Why it browns
Mint leaves contain enzymes that cause browning as soon as the tissue is damaged, the same broad process that darkens a cut apple. Warmth accelerates it, and a leaf sitting in hot syrup browns within minutes.
The aroma is a separate problem. Mint's volatile compounds escape readily with heat, so simmering the leaves drives off exactly what you wanted.
Both are solved by the same approach: blanch the mint very briefly in boiling water to knock out the enzymes, refresh it in iced water to stop the cooking, and then infuse it in syrup that is warm rather than hot.
The method
Blanch, refresh, infuse cool. FoodHQ does not publish keeping times or preservative quantities for home-made cordials. Those are safety numbers rather than matters of taste, and in the UK the Food Standards Agency is the authority — follow its guidance on sterilising bottles and on storing, refrigerating and freezing what you make.
- Make a simple syrup: equal weights of sugar and water warmed until the sugar dissolves. Take it off the heat and let it cool to lukewarm.
- Bring a separate pan of water to the boil and set a bowl of iced water beside it.
- Drop the picked mint leaves into the boiling water for ten to fifteen seconds only. No longer.
- Lift them straight into the iced water. They should stay bright green.
- Squeeze them dry and blitz them with the lukewarm syrup until smooth.
- Strain through muslin, pressing gently. Add a squeeze of lemon, which helps hold the colour.
- Chill immediately and keep it cold. Mint syrup fades with time and light, so freeze what you will not use soon.
What to do with it
- In a mojito or a mint julep, where it replaces muddling.
- Over a fruit salad, particularly melon, strawberries or peaches.
- In a lemonade, a spoonful in the glass.
- Over chocolate ice cream or a chocolate pudding.
- In a granita, with lime.
- Brushed over a sponge cake with lemon.
- In a dressing for a grain salad, with lemon and oil.
- Poured over yoghurt with pomegranate, which is a Middle Eastern instinct and a good one.
Notes
- Which mint
- Spearmint for a culinary syrup. Peppermint gives a much more menthol result, closer to confectionery.
- Colour
- Bright green when made and fading within days. Keep it cold and dark, and freeze for longer.
- Stalks
- Use leaves only. Mint stalks are tough and slightly bitter.
- Quantity
- A large bunch of mint to a modest quantity of syrup. Mint is bulky and gives up less than it looks.
- Other herbs
- The same blanch-and-infuse method works for basil, tarragon and lemon verbena.
Common questions
Why did my mint syrup go brown?
The leaves were heated without blanching. Blanch for ten seconds, refresh in iced water, then infuse in lukewarm syrup.
Why does it taste stewed?
The mint was simmered. Its aroma is volatile and disappears with sustained heat.
Spearmint or peppermint?
Spearmint for food and drinks. Peppermint is much more menthol and reads as confectionery.
How long does the colour last?
A few days in the fridge. Freeze it in cubes to keep it green longer.
Does this work for basil?
Yes. The same method suits basil, tarragon and lemon verbena.
Try this next
- Mint the herb, and its varieties
- How to use herbs why soft herbs go in late
- How to make lemon cordial what to add it to