Low final pH (3.95). How did this happen?

[jeremyross]

My most recent beer, a hoppy blonde, ended up a little on the tart side, so I measured the pH at 3.95 (Milwaukee meter). This explains the tartness, but it doesn't explain why I ended up at 3.95, and not something closer to 4.3-4.5.

I believe that my brewing hygiene and sanitization practices are strong. I can't think of how I might have induced an infection. The most likely cause of infection would have to be my siphon and hose, although they both spent 30 minutes in a star san bath.

I've heard of this yeast (Wyeast - Kölsch 2565) getting down as low as 4.1, but I'm quite a bit south of that.

The fermentation seemed healthy. It kicked off pretty quickly and the attenuation was a little higher than expected.

Any thoughts on what could have caused this?

Recipe:

Original Gravity: 1.045
Final Gravity: 1.010
ABV (standard): 4.5%

8.4375 lb - American - Pilsner (90%)
0.9375 lb - American - Wheat (10%)

0.4 oz - Nugget, Type: Pellet, AA: 15, Use: Boil for 60 min, IBU: 24.84
1 oz - Cascade, Type: Pellet, AA: 7, Use: Whirlpool for 20 min at 170 °F, IBU: 0.95
1 oz - Columbus, Type: Pellet, AA: 15, Use: Whirlpool for 20 min at 170 °F, IBU: 2.04
1 oz - Centennial, Type: Pellet, AA: 10, Use: Whirlpool for 20 min at 170 °F, IBU: 1.36
1 oz - Citra, Type: Pellet, AA: 11, Use: Dry Hop for 8 days
0.5 oz - Amarillo, Type: Pellet, AA: 8.6, Use: Dry Hop for 8 days
1 oz - Citra, Type: Pellet, AA: 11, Use: Dry Hop for 4 days
0.5 oz - Amarillo, Type: Pellet, AA: 8.6, Use: Dry Hop for 4 days

Mash: Infusion, Temp: 155 F, Time: 60 min
Mash pH: 5.3

Wyeast - Kölsch 2565
Pack was 3+ months old, so did a 2-step starter.

 

[jaspass]

A quick question. Have you been consistent in calibrating the pH meter? Both on brew day, and later for final sample reading?

 

[jeremyross]

Yes, I calibrate if it's been more than an hour or so since last calibration.

 

[Silver_Is_Money]

Perhaps there's a reason why they call it Alpha Acid.

 

[jeremyross]

Most anecdotes I've seen here and elsewhere is that (dry) hop additions tend to raise pH.

 

[jeremyross]

Bumping, but also would like to ask a slightly different question. Is it possible that this beer reached 3.9 pH without an infection? Could it be the wheat? Or the fermentation wasn't ideal? or something else?

 

[Silver_Is_Money]

How does it taste? Are you seeing any bottle gushers?

 

[jeremyross]

Does taste a bit on the bright side, but I wouldn't call it tart. The beer is kegged, so no chance for bottle gushing.