Meat Temperature Phases

Enzymes in the meat are breaking down the fibres

Proteins begin to denature and enzymes stop working before 50°C  (122°F)

The longer you take to heat the meat, the more time the enzymes have to work and the softer the fibres will become.

In addition, a gentle heating process reduces tension on the meat

Meat is Rare

Red meat becomes pink as the pigment Myoglobin breaks down and the meat becomes medium-rare.

Red Myoglobin turns from pink, to brown and eventually grey.

Protein fibres shrink considerably and expel moisture, this transition from medium-rare to medium to medium-well can happen quickly if you are using high heat.

Be aware that between 60°C (140°F) and 65°C (149°F) there is significant moisture loss.

If you are cooking Low N slow, this is the point you would wrap the meat. 

Connective tissue begins to denature.

Protein shrinkage and water loss are significant, the meat becomes well-done meat and has a tough and dry texture.

Prime cuts should not be taken above this temperature

For Low N Slow with a Secondary Cut, you will need to continue slowly past 82°C (180°F) and beyond up to 93°C (200°F) at these temperatures’ Collagen begins to dissolve into Gelatine.