Saturday, May 2, 2020

Small Batch Lemon Curd

Continuing with the Small Batch theme, I present my recipe for Small Batch Lemon Curd!

This recipe is a scaled down version of the Zesty Lemon Curd in my debut cookbook "Scientifically Sweet: A Scientific & Delicious Approach to Artisanal Baking".

How do you make Lemon Curd?

This recipe is the easiest you will come by because you literally place everything in a bowl and stir over simmering water until it is thick!

The extra step that makes it taste extra lemony is to rub the sugar together with the lemon zest. Why? The yellow part of lemon skin contains essential oils (the same ones used to make citrus fragrances in perfumes and lemon-scented soaps) and when you rub sugar against them, it releases these oils. In turn the oils coat the flat surfaces of the sugar crystals - a technique that's know as "plating" in the food industry. Sugar also acts as an abrasive to help break down the zest so that there aren’t large stringy pieces of it that would distract from the silky smooth texture of this curd.

What's the science behind how it works?

Lemon curd is a type of stirred custard made from a cooked, thickened egg mixture. In the presence of heat and acid, egg proteins begin to bond to one another, transforming the liquid mixture into a smooth thick mass. In order to do this, gentle cooking is necessary to minimize the possibility of curdling. The acid from lemon juice helps to transform the ultimate structure of proteins (a process called denaturation) which unravels their natural folded structure so that their side chains are exposed to react with the surrounding environment. When this happens, the proteins begin to form bonds with each other, or coagulate, in a gentle way to form a continuous network of proteins with water held between them. This is what creates the thick and silky texture of citrus curd. 

Overcooking will cause proteins to bond too tightly, squeezing water out from between them and giving them a rubbery, lumpy texture. For insurance, indirect heat via steam is used to moderate the cooking temperature since boiling water cannot exceed 100°C. This recipe uses whole eggs to add firmness for a thick, spoonable texture, while the extra yolk adds creaminess and tenderness.

For an extra rich and extra yellow curd, add 1 extra egg yolk to this recipe. It will provide a firmer set and thicker consistency with richer mouthfeel - you decide! 

For more Small Batch recipes:
- Small Batch Chewy Chocolate Chip Cookies
- Small Batch Fudge Brownies
- Small Batch Double Chocolate Chip Cookies

Small Batch Lemon Curd
makes ½ cup

3 tbsp (42g) granulated sugar
zest of one lemon
1 large egg
3 tbsp (45ml) lemon juice
2 tbsp (28g) salted butter, cut in small pieces

Combine sugar and lemon in a bowl and use the back of a spoon or your fingertips to rub the zest into the sugar. This will coat the sugar crystals with fragrant oils from the lemon peel, adding a whole new dimension of intense lemon flavour to this curd.

Combine egg, extra egg yolk (if using), lemon sugar and lemon juice in a medium heatproof bowl and whisk until smooth. Add butter and set the bowl over a pot with ½-inch of simmering (or use a double boiler). Whisk gently over the for 5-7 minutes until thick enough to coat the back of a spoon (using a spatula prevents the incorporation of many tiny air bubbles that whisking would otherwise cause). Immediately pour it into a small jar or airtight container, place a piece of plastic wrap directly in contact with the surface and refrigerate until thoroughly chilled. This curd will last for about a week in the refrigerator.

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  1. Hi! By granulated sugar you mean the big granules right? or do you mean castre sugar? Could you please clarify. Thanks!!

  2. I made this originally with white granulated sugar, and it turned out AMAZING! The next time I tripled the recipe for more people, and used Lakanto brand golden monkfruit sweetener with Erythritol (1:1, zero calories and suitable for keto diets) and, again...AMAZING!