Fermenting Lemon Juice
TroubleShooting
Peter Owens — Australia asks,
I recently attempted a lemon alcoholic brew, because we had a full fruiting lemon tree in our backyard and had more lemons than we knew what to do with. The cultivar is Meyer lemon, which is both juicy and a little less astringent than normal Store-bought lemons.
Using a champagne yeast, this brew took many days to begin fermenting and then weeks to finish fermenting. I expected an infection but am happy to report that did not happen. In fact it never actually fermented fully; I was left with a sweet low-alcohol product. It was only drinkable if you further backsweetened.
I have been advised to carefully look at the pH as this might be partly responsible. Naturally I will defer any further experiments until I can pinpoint the probable causes of my initial result. If you have time I’d greatly appreciate any comments you think might help.
It seems that people, past and present, have accidentally or intentionally fermented just about everything. The easy way to categorize alcoholic beverages is by raw material; beer is made from grains, wine is made from fruit, and mead is made from honey. One commonality with all of these beverages is that the starting point (brewer’s wort or winemaker’s and meadmaker’s must) is a relatively friendly environment for yeast. Although the modern zymurgist often adds nutrients to optimize growth conditions, wort and must can quickly be fermented by wild and cultured yeast. Lemon juice, on the other hand is not so friendly.
The pH of lemon juice is very low and is typically reported to be around pH 2.2. To put this in perspective, this is about 1,600 times more acidic, as defined by the concentration of hydrogen ions, than wort at pH 5.4, and 16 times more acidic than grape must at pH 3.4. Yeast are effected by environmental pH and don’t perform well when the pH drops below about 3. Brewers who successfully bottle condition sour beers know this step can be tricky because the combination of low pH and alcohol requires acid-tolerant yeast strains for conditioning. Lemon juice is truly an extreme environment and the very limited fermentation you experienced is typical for the descriptions of lemon juice fermentations reported by others.
If you simply want to ferment lemon juice into a mildly alcoholic beverage and not follow traditional methods, I would suggest a few things to improve the environment before adding your yeast. Start with the pH obstacle and do something to move the pH upward. One way to do this would be to dilute the lemon juice with wort. Wort is a good source of amino acids, which serve the role of pH buffer and nutrient. Not too different from a kettle sour, except here wort is added to make the juice less acidic. Dried malt extract would make this process easier and a handy method for a quick brew day. Not too interested in a lemon beer? Consider making sima, a Finnish mead made with honey and lemons. The important thing is to bring the pH into a friendlier range.
The other challenge that should be addressed when fermenting lemon juice is nitrogen; lemon juice does not have much and yeast need it for growth. Although yeast nutrients have become fairly common in brewing as brewers have pushed the envelope, all-malt worts made for traditional styles are a good source of nitrogen and many brewers don’t have much need for or experience with nutrients. Wine and meadmakers, on the other hand, are well-versed in the use of nutrients because the musts used for wine and mead are usually deficient in nitrogen. Consider using a general purpose yeast nutrient like Superfood that contains a blend of amino acids, diammonium phosphate, and vitamins.
I hope this high-level answer gives you a little insight into some of the things you may want to consider the next time you attempt fermenting lemon juice. Definitely an interesting ingredient with some fun challenges.
