Hydrolyzed vegetable protein (HPV)is vegetable protein, principally soya, hydrolyzed such that it is split into its constituent amino acids. It is a very strong stimulator of the umami taste receptors. It is used in many food products, of note are cheap gravy granules which are largely potato starch with a little HPV, and cheap soy sauce which is largely HPV and burnt wheat in water. As I understand it these would include milligrams of HPV per pack. I think it has similarities to monosodium glutamate in use and quantities.
One can purchase it in kilogram/tonne quantities in China, in the price range $5 - $20 per Kg.
Is it possible to buy HPV in consumer quantities without having to have it mixed with something else, such as potato starch or burnt wheat?