Vorlauf help! Horrible tannin from the BK

[TheSlash]

I've done 2 extract and 3 all grains now. I've had this horrible astringent tannin like bitterness in the back of all but 1 extract. Assuming I steeped to hot or something on the other extract.

Have tried numerous fixes and nothing. Well yesterday's brew (Centennial Blonde 5g all grain) I forgot about numbers and really focused on the process. Tasting every step of the way.

I think I've nailed down this dreaded astringent, but would like verification? Please review my process.

Brought 3.5 gallons of spring water to 162 degrees added it to my cooler mash tun with a SS braid. Dumped in my 8ish pounds of grain (barley crusher set to 1 o'clock position). Stirred well and closed. Thought I could be having PH issues so checked it at 15 minutes and PH strip was bright purple indicating like 6-7ph! Added 3ml of lactic acid and mash ph dropped to 5.3-5.4 area for the remaining 60 minute mash at 150 degrees.

Tasted wort coming from mash tun and it was sweet. Here is where I think I make the mistake though...
I only vorlauf maybe 1/2 a quart to a quart, then close valve, poor it back in and then vorlauf to kettle.

When people say vorlauf till clear I assumed you would never be able to get a completely clear running, as I still saw specs small enough that they could easily go through the braid.

Now I had a good 1 hour boil, and tasted the cooled beer going to the fermenter and it had the exact horrid astringent taste I get in the final beer. This taste never mellows FYI, I let a brown ale sit for 3 months in the keg and if anything it got worse.

So I think I'm boiling too much of the grain husks from not vorlaufing long enough. The wort from mash tun to BK is a bit cloudy with tons of "specs"...

So I think I can rule out anything pre and post boil. Like water and Ph, infection, etc etc.

Does this sound right? Can someone help me with vorlaufing if so?

This beer called for 3.5 gal strike and 5gal sparge, I was confused about vorlaufing such a loose grain bed too as I had gallons of sparge sitting on top..

6 months of astringent beer, I pray this is why and I can make some good beer!

P.S. All i've made has been drinkable, but too much tannin to really enjoy.

 

[ArcaneXor]

Some suggestions:

- Condition your malt before cracking it. This will preserve the husks and reduce the amount making it past the vorlauf into the boil kettle.
- Vorlauf more.
- Switch to another water source (store-bought).
- Treat your sparge water so that the pH doesn't rise above 5.8.
-

 

[RugenBrau]

What do you mean by "condition your malt" before cracking?

 

[TheSlash]

Some suggestions:

- Condition your malt before cracking it. This will preserve the husks and reduce the amount making it past the vorlauf into the boil kettle.
- Vorlauf more.
- Switch to another water source (store-bought).
- Treat your sparge water so that the pH doesn't rise above 5.8.
-

I did think about conditioning... I'll try that. I did use store bought spring water. I def need to vorlauf more, anyone have a good technique? Should I never close the valve, stir before, etc?

 

[samc]

Make a grain bag out of Voile fabric. It makes clean up a breeze and gives you very clear runnings into the BK.

 

[TheSlash]

Make a grain bag out of Voile fabric. It makes clean up a breeze and gives you very clear runnings into the BK.

Interesting... No issues stirring?

The particles that get through my braid are sooo small though, like specs.

I am hoping I just need to vorlauf more like a gallon+

So the goal is VERY clear runnings?

 

[TheSlash]

What do you mean by "condition your malt" before cracking?

He means spreading it out and lightly spraying it with water. When you grind then it doesn't create as much "flour" or dust.

 

[ArcaneXor]

I did think about conditioning... I'll try that. I did use store bought spring water. I def need to vorlauf more, anyone have a good technique? Should I never close the valve, stir before, etc?

Don't use spring water - it has way too much carbonate in it. Use either filtered municipal water or RO/distilled, and build it back. You usually only need a bit of gypsum and/or calcium chloride to do that.

 

[TheSlash]

Don't use spring water - it has way too much carbonate in it. Use either filtered municipal water or RO/distilled, and build it back. You usually only need a bit of gypsum and/or calcium chloride to do that.

