Updated on August 16, 2026
How to Ferment L. reuteri in Juice:
Probiotic Juice as an Alternative to L. reuteri Yogurt
L. reuteri does not necessarily have to be fermented in milk.
Fruit juices can also provide a plant-based fermentation medium for probiotic bacteria.
Scientific research shows that L. reuteri can be used in different fruit juices, including apple juice, orange juice, pineapple juice, and mango juice.
This opens up an interesting alternative to our classic L. reuteri yogurt, especially for anyone interested in dairy-free probiotic fermentation.
Is Probiotic Juice the Same as Kombucha?
No.
Although both beverages are produced through fermentation, L. reuteri fermented juice is not kombucha.
Kombucha is traditionally fermented using a mixed culture of bacteria and yeasts.
With probiotic L. reuteri juice, L. reuteri is deliberately added as the bacterial starter culture.
The basic principle, however, is similar:
microorganisms metabolize components of the juice and transform the original product during fermentation.
Can L. reuteri Metabolize the Sugar in Fruit Juice?
L. reuteri belongs to the group of lactic acid bacteria and can metabolize carbohydrates.
Fruit juice naturally contains sugars that can serve as substrates for bacterial metabolism during fermentation.
Research into the fermentation of fruit juices with lactic acid bacteria shows that this principle works in practice.
During fermentation, organic acids and other metabolites can be produced, changing the taste, aroma, and composition of the original juice.
Which Fruit Juices Have Been Studied with L. reuteri?
Apple Juice
Apple juice is particularly interesting for fermentation with L. reuteri.
In one scientific study, apple juice was fermented with L. reuteri and analyzed after 0, 6, 12, 18, 24, and 30 hours.
Under the conditions investigated, the optimal fermentation time was approximately 18 hours.
The fermentation affected, among other things, the composition of aroma compounds, organic acids, and polyphenols in the apple juice.
Another study also demonstrated that L. reuteri can remain viable in apple juice.
Orange Juice
Orange juice has also been investigated as a medium for L. reuteri.
Research demonstrated that L. reuteri can remain viable in orange juice, making it another potentially interesting basis for probiotic beverages.
Pineapple Juice
The same applies to pineapple juice.
L. reuteri has also been shown to remain viable in pineapple juice.
Mango Juice
The targeted fermentation of mango juice with L. reuteri has also been scientifically investigated.
During fermentation, researchers observed changes in the sugar content and metabolic profile of the juice.
These findings provide further evidence that fruit juice can serve as a fermentation medium for L. reuteri.
Why Fermentation Time Matters
If you already prepare our L. reuteri yogurt, you know how important a constant temperature and the correct fermentation time are.
The same basic principles apply to juice, although the optimal conditions can differ from those used for yogurt.
This is illustrated particularly well by the apple juice study.
Researchers analyzed L. reuteri fermented apple juice after 0, 6, 12, 18, 24, and 30 hours.
Under the conditions investigated, approximately 18 hours provided the optimal fermentation time.
This illustrates an important principle:
Longer fermentation does not automatically mean better fermentation.
The optimal fermentation time depends on the bacteria, fermentation medium, temperature, pH, and other conditions.
Different L. reuteri cultures can also behave somewhat differently, so the approximately 18-hour fermentation period should be regarded as a scientifically investigated starting point rather than a guaranteed optimum under every possible condition.
How to Make L. reuteri Fermented Apple Juice
The following recipe translates the available scientific findings on L. reuteri and fruit juice fermentation into a simple method for experimenting at home.
Ingredients and Equipment for 1 Liter
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1 liter (approximately 34 fl oz) of 100% pasteurized apple juice
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1 capsule L. reuteri containing 5 billion CFU
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A clean fermentation vessel with sufficient headspace
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A fermentation airlock
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A yogurt maker or another device capable of maintaining approximately 37°C / 99°F
Choosing the Right Apple Juice
Use 100% pasteurized apple juice without preservatives.
Always check the ingredient list before purchasing the juice.
In particular, it should not contain potassium sorbate or sodium benzoate.
Dr. William Davis specifically recommends using juice without preservatives for juice fermentation and explicitly mentions avoiding potassium sorbate and sodium benzoate.
This makes microbiological sense:
preservatives are added to foods precisely because they inhibit the growth of microorganisms.
During fermentation, however, we want the opposite, we want the added bacteria to remain metabolically active and multiply.
Step 1: Prepare the Apple Juice
Open a fresh container of pasteurized apple juice and pour 1 liter into a thoroughly cleaned fermentation vessel.
