"The raw materials undergo a gentle, enzymatic hydrolysis of the collagen polypeptides until the desired collagen peptide molecular weight is achieved. Subsequently, the liquid hydrolysed collagen is spray-dried and partly agglomerated."
So A homemade low cost collagen is to blend gelatin powder in water with enzyme like papain. Cheap papain I use is meat tenderizer bought from Chinese goccery.
These meat tenderziers usually also contains corn flour, some even also contain salt and sugar.
Yes, the end product after blending doesn't gel......So this is my version of cheapo collagen.
The amount of papain in different brands of tenderizers differs, so you have to experience what is the minimum quantity required for the transformation.