A few months ago I was talking to a friend at a local market about making my own washing up liquid and the difficulty in getting the balance just right between cleaning power and general user-friendliness. She mentioned a fermented citrus cleaner she makes and sent me the recipe. It sat in my email inbox for months until I caught a cold in early December and got tore into serious quantities of hot lemon and honey drinks. As the lemon rinds began to pile up in the compost bin, I suddenly remembered the cleaner recipe.
The fruit I’ve used is all grown here on the quinta, so is about as natural, organic and fresh as it gets. I made two bottles with the lemon peel from the cold remedies, then after Christmas the oranges started coming ripe so the 5th bottle is now on the go.
- Approx. one litre of sliced citrus peel
- Approx. 7 tbs (80-100g) sugar
- 1 litre water
Slice the citrus peel into strips thin enough to fit through the neck of a 2-litre plastic soda bottle and fill to about half full. Dissolve the sugar in hot water and top up to one litre with enough hot or cold to bring it to just a little over body temperature. Pour into the soda bottle. Cap and shake thoroughly, then set aside in a warm room to ferment.
The fermentation should start almost immediately and be well away after 24 hours. Shake well and release the cap – just enough to allow the pressure built up inside to escape – 2-3 times a day until the fermentation starts to slow down after 5 days or so. Thereafter you can safely leave the bottle for longer, but continue to release the excess pressure regularly for at least the first 3 weeks and maybe once a week after that. At this stage you could also move the bottles to a cooler location if need be.
Let the mixture ferment out for around 3 months in total, then strain and use, either neat or diluted depending on application.
Be careful to store the cleaner in an airtight container and exclude as much air as possible. If you use it as you go and produce as much as you need on a continual rotation, this isn’t quite so important as if you produce more when oranges are in season and store for later use. But your cleaner could become vinegary if you don’t (see below).
Cleaning up some misconceptions
During the many weeks of waiting for my first batch of cleaning fluid to be ready to clean, I got curious about it so spent a rainy afternoon on the internet researching some details. I came across some misconceptions, bad experiences and slightly dubious recommendations on a whole host of housewifely blogs. It seems the subject could maybe benefit from a bit of a clean-up.
Citrus Enzyme Cleaner
Variants of this recipe are widely published and almost universally billed as ‘Citrus Enzyme Cleaner‘. The thing is, it doesn’t appear to be an enzyme cleaner. Despite searching, I couldn’t track down any reference to specific enzyme(s) supposedly contained in this recipe or what they might act on, since enzymes are generally very specific in their action.
The enzymes most commonly used in cleaning products are ones which digest protein stains like blood, egg, grass, urine and sweat. Being as these are the most difficult stains for ordinary detergents to remove, the addition of protein-digesting enzymes to deal with them makes sense. (Some detergents also contain enzymes which break down fat and starch as well.) Enzymes in laundry detergents are mostly bacterial in origin, not plant-based, and plant-based protein-digesting enzymes are mostly extracted from pineapple, papaya and fig, not citrus fruits. So it seems the predominant cleaning action in this formulation is most likely down to the alcohol (produced by fermentation) and citrus oils, both of which are solvents.
I found another blogger who came to the same conclusion.
So are there enzymes in citrus peel which could conceivably contribute to the cleaning process? There are quite high concentrations of protein-digesting enzymes in citrus rind but they’re of the kind that modify proteins just a wee bit rather than dissolving them altogether, so possibly not much use on a blood stain. There’s a fair bit of ascorbic acid (Vitamin C) in citrus peel and there’s also an enzyme which breaks it down, which is also present in the peel, and this process can produce hydrogen peroxide which also has cleaning action. Could these reactions explain some of the reported successes of this cleaner and be a decent enough basis for calling it an enzyme cleaner? Maybe. But then again maybe not. My cleaner isn’t quite ready yet so I haven’t been able to experiment and test out these ideas. Watch this space …
Yeast and the fermentation process
Fermentation is the process by which yeasts break down sugars and convert them into alcohol (ethanol) and carbon dioxide. Many recipes for this cleaner specify brown sugar. As far as I can see, this isn’t important. Yeast will feed on most types of sugar (though it struggles with lactose) and there’s little to no difference in the sugars present in white and brown sugar. Maybe brown sugar is specified because commercially, yeast is cultured on molasses. I can’t think of any other reason.
I came across a lot of recipes calling for added yeast, the object being, apparently, to speed the whole process up to make it ready in 2 weeks rather than 3 months. The thinking behind this seems a bit suspect. The prime determinant of the speed of fermentation isn’t the initial amount of yeast. Yeast multiplies incredibly rapidly in the right conditions and will naturally reach its population ceiling (determined by the amount of available sugar) if left to its own devices within a very short space of time. To be sure, more yeast will consume the sugar a wee bit faster, but it’s not a difference you’re really likely to notice. You’re just going to end up with a lot more dead yeast cells when the sugar gets finished, giving you more sediment and a bit of a yeasty smell. The important point to note is that in optimum conditions the primary fermentation will be complete within about a week, regardless of whether or not you add extra yeast.
