Vol. XVI · Moist Heat Plate 1 of 11boiling, simmering, poaching, water temperature, bubbles, chicken breast, juicy, gentle heat, 白切鸡HT

Boil, Simmer, Poach.

A chicken breast poached at 75 °C is juicy to the edge; boiled at 100 °C, it is dry on the outside before the middle is done.

Water carries heat into food far better than air (II.3), and it cannot be hotter than its boiling point (III.2). Within that limit the cook chooses: a poach at 70–80 °C, with the surface barely trembling; a simmer at 85–95 °C, small bubbles rising lazily; a boil at 100 °C, large bubbles breaking all over. The bubbles are the only gauge most cooks need, though a thermometer is better.

Lower water temperatures give gentler cooking for the same reason a low oven does (XV.6): the outside is never much hotter than the target, so proteins at the surface do not overcook and squeeze out juice while the centre catches up. Chinese 白切鸡 is poached just below a simmer and left to steep off the heat; fish is poached at 70–80 °C; eggs for poaching sit in water that barely moves (XVII.3). A full boil is for food that needs it: pasta and noodles, blanching vegetables (XVI.2), reducing liquids. The workshop poaches a chicken breast.

Below: a 25 mm chicken breast cooked in water held at the temperature you choose until its centre reaches 70 °C (thermal bench): time, juice lost and how far the outside overshoots, compared with poaching, simmering and boiling.

What you will learn
Workshop
Thermal bench: chicken breast, 25 mm slab, from 5 °C, in water at the temperature chosen (heat-transfer coefficient rising from 300 W/m² K for still poaching water to 800 for a rolling boil) until the centre reaches 70 °C. Juice loss from the course loss curve against the highest temperature each layer reached.

Read the bubbles

In this model the breast poached at 75 °C takes about 27 minutes to reach 70 °C at the centre and loses about 26 % of its weight as juice; boiled at 100 °C it is done in 11 minutes but loses 30 %, because its outer layers were driven far past 70 °C. The gentle poach takes more than twice as long, but it is juicier, and its outer layers never pass 75 °C, so the texture is even from edge to centre.

Practical rules. Poach fish, chicken breast, eggs and delicate dumplings in water that barely moves; simmer stocks (a boil clouds them, XXII.1), braises and beans; boil pasta, noodles and green vegetables in plenty of salted water so it comes back to the boil quickly. A lid helps water reach temperature faster (III.5) but makes it easy to boil over: set it ajar for a simmer. And remember altitude: at 2 000 m water boils near 93 °C, and everything that relies on boiling takes longer (III.3).

At the stove

Poach two chicken breasts, one in water at a bare tremble (check with a thermometer: about 75 °C) and one at a rolling boil, each until 70 °C at the centre. Weigh them before and after, and taste.

The French and Chinese kitchens both name water by its look: frémir (to shiver) for poaching water, and in Chinese 虾眼水 ("shrimp-eye water") for the small bubbles before a simmer and 蟹眼水 ("crab-eye water") for larger ones.

Terms

Poach
Cooking in water at about 70–80 °C, barely moving.
Simmer
About 85–95 °C, small bubbles rising gently.
Boil
100 °C at sea level, large bubbles breaking all over.
白切鸡
Cantonese poached chicken, steeped below a simmer.
Poach 70–80 °C, simmer 85–95 °C, boil 100 °C. Gentler water overcooks the outside less and keeps food juicier.

Sources

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