Leave sufficient empty space at the top of the vessel.
Step 2: Add the L. reuteri
Open 1 L. reuteri capsule containing 5 billion CFU and add the entire contents to 1 liter of apple juice.
Mix thoroughly to distribute the starter culture throughout the juice.
This provides an initial concentration of approximately 5 million CFU per milliliter of apple juice.
Step 3: Use a Fermentation Airlock
Never ferment the juice in an airtight, completely sealed container.
Gas can be produced during fermentation, potentially creating substantial pressure inside a sealed vessel.
Use a fermentation airlock that allows fermentation gases to escape while helping to protect the ferment from contamination from the surrounding environment.
This principle is also familiar from other fermentation methods, including kombucha and other fermented beverages.
Step 4: Ferment at Approximately 37°C / 99°F
L. reuteri is typically cultivated at approximately body temperature.
As a practical starting point, maintain the apple juice at approximately 37°C / 99°F throughout fermentation.
Keeping the temperature as stable as possible is important.
Step 5: Ferment for Approximately 18 Hours
As a starting point for apple juice, ferment for approximately 18 hours.
This recommendation is based on scientific research in which apple juice fermented with L. reuteri was analyzed after 0, 6, 12, 18, 24, and 30 hours.
Under the conditions investigated, approximately 18 hours was identified as the optimal fermentation time.
However, 18 hours should not be considered a universally guaranteed optimum for every L. reuteri culture.
Fermentation involves living microorganisms, and results can vary depending on the bacterial culture, juice, starting bacterial count, pH, and fermentation conditions.
Step 6: Stop the Fermentation by Refrigerating
Once fermentation is complete, place the juice directly in the refrigerator.
The substantial reduction in temperature greatly slows bacterial metabolic activity and therefore further fermentation.
Keep the finished probiotic juice refrigerated.
Do You Need Inulin or Acacia Fiber?
Not necessarily.
Unlike milk, fruit juice already contains substantial amounts of naturally occurring sugars that can serve as substrates for bacterial metabolism.
Research on fruit juice fermentation with L. reuteri demonstrates that fermentation can occur without adding the inulin commonly used in our L. reuteri yogurt preparation.
Whether adding prebiotic fibers such as inulin or acacia fiber could further improve fermentation for a particular L. reuteri culture is a separate question and requires further investigation.
Why Can Fermentation Results Vary?
L. reuteri is a living microorganism.
How successfully fermentation proceeds depends on several factors, including temperature, fermentation time, initial bacterial concentration, pH, and the composition of the juice.
Different L. reuteri cultures can also vary in their metabolic characteristics.
Scientific research nevertheless demonstrates the fundamental principle that fruit juices can provide a suitable medium for L. reuteri and that L. reuteri can remain viable or actively ferment fruit juice under appropriate conditions.
L. reuteri Juice or L. reuteri Yogurt?
Our L. reuteri yogurt remains the established preparation method covered by our existing fermentation instructions.
Juice fermentation offers an additional and exciting option, particularly for people interested in plant-based or dairy-free fermentation.
Research increasingly demonstrates that L. reuteri is not limited to yogurt-like fermentation, fruit juices such as apple juice can also be used as a fermentation medium for L. reuteri.
This makes probiotic juice an interesting new way to explore L. reuteri fermentation.
Tolerance note:
Fermented fruit juice may be less well tolerated than L. reuteri yogurt, particularly by people who are sensitive to fructose, fruit acids, fermented foods, or FODMAPs.
Fermentation does not necessarily remove all of the naturally occurring sugar from the juice.
If you are trying probiotic juice for the first time, start with a small amount and assess your individual tolerance.
Scientific Sources
Ji G. et al. (2023). Influence on the aroma substances and functional ingredients of apple juice by lactic acid bacteria fermentation. Food Bioscience, 51, 102337.
Apple juice was fermented with L. reuteri and analyzed at different fermentation times. Under the experimental conditions, approximately 18 hours was identified as the optimal fermentation time.
Perricone M. et al. (2014). Viability of Lactobacillus reuteri in fruit juices. Journal of Functional Foods, 10, 421–426.
This study investigated L. reuteri in different fruit juices, including apple, orange, and pineapple juice.
Guo W. et al. (2025). Improvement of physicochemical characteristics, bioactivity, flavor and metabolic profiles of mango juice fermented by Limosilactobacillus reuteri. International Journal of Food Microbiology.
This study investigated the fermentation of mango juice with L. reuteri and documented changes in sugar content, metabolites, and other characteristics during fermentation.
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