Apple Cupcakes with Caramel(an, en and in) Buttercream

From the "chemistry-science" perspective, caramel, or, to be more precise, the process of caramelization, seems pretty complicated... Although it is really cool to understand the chemistry behind this golden delight, it might scare you off from trying to cook it on your own. Nevertheless, after my first successful attempt, I can assure you it is actually easier than it looks. Although one must really pay attention to the tiniest details, it is a surprisingly quick process and the end product is definitely worth it.

It all starts with sugar dissolving in water (for the so called "wet caramelization"), and sucrose breaking down into fructose and glucose by hydrolysis. The second step, condensation, is very easy to detect, because you start noticing the aromas coming out of the pot. This signals that glucose and fructose started to break down into smaller, more volatile compounds. You might be able to smell the nutty aroma of furans, buttery smell of diacetyl, toasty fragrance of maltol, and fruity scent of ethyl acetate...  

This second step can be, in theory, accelerated, if you add a little lemon juice to the sugar mixture...the breakdown of fructose and glucose is acid catalyzed, thus adding an acid, such as the citric one, should enable the reaction to occur faster and at lower temperature. I have not tried that, so my recipe below does not include lemon juice... it could, however, be a nice experiment...

Oligomerization is the next step in caramelization process. These reactions further contribute to the development of brown colour and portions of the texture. First, dimerization occurs. In the case of fructose, the dimer is called di-D-fructose dianhydride. There are three different pathways on which these dimers can react further. These differ in the number of water molecules that are lost in the reaction. One of them results in the formation of caramelan (C12H12O9) aggregates of which form small, brown particles about 460 nm in size , another one can form caramelen (C36H18O24), a polymer that has aggregates of 950 nm in size, and the third one produces another polymer called caramelin (C24H26O13) which aggregates in particles that are darker in colour and are about 4333 nm in size. These oligomers assemble into particles and networks and create the unique texture of caramel. The presence of free radicals is believed to be partially responsible for the typical caramel stickiness.

Apple Cupcakes with Caramel Buttercream Frosting

Ingredients (makes for about 12 medium cupcakes)

     Cupcakes
1&1/2 cup plain flour
1 cup grated apples
1 cup brown sugar
1/2 cup vegetable oil
1/8 cup lemon juice
2 tsp. baking powder
1 tsp. vanilla extract* (not the Dr.Oetker clear essence!)
0.5 tsp. salt
0.5 tsp. cinnamon
2 large eggs
*the only good vanilla extract I discovered in CZ/SK so far is the one from Marks and Spencers, in the UK I like the one from Dr.Oetker (brownish and thick, available with, or without the vanilla seeds)

     Caramel Buttercream Frosting & Caramel Topping
170 g unsalted butter (softened)
1/2 cup brown sugar
1/8 cup water
1/8 cup heavy cream
1 tsp. vanilla extract
0.25 tsp. salt
2 large egg whites

Directions
      Cupcakes
1. Preheat oven to 180°C
2. Beat together the eggs and sugar until creamy
3. Beat in the lemon juice, vanilla extract, and oil
4. Mix the remaining dry ingredients and slowly add the dry mixture to the wet one and beat thoroughly until smooth
5. Stir in the grated apples
6. Line a cupcake/muffin pan with cupcake cases and fill each one a about 3/4 full
7. Bake for about 20 minutes (toothpick inserted in the centre should come out mostly clean)

     Caramel/Caramel Topping
1. Bring 1/4 cup sugar and the water to boil, cook and stir with a wooden spoon occasionally until the caramel is dark amber
2. Remove from heat and add cream, salt and 0.5 tsp. vanilla extract, stir with a wooden spoon until smooth
3. Let cool
     Caramel Buttercream
1. Beat butter with a mixer until pale and fluffy (about 3 min)
2. Put the egg whites and 1/4 cup sugar in a heatproof  bowl and set it over a pot of simmering water
3. Whisk until sugar dissolves and remove from heat
4. Whisk the sugar-egg mixture on medium speed for about 5 min
5. Increase the speed to medium-high and whisk until stiff and glossy (about 6 min)
6. Reduce speed to minimum, slowly add beaten butter, whisking well after each addition
7. Whisk in vanilla extract and add about 1/3 (or more) of the caramel and beat until smooth (3-5 min)