Kombucha is a fizzy, tangy drink made by fermenting tea. But brewers are now fermenting other plant-based drinks to explore nutritional properties and flavors. Researchers in ACS Agricultural Science & Technology compared the biochemistry and flavor of kombucha with brews made from apple and passion fruit juices. They found that the apple beverage contained high levels of bioactive compounds called flavonoids and ranked highly among taste testers, signaling its promise as a kombucha alternative.

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

Few studies have investigated whether liquids other than tea could be brewed as kombucha-like beverages with boosted antioxidant levels or unique flavors. So, Socorro Vanesca, Frota Gaban and coworkers 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 jars for 10 days at room temperature, the researchers measured the levels of several bioactive compounds in each brew and found that:

• All three brews had similar amounts of anthocyanin, a red-colored antioxidant.
• The apple beverage had the highest level of flavonoids, followed by kombucha and the passion fruit drink.
• The kombucha and apple beverages had comparable levels of phenolic compounds that were higher than those of the passion fruit beverage.

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The researchers asked 12 volunteer taste testers to evaluate each beverage’s color, aroma and flavor. The taste testers noted an amber color for the apple beverage, yellow for passion fruit and gold for the kombucha. The volunteers reported stronger, fruitier aromas for the fermented fruit juices compared with the tea. However, the passion fruit drink tasted more bitter than the sweeter apple and tea drinks, both of which received equal votes as the favorite beverage. Because fermented apple juice has more flavonoids and a pleasant taste compared with the other beverages, the researchers say it could be a successful alternative to kombucha made from tea. They plan to explore health benefits and flavors of other fermented fruits in the future.

IMAGE CREDIT: Adapted from ACS Agricultural Science & Technology 2024, DOI:10.1021/acsagscitech.4c00372