Why it works: Sugar and syrup match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 5,842 recipes. Both carry ethanol, which smells alcoholic, ethereal. The science ↓
To Preserve Watermelon Rind and Citron
Ingredients
Directions
Prepare the rind
Pare off the green skin.
Cut the watermelon rind into pieces.
Weigh the pieces. Use 1.5 pounds of sugar for each pound of rind.
Simmer the rind
Line a kettle with green vine leaves.
Add the rind without sugar. Cover each layer with vine leaves.
Pour in enough water to cover the rind.
Place a thick cloth over the kettle.
Simmer for two hours.
Add a few bits of alum.
Spread the rind on a dish to cool.
Make the syrup
Melt the sugar with 1 pint of water for every 1.5 pounds of sugar. Mix in the beaten egg white.
Boil and skim the sugar until clear.
Add the rind.
Boil for two hours.
Remove the rind.
Boil the syrup again.
Pour it over the rind.
Let it sit overnight.
Finish and jar
Boil the syrup with lemon juice until thick enough to hang from a spoon.
Put the rind in jars.
Pour the syrup over it.
Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.
Explore the science
The flavor team
The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.
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Sugar + syruptop 6% of all pairsSmell alikestrongCooked together5,842 recipes
Shared aroma: ethanol (alcoholic, ethereal).
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Sugar + lemontop 18% of all pairsSmell alikelowCooked together53,532 recipes
Shared aroma: 2-nonenal (fatty, green).
-
Egg + lemontop 19% of all pairsSmell alikelowCooked together44,316 recipes
Shared aroma: (e,e)-2,4-decadienal (fatty, deep fried).
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Lemon + syruptop 20% of all pairsSmell alikelowCooked together2,235 recipes
Shared aroma: ethanol (alcoholic, ethereal).
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Sugar + eggtop 21% of all pairsSmell alikemoderateCooked together122,807 recipes
Shared aroma: 2-nonenal (fatty, green).
Sugar and lemon barely smell alike, yet cooks put them together in 53,532 recipes: they work on texture and structure more than aroma.
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Watermelon rind
- Forms the preserve itself, becoming tender and translucent as it cooks in syrup.
- Loaf sugar
- Sweetens the preserve and, at high concentration, helps preserve the rind and thicken the syrup.
- Egg white
- Clarifies the syrup, binding impurities that are then skimmed off so the syrup runs clear.
- Alum
- Firms the rind so it keeps its shape and texture during long cooking.
- Lemon juice
- Adds acidity that brightens the sweet syrup and helps it set thick.
The step that matters
Boil the syrup until it hangs from a spoon. Sugar concentration determines whether the syrup thickens and preserves the rind. Too little boiling leaves a thin syrup that spoils or drips off; overcooking can turn it grainy or hard.
Swap the lemon
How well each one fits the dish's main ingredients (sugar, egg, syrup):
- Vanillafits better
- Raisinfits better
- Lemonthe original
- Figfits about as well
Fit is the average pairing score against sugar, egg, syrup. Candidates are from the same food group and used in at least 100 recipes.
“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.
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