Vol. XVI · Moist Heat Plate 9 of 11slow cooker, crock-pot, low, high, braising, danger zone, frozen meat, kidney beans, safety, heating timeSH

Slow Cookers.

On low, a full slow cooker takes a couple of hours just to pass 60 °C from fridge-cold. That is why frozen meat should not go in.

A slow cooker is a ceramic or metal pot over a low-power element, typically 150–300 W, with a lid that keeps the steam in. Its contents settle at a temperature set by the balance between that power and the heat lost through the pot: roughly 80–90 °C on low and 90–100 °C on high. That is ideal for braising (XVI.4): long hours just below the boil, with no attention needed. Tough cuts, beans (once boiled), stews and stocks all do well.

The weakness is the start. With so little power, a full pot from the fridge takes hours to warm through the danger zone (XII.3), longer still if the meat is frozen, because melting ice absorbs a great deal of heat. So: thaw meat first, start with hot liquid, do not overfill, and keep the lid on. And because the pot may never boil, raw kidney beans must be boiled hard for ten minutes before going in (XII.9). The workshop warms a slow cooker from cold.

Below: the temperature of a slow cooker's contents against hours on low and high, starting fridge-cold or frozen (a lumped teaching model of a 4 kg load), with the time spent below 60 °C.

What you will learn
Workshop
Teaching lumped model: 4 kg of contents (specific heat 3.8 kJ/kg K) with the element delivering 180 W on low and 260 W on high, settling at 85 °C and 95 °C. A frozen start adds warming from −18 °C and melting ice in 70 % of the load (334 kJ/kg). Real cookers vary; check yours with a thermometer.

Start warm, never frozen

In this teaching model a 4 kg load from the fridge takes about 2.2 hours on low to pass 60 °C; started frozen, about 4.1 hours, most of it melting ice at 0 °C before the warming even begins; with boiling liquid added to bring it to 40 °C at the start, about 0.6. Food-safety agencies advise against putting frozen meat in a slow cooker for this reason, and suggest starting with hot liquid or a high setting for the first hour.

What slow cookers do well: braises, stews, pulled pork, beans (boiled first), stocks — anything that wants hours at 85–95 °C. What they do badly: browning (do that in a pan first, VIII.1), thickening (reduce or thicken at the end, XVI.5), delicate vegetables and fish (add them late), and dairy, which can split over hours (add at the end, XVII.8). Do not lift the lid often: each look costs a lot of the little heat the pot has.

At the stove

Put a thermometer in your slow cooker's contents at the start of a recipe and read it every hour. Note how long it takes to pass 60 °C on low.

The Crock-Pot was launched in 1971 from a bean cooker designed by Irving Naxon, inspired by his grandmother's stories of cholent, the Sabbath stew left to cook overnight in the baker's cooling oven in Lithuania.

Terms

Slow cooker
A low-power electric pot for long, gentle cooking.
Low and high
Settings that settle around 80–90 °C and 90–100 °C.
Come-up
The time for the contents to heat from cold.
Cholent
A Jewish Sabbath stew cooked slowly overnight.
Slow cookers braise at 80–100 °C but heat slowly from cold: start with thawed food and hot liquid, keep the lid on, and boil kidney beans first.

Sources

  1. USDA Food Safety and Inspection Service, "Safe Minimum Internal Temperature Chart" (foodsafety.gov), 2024.
  2. U.S. FDA, Bad Bug Book, 2nd ed. (2012): Bacillus cereus emetic toxin is heat-stable and is formed in starchy foods held warm; Staphylococcus aureus enterotoxin survives cooking; scombrotoxin (histamine) forms in temperature-abused fish and is not destroyed by cooking; phytohaemagglutinin in raw red kidney beans — a few raw beans can cause illness; boiling 10 minutes destroys it, while heating to only about 80 °C can increase toxicity.
  3. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.