Abstract: A mushroom growth enhancer is provided consisting of a cracked soybean product in combination with a preservative agent. The cracked soybean product is size-adjusted to -10+30 U.S. standard mesh and dehulled. The dehulled, size-adjusted product is then combined with a preservative agent. The resulting combination is pasteurized at 220.degree. F. for 5 minutes. After pasteurization, excess water is evaporated to prevent spoilage by microorganisms not destroyed during pasteurization. After water evaporization, the resulting product is rapidly cooled. Rapid cooling prevents denaturation of the soybean protein. Because the present invention consists of a substantially undenatured protein product, the use of adversely high temperature conditions and harmful chemical denaturants is not required.