The Spring water I purchased in 5gal jugs was from a local water place called Besco, that uses well water in our area ran through filters. Is that still bad?

 

[Mysticmead]

Don't use spring water - it has way too much carbonate in it. Use either filtered municipal water or RO/distilled, and build it back. You usually only need a bit of gypsum and/or calcium chloride to do that.

That all depends on the source and how the water is treated if at all. It might be perfect for brewing, it might be horrible. Only a water test would tell you if it's to high in anything. RO or Distilled would be the only way to know exactly what was in the water since it would have to be added by the brewer.


that said, to vorlauf or not to vorlauf. I do BIAB and don't vorlauf at all, yet my beers do not have an astringent mouth feel (it's not a taste its more like a dryness like sucking on a teabag) even though they are very cloudy in the kettle until I whirlpool and drain off the trub. Unless you have the PH way out of whack or are boiling a LOT of husks not having a totally clear vorlauf is not the cause. If it's fine pieces of husk you see in the wort, then you're tearing the husk and not simply crushing it. conditioning the malt will help with that. a LIGHT misting of water and letting it rest will make the husk less likely to shred while crushing.

 

[TheSlash]

What else could be happening in the boil? The wort coming from the mash tun tastes sweet and good. The wort leaving the BK has such overpowering tannin qualities. What should the wort taste like coming from the bk? Just a sweet hoppy malt right?

 

[Denny]

When you talk about "bitterness" it makes me question whether tannins are the problem. Astringency is not a flavor, it's a dry mouthfeel.

 

[Homercidal]

Vorlauf has nothing to do with tannins or astringency. It can help clarify the wort.

More than likely you have high alkalinity in your water and when sparging with hot water this can lead to tannins being extracted.

In this case you would get a water report and see what your water chemistry is. Then possibly treat your sparge water with acid or acidulated malt to counter the alkalinity of the water during the sparge. The first drain is probably ok since you have acid from the grain buffering the alkalinity, but the more you sparge, the higher the alkalinity rises until you start leeching tannins.

My water up here is so alkaline that I have to treat my sparge water even when I'm making a stout.

Or it could be some other cause, like water that has been chemically treated for your safety, but that is not generally thought of as a dry or astringent taste.

 

[TheSlash]

Vorlauf has nothing to do with tannins or astringency. It can help clarify the wort.

More than likely you have high alkalinity in your water and when sparging with hot water this can lead to tannins being extracted.

In this case you would get a water report and see what your water chemistry is. Then possibly treat your sparge water with acid or acidulated malt to counter the alkalinity of the water during the sparge. The first drain is probably ok since you have acid from the grain buffering the alkalinity, but the more you sparge, the higher the alkalinity rises until you start leeching tannins.

My water up here is so alkaline that I have to treat my sparge water even when I'm making a stout.

Or it could be some other cause, like water that has been chemically treated for your safety, but that is not generally thought of as a dry or astringent taste.

UGG back to square 1...

My strike was 162 for a 150 mash. My sparge was 168. So heat cannot be an issue. I also lowered my mash PH with lactic acid to the low 5's. I used spring water that was filtered from a local well... They said zero chlorine/chloromine.

It is a mouthfeel, like when you suck a teabag, not only is it astringent, but it has a bitterness also. Reading through palmers again and he does mention astringent can be bitter and tanic.

I don't know.. It tasted great coming out of the mash tun. I tasted all the runnings. Tasted bad coming from the BK after a 1 hour boil. I didn't add lactic acid to the sparge water though... that was 5 gallons. But it was store bought water compared to tons of people that just use tap water!

5 brews in and not 1 tastes good. Maybe the thousands I've spent on gear should have just gone to purchasing craft beer... sad day

 

[bob1852]

What kind of brew kettle?

Any hardware (valves, etc.)?

How are you chilling?

Name all your recipes (style is fine), and include what hops you used...

