Putting uncooked kidney beans in a slow cooker can be dangerous if not done properly. Raw kidney beans contain a toxin called phytohaemagglutinin that can cause severe stomach issues when eaten. However, with some precautions, it is possible to safely cook uncooked kidney beans in a slow cooker.
Quick Answer
Yes, you can put uncooked kidney beans in a slow cooker, but you need to boil them first for 10 minutes to destroy the phytohaemagglutinin toxin. After boiling, drain and rinse the beans before adding to the slow cooker. Cooking beans from dry in a slow cooker without boiling first can allow the toxin to linger and cause illness.
Phytohaemagglutinin Toxin in Raw Kidney Beans
Kidney beans contain high levels of phytohaemagglutinin, which is a lectin or carbohydrate-binding protein that is toxic to humans. The toxin is found in higher concentrations in raw kidney beans and especially red kidney beans. Eating even 4-5 undercooked beans can bring on symptoms within a few hours.
Phytohaemagglutinin acts as a pest deterrent in the plants. When consumed by humans, it can bind to receptors on the cell membrane of the stomach and small intestine. This disrupts digestion and causes extreme nausea, vomiting, and diarrhea that can last for several hours. In severe cases, it has led to paralysis and even death when very high doses were consumed.
Amount of Phytohaemagglutinin in Common Bean Varieties
| Bean Type | Toxin per 100g dry weight |
|---|---|
| Red kidney beans | 20,000 to 70,000 hau |
| White kidney beans | 11,000 to 39,000 hau |
| Pinto beans | 13,000 to 35,000 hau |
| Black beans | 8,000 to 30,000 hau |
| Broad beans | 6,000 to 17,000 hau |
| Navy beans | 2,000 to 4,000 hau |
*hau stands for haemagglutinating units – a measure of lectin content
As you can see, red and white kidney beans tend to have the highest phytohaemagglutinin content. Navy beans have relatively low levels in comparison.
Proper Preparation to Remove Toxin
To safely consume kidney beans and eliminate the phytohaemagglutinin toxin, they must be boiled for at least 10 minutes. The high temperatures break down the lectins so they are no longer harmful.
Simply soaking beans overnight is not enough to remove the toxins. The temperature of the water during soaking does not get hot enough. Boiling is required.
After boiling the beans, the water should then be discarded and the beans rinsed before using in a recipe. Adding salts or acids like lemon juice or vinegar to the soaking or cooking liquid can also help neutralize phytohaemagglutinin.
Steps for Using Uncooked Beans in a Slow Cooker
- Rinse the dry beans and pick out any debris
- Place beans in a pot, cover with water, and bring to a boil for 10 minutes
- Drain and rinse the boiled beans
- Add the beans to the slow cooker with other ingredients
- Cook on low for 7-8 hours or high for 4-5 hours
- Stir occasionally and add more liquid if needed
Following this process destroys any toxins and allows the beans to cook thoroughly in the slow cooker.
What Happens if You Don’t Boil Before Slow Cooking
Putting dry, unboiled kidney beans directly into a slow cooker can potentially keep the toxins active. This is because the beans may not reach a high enough temperature for long enough to degrade the phytohaemagglutinin.
Since slow cookers heat to around 190°F and bean toxins start to break down around the boiling point, 212°F, the slow cooking alone may not be sufficient.
If you cook the beans long enough, about 12+ hours on low, the toxins can eventually break down. However, shorter cooking times pose a risk if the beans weren’t pre-boiled.
Signs of Phytohaemagglutinin Poisoning
- Nausea, vomiting, diarrhea – within 3-5 hours after ingesting
- Abdominal pain and intestinal cramping
- Difficulty breathing in severe cases
- Hypotension and irregular heartbeat
- Extreme hypothermia
- Burning sensation in the mouth
Seek immediate medical attention if these symptoms occur after eating slow-cooked kidney beans. Proper boiling of the beans prior to slow cooking can prevent this type of poisoning.
Other Ways to Cook Uncooked Kidney Beans
Besides using a slow cooker, here are some other methods to safely prepare dry kidney beans:
On the Stovetop
After boiling the beans for 10 minutes, you can simmer them on the stovetop in a pot with fresh water or broth until fully tender. Make sure the pot is large enough that the liquid doesn’t boil off completely. Cook times range from 1-2 hours.
In the Oven
Pre-boiled beans can be baked in the oven in a covered dish with liquid at 300°F-325°F for about 1 1/2 hours until soft.
In a Pressure Cooker
Pressure cooking reaches high enough temperatures to destroy the toxins in kidney beans. Pre-boil them first, then cook with additional water for about 25 minutes on high pressure.
Canned Beans
Canned kidney beans have already been pre-cooked properly during the canning process to eliminate phytohaemagglutinin. Rinsing them before use will remove excess sodium from the canning liquid.
Conclusion
Cooking uncooked kidney beans in a slow cooker can lead to phytohaemagglutinin poisoning if not done carefully. Always make sure to boil kidney beans for at least 10 minutes before adding to the slow cooker. This prevents the toxins from causing extreme nausea, stomach pains, and other complications.
Proper preparation opens up many possibilities for incorporating beans into your slow cooker for tender, flavorful meals. Taking the time to pre-boil dry kidney beans prevents the dangers of undercooked toxins and allows you to safely reap their nutritional benefits.