Method for producing a protein hydrolysate with low bitterness

A method of making a product selected from the group consisting of foodstuffs, infant formula, medicinal diets, seasonings, flavor-modifying materials, food property-modifying materials, food additives, and feeds, comprising:

• (A) contacting a protein with a thiol protease obtainable from germinating soybean iotyledons to produce a protein hydrolysate with a bitterness of 0.05% or less and a content of free amino acids of 5% or less,
• wherein the thiol protease has the following properties:
• (1) molecular weight (SDS-PAGE):
• 26 to 30 kDa,
• (2) optimum pH:
• about 3 to 7,
• (3) optimum temperature:
• about 30 to 50° C., and
• (4) inhibitors:
• trans-epoxysuccinyl-L-leucylamide(4-guanizino)-butane (E-64), and
• (5) activators:
• 2-mercaptoethanol, cysteine, and reduced glutathione, and
• (B) incorporating the protein hydrolysate into the product.