Organic Mustard Black Seeds (Brassica Juncea) are either dry roasted, or “tempered” in a hot oil with fresh curry leaves making them impart their nutty character in southern Indian cooking. It is also known as Rai in Hindi and harvested from mid February to mid April. It has a warm, earthy and pungent taste. Powdered mustard is simply finely ground mustard seed. In powdered form, mustard has no smell when dry, but it has a hot flavor when mixed with water.