Ask The Brewmasters

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• - Yes, pulled from both zwickle and tank bottom (but good idea!)
• ​ - stirred mash @ 65C for 30 min, then a 36 min ramp to 78C. COA is below. (Key: pils/spec malt 1/spec malt 2  NR=Not Reported)
  • Malt Color: 4.5 EBC/85 EBC/28 EBC
  • Moisture 4.5%/5.6%/6%
  • Extract (dry) 81.9%/75.4%/77.4%
  • Friability 87.2%/NR/NR
  • Glassy kernels 1.2%/NR/NR
  • Wort pH 5.83/NR/NR
  • Total Protein 10.3%/NR/NR
  • Kolbach 41.4%/NR/NR
  • Unfortunately, the large European maltster doesn't report DP, AA, or FAN; whereas my local maltster does.
• ​​ -
  • There are a lot of dextrins in this wort, but 3.9P is on the high side of true to brand for this beer. RDF for this batch was 60.6% whereas 63-64% RDF is typical for this brand. That said, remember that the pils malt was a substitution vs the (slightly more modified) estate-grown pils typically used in this brand. Also, there's typically a long tail on the first cycle of 34/70. I bet the next time I check FG, it will be 1 or 2 tenths lower.
  • RDF on the helles was 64.3%
  • This is a tiny brewpub, we don't have GCMS
  • No, I can't rule out human error in tasting - more on that below.
  • I never said that it was dry yeast (I use both liquid and dry), but in this case it was. I've started up 34/70 via dry yeast many, many times and it's always gone well/been clean. I'm not inclined to lay blame there. I do see a longer tail (as mentioned above) on the first cycle with most dry yeasts, and definitely this one.
• ​​​ - can't rule out wild yeast yet, but I think it's very unlikely
• - very good points, but there is zero chlorine in that brewery. At its peak, I'd describe it as rubber/burnt rubber. 
• - See above for mash/materials info. I assume low is < 65C? I'd like to read more about low mash temps causing POF...is this the ferulic acid issue I mentioned briefly above? Can you point to any resources?
• ​​​​ - That is obviously true - no one is suggesting otherwise. That said, my money is on the root cause NOT being micro and I want to understand all potential non-micro causes.
• - It's not the stone. Stone gets soaked in nitric acid between each use, then I run 185+ water through it for 30+ min prior to cast. This place is on well water. No chlorine in the water or brewery.

1. I tasted again on Saturday and could barely notice any POF. It's still there but substantially dissipated. That said, I thought the same thing at 33.8 days, then got it again big time at 42.7 days. It will be interesting to see what I can/can't taste later this week.
2. What are potential causes in which the POF could dissipate over time?
3. Does that mean the POF is adhered to yeast/protein in the haze and is dropping out over time?
4. I drank Simply Orange juice every morning for a decade. Almost exactly 1 year ago, I tasted the exact same phenolic note in their juice. I tried several different bottles and got it in 3 or 4 of them. It was disgusting, I couldn't drink the stuff, and I moved on to a different brand. My wife thought the juice tasted fine. I reported it to Coca-Cola and reached out to a few food science friends about my experience. My memory is hazy, but I believe someone told me POF can occur in fruit juice via a reaction with stabilizers. 
5. The isinglass is stabilized with sodium metabisulphate. Any chance the stabilizer could react to cause POF? If so, what would it be reacting with that would be in this batch and none of the (countless) others?  

