Hydrolysis of brewer's spent grain

A brewing process for obtaining a low glycaemic index beer, the brewing process comprising the steps of:

• 1) adding water and a brewer's spent grain hydrolysate, in a mashing tun,
• 2) adding ground malt, thus proceeding to the mashing,
• 3) filtering the wort resulting from step 2),
• 4) boiling the wort and adding hops,
• 5) separating the wort from hops and fermenting in the presence of yeasts,
• 6) separating the yeasts and solid residues from the beer thus obtained, and optionally
• 7) letting the beer to age,
• wherein the brewer's spent grain hydrolysate is obtained by a preparation process comprising the steps of:
• i) mixing brewer's spent grain and water, in a weight ratio of 1:1 to 1:5, to obtain a mixture;
• ii) adding to the mixture thus obtained up to 2 wt %, based on the weight of the mixture, of an enzyme consisting of:
• a) xylanase, or
• b) an enzymatic complex of xylanase, amylase and glucanase,
• and letting to react for 1-6 hours at a temperature of 45-65° C. and pH of 4-6,
• iii) deactivating the enzyme of step ii), by increasing the temperature to 80-90° C. for at least 5 minutes, and
• iv) separating the liquid component from the solid component obtained at the end of step iii), thus keeping the liquid component, which is the brewer's spent grain hydrolysate,
• and wherein the low glycaemic index beer is a beer having a lower glycaemic index than a beer obtained without adding in step 1) the brewer's spent grain hydrolysate.