I’ve never managed to lower my pH enough when making light lagers but I’ve never tried using acid malt so I thought it would be a good one to make for my ever increasing stash of malts. Acidulated malt or acid malt is an ace up the sleeve for brewers who want to lower their mash pH or to add a slight sour flavour. Acid malt utilizes lactic fermentation to achieve its sourness just like yogurt, sauerkraut and of course lambic beers. To make my acid malt I started with green malt (germinated barley that has not been kilned yet). Since lactic fermentation occurs anaerobically (without oxygen) I put it in a ziplock freezer bag, wet it, sucked all the air out of it with a straw then sealed it up. I kept it warm at 35C or 95F for 36 hours. Occasionally I had to squeeze any air out of the bag and seal it up again. It turned a caramel brown colour and looked pretty slimy by the end of it. You can also keep it at 25 C for 4-5 days but thinking back to my first Munich malt disaster I thought it would be too risky to keep it for such a long period. When I poured it out and put it in the oven to dry at 95 F my daughter said it smelled like sushi rice and she was totally right. It makes a lot of sense because if you’ve ever made sushi rice you’ll know that it has rice wine vinegar and sugar in it. I guess the lactic acid and the sweetness from the malt create a very similar smell. After a few hours in the oven I tried a kernel. It was sour, the flavour actually made me think of sauerkraut. Then it dawned on me that I had three cabbages from our garden sitting on the balcony just waiting to be turned into something funky. So while I was making some acid malt I figured I might as well make some sauerkraut, same bacteria different host.
To test my acid malt I took an ounce of pilsner malt and mashed it with 75mL of water at 154 F I then added what would equate to 5 % acid malt. 10 minutes later the pH had dropped from 5.75 to 5.45. It went up after another ten minutes to 5.5 perhaps due to the drop in temperature. I warmed it back up and added another 5 % and lo and behold the pH dropped to 5.2. This stuff actually works!