Mustard seeds need to crackle during tempering because this indicates they have released their essential oils and flavor compounds, resulting in a more potent and aromatic seasoning. If they don't crackle, they'll taste bitter and won't impart the desired flavor.
Tempering, also known as 'tadka' or 'chhonk,' is a cooking technique common in Indian cuisine where spices are briefly roasted in hot oil or ghee to release their flavors. Mustard seeds are frequently used in tempering, and the crackling sound is a crucial indicator of their readiness.
Here's a breakdown of why the crackling is important:
In essence, the crackling sound is a signal that the mustard seeds have been properly activated and are ready to impart their full flavor to the dish.
To prevent mustard seeds from burning before they crackle, use medium-low heat and ensure the oil is hot but not smoking. Cover the pan loosely with a lid to contain the splattering seeds and help them cook evenly.