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• - Yes, pulled from both zwickle and tank bottom (but good idea!)
• ​ - stirred mash @ 65C for 30 min, then a 36 min ramp to 78C. COA is below. (Key: pils/spec malt 1/spec malt 2  NR=Not Reported)
  • Malt Color: 4.5 EBC/85 EBC/28 EBC
  • Moisture 4.5%/5.6%/6%
  • Extract (dry) 81.9%/75.4%/77.4%
  • Friability 87.2%/NR/NR
  • Glassy kernels 1.2%/NR/NR
  • Wort pH 5.83/NR/NR
  • Total Protein 10.3%/NR/NR
  • Kolbach 41.4%/NR/NR
  • Unfortunately, the large European maltster doesn't report DP, AA, or FAN; whereas my local maltster does.
• ​​ -
  • There are a lot of dextrins in this wort, but 3.9P is on the high side of true to brand for this beer. RDF for this batch was 60.6% whereas 63-64% RDF is typical for this brand. That said, remember that the pils malt was a substitution vs the (slightly more modified) estate-grown pils typically used in this brand. Also, there's typically a long tail on the first cycle of 34/70. I bet the next time I check FG, it will be 1 or 2 tenths lower.
  • RDF on the helles was 64.3%
  • This is a tiny brewpub, we don't have GCMS
  • No, I can't rule out human error in tasting - more on that below.
  • I never said that it was dry yeast (I use both liquid and dry), but in this case it was. I've started up 34/70 via dry yeast many, many times and it's always gone well/been clean. I'm not inclined to lay blame there. I do see a longer tail (as mentioned above) on the first cycle with most dry yeasts, and definitely this one.
• ​​​ - can't rule out wild yeast yet, but I think it's very unlikely
• - very good points, but there is zero chlorine in that brewery. At its peak, I'd describe it as rubber/burnt rubber. 
• - See above for mash/materials info. I assume low is < 65C? I'd like to read more about low mash temps causing POF...is this the ferulic acid issue I mentioned briefly above? Can you point to any resources?
• ​​​​ - That is obviously true - no one is suggesting otherwise. That said, my money is on the root cause NOT being micro and I want to understand all potential non-micro causes.
• - It's not the stone. Stone gets soaked in nitric acid between each use, then I run 185+ water through it for 30+ min prior to cast. This place is on well water. No chlorine in the water or brewery.

1. I tasted again on Saturday and could barely notice any POF. It's still there but substantially dissipated. That said, I thought the same thing at 33.8 days, then got it again big time at 42.7 days. It will be interesting to see what I can/can't taste later this week.
2. What are potential causes in which the POF could dissipate over time?
3. Does that mean the POF is adhered to yeast/protein in the haze and is dropping out over time?
4. I drank Simply Orange juice every morning for a decade. Almost exactly 1 year ago, I tasted the exact same phenolic note in their juice. I tried several different bottles and got it in 3 or 4 of them. It was disgusting, I couldn't drink the stuff, and I moved on to a different brand. My wife thought the juice tasted fine. I reported it to Coca-Cola and reached out to a few food science friends about my experience. My memory is hazy, but I believe someone told me POF can occur in fruit juice via a reaction with stabilizers. 
5. The isinglass is stabilized with sodium metabisulphate. Any chance the stabilizer could react to cause POF? If so, what would it be reacting with that would be in this batch and none of the (countless) others?  

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• - Yes, pulled from both zwickle and tank bottom (but good idea!)
• ​ - stirred mash @ 65C for 30 min, then a 36 min ramp to 78C. COA is below. (Key: pils/spec malt 1/spec malt 2  NR=Not Reported)
  • Malt Color: 4.5 EBC/85 EBC/28 EBC
  • Moisture 4.5%/5.6%/6%
  • Extract (dry) 81.9%/75.4%/77.4%
  • Friability 87.2%/NR/NR
  • Glassy kernels 1.2%/NR/NR
  • Wort pH 5.83/NR/NR
  • Total Protein 10.3%/NR/NR
  • Kolbach 41.4%/NR/NR
  • Unfortunately, the large European maltster doesn't report DP, AA, or FAN; whereas my local maltster does.
• ​​ -
  • There are a lot of dextrins in this wort, but 3.9P is on the high side of true to brand for this beer. RDF for this batch was 60.6% whereas 63-64% RDF is typical for this brand. That said, remember that the pils malt was a substitution vs the (slightly more modified) estate-grown pils typically used in this brand. Also, there's typically a long tail on the first cycle of 34/70. I bet the next time I check FG, it will be 1 or 2 tenths lower.
  • RDF on the helles was 64.3%
  • This is a tiny brewpub, we don't have GCMS
  • No, I can't rule out human error in tasting - more on that below.
  • I never said that it was dry yeast (I use both liquid and dry), but in this case it was. I've started up 34/70 via dry yeast many, many times and it's always gone well/been clean. I'm not inclined to lay blame there. I do see a longer tail (as mentioned above) on the first cycle with most dry yeasts, and definitely this one.
• ​​​ - can't rule out wild yeast yet, but I think it's very unlikely
• - very good points, but there is zero chlorine in that brewery. At its peak, I'd describe it as rubber/burnt rubber. 
• - See above for mash/materials info. I assume low is < 65C? I'd like to read more about low mash temps causing POF...is this the ferulic acid issue I mentioned briefly above? Can you point to any resources?
• ​​​​ - That is obviously true - no one is suggesting otherwise. That said, my money is on the root cause NOT being micro and I want to understand all potential non-micro causes.
• - It's not the stone. Stone gets soaked in nitric acid between each use, then I run 185+ water through it for 30+ min prior to cast. This place is on well water. No chlorine in the water or brewery.

