![enter image description here](https://i.sstatic.net/Hemoglobin Hemoglobin is concentrated inside red blood cells and gives them the red colour. If the heat is high enough red and other cells, including bacteria, are destroyed. The red juices contain intact red blood cells and turn clear as the haemoglobin spills out of the destroyed cells and is diluted by the other juices. If you can destroy all red blood cells it is assumed you are also destroying the bacterial cells..jpg)