Temperature

The temperatures used in sous vide cooking are always below that of simmering water, which is about 87° to 93°C (190° to 200°F). The highest temperature we use, almost without exception, is 85°C (185°F), and this is exclusively for vegetables. Plant cell walls are weakened at this temperature, and so the vegetable becomes tender.

Meat and fish cooking temperatures are more varied. Fish proteins generally are delicate, and they denature and coagulate—that is, cook—at about 6.6°C (11.9°F) lower than meat proteins do. For meat, the cells begin to contract and thus squeeze out water and become tough at about 60°C (140°F). At about 70°C (160°F), the meat will have squeezed out much of its moisture, but the cells are easier to pull apart and the collagen will have begun to melt into gelatin (resulting in the very tender meat we expect from a braise).