1. I tasted again on Saturday and could barely notice any POF. It's still there but substantially dissipated. That said, I thought the same thing at 33.8 days, then got it again big time at 42.7 days. It will be interesting to see what I can/can't taste later this week.
2. What are potential causes in which the POF could dissipate over time?
3. Does that mean the POF is adhered to yeast/protein in the haze and is dropping out over time?
4. I drank Simply Orange juice every morning for a decade. Almost exactly 1 year ago, I tasted the exact same phenolic note in their juice. I tried several different bottles and got it in 3 or 4 of them. It was disgusting, I couldn't drink the stuff, and I moved on to a different brand. My wife thought the juice tasted fine. I reported it to Coca-Cola and reached out to a few food science friends about my experience. My memory is hazy, but I believe someone told me POF can occur in fruit juice via a reaction with stabilizers. 
5. The isinglass is stabilized with sodium metabisulphate. Any chance the stabilizer could react to cause POF? If so, what would it be reacting with that would be in this batch and none of the (countless) others?  

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• - Yes, pulled from both zwickle and tank bottom (but good idea!)
• ​ - stirred mash @ 65C for 30 min, then a 36 min ramp to 78C. COA is below. (Key: pils/spec malt 1/spec malt 2  NR=Not Reported)
  • Malt Color: 4.5 EBC/85 EBC/28 EBC
  • Moisture 4.5%/5.6%/6%
  • Extract (dry) 81.9%/75.4%/77.4%
  • Friability 87.2%/NR/NR
  • Glassy kernels 1.2%/NR/NR
  • Wort pH 5.83/NR/NR
  • Total Protein 10.3%/NR/NR
  • Kolbach 41.4%/NR/NR
  • Unfortunately, the large European maltster doesn't report DP, AA, or FAN; whereas my local maltster does.
• ​​ -
  • There are a lot of dextrins in this wort, but 3.9P is on the high side of true to brand for this beer. RDF for this batch was 60.6% whereas 63-64% RDF is typical for this brand. That said, remember that the pils malt was a substitution vs the (slightly more modified) estate-grown pils typically used in this brand. Also, there's typically a long tail on the first cycle of 34/70. I bet the next time I check FG, it will be 1 or 2 tenths lower.
  • RDF on the helles was 64.3%
  • This is a tiny brewpub, we don't have GCMS
  • No, I can't rule out human error in tasting - more on that below.
  • I never said that it was dry yeast (I use both liquid and dry), but in this case it was. I've started up 34/70 via dry yeast many, many times and it's always gone well/been clean. I'm not inclined to lay blame there. I do see a longer tail (as mentioned above) on the first cycle with most dry yeasts, and definitely this one.
• ​​​ - can't rule out wild yeast yet, but I think it's very unlikely
• - very good points, but there is zero chlorine in that brewery. At its peak, I'd describe it as rubber/burnt rubber. 
• - See above for mash/materials info. I assume low is < 65C? I'd like to read more about low mash temps causing POF...is this the ferulic acid issue I mentioned briefly above? Can you point to any resources?
• ​​​​ - That is obviously true - no one is suggesting otherwise. That said, my money is on the root cause NOT being micro and I want to understand all potential non-micro causes.
• - It's not the stone. Stone gets soaked in nitric acid between each use, then I run 185+ water through it for 30+ min prior to cast. This place is on well water. No chlorine in the water or brewery.

