Learn the science behind:
Why Soak Your Fruit For Weeks For a Christmas Cake
Some say you need a year, others say you can’t start any later than at Stir-Up Sunday, and yet others make it in a day: Christmas cake (or pudding, definitions overlap somewhat but not completely). So what’s the correct answer? We decided to investigate and came across disappointingly little science, but, a lot of experience (and opinions).
There’s not a single piece of scientific literature that gets even close to trying to answer that question. So, we did a little test ourselves and gathered information, because, it turns out, it depends. You can make a great cake a few days in advance, but it will likely be a slightly different one than the one you’d make well ahead of time.
- Some fruits simply take longer
- Larger pieces need longer
- Flavors mellow and even out
- Not all fruits benefit from a longer time!
Christmas cake, pudding, or fruit cake
Things started getting complicated right from the get-go. Depending on where you live, the cake we’re discussing might be called different, and have a slightly different composition. A Christmas cake to one, may be a Christmas pudding to others, a fruit cake, black cake, or something different yet again.
That is: cake with a LOT of fruit
What we’re looking at are cakes that contain a lot of dried, then soaked fruits, and are then baked into an equal amount, or less of cake batter. ‘Normal’ cakes tend to contain at least twice the amount of batter than filling, if not much more. Because of this high quantity of fruit, the texture of the cake heavily depends on these fruits and how they’ve been treated.
That needs soaking
The reason many of these cakes may need to be made well in advance is that the fruits or even the cake itself need to be soaked, often in an alcohol-containing liquid.
Soaking is quite an interesting phenomenon. When you soak dried fruits, or a cake for that matter, moisture migration occurs. That is, water moves from one component to the other. Water will always travel from a high to a low concentration. So, if you mix dry raisins with water (or liquor) that water will immediately start moving into the raisins until the concentration of water in- and outside of the raisin is the same.
Technically speaking, water moves from a place with a high water activity to a low water activity component, which we discuss in more detail here.
Reasons for soaking fruits
Christmas cakes, as we’ll refer to them here, aren’t the only foods that call for soaking ingredients. Many recipes do, for a variety of reasons.
To add moisture
This reason may seem obvious, but soaking fruits adds moisture to a cake. And, it also helps to control the consistency of the cake. Dried fruits will absorb any water they can find around them. If you add dried fruits straight into a cake batter they’ll try to absorb moisture from the batter, and once baked, they’ll try to absorb moisture from the cake. This can make a cake turn out dried than you’d expect. By pre-soaking the fruit though, they’ll have absorbed all of that moisture already.
To add flavor
When dried fruits are submerged into a liquid, they’ll absorb that liquid. If the liquid has any particular flavors, those flavors too get absorbed by the fruits. It’s why soaking fruits in a little bit of orange juice gives them some extra ‘zing’ and why a flavorful liquor can add a lot to soaked fruits. This is also why it’s best to choose a liquor for soaking that tastes good. You’ll taste at least some of the flavor in the soaked fruit.
To soften the texture
Dried fruits are quite chewy. By soaking them in liquid, they turn more plumb and become a lot softer and easier to eat. If you’d
To prevent burning
This last reason is less relevant for Christmas cakes, but not completely so. Our raisin oliebollen recipes also calls for soaking the raisins before incorporating them into the batter. The reason for doing so in this particular dish is to prevent burning. Dried fruits burn easily because they contain a lot of sugars, especially if they stick out of the batter slightly. Once soaked, the water protects the fruit, by keeping it moist and thus cooler. Soaked raisins are far less likely to burn in both deep fried as well as baked goods. Christmas cakes don’t have a lot of fruits sticking out, but, if some do, their soaks will help ensure they don’t get burned.
Soaking cake vs. fruits
Almost every Christmas cake recipe that uses a lot of dried fruits will call for soaking the fruits before baking. Some call for a long soak of the fruits, and then baking just before eating. Yet others use a relatively short soak up front, but then soak the cake itself for a (long) period of time.
Personally, we prefered the first method. The cake soaked in liquor tastes more strongly like liquor than the one that only soaked the fruits. This makes sense, since the liquor had a lot more time to mingle with all the sweet fruits and mellow, as opposed to soaking the cake. Both work, depending on your personal preferences and you can even combine both methods!
But why soak them for so long?
As we mentioned at the start, some recipes call for soaking fruits for a few hours, whereas others require months. Even though it’s not exactly clear to us what happens over a very long period of time. There are a few basic principles that guide soaking time.
