at 20 °C (F2). After F1, Test 2 samples showed higher concentrations of glycerol and higher alcohols (isoamyl alcohol, benzeneethanol) and lower concentrations of esters (isoamyl acetate, ethyl hexanoate, ethyl octanoate) compared to Test 1. After F2, the differences in higher alcohol content became less significant, whereas ester concentrations, particularly ethyl acetate and ethyl octanoate, were significantly higher in Test 2. Sensory evaluation revealed that beers from Test 2 exhibited more pronounced floral and fruity notes and achieved higher overall scores in the panel assessment. These findings indicate that sequential inoculation with M. pulcherrima 62 followed by S. cerevisiae enhances both the chemical complexity and sensory appeal of APA beers, highlighting the strain’s potential as a valuable tool for developing specialty beers with unique aromatic profiles.