Dynamics of mustard seed spluttering and popping in heated cooking oil

Oil spluttering during cooking is a major safety concern, often leading to skin burns, wall deposition, and overall hazards in the kitchen. In this study, we experimentally investigate the spluttering dynamics of mustard seeds in heated cooking oil, a common practice in Indian cuisine. A controlled experimental set-up was employed, where a single mustard seed was introduced into a pool of preheated sunflower oil in a Petri dish. High-speed shadow imaging technique was utilized to visualize the flow dynamics. The observations unveil a complex, highly dynamic, multiphase flow process occurring in sequential stages, primarily governed by the moisture content of the seed. Initially, microbubbles are generated from the upper hemisphere of the seed, followed by high-frequency oscillatory flows near the oil–air interface caused by seed popping. On the lower hemisphere, bubbles attach to the solid bottom surface, merge, and grow, contributing to pressure buildup that either causes significant perturbations at the oil–air interface or ejects the seed, both mechanisms leading to droplet formation. Experiments conducted at different oil temperatures (200, 250, and 300 °C) and oil depths revealed their respective influences on seed dynamics. A broad range of droplet sizes (∼ 150 to 1000 μm) was observed across all cases, with smaller characteristic droplet sizes at higher oil temperatures. A theoretical model has been developed to explain the liftoff dynamics of the mustard seeds. The findings offer valuable new insights into the dynamic behavior of mustard seeds during the cooking process.