Making Rhubarb and Custard Sweets

Rhubarb and Custard Sweets, ironically, contain neither rhubarb nor custard. Their history is based on a rhubarb and vanilla custard pudding that was popular, then when candy making became popular due to the importing of sugar, this pudding was made into a hard sweet. Ever since they have been popular- they’ve always been my favourite sweet (and believe me I ate many of them as a child)- and you’ll find these in most traditional British sweet shops. So, if rhubarb and custards don’t have rhubarb or custard, what do they have?

Tartaric acid, possibly better known as E334, is one of the key ingredients in rhubarb and custard sweets. You won’t find it in supermarkets, but is is easy to get hold of online. It occurs naturally in some fruits, particularly bananas and grapes, the latter suggesting why tartaric acid is one of the main acids in wine. You may have notice small crystals on the corks of wine bottles from time to time- these are tartrate crystals forming, totally harmless and not a fault with the wine. So what does tartaric acid do? Basically, I would say it is ‘pure sour’. I dipped my finger into the tub to taste a little bit before making the sweets- my goodness!- even worse than the acid from pinot grigio, if that is possible. I imagine the tartaric acid is used in many other sour sweets as well, as the taste was quite familiar. A lot of fun to have tried a little of the acid, and key taste in the sweets, but a little will clearly go a long way in making the rhubarb and custards.

On to the sweet-making process. In some sense, making hard candy like this is similar to making nougat (my post there has a few more details on the process). You start off with a sugar syrup, heat it up until the water concentration decreases to the level which will give you the texture you want, then cool it. The cooling process itself is quite interesting. Often the candy is aerated, to help stability and create a chewier candy- this video is a nice example. In nougat, the air comes in the meringue, but with sweets, it is usually pulling, or working the sugar that provides this aeration and change in texture. This aeration makes the key difference in texture between the ‘rhubarb’ and the ‘custard’. Both start from the same syrup, but the custard is the part which is aerated, giving it a very different texture than the harder, brittler rhubarb part. Interestingly as well:

When the high-boiled sweet is cooled, it is in a glassy state or it is a liquid with extremely high viscosity and non-crystalline in nature. The high viscosity of the doctoring agent [liquid glucose here] slows or stops the migration of sucrose molecules and thus interferes with the process of recrystallization. Although highboiled sweets appear solid, they are, in fact, supercooled, non-crystalline liquids, which are so far below their softening or melting point that they assume solid properties without crystallizing.

So how well would these processes work in the domestic kitchen? Well, making the sugar syrup itself is no problem, but when I tried it, manipulating the syrup was more tricky. First of all it will be no surprise to hear it was very very sticky, so moving it from place to place, especially when it was spread out over a large surface, was no easy task. But most of the difficulty came in keeping it easy to aerate. To work the candy at home, you pull and twist the ball of warm sugar. For this, you’ve got a balance- either the sugar is hot, and easy to aerate, but hard to handle with your hands, or cold, and hard to aerate as it is tough to work, but easier to handle. Either way, I got a whole load of blisters trying to aerate it, and I’m not sure whether it was the heat, the toughness, or both. It is easy to see why they industrialised this.

One Saturday, when a friend was over to do some cooking, we decided to have a go at making rhubarb and custards. Despite the above difficulties, we were very pleased with the results, the sweets tasting very much like the ones bought from the store, and the real vanilla adding a nice touch. The texture was good as well, very hard and sticky as they cooled. The rhubarb strand and the custard strand had no problem sticking together and staying that way. A lot of fun to have made, but given the state of my hands afterwards, I might stick to the bought version next time!

Rhubarb and Custard Sweets

The recipe here is based on one from The Home-Made Sweet Shop. You’ll need some kit for this- a pastry scraper being the main one, it will be very useful in handling the hot sugar syrup. The book suggests using a marble slab to put the sugar syrup on, but I used a baking tray covered with a silicone baking sheet. I would imagine that regular baking paper wouldn’t work here, likely tearing at several points. A sugar thermometer is also key. This recipe will make a jar’s worth of rhubarb and custards- mine filled a small coffee jar, apart from the, er, casualties along the way.

450g caster sugar
150ml water
1.5ml cream of tartar
15ml liquid glucose
2tsp tartaric acid
1 vanilla pod
pink food colouring

1. Make the sugar syrup.
Prepare an ice/water bath- big enough to put a saucepan in. Add the sugar, water, cream of tartar and liquid glucose into a pan and heat gently until the sugar is dissolved. Turn up the heat, and boil until the soft crack stage, 143°C. Add the tartaric acid, stir in, and place the pan into your ice/water bath. Pour the half syrup onto a marble slab/non-stick baking tray, then put the saucepan with the other half in back onto a low heat on the hob (just to keep the syrup liquid).
2. Work the sugar syrup. Scrape the seeds from the vanilla pod, and pour over the sugar syrup on the marble slab/non-stick baking tray. Using the pastry scraper, fold the edges into the centre of the sugar syrup. Preheat the oven to 120°C. When cool enough to handle, lift the syrup off the marble slab/non-stick baking tray, and work it into a cylindrical shape. Take the ends of the syrup strand, pull them together to form a ‘U’ shape, twist the two strands together, and work into a cylindrical shape again. Continue this for around 15-20 minutes, placing the strand into the oven if it gets too tough. When you are done, put the strand back in the oven until you need it.

The yellow strand. It was long.

3. Assemble the sweets. Working quickly, pour the rest of the sugar syrup onto the marble slab/non-stick baking tray. Add 2-3 drops pink food colouring, and, when the syrup is cool enough, shape into a long cylindrical strand. This syrup will be quite gloopy, so you might want to leave it to cool a bit more than you think you need to. Take the yellow syrup from the oven, and shape into a cylindrical strand of the same length as the pink strand. Tease the two strands together. Oil some scissors and cut the strands into the right sized pieces. Dust with caster sugar.


4 Comments (+add yours?)

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  4. Catherine Dream
    Nov 04, 2014 @ 01:17:35

    This was absolutely fascinating to read, while chewing on a rhubarb custard for the first time in my life – I especially loved the bit about high viscosity and crystals, and the technical stuff. I have no interest in attempting to make these, BUT it’s a brilliant post to enjoy.


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