Methods and systems for isolating a high purity starch stream are provided. The methods provide an initial treatment step in advance of traditional grinding or fractionation operations (such as dry milling or wet milling operations) that facilitate separation of starch from other components of starch-based grains, for example facilitate separation of soft endosperm from other components of corn kernels including hard endosperm. The systems include a first treatment system for separating a high purity starch stream from other components of the grain stream, wherein the system can be configured as a bolt on for traditional milling operations such as wet milling and dry milling operations.