No, that's not true. First, most bars don't use pet blood supplements at all. It is expensive and requires high technological discipline ...
Secondly, a small part of Hematogen bars use Albumin, a type of protein found in the blood. In particular, in pharmacology (and confectionery production), bovine serum albumin (abbreviated BSA, English Bovine Serum Albumin, BSA) is used - a bovine blood plasma protein with a molecular weight of 69,000 Da, single-chain, consisting of 607 amino acid residues.
However, no blood is added to the hematogen! Protein obtained from blood is added.
There is a simplified technology (for technical needs) that has been banned in food production since the middle of the last century - when acetic acid was added to the blood, then it was diluted, acid neutralized, filtered, evaporated, etc.
One of the modern (insufficiently perfect methods) is a method of obtaining a fraction of serum albumin by adsorption on water-insoluble cross-linked polyelectrolyte copolymers of ethylene with maleic acid anhydride ...
Yes, if there is black food albumin in the composition. Initially, bovine blood was used , which was specially processed to exclude the possibility of infection. Now some producers indicate pork too. Blood is used as an available source of iron. In addition, other ingredients are added for flavor or additional effect.
Hematogen was first released in 1980 in Switzerland as a liquid potion.
And in Russia, he gained great popularity in the form of bars that have an external resemblance to chocolate. It was used for the prevention and treatment of iron deficiency anemia.