Salt is added to the water when par-boiling rice for biryani to season the rice from within and to help prevent it from becoming mushy by strengthening the starch structure.
Adding salt to the water during the par-boiling process of rice for biryani serves two primary purposes. First, it seasons the rice grains internally. Since the rice will be layered with other flavorful ingredients in the biryani, starting with seasoned rice ensures a more balanced and flavorful final dish. The salt permeates the rice as it absorbs water, enhancing its taste.
Second, salt helps to control the starch gelatinization process. Salt strengthens the starch granules, preventing them from absorbing too much water and becoming overly soft or mushy. This is crucial for biryani, where the rice grains need to remain separate and distinct after cooking. The salt essentially toughens the outer layer of the rice, allowing it to withstand the subsequent cooking stages without falling apart.
Use sea salt or kosher salt instead of iodized table salt. Iodized salt can sometimes impart a slightly metallic taste to the rice, while sea salt and kosher salt offer a cleaner, more natural flavor.