Sourest Day

What the day is

Sourest Day is observed on October 25. It exists as a joke at the expense of Sweetest Day, the regional Midwestern observance kept on the third Saturday in October, and it lands a few days after it.

The premise is straightforward mockery: if a candy-industry holiday can celebrate sweetness and affection, something should speak for the opposite.

Origin and background

The origin of the observance is not documented, and it appears to have circulated informally rather than being established by anyone in particular.

Sourness itself is worth the attention. It is one of the basic tastes, and it is detected quite differently from the others: taste cells respond to the acidity itself, to hydrogen ions entering the cell, rather than to a molecule binding a receptor. That is why sourness tracks acid concentration so directly.

Its evolutionary role is debated and probably double-edged. Sourness signals unripe fruit and spoiled food, which argues for avoidance, but it also indicates fermentation and vitamin C, both of which were useful. Human responses to sour are unusually variable and strongly learned, which is why children generally reject it and adults often seek it out.

In cooking, acid is the most commonly missing element in a dish that tastes flat. Salt gets the attention, but a squeeze of lemon or a splash of vinegar frequently fixes what more salt cannot, by cutting fat and lifting other flavors. Professional kitchens reach for acid constantly, and home cooks largely do not.

How to take part

• Taste something genuinely sour on purpose: a lemon wedge, unsweetened cranberry, or a good vinegar.
• Fix a flat dish with acid rather than salt and notice the difference.
• Try a sour beer, a proper sourdough or a fermented vegetable.
• Keep more than one vinegar. Sherry, rice and cider vinegars do quite different jobs.
• If the day appeals as a mood rather than a taste, be pleasantly sour about the greeting card industry for an afternoon.