In Great Britain the final day to start soaking your fruit and/or cake for a traditional Christmas pudding is stir up Sunday. This is the 5th Sunday before Christmas (or the last Sunday before the Advent starts, approx. last week of November) and should give you just enough time to gets everything in order!
Some fruits simply take longer
If you’ve soaked raisins before, you’ll know that in a matter of hours, they’ll have turned beautifully plump and soft. They don’t need a lot of soaking time. However, other types of fruits may take significantly longer. For instance, we added dried mango, which took a longer time to properly and evenly soften up.
Larger pieces need longer
Chop fruits into small pieces and all of a sudden liquid can enter the fruits on just about every side. Torn and cut skins make it a lot easier for liquids to enter the fruit. Same for smaller pieces. It’s why it will take a lot longer for a whole dried prune to soften up than it will for a finely chopped one. Cakes with bigger pieces of fruit will thuse require more soaking time.
Flavors mellow and even out
This one is a little harder to quantify, but if you soak a fruit mixture for some time and taste it regularly, you will notice that the flavors change. With the moving moisture within the fruits, flavor molecules travel along as well, as well as protons, which define the acidity of fruits. This movement of components causes flavors to change and mellow. The flavors become less harsh and intense. We also noticed that the alcohol flavor mellows down over time. Yes, the alcohol will still be there, but it will become part of the overall flavor profile instead of a distinct one.
Know who else use this principle? Whisky makers, beer brewers and more, when aging their drinks in wooden barrels. Here, flavor molecules from the barrels enters the drink, changing the overall flavor profile.
Use glass jars
This is especially helpful if you’re soaking for a long period of time, think months. Flavor molecules are moving around and over these long periods of time, even flavors from a plastic container can migrate into the fruits. This is not necessarily harmful, but probably isn’t the best for the overall flavor. Glass on the other hand is pretty much inert, no flavors will migrate over!
Not all fruits benefit from a longer time!
Keep in mind that we’re assuming that you’re using a selection of sturdy dreid fruits, think raisins, currants, cranberries, prunes, plums, black currants, maybe some almonds or other nuts even. These all don’t really mind soaking a few days or weeks extra. However, if you’re using very delicate fruits, such as strawberries, longer often is not better. Too long a soak can make them soggy, so either reduce the overall soaking time or just add these more delicate fruits later in the process.
Alcohol serves as a preservative
Almost any recipe that calls for soaking fruits for a long period of time, that is several days, weeks, or months, will use some sort of liquor to soak the fruits. You can’t just replace this liquor with water or a non-alcohol containing liquid. Alcohol serves as a perservative here. The high alcohol content ensures the soaking fruits won’t spoil since yeast, molds and bacteria can’t grow under these conditions.
If you do not want to use alcohol, you’ll have to revert to shorter soaking times, though you can stretch them slightly by refrigerating the fruits while soaking them.
We were surprised how long our cake soaked in just 2-3 tablespoons of liquor kept! We ‘fed’ an extra tablespoon every two weeks, but even 6 weeks later not a trace of molds or yeast. The alcohol had clearly been doing its job!
The type of liquor doesn’t really matter
Many Christmas cakes are made with rum (sometimes called rum cakes), but a wide variety of other liquors can be used. What’s important is their high alcohol content. Also, as mentioned earlier, it’s best to use a liquor that you find tastes good. It will impact the flavor of the cake, so very bitter liquors for instance, or heavily spices might not always work great. Another commonly used liquor is brandy.
Bake it low and slow
Christmas cake batters are very moist, because of all that juicy, plump fruit. On top of that, they contain quite a bit of sugar. As a result, they brown quite easily, but, that also means they might burn quickly. The additional moisture on the other hand makes for a longer baking time, to evaporate some of that excess moisture and ensure the cake has time to firm up. It’s why cakes full of soaked fruits are best baked low and slow. Some even insulate the outside of the cake tin with newspaper to ensure it doesn’t heat up too quickly and has enough time to evenly heat throughout!
Soaking fruit in alcohol, Discussion on Seasoned advice on Stack Exchange, link, visited Jan-2023 ; valuable resource to see how everyone might prefer things just a little different.
Is 3 days too long to soak dried fruit for my fruitcake?, Seasoned Advice onf Stack Exchange link, visited Jan-2023