1. I tasted again on Saturday and could barely notice any POF. It's still there but substantially dissipated. That said, I thought the same thing at 33.8 days, then got it again big time at 42.7 days. It will be interesting to see what I can/can't taste later this week.
2. What are potential causes in which the POF could dissipate over time?
3. Does that mean the POF is adhered to yeast/protein in the haze and is dropping out over time?
4. I drank Simply Orange juice every morning for a decade. Almost exactly 1 year ago, I tasted the exact same phenolic note in their juice. I tried several different bottles and got it in 3 or 4 of them. It was disgusting, I couldn't drink the stuff, and I moved on to a different brand. My wife thought the juice tasted fine. I reported it to Coca-Cola and reached out to a few food science friends about my experience. My memory is hazy, but I believe someone told me POF can occur in fruit juice via a reaction with stabilizers. 
5. The isinglass is stabilized with sodium metabisulphate. Any chance the stabilizer could react to cause POF? If so, what would it be reacting with that would be in this batch and none of the (countless) others?  

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• - Yes, pulled from both zwickle and tank bottom (but good idea!)
• ​ - stirred mash @ 65C for 30 min, then a 36 min ramp to 78C. COA is below. (Key: pils/spec malt 1/spec malt 2  NR=Not Reported)
  • Malt Color: 4.5 EBC/85 EBC/28 EBC
  • Moisture 4.5%/5.6%/6%
  • Extract (dry) 81.9%/75.4%/77.4%
  • Friability 87.2%/NR/NR
  • Glassy kernels 1.2%/NR/NR
  • Wort pH 5.83/NR/NR
  • Total Protein 10.3%/NR/NR
  • Kolbach 41.4%/NR/NR
  • Unfortunately, the large European maltster doesn't report DP, AA, or FAN; whereas my local maltster does.
• ​​ -
  • There are a lot of dextrins in this wort, but 3.9P is on the high side of true to brand for this beer. RDF for this batch was 60.6% whereas 63-64% RDF is typical for this brand. That said, remember that the pils malt was a substitution vs the (slightly more modified) estate-grown pils typically used in this brand. Also, there's typically a long tail on the first cycle of 34/70. I bet the next time I check FG, it will be 1 or 2 tenths lower.
  • RDF on the helles was 64.3%
  • This is a tiny brewpub, we don't have GCMS
  • No, I can't rule out human error in tasting - more on that below.
  • I never said that it was dry yeast (I use both liquid and dry), but in this case it was. I've started up 34/70 via dry yeast many, many times and it's always gone well/been clean. I'm not inclined to lay blame there. I do see a longer tail (as mentioned above) on the first cycle with most dry yeasts, and definitely this one.
• ​​​ - can't rule out wild yeast yet, but I think it's very unlikely
• - very good points, but there is zero chlorine in that brewery. At its peak, I'd describe it as rubber/burnt rubber. 
• - See above for mash/materials info. I assume low is < 65C? I'd like to read more about low mash temps causing POF...is this the ferulic acid issue I mentioned briefly above? Can you point to any resources?
• ​​​​ - That is obviously true - no one is suggesting otherwise. That said, my money is on the root cause NOT being micro and I want to understand all potential non-micro causes.
• - It's not the stone. Stone gets soaked in nitric acid between each use, then I run 185+ water through it for 30+ min prior to cast. This place is on well water. No chlorine in the water or brewery.

