Supplementation of Chlorella vulgaris Extracts During Brewing: The Effects on Fermentation Properties, Phytochemical Activity and the Abundance of Volatile Organic Compounds

Chlorella vulgaris, a microalga rich in secondary metabolites and nutrients, offers a promising alternative for promoting microbial growth in food fermentation processes. This study aimed to evaluate the effects of C. vulgaris extracts on fermentation kinetics, sensory characteristics, phytochemical composition, antioxidant activity, and the abundance of volatile organic compounds (VOCs) in treated versus control beers. The bioactive compounds from C. vulgaris were extracted using an ultrasound-assisted method with water as the solvent. A German Pilsner-style lager beer (GPB) was brewed and supplemented with 0.5, 1, and 5 g/L of C. vulgaris extracts prior to primary fermentation. Yeast viability, °Brix, and pH levels were monitored to assess fermentation progress. Phytochemical composition was analyzed by quantifying total polyphenols and flavonoids. The antioxidant activity of the beer was evaluated using both the 2,2-diphenyl-1-picrylhydrazyl (DPPH●) and hydrogen peroxide assays. The addition of C. vulgaris extracts resulted in increased yeast viability and slight variations in gravity during the 7-day fermentation period. Moreover, the beers supplemented with C. vulgaris extracts demonstrated higher levels of total polyphenols, flavonoids, and antioxidant activity compared to the GPB. Specific volatile organic compounds, including 2-methyl-1-propanol, 1-hexanol, isopentyl hexanoate, 2-methylpropyl octanoate, β-myrcene, and geranyl acetate, were significantly more abundant (p < 0.05) in the treated beers than in the control. Sensory evaluations revealed a favorable impact of the treatment on aroma scores compared to the GPB. Overall, the findings indicate that C. vulgaris extracts could be a valuable ingredient for developing functional beers with enhanced health benefits, particularly regarding antioxidant activity. Additionally, the results underscore the importance of exploring innovative approaches that utilize natural sources like Chlorella to enrich the nutritional profile and sensory qualities of fermented products.