 

[Minky]

When I first started brewing, I had a similar mystery taste that I blamed on a bunch of different things. It turned out that, in my attempt to make hoppy beers, I was simply using too much bittering hops relative to malt content. Once I understood how a hop schedule worked, the horrible taste went away.

 

[TheSlash]

What kind of brew kettle?

Any hardware (valves, etc.)?

How are you chilling?

Name all your recipes (style is fine), and include what hops you used...

HLT = 9gallon ss 2 full welds with sight glass and ss valve.
MT = 10 gallon cooler with brass valve and SS braid.
BK = 9gallon SS with 2 full welds and a false bottom, thermometer and SS valve. Silicone drain hoses. I drained the BK into a filter, but taste was already there.

Clean with oxy, san with starsan. I chill with a homemade copper coil. 25 foot coiled. I put it in the BK when I have 15 minutes left but I do starsan spray it prior.

Last recipe was the cenntenial blonde. 9lbs pale, small amount of vienna, dextrine, c10 etc. Only 1oz of cascade and 1oz of cent split in 4 additions 55, 35, 20, 5.

Added 3.5g 162 degree spring water to the MT, added grain, mashed at 150 for 60 minutes. Vorlauf to BK, added 5g of 168 degree water, stirred, vorlauf to BK. Brought to a boil and started my 60min timer. Did the planned hop additions. At 15 min I added the copper chiller. Cooled to 68 degrees transferred to better bottle, shook, pitched hydrated yeast.

My crush wasn't super fine at all. My water PH came down to low 5's. Gravities were all good. Wort from BK not clear though, floaties all through it. Somewhat like this going into the BK.

False bottom in kettle does keep a lot of hops out.


I use gravity to transfer, and I use 2 1500watt heatsticks to heat. I do not cover the BK or HLT at all.

 

[bob1852]

Have you tasted post-boil, pre-chilled?

Trying to help isolate the point of offness....

 

[TheSlash]

Have you tasted post-boil, pre-chilled?

Trying to help isolate the point of offness....

Mmmmm no, didn't pull any and let it cool.

Tastes great leaving MT, and bad leaving BK. Was praying it was my vorlauf, as I really don't run off more then maybe 8-16 ounces and def don't wait until it is "clear"

I wish I knew exactly how to describe the taste. To me it is astringent. Its a bitter I feel at the back of my mouth that ruins the taste after it is swallowed.

Tastes ok on the front of the tongue. It makes me want to stick my tongue out and go ACK.

 

[bobbytuck]

Sounds like the spring water is the culprit -- especially if it's treated well water. A better approach is to use distilled water or RO water and build your profile from scratch. I can't believe vorlaufing is the issue. I do know from experience that well water can potentially make a horrific batch of beer. A buddy of mine used well water with misplaced salt additions and it tasted like alka seltzer.

Yesterday, for example, I probably overextracted my Irish Red as I finished fly sparging. I checked the runnings and saw it was around 1.004 -- much lower than desired. But after I boiled for 90 mins and tasted the cooled wort, it was fine -- no off flavors and just a mild hoppiness (which is what I wanted for the style). Fermentation took off within 8 hours with a couple packs of Safale05.

I run an eHERMS and recirc during the entire mash, so by the time I gather the wort for the boil -- it's crystal clear. But even before my HERMS when I was using coolers and and a plastic pitcher for the vorlauf, I never had a tannic taste. I vorlaufed only a few pitcher-fulls per batch and always had bits of grains in the BK -- but no tannic tastes.

I treat my sparge with either phosphoric or lactic acid and aim for a sparge water pH of 5.8 to 6.0 @ room temp. (You might also check everything with a calibrated pH meter. The pH meter has made a massive difference in the way I approach brewing -- and I feel like I finally have control over each batch.)

My current water is charcoal filtered tap water -- moderately hard, low in sodium, moderate-to-high (107 or so) alkalinity, and I treat it with just acid malt and a sulfate/chloride additions (minimal -- usually only a few grams of one or the other or both to balance out the ratios) to hit a mash pH of 5.2 to 5.4 @ 70F. I brew darker beers -- which is what my water seems to be good for -- so I'm able to make minimal adjustments. But I've never had any kind of tannic taste in either the wort or finished beer. My issue was always minimal hop flavor until I started making water adjustments via the Bru'n spreadsheet. The pH meter was probably what changed things for me, though.