1. I tasted again on Saturday and could barely notice any POF. It's still there but substantially dissipated. That said, I thought the same thing at 33.8 days, then got it again big time at 42.7 days. It will be interesting to see what I can/can't taste later this week.
2. What are potential causes in which the POF could dissipate over time?
3. Does that mean the POF is adhered to yeast/protein in the haze and is dropping out over time?
4. I drank Simply Orange juice every morning for a decade. Almost exactly 1 year ago, I tasted the exact same phenolic note in their juice. I tried several different bottles and got it in 3 or 4 of them. It was disgusting, I couldn't drink the stuff, and I moved on to a different brand. My wife thought the juice tasted fine. I reported it to Coca-Cola and reached out to a few food science friends about my experience. My memory is hazy, but I believe someone told me POF can occur in fruit juice via a reaction with stabilizers. 
5. The isinglass is stabilized with sodium metabisulphate. Any chance the stabilizer could react to cause POF? If so, what would it be reacting with that would be in this batch and none of the (countless) others?  

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• - Yes, pulled from both zwickle and tank bottom (but good idea!)
• ​ - stirred mash @ 65C for 30 min, then a 36 min ramp to 78C. COA is below. (Key: pils/spec malt 1/spec malt 2  NR=Not Reported)
  • Malt Color: 4.5 EBC/85 EBC/28 EBC
  • Moisture 4.5%/5.6%/6%
  • Extract (dry) 81.9%/75.4%/77.4%
  • Friability 87.2%/NR/NR
  • Glassy kernels 1.2%/NR/NR
  • Wort pH 5.83/NR/NR
  • Total Protein 10.3%/NR/NR
  • Kolbach 41.4%/NR/NR
  • Unfortunately, the large European maltster doesn't report DP, AA, or FAN; whereas my local maltster does.
• ​​ -
  • There are a lot of dextrins in this wort, but 3.9P is on the high side of true to brand for this beer. RDF for this batch was 60.6% whereas 63-64% RDF is typical for this brand. That said, remember that the pils malt was a substitution vs the (slightly more modified) estate-grown pils typically used in this brand. Also, there's typically a long tail on the first cycle of 34/70. I bet the next time I check FG, it will be 1 or 2 tenths lower.
  • RDF on the helles was 64.3%
  • This is a tiny brewpub, we don't have GCMS
  • No, I can't rule out human error in tasting - more on that below.
  • I never said that it was dry yeast (I use both liquid and dry), but in this case it was. I've started up 34/70 via dry yeast many, many times and it's always gone well/been clean. I'm not inclined to lay blame there. I do see a longer tail (as mentioned above) on the first cycle with most dry yeasts, and definitely this one.
• ​​​ - can't rule out wild yeast yet, but I think it's very unlikely
• - very good points, but there is zero chlorine in that brewery. At its peak, I'd describe it as rubber/burnt rubber. 
• - See above for mash/materials info. I assume low is < 65C? I'd like to read more about low mash temps causing POF...is this the ferulic acid issue I mentioned briefly above? Can you point to any resources?
• ​​​​ - That is obviously true - no one is suggesting otherwise. That said, my money is on the root cause NOT being micro and I want to understand all potential non-micro causes.
• - It's not the stone. Stone gets soaked in nitric acid between each use, then I run 185+ water through it for 30+ min prior to cast. This place is on well water. No chlorine in the water or brewery.

1. I tasted again on Saturday and could barely notice any POF. It's still there but substantially dissipated. That said, I thought the same thing at 33.8 days, then got it again big time at 42.7 days. It will be interesting to see what I can/can't taste later this week.
2. What are potential causes in which the POF could dissipate over time?
3. Does that mean the POF is adhered to yeast/protein in the haze and is dropping out over time?
4. I drank Simply Orange juice every morning for a decade. Almost exactly 1 year ago, I tasted the exact same phenolic note in their juice. I tried several different bottles and got it in 3 or 4 of them. It was disgusting, I couldn't drink the stuff, and I moved on to a different brand. My wife thought the juice tasted fine. I reported it to Coca-Cola and reached out to a few food science friends about my experience. My memory is hazy, but I believe someone told me POF can occur in fruit juice via a reaction with stabilizers. 
5. The isinglass is stabilized with sodium metabisulphate. Any chance the stabilizer could react to cause POF? If so, what would it be reacting with that would be in this batch and none of the (countless) others?  

