Vol. XXII · Stocks, Soups and Sauces Plate 4 of 11soup, clear soup, consommé, cream soup, purée, potage, bean soup, minestrone, 羹, 汤, seasoning, salt, stock cubes, bouillon, sodiumTF

Soups.

A soup made with stock cubes and salted "to taste" while it is still reducing can end up twice as salty as anyone wanted. The salt was there before the cook added any.

Most soups fall into four families. Clear soups — consommé, Chinese 清汤 soups, Japanese suimono — are stock with garnish, and their quality is the stock's. Cream soups are stock thickened with roux or starch and finished with cream or milk (XXII.5), or thickened with egg yolk and cream (a liaison, XVII.5). Purée soups are thickened by the vegetables themselves — potato and leek, carrot, squash, pea — cooked soft and blended, their starch and fibre giving body (XX.2). Bean and grain soups (minestrone, lentil soup, 绿豆汤) are thickened by starch from the legumes or grains as they break down. Chinese 羹 are thickened with a starch slurry until spoon-coating (XXII.9).

All of them need seasoning, and salt is where soups go wrong. A pleasant savoury soup is roughly 0.7–1.0 % salt by weight (XI.3). Commercial stocks and cubes are made at about that concentration already, or more; homemade stock has almost none. Reducing a soup concentrates the salt with it (XXII.8). So the sensible order is: season at the end, after reduction, knowing what the stock brought. The workshop balances the salt.

Below: the salt to add to a soup of the volume you choose made with the stock you choose, to reach 0.8 % salt after reducing by the share you choose (exact mass balance; negative means dilute instead).

What you will learn

Name the four families of soup.
Thicken soups by purée, starch or liaison.
Season soup by mass balance.
Account for stock cubes and reduction.

Workshop

Mass balance, exact: salt needed = target 0.8 % × final weight − salt already present. Stock salt contents: homemade unsalted about 0.05 %, low-sodium carton about 0.3 %, standard carton or cube made up as directed about 0.9 % (typical label values). Soup density taken as 1 kg/L; vegetables and other ingredients assumed unsalted.

Season last, and count the stock

A soup made from a standard stock or cube at about 0.9 % salt is already at the target before anyone touches the salt; reduce it by a fifth and it is at 1.12 % — too salty — and needs unsalted liquid, not salt. The same soup from 1.5 litres of homemade unsalted stock, reduced by a fifth, needs about 9 g of salt (two level teaspoons). So taste near the end, after reducing, and add salt in steps (I.7); with bought stock, choose low-sodium and season yourself.

Family methods. Purée: sweat onion or leek in butter, add potato or the main vegetable and stock to cover, simmer until very soft, blend until smooth, adjust thickness with stock, season, finish with cream or butter. Cream: thicken stock with a blond roux (XXII.6), add the cooked vegetable, blend, finish with cream; or thicken off the heat with yolks and cream, never boiling after (XVII.5). Bean: soak and cook beans (XX.8), add vegetables in order of cooking time, mash some beans for body. Chinese 羹: bring stock and diced ingredients to the boil, stir in a starch slurry to coat a spoon, then swirl in beaten egg off the boil (XXII.9).

At the stove

Read the salt per 100 mL on a carton or cube of stock you use. Multiply by the litres in your next soup and compare with 0.8 % of its final weight before you add any salt.

The French potage and Chinese 羹 both descend from medieval thickened broths; the word "soup" itself comes from "sop", the bread over which broth was poured — a meaning that survives in French onion soup and in 泡馍.

Terms

Consommé: A clarified, intensely flavoured clear soup.
Purée soup: A soup thickened by its own blended vegetables or legumes.
Liaison: Egg yolk and cream used to thicken and enrich a soup off the boil.
羹: A Chinese soup thickened with a starch slurry.

Soups are clear, cream, purée or bean. Season them last, by mass balance: about 0.8 % salt of the final weight — and count what the stock brought, and what reduction concentrated.

Sources

A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.