Lemon

Pick up a lemon and give it a squeeze before you buy it. It should feel heavy for its size and slightly springy, never hard as stone and never soft. A heavy lemon means juice inside, not dried-out pulp. The skin should be tight and bright, and a good lemon smells fresh and zesty right through the peel; if it smells of nothing, pick another.

Here's the mechanism, and it's a simple one. Lemon juice is acidic, and that acid does real work in the kitchen: it firms up proteins in fish and meat, it stops cut apples and avocados from browning, it balances fat and sugar in a sauce. This is chemistry you can taste.

Now, some people say a lemon with thick, bumpy skin is the juiciest one. No! Thick skin usually means more pith and less juice. A smooth, thin-skinned lemon, heavy in the hand, is your best bet. Chase the bumpy giants thinking they'll give you more juice, and you'll end up squeezing hard for very little reward — and tossing half a fruit into the bin.

For 100 grams raw: 29 kcal, 1.1 g protein, 0.3 g fat, 9.32 g carbs.