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• - Yes, pulled from both zwickle and tank bottom (but good idea!)
• ​ - stirred mash @ 65C for 30 min, then a 36 min ramp to 78C. COA is below. (Key: pils/spec malt 1/spec malt 2  NR=Not Reported)
  • Malt Color: 4.5 EBC/85 EBC/28 EBC
  • Moisture 4.5%/5.6%/6%
  • Extract (dry) 81.9%/75.4%/77.4%
  • Friability 87.2%/NR/NR
  • Glassy kernels 1.2%/NR/NR
  • Wort pH 5.83/NR/NR
  • Total Protein 10.3%/NR/NR
  • Kolbach 41.4%/NR/NR
  • Unfortunately, the large European maltster doesn't report DP, AA, or FAN; whereas my local maltster does.
• ​​ -
  • There are a lot of dextrins in this wort, but 3.9P is on the high side of true to brand for this beer. RDF for this batch was 60.6% whereas 63-64% RDF is typical for this brand. That said, remember that the pils malt was a substitution vs the (slightly more modified) estate-grown pils typically used in this brand. Also, there's typically a long tail on the first cycle of 34/70. I bet the next time I check FG, it will be 1 or 2 tenths lower.
  • RDF on the helles was 64.3%
  • This is a tiny brewpub, we don't have GCMS
  • No, I can't rule out human error in tasting - more on that below.
  • I never said that it was dry yeast (I use both liquid and dry), but in this case it was. I've started up 34/70 via dry yeast many, many times and it's always gone well/been clean. I'm not inclined to lay blame there. I do see a longer tail (as mentioned above) on the first cycle with most dry yeasts, and definitely this one.
• ​​​ - can't rule out wild yeast yet, but I think it's very unlikely
• - very good points, but there is zero chlorine in that brewery. At its peak, I'd describe it as rubber/burnt rubber. 
• - See above for mash/materials info. I assume low is < 65C? I'd like to read more about low mash temps causing POF...is this the ferulic acid issue I mentioned briefly above? Can you point to any resources?
• ​​​​ - That is obviously true - no one is suggesting otherwise. That said, my money is on the root cause NOT being micro and I want to understand all potential non-micro causes.
• - It's not the stone. Stone gets soaked in nitric acid between each use, then I run 185+ water through it for 30+ min prior to cast. This place is on well water. No chlorine in the water or brewery.

1. I tasted again on Saturday and could barely notice any POF. It's still there but substantially dissipated. That said, I thought the same thing at 33.8 days, then got it again big time at 42.7 days. It will be interesting to see what I can/can't taste later this week.
2. What are potential causes in which the POF could dissipate over time?
3. Does that mean the POF is adhered to yeast/protein in the haze and is dropping out over time?
4. I drank Simply Orange juice every morning for a decade. Almost exactly 1 year ago, I tasted the exact same phenolic note in their juice. I tried several different bottles and got it in 3 or 4 of them. It was disgusting, I couldn't drink the stuff, and I moved on to a different brand. My wife thought the juice tasted fine. I reported it to Coca-Cola and reached out to a few food science friends about my experience. My memory is hazy, but I believe someone told me POF can occur in fruit juice via a reaction with stabilizers. 
5. The isinglass is stabilized with sodium metabisulphate. Any chance the stabilizer could react to cause POF? If so, what would it be reacting with that would be in this batch and none of the (countless) others?  

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

I apologize for failing to follow up on this. Life got busy but EP301 of the Master Brewers Podcast led to rehashing this post. Dan was right - it was the specialty malt, which came from a major European maltster. Like a dummy, I hadn't chewed the malt before I added it to the mill. Probably because I'd used the same product many times before and got lazy. The off-flavor was prominent in the hot steeps, then I chewed some of the malt that I still had on hand, and boom: there it was, clear as day.

