a human or animal dietary supplement that has a very high protein content and is extracted or prepared from vegetable or animal matter. The most common of such substances are leaf protein concentrate (LPC) and fish protein concentrate (FPC).

LPC is prepared by grinding young leaves to a pulp, pressing the paste, then isolating a liquid fraction containing protein by filter or centrifuge. Herbaceous plants and legumes, such as clover and lucerne, produce higher yields of protein concentrate than perennial grasses. The protein quality of some LPCs has been found to approach that of the soybean, the most protein-rich of the oilseeds; all LPCs require supplements, however, because they are deficient in two of the nutritionally essential amino acids, lysine and methionine.

FPC, processed directly from fish, is most commonly incorporated in cereal or wheat-based foods as a source of lysine. FPC flour is made by grinding the fish and adding to it an isopropanol solvent, which separates liquids and solids; the solid material is then extracted by centrifuge, and the process may be repeated several times. After the final centrifuging, the solid material is dried and ground.