Sprouting barley activates the enzyme diatase, which converts the inherent starch compounds to maltose- a basic sugar necessary for fermentation. The reason why half is grueled and half is baked is, the biscuit maneuver facilitates still more enzymatic activity necessary for fermentation, while the barley gruel provides lactic acid which inhibits nasties while somehow attracting Saccharomyces Cerevisiae- the yeast we want.