I apologize for failing to follow up on this. Life got busy but EP301 of the Master Brewers Podcast led to rehashing this post. Dan was right - it was the specialty malt, which came from a major European maltster. Like a dummy, I hadn't chewed the malt before I added it to the mill. Probably because I'd used the same product many times before and got lazy. The off-flavor was prominent in the hot steeps, then I chewed some of the malt that I still had on hand, and boom: there it was, clear as day.

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

Hi John
a number of years ago we had a phenolic taint in a large brewery I worked in - in Australia. 

a large technical team took an age to solve it. 

turned out to be a fungicide on wooden pallets that some empty cans were stored on. From memory I think the compound was isolated as Tri-bromo-anisol - similar to TCA cork taint in wine. Extremely low flavour threshold - in parts per billion. 

are you using any wooden pallets? Malt on wooden pallets / isinglass etc?

good luck and I'll follow with interest and certainly if I think of anything else will be in touch.  

cheers 

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

Hi John
a number of years ago we had a phenolic taint in a large brewery I worked in - in Australia. 

a large technical team took an age to solve it. 

turned out to be a fungicide on wooden pallets that some empty cans were stored on. From memory I think the compound was isolated as Tri-bromo-anisol - similar to TCA cork taint in wine. Extremely low flavour threshold - in parts per billion. 

are you using any wooden pallets? Malt on wooden pallets / isinglass etc?

good luck and I'll follow with interest and certainly if I think of anything else will be in touch.  

cheers 

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

Hi John
a number of years ago we had a phenolic taint in a large brewery I worked in - in Australia. 

a large technical team took an age to solve it. 

turned out to be a fungicide on wooden pallets that some empty cans were stored on. From memory I think the compound was isolated as Tri-bromo-anisol - similar to TCA cork taint in wine. Extremely low flavour threshold - in parts per billion. 

are you using any wooden pallets? Malt on wooden pallets / isinglass etc?

good luck and I'll follow with interest and certainly if I think of anything else will be in touch.  

cheers 

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)

• Standard ingredients from well known, reliable suppliers
• Brand new, fresh pitch of 34/70 lager yeast (which as we all know is POF-)
• Pitch rate, wort aeration, temperatures all at normal specs
• Normal attenuation, pH, etc.
• Yeast was harvested and repitched a helles. Helles is totally clean, has zero POF (and is probably the best beer I've ever brewed).
• Both the maerzen & helles were fined with 500ml/hl RFU isinglass, which was prepared and added to spec

• I have not run any micro yet, but am assuming POF would have also been present in the helles if cause = micro. Right?
• Nothing on Casey's Process Control to Prevent Medicinal/Phenolic/Astringent/Grainy Off-Flavors in Beer fishbone jumps out at me. There are plenty of things to chase down, but not a lot of variables that were terribly different between the maerzen and the helles (or any of the other countless lagers that I've produced).
• I am suspicious of the isinglass addition (even though this was a routine dosage), only because I first noticed the POF 3 days after that addition, which took place well into cold maturation. That said, while I definitely tasted throughout the 1st ~13 days when pulling samples (and absolutely tasted during the VDK test @ 12.8 days) I don't have a record of any sensory between then and when I first noticed the POF @ 25.9 days. (BTW I have now changed my logs/process to indicate whether or not I tasted at each data entry to aid future troubleshooting.)
• I am suspicious of the malt, even thought it came from a well known vendor, whom I've used extensively for many years. Why? Because:
  • We should always blame the maltster (just kidding)
  • While I've used this reliable European pils malt for many years, I rarely use it these days because most of our malt is now estate-grown. I just happened to sub the European pils on this one batch due to a timing issue. ie the Helles was brewed with our own barley and processed into pils malt by my local maltster (who did a killer job with it).
  • There's also the specialty malts in the maerzen (from the same well-known European supplier), however Casey's fishbone shows an inverse relationship between production of medicinal/astringent/grainy/phenolic off-flavors in beer and specialty malts, citing thermal decarboxylation of ferulic acid)