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Porter with lactose occasionally develops a "sour milk" flavor

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  • Porter with lactose occasionally develops a "sour milk" flavor

    I have a porter we make with coffee, cocoa nibs, and lactose which is served on nitrogen (Cellarstream device). Occasionally, the porter will develop a "sour milk" flavor I am assuming from the lactose. We add the lactose to the boil with about 10 minutes left and it doesn't happen all the time. Unfortunately, I have to toss about a half batch because of this unwanted souring.

    Has anyone else had this problem? Does anyone have a possible solution? Would like to keep making this beer as it is a good seller but I also don't want to have to toss batches from time to time.

  • #2
    Does it develope this flavor over time in the kegs, or serving tank? Or does this happen directly after fermentation?

    My thought process: take the coffee out of the recipe- coffee is acrid and acidic and will make beer seem thinner- contradicting the lactose addition. With all the dark grain in a stout or porter I feel they can get thin mouthfeel just on their own sometimes, adding another acrid ingredient can only increase the perception of "sourness".
    Coffee can also add a stale Jalepeno-green pepper flavor to beer- which might be part of the "sour milk" perception.
    Last edited by Junkyard; 09-15-2016, 08:09 PM.

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    • #3
      Originally posted by Junkyard View Post
      Does it develope this flavor over time in the kegs, or serving tank? Or does this happen directly after fermentation?

      My thoughts are: take the coffee out of the recipe- coffee is acrid and acidic and will make beer seem thinner- contradicting the lactose addition. Coffee can also add a stale Jalepeno-green pepper flavor to beer- which might be part of the "sour milk" perception.
      This particular batch was 2 bbls that were kegged. The first two kegs were fine, the 3rd and 4th kegs were sour. Kegs were stored in cooler after kegging.

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      • #4
        Originally posted by rlbrewingco View Post
        This particular batch was 2 bbls that were kegged. The first two kegs were fine, the 3rd and 4th kegs were sour. Kegs were stored in cooler after kegging.
        Interesting that it doesn't happen every batch, but not being able to taste the beer before and after- I would definitely start by removing the coffee if It were me.

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        • #5
          Was going to convert the porter to a Chocolate Pumpkin Porter for the fall. Keep the lactose and nibs, drop the coffee, add pumpkin puree to mash and pie spice to boil.

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          • #6
            How are you adding the cocoa nibs and coffee? Those additions (unless they are added hotside) would be a more likely culprit for souring than the lactose. Another thought I had should always be our primary concern, as brewers, when chasing down a potential off flavor. "Know thine enemy!" Send out a sample for testing and find out what is making that flavor. Then, trace it back to the most logical culprit. Good luck. Cheers!

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            • #7
              Originally posted by rlbrewingco View Post
              This particular batch was 2 bbls that were kegged. The first two kegs were fine, the 3rd and 4th kegs were sour. Kegs were stored in cooler after kegging.
              That to me would indicate that the kegs themselves are the issue. I would pull them apart and take a look at them
              Mike Eme
              Brewmaster

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              • #8
                Originally posted by TheHumbleBrewer View Post
                How are you adding the cocoa nibs and coffee? Those additions (unless they are added hotside) would be a more likely culprit for souring than the lactose. Another thought I had should always be our primary concern, as brewers, when chasing down a potential off flavor. "Know thine enemy!" Send out a sample for testing and find out what is making that flavor. Then, trace it back to the most logical culprit. Good luck. Cheers!
                Nibs are added to the boil with 10 minutes left in the boil and coffee is steeped after flameout.

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                • #9
                  Originally posted by rlbrewingco View Post
                  I have a porter we make with coffee, cocoa nibs, and lactose which is served on nitrogen (Cellarstream device). Occasionally, the porter will develop a "sour milk" flavor I am assuming from the lactose. We add the lactose to the boil with about 10 minutes left and it doesn't happen all the time. Unfortunately, I have to toss about a half batch because of this unwanted souring.

                  Has anyone else had this problem? Does anyone have a possible solution? Would like to keep making this beer as it is a good seller but I also don't want to have to toss batches from time to time.
                  Lactose itself will not lend any sour flavor. Lactose is a long chain sugar that can be broken down by souring organisms such as lactobacillus. Begin by checking the pH of your completed beer to determine if the sour flavor you are picking up on is the direct result of a substantial drop in pH. If so, evaluate your process to determine if there is a point where you could be picking up bacteria. I would be curious about the cocoa nibs in particular. Coffee and cocoa added at warm temperatures could be the problem. You should experience very little issue if you are adding these ingredients cold and keeping the beer cold thereafter.

                  [edit] just read about how you add the coffee. You may be picking up extra acidity from adding the coffee warm. Heat makes coffee more acidity. Like I said, check your pH and and report back. On the next batch, try cold brewing your coffee and mixing it the brite or kegs.
                  Last edited by claponsie; 09-17-2016, 05:50 AM.

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                  • #10
                    Originally posted by beerguy1 View Post
                    That to me would indicate that the kegs themselves are the issue. I would pull them apart and take a look at them
                    Were all of the kegs sampled simultaneously? It could be that all of the kegs had the same contamination issue, but kegs 1 & 2 were consumed prior to off flavors having a chance to develop. If kegs 3 & 4 were known to be sour at the same you were pouring good beer from kegs 1 & 2, then logically the issue is definitely in the kegs or how they are stored.

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                    • #11
                      Tested the Porter. pH is 4.3. Tested all my other beers and they were in the same range.

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