What technique did Birdseye use in the US to mimic the near-instantaneous freezing witnessed in the Arctic?

Submerging food in super-chilled brine solution

Upon returning to the United States, Birdseye actively worked to replicate the rapid freezing observed in the Arctic. His engineered solution involved utilizing super-chilled brine (salt water) as a highly conductive medium to draw heat out of the food very quickly. He would often pack food in small containers and submerge them directly into this brine, which could reach intensely low temperatures, sometimes as low as $-40^ extrm{o}$F ($-40^ extrm{o}$C). This direct contact with the extremely cold liquid ensured rapid heat transfer from the food item to the chilling agent, effectively achieving the swift freezing rate necessary to minimize damaging ice crystal growth and preserve the food's initial quality.