ICMR says boiling or pressure cooking can improve the nutritional quality of pulses; here’s how to do it right

Pulses, a staple in many Indian diets, are renowned for their exceptional nutritional value, particularly their rich protein content. However, improper handling and cooking methods can significantly diminish the bioavailability of these essential proteins. 

In an effort to ensure that individuals can reap the full benefits of pulse consumption, the Indian Council of Medical Research (ICMR) has provided comprehensive guidelines on preserving the protein profile in legumes. 

According to the guidelines, “Boiling or pressure cooking is the best way to improve the nutritional quality of pulses since anti-nutritional factors (enzyme inhibitors that do not allow nutrients to get digested) are destroyed during boiling and pressure cooking. Hence these methods increase the digestibility and therefore protein availability.”

Boiling just enough water, it states, without having to drain the water is the best method to retain folate in legumes. This method of cooking improves the palatability of pulses.

Furthermore, the ICMR stresses, “Longer cooking causes a drop in the nutritive value of pulses as it results in the loss of lysine. Remember to add only the required amount of water during boiling.”

The biochemical changes that occur in pulses when they are boiled or pressure cooked

Kanikka Malhotra, consultant dietician and certified diabetes educator, says, “Both boiling and pressure cooking use heat to denature proteins (unfold their structure). However, pulses offer a distinct edge. They have heat-stable proteins called globulins. These globulins are less prone to denaturation than animal proteins, hence a significant fraction remains intact after cooking.”

Boiling includes simmering in water, she says, which can extract some soluble proteins. Pressure cooking, on the other hand, operates in a closed atmosphere with little water. This minimizes protein loss via leaching.

Pressure cooking may offer a modest advantage in retaining protein content over boiling, although both methods retain a large percentage of the important pulse protein. Both boiling and pressure cooking can successfully destroy lectins. “These proteins can irritate the digestive tract, but heating makes them harmless,” Malhotra says.  

Phytic acid is a molecule that can bind to minerals such as iron and zinc, lowering their bioavailability. Boiling has little effect on phytic acid, she states, however pressure cooking may be more effective because of the greater temperature and shorter cooking time.

Soaking pulses overnight can help reduce cooking time. (Source: Freepik)

How can one ensure that pulses are cooked just enough to retain their protein quality? 

By following these tips recommended by Malhotra, you can ensure your pulses are cooked perfectly, retaining their protein quality and delightful texture:

Know Your Pulses: Cooking times vary with different pulses. Lentils cook faster than chickpeas and black beans. 

The “Tender But Bite Test”: The greatest way to determine whether your dal is cooked is through tasting. Take a sample pulse at regular intervals while cooking. It should be delicate when bitten, yet with a small stiffness in the core. 

Start with Less Water: Pulses absorb water as they cook. Using too much water will lead to longer cooking times and a higher risk of overcooking. Add just enough to cover the pulses by an inch or two. 

Simmer, Don’t Boil: A gentle simmer is all you need. Boiling can cause the pulses to burst and become mushy. 

Turn Off the Heat Early: Once the pulses are close to being done, remove them from the heat and let them sit in the hot water for 10-15 minutes. This allows them to finish cooking gently without further heat exposure. 

 Practical tips for home cooks to get this right for boiling pulses

According to Malhotra, pulses contain B vitamins and vitamin C, which dissolve in water. Using excessive water can leach out these vitamins during cooking. Some minerals, like potassium and magnesium, are also water-soluble and can be lost in cooking water.

She recommends, “Aim for just enough water to cover the pulses by an inch or two. This ensures even cooking without excessive leaching. Don’t throw away the water after cooking! It’s packed with nutrients leached from the pulses. Use it in soups, stews, or sauces to reap the full nutritional benefit.”

Soaking pulses overnight can help reduce cooking time and potentially lessen vitamin C loss, she adds. However, research on the exact impact of soaking on nutrient retention is ongoing. 

You can also opt for a combination approach. Soak your pulses overnight, then pressure cook them with minimal water. This strategy helps reduce cooking time (minimising vitamin loss) and ensures optimal nutrient retention.

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