I brewed up 10 gal. of octoberfest back in September. After kegging it and letting it lager for a few weeks I detected a strong sulphury, onion / garlic flavor and aroma. I was going to dump it but just didn't "get around to it". After it sat for awhile longer this off flavor seems to be dissipating. After boiling the wort I realized I had a couple extra gallons. I pitched Nottingham in the couple extra gallons. The "Octoberfest Ale" doeesn't have this off aroma / flavor. My recipe is listed below. One note with the yeast starter. I originally made 2 - 1L starters with the Octoberfest blend. The friend I brew with couldn't brew that particular weekend so I mixed them together in a glass growler and put them in my beer cooler / keezer. Then the week before we brewed I built up the starter. I decanted most of the liquid from the starter so I wouldn't add too much volume to each fermentor. I fermented in two 6gal glass carboys. I'm not sure if this is an ingredient issue or a process issue. I have made this beer before but only changed the 15 minute hop addition to strisselspalt since I had it available. I used a different hop last year and didn't get that flavor in my beer. Any help with this phenomenon would be appreciated.
74% Briess Bonlander Munich
26% Briess Pilsen
28.35g Yakima Magnum, boil @ 60min
28.35g Strisselspalt, boil @ 15min
6g calcium chloride, mash
2.5g gypsum, mash
15mL phosphoric acid, mash
2pkg Wyeast Octoberfest Blend into 1gal starter
Decoction mash with short rest at 122 deg F, then a rest at 146 deg F then 156 deg F then mash out at 168 deg F. Fly sparge for 1 hour.
Boil for 90 minutes.
Chill to 45 deg. F then transfer to carboys.
Pitch yeast. Ferment at 50deg. for 3 weeks then short diacetyl rest.
Transfer to kegs and crash to 35 deg F.