Yeasts naturally congregate on any fruit because they feed on fruit sugars and multiply. They float about in the air all around us (that’s how sourdough starters are made). Even if the fruit you’re using is fresh from the store and has been waxed and treated with so many biocides it’s a microbial dead-zone, after a warm (not hot) water wash and scrub with a bit of baking soda to remove wax coatings, then a few days in your fruit bowl, the resident yeast population will soon be restored. (Much better though to use fruit that hasn’t been waxed or covered in pesticides in the first place.)
About the only situation I can think of where added yeast might be necessary is if you’re using fruit that’s not so fresh and where the peel is starting to get a bit dried out.
Keeping citrus peel in the freezer until there’s enough to make the recipe is fine. Just make sure it’s completely defrosted and at room temperature before adding the sugar liquid. Freezing won’t kill the natural yeasts (they just go dormant), but the microwave possibly will, so avoid using it to defrost the peel.
I said the prime determinant of the speed of fermentation isn’t the initial amount of yeast. It isn’t. If you want to control the speed of fermentation, you do it with temperature.
Yeast is happiest in a temperature range that’s just a little below our body temperature. Start off with liquid in the optimum temperature range and within 24 hours your citrus mixture should be fermenting furiously.
Keep the mixture in a comfortably warm room. I came across comments from people who’d put it in the fridge and then wondered why it didn’t work very well. Others who’d put it in a cold garage. You wouldn’t put bread dough in the fridge or garage to rise, right? You might put wine in a cool room, but that’s because you want the fermentation to proceed slowly. If you’re so impatient you really can’t bear to wait 3 months for your first batch of cleaner, then keep the mixture warm (around 85°F/30°C is optimum) and the process will complete as fast as is feasible.
Fermentation ceases when either all the sugar is consumed or the concentration of ethanol (alcohol) gets high enough to kill off the yeasts. Once the primary fermentation (the furiously bubbling stage) completes in the first week, the remaining 2½ months are just to let slower secondary fermentation proceed and naturally come to a full stop, which is when all the gas has come out of solution. If you’re really desperate to use the cleaner, there’s nothing to stop you doing so after a couple of weeks, though it won’t be quite so stable as it would be if you waited and you may end up having to throw it out before you get to the end of the bottle. Like a good wine, it will benefit from a bit of maturation.
When things go wrong
For yeasts to ferment, you have to exclude oxygen. Once the fermentation process kicks off, there will be a build-up of carbon dioxide – the fizz – in your container which will protect the fermenting liquid from oxygen, but only if you’re not venting it all off faster than it can be replaced. Many recipes recommend leaving the cap/lid loose on top of the container to allow the CO2 to escape, so preventing explosions. This isn’t really a secure enough way of keeping oxygen out to guarantee success. It’s better to use a plastic soda bottle with the cap screwed on (soda bottles are made to take liquids under pressure), and release the pressure 2-3 times a day (while necessary) than it is to leave the cap unfastened. That positive pressure in the container tells you it’s full of CO2 and by loosening the cap just enough to let all the surplus out, then retightening immediately, you’re not letting any significant amount of oxygen in. (Either that, or you could use a wine-making fermentation lock.)
If too much oxygen gets in, then the yeast stops fermenting and your nutrient-rich, warm sweet liquid becomes the perfect breeding ground for all manner of bacteria and fungal spores. If the yeast has had enough time to make some alcohol, then a particular species of bacteria will start turning the alcohol to vinegar. Many people report ending up with nasty-smelling liquid, anything from vinegar to vomit, and this is most likely what has happened. Too much oxygen and other organisms have got in and the citrus peel is rotting rather than fermenting. It should not smell bad. The dominant smell should be of citrus oils.
Some commenters mentioned adding more sugar to cure a whitish film developing on the surface of the liquid. This film is probably indicative of other things starting to grow in an environment where oxygen isn’t sufficiently excluded. Adding more sugar works because it stimulates the yeast to produce more carbon dioxide, so those organisms which need oxygen to survive will then disappear again, but the better remedy for the situation is to keep the oxygen out in the first place rather than add more sugar. If you add more sugar, you’ll end up with a higher proportion of alcohol in your final product and it will smell of it. If too much oxygen then gets in, you’ll end up with vinegar dominating instead. Or worse, the citrus rind will start to rot.
Ferments with higher alcohol content, even vinegar if oxygen has got in, will still clean well – both alcohol and vinegar are good cleaners – you’ll just have a lower proportion of citrus oil in your mix and it will smell accordingly.
As with most things, the secret to getting the balance right is getting the balance right, though as with most natural preparations, there is also an enormous amount of latitude. You can make a straight-up vinegar-citrus cleaner just by steeping citrus peel in vinegar for 4-6 weeks. No need to ferment it. You can do the same with a bottle of vodka. But personally I like this recipe better … even if I’ve still to test it as a cleaner! There’s a certain magic in fermentation and the recipes with straight alcohol or vinegar are a bit too in-your-face (or in-your-nose) for my preference. Plus there’s that elusive possibility that there may actually be some enzyme action involved in the cleaning …