Organic Rye Berries. 25 pound bag. 100% USDA certified organic non-GMO grains. Rye berries are regarded as the highest quality grain to make mushroom spawn out of. A common preparation method is to thoroughly rinse the rye berries, soak in water for 12-24 hours, boil for 10 minutes then load into jars or filter patch mycobags for sterilization. Pressure cook for 90-120 minutes at 15 PSI.