But YMMV.

EDIT: My wort out of the BK has the same residual sweetness that the wort from the MLT has. The main difference is that there's a hop flavor out of the BK. But even with the hoppiest beers, the hop flavor is still a bit muddled with the sweetness (which is a bit thicker out of the BK than it was out of the MLT -- which makes sense). For my Irish Red, I was pleased that it also was a bit brighter -- hard to describe -- out of the BK. Hoppy and bright. This might be due to the low(er) pH -- but very pleasant.

 

[BeerLogic]

I may be totally wrong, but I suspect you simply oversparged. According to what you wrote you used 8.5 gallons of water total. With an expected absorption of .8 gallons, that means you ran 7.7 gallons of water through 8 lbs. of grain! I would guess that the PH of your last runnings shot up way too high. Did you check the ph of the sparge runnings, or just the mash? What about the sparge gravity? Usually it's not good to let it drop below 1.010...

 

[TheSlash]

I may be totally wrong, but I suspect you simply oversparged. According to what you wrote you used 8.5 gallons of water total. With an expected absorption of .8 gallons, that means you ran 7.7 gallons of water through 8 lbs. of grain! I would guess that the PH of your last runnings shot up way too high. Did you check the ph of the sparge runnings, or just the mash? What about the sparge gravity? Usually it's not good to let it drop below 1.010...

Ya know, I plugged BM's recipe into beersmith2 and that is what it told me. 8.5 gallons gave me 6.5 to the kettle, I boiled off close to 1.5 gallons. Does seem like I had a lot of water in there for the sparge though. I was watching my runnings for gravity but not PH, I just kept tasting it.

Either way though, I've had this flavor in all my batches..

I'll list what all variables I've tried...

 

[TheSlash]

Sounds like the spring water is the culprit -- especially if it's treated well water. A better approach is to use distilled water or RO water and build your profile from scratch. I can't believe vorlaufing is the issue. I do know from experience that well water can potentially make a horrific batch of beer. A buddy of mine used well water with misplaced salt additions and it tasted like alka seltzer.

Yesterday, for example, I probably overextracted my Irish Red as I finished fly sparging. I checked the runnings and saw it was around 1.004 -- much lower than desired. But after I boiled for 90 mins and tasted the cooled wort, it was fine -- no off flavors and just a mild hoppiness (which is what I wanted for the style). Fermentation took off within 8 hours with a couple packs of Safale05.

I run an eHERMS and recirc during the entire mash, so by the time I gather the wort for the boil -- it's crystal clear. But even before my HERMS when I was using coolers and and a plastic pitcher for the vorlauf, I never had a tannic taste. I vorlaufed only a few pitcher-fulls per batch and always had bits of grains in the BK -- but no tannic tastes.

I treat my sparge with either phosphoric or lactic acid and aim for a sparge water pH of 5.8 to 6.0 @ room temp. (You might also check everything with a calibrated pH meter. The pH meter has made a massive difference in the way I approach brewing -- and I feel like I finally have control over each batch.)

My current water is charcoal filtered tap water -- moderately hard, low in sodium, moderate-to-high (107 or so) alkalinity, and I treat it with just acid malt and a sulfate/chloride additions (minimal -- usually only a few grams of one or the other or both to balance out the ratios) to hit a mash pH of 5.2 to 5.4 @ 70F. I brew darker beers -- which is what my water seems to be good for -- so I'm able to make minimal adjustments. But I've never had any kind of tannic taste in either the wort or finished beer. My issue was always minimal hop flavor until I started making water adjustments via the Bru'n spreadsheet. The pH meter was probably what changed things for me, though.

But YMMV.

