Even in this case, however, a bite of the fruit, or a sip of its juice, will still be very acidic. It may surprise you to discover that scientists have only recently established the true origin of this acidity. The credit goes to the lemon's ability to ‘pump’ hydrogen ions, which according to the rules of basic chemistry are the indicators of high acidity. But why does lemon need to be so acidic, to the point that its pH can drop to 2? It seems that it is a kind of trick to fight microorganisms and predators. After all, the juice is often used as a preservative, so the fruit is a sort of self-preservative. You may have noticed, in fact, that a lemon hardly rots. On the contrary, it tends to dry out thanks to its acidity.
This mix of bright colour and bold flavour makes the lemon a unique fruit, and widely used in both savoury and sweet preparations. One of the best way to enhance lemon is preparing an excellent jam, which by the way is a greedy way to learn the science behind this fruit.
How to make lemon jam:
1) To prepare lemon jam you will need a kilo of untreated natural lemons, ideally of the Sorrento type, which have a sweeter pulp. Then you need 600 grams of sugar and a little bit of water.
2) Brush the peel of the lemons while you wash them, then dry them and cut them into very thin slices, removing the seeds. Place the slices in a bowl, fill it with water and put it in the fridge for 24 hours.
3) Once this is done, drain the lemon and repeat the operation with fresh water for another 24 hours.
4) After draining the slices again, put them in a saucepan, cover them with clean water, and bring to a boil, then keep boiling until about half the water evaporates.
5) Add the sugar, and stir, then cook for an hour and a half, stirring occasionally.
6) At the end, pour into the sanitised jars, following the classic procedure that can be used with any jam.
In addition to finding yourself an excellent dessert, you will have a sweet excuse to put what you have learned into practice. Where does the colour come from? It’s thanks to the carotenoids. What about the taste? That’s thanks to the acidity of the fruit. And the density? That’ll be the pectin, a carbohydrate that is present in lemon peel and used as a natural thickener. Now all you have to do is think of bread and butter.