Have you ever thought why is it recommended to soak beans before cooking? What a stupid question you might think. Of course, to reduce the cooking time! Indeed, during soaking the water is dispersed into the starch granules and protein fractions of beans, which facilitate processes (such as gelatinization and protein denaturation) to soften the texture and to break down some complex sugars for better digestion with less gas production.
You can optimize soaking by adding some salt in the soaking water. Salt addition results in a tender skin due to sodium ions replacing calcium and magnesium ions bound to pectin in the cell walls.
But the best results you can achieve by adding a baking soda (2.3 g/100 ml) and letting it first soak for 13.1 hours, and then dry at temperature of 50 °C. In this way you reduce the cooking time of the beans by 53%!
Adding a baking soda has another big advantage. It also helps remove the anti-nutrients, such as tannins and phytic acid, or reduce trypsin inhibitor activity. Why would you care about this?
Tannins can be toxic to your body if taken in large amounts. They interfere with normal digestion and nutrient absorption by inactivating digestive enzymes. As a result, you can suffer from nausea, vomiting, constipation, abdominal pain, and liver damage.
Phytic acid decreases the absorption of iron, zinc and calcium and can lead to mineral deficiencies.
Trypsin inhibitor activity has also an antinutritional effect as trypsin inhibitor competes with enzyme trypsin, that helps us digest protein, and therefore makes it unavailable to bind with proteins for our digestion process.
Here I want to highlight that just soaking will not help you in reducing the tannin content. You need to add baking soda to eliminate tannins and reduce trypsin inhibitor activity in beans.
Another interesting scientific fact that might surprize you. The distilled water will not improve the soaking process. According to research, soaking peas in distilled water increases trypsin inhibitor activity by 3.2–19.3%!