Over the last few years I have made many Guinness clones with great success. My latest attempt however is missing that roast barley bite. I use the same recipe every time, ie pale malt, rolled barley and roast barley. I grind all my own grains. With the roast barley I usually grind the grain in a coffee grinder and add towards the end of the mash. This has always worked for me. The roast barley I used may have been over 12 months old. I it likely that it has gone stale and lost its astringency?