Mash parameters effecting attenuation
Posted: Sat May 28, 2016 3:56 pm
After switching to the LoDO method a few months ago I have noticed a reduction in attenuation compared to my previous brewing experience. My redesigned mashing system is a fairly standard unit based off some of the less complicated designs from other members here. It is simply an 8.5 gal kettle with two ports, a false bottom and a chugger pump for circulation. I use manual direct fire gas heating that is very controllable in intensity. The general mash program I’ve been using is: dough in by underletting with 65c water, adjust to 62c and hold for 1 hour. Then heat @~1c/min to 71 and hold for an additional hour. I have and use 3 separate thermometers including a calibrated thermopen.
Research and consultation with a couple members have pointed to the following as possibilities:
-A combination of hot spots or heat gradients in the kettle due to too little circulation or too high heat input. If this is the problem then it will be difficult to improve without pulling too much volume though the grain bed and thus compacting it and restricting the flow. This then just aggravates the situation.
-Slow strike underlet transfer rate at too high a temperature, attempting to account for loss of heat to grain and end up with an ideal initial mash temperature of not below 62c. Thus the bottom of the grain bed is seeing higher temps during underlet transfer favoring alpha amylase. Usually my initial transfer is complete in under 8 minutes but some high diastatic grains can fully convert in 20 minutes in the alpha temperature range. I might have to rethink keeping the initial mash temp at or above 62c.
-Thin mash due to full volume mash diluting and or stressing beta amylase. Seems the jury is still out on how much of an effect thin mashes have on enzyme performance. To test this theory I would have to devise a way of doing a smaller volume mash in the beta range then continue to transfer the full water volume in during the alpha temp range. Then the issue becomes how to hold two volumes of water and protect them both from oxygen ingress.
-pH of mash. All of my LoDO mashes have been falling in between 5.38 to 5.55 and while there is contrary information as to the proper pH for beta-amylase I believe that this pH range should not be putting undue stress on beta.
-Turbulence from the pump or pressure drop due to valve restriction or recirculation through lines damaging enzymes. I’m not sure if this is a thing that could effect enzyme performance but is another new parameter that has been introduced in the change to LoDO.
-And lastly there is a possibility that the metabisulfite addition or the reduced oxygen situation in the mash it creates could be hindering beta performance. No idea here however I am certain about is that in my previous HiDO life, attenuation was never an issue, now it is and so all possibilities must be considered.
Slowly working this problem by only altering one parameter at a time is taking a while to track down the attenuation issue. I thought I’d toss this out there to see if others have had any similar experiences they would like to share.
Research and consultation with a couple members have pointed to the following as possibilities:
-A combination of hot spots or heat gradients in the kettle due to too little circulation or too high heat input. If this is the problem then it will be difficult to improve without pulling too much volume though the grain bed and thus compacting it and restricting the flow. This then just aggravates the situation.
-Slow strike underlet transfer rate at too high a temperature, attempting to account for loss of heat to grain and end up with an ideal initial mash temperature of not below 62c. Thus the bottom of the grain bed is seeing higher temps during underlet transfer favoring alpha amylase. Usually my initial transfer is complete in under 8 minutes but some high diastatic grains can fully convert in 20 minutes in the alpha temperature range. I might have to rethink keeping the initial mash temp at or above 62c.
-Thin mash due to full volume mash diluting and or stressing beta amylase. Seems the jury is still out on how much of an effect thin mashes have on enzyme performance. To test this theory I would have to devise a way of doing a smaller volume mash in the beta range then continue to transfer the full water volume in during the alpha temp range. Then the issue becomes how to hold two volumes of water and protect them both from oxygen ingress.
-pH of mash. All of my LoDO mashes have been falling in between 5.38 to 5.55 and while there is contrary information as to the proper pH for beta-amylase I believe that this pH range should not be putting undue stress on beta.
-Turbulence from the pump or pressure drop due to valve restriction or recirculation through lines damaging enzymes. I’m not sure if this is a thing that could effect enzyme performance but is another new parameter that has been introduced in the change to LoDO.
-And lastly there is a possibility that the metabisulfite addition or the reduced oxygen situation in the mash it creates could be hindering beta performance. No idea here however I am certain about is that in my previous HiDO life, attenuation was never an issue, now it is and so all possibilities must be considered.
Slowly working this problem by only altering one parameter at a time is taking a while to track down the attenuation issue. I thought I’d toss this out there to see if others have had any similar experiences they would like to share.