Fruit juices revisit kombucha

Kombucha is a carbonated and tangy drink obtained from the fermentation of tea. But brewers are now fermenting other plant-based beverages to explore their nutritional properties and flavors. In a study published in ACS Agricultural Science and TechnologyResearchers compared the biochemistry and flavor of kombucha with infusions made from apple and passion fruit juice. They found that the apple drink contained high levels of bioactive compounds called flavonoids and ranked highly among taste testers, signaling its promise as an alternative to kombucha.

To make kombucha, brewers ferment sweet tea with a spongy disk of microbes called a SCOBY, or symbiotic culture of bacteria and yeast. The resulting beverage contains beneficial bacteria from the fermentation process and bioactive compounds in tea, including flavonoids, phenolic compounds and anthocyanins which may have antioxidant and anti-inflammatory properties.

Few studies have examined whether liquids other than tea can be brewed as kombucha-like drinks with increased antioxidant levels or unique flavors. So Socorro Vanesca, Frota Gaban and their colleagues fermented antioxidant-rich apple and passion fruit juices with a SCOBY to find out.

After fermenting apple juice, passion fruit juice and tea in separate pots for 10 days at room temperature, the researchers measured the levels of several bioactive compounds in each brew and found that:

• The apple drink had the highest level of flavonoids, followed by kombucha and passion fruit drink.
• The kombucha and apple drinks had comparable levels of phenolic compounds, higher than the passion fruit drink.
• All three beers contained similar amounts of anthocyanin, a red-colored antioxidant.

The researchers asked 12 volunteer taste testers to rate the color, aroma and flavor of each drink. Tasters noted an amber color for the apple beverage, yellow for the passion fruit and golden for the kombucha.

Volunteers reported stronger, fruitier aromas for fermented fruit juices compared to tea. However, the passion fruit drink tasted more bitter than the sweeter apple and tea drinks, both of which received equal votes as favorite drink.

Because fermented apple juice contains more flavonoids and a pleasant taste compared to other drinks, researchers say it could be an effective alternative to tea-based kombucha. They plan to explore the health benefits and flavors of other fermented fruits in the future.