EDIT: My wort out of the BK has the same residual sweetness that the wort from the MLT has. The main difference is that there's a hop flavor out of the BK. But even with the hoppiest beers, the hop flavor is still a bit muddled with the sweetness (which is a bit thicker out of the BK than it was out of the MLT -- which makes sense). For my Irish Red, I was pleased that it also was a bit brighter -- hard to describe -- out of the BK. Hoppy and bright. This might be due to the low(er) pH -- but very pleasant.

Very nice post. However I have used different types of store bought spring water and also used filtered tap water twice. Taste is in all. I know there are guys by me that use tap straight to brew and it tastes fine.

They don't do anything with PH even. You say you vorlauf a few pitchers full? I haven't even been doing 1 glass full...

I really need to send water to ward, but can't decide what water I even want to use yet.

Could I be grinding too fast with my drill, should I hand grind the next batch?

I think I need to get a good PH meter too just for piece of mind.

Here are the variables I have done and still get the same flavor...

Multiple water types.
Fine crush, coarse crush
adjusting the mash PH
different hops
I've done a pot on the stove, and also heatsticks
I even had this in an extract batch, but I think I steeped too hot and too long as it was my first batch. I do use fermcap foam control but only 3-4 drops.
Irish moss a couple of times, but not all.
Wirfloc 1 time
I've stirred the mash every 10 minutes, I've also left it alone for the whole time.

My wort is definitely not sweet and good coming out of the BK. It is astringent as hell. Totally different then coming out of the mash. Even final runnings were .012 area and tasted sweet and clean.

 

[TheSlash]

Here is the recipe I used
https://www.homebrewtalk.com/f66/centennial-blonde-simple-4-all-grain-5-10-gall-42841/
by BM

 

[bob1852]

I'm leaning towards your homemade copper IC adding something somehow...

 

[TheSlash]

I'm leaning towards your homemade copper IC adding something somehow...

I've wondered this as well, but isn't a copper chiller a copper chiller? It is tarnished looking, but doesn't all copper tarnish?

Seems like it would be metallic taste? That is easy to test though, I can pull a sample right before I put in the chiller.... Nice idea.

 

[Geigon]

Are you sure this isn't the hops you are tasting? Certainly the wort post-boil with hops in it tastes very bitter and not nearly as pleasant as the sweet pre-boil pre-hops mash. Try boiling some hops in water for 60 min then taste the result and compare this to what you're tasting in your beer. I would expect any astringency introduced by the mash to be apparent in your mash taste test.

 

[TheSlash]

Are you sure this isn't the hops you are tasting? Certainly the wort post-boil with hops in it tastes very bitter and not nearly as pleasant as the sweet pre-boil pre-hops mash. Try boiling some hops in water for 60 min then taste the result and compare this to what you're tasting in your beer. I would expect any astringency introduced by the mash to be apparent in your mash taste test.

Yes I'm sure. I'm a hophead.

It also never mellows. I've done up to 6 weeks primary and 3 months kegged and it stays.

 

[TheSlash]

The more I read around the more I see on people that don't vorlouf get an aftertaste... Once guy solved his by vorlaufing more and running through a cheese cloth. he said he still caught 1/4 cup of grain bits in the cloth...

Maybe my SS braid sucks and I'm getting WAY too much grain through? If I had to guess by the look of it, I'm prolly putting a cup+ of grain bits in the kettle. Think that is enough to make it astringent?

 

[TheSlash]

AZ IPA... You said this 2 years ago
"I forgot to vorlauf an IPA - tasted great to me; but in a contest all 3 BJCP judge noted astringency. I couldn't detect it, but they could -- not saying that it was the result of not vorlaufing, but it could have been.

oh, extreme Coleman MLT with SS braid...."

LOL

 

[Geigon]

So you had this same astringency in one of your extract brews? From your descriptions so far this sounds like something unrelated to your vorlaufing (or your have a couple of different things going on). The high pH of your mash prior to the correction could extract tannins, but again I would expect that to be evident in the pre-boil taste. Given that this occurred in both an extract brew and an all grain brew I'd look for something in your boiling process/equipment. And it's not a metallic taste. Right?

 

[TheSlash]

So you had this same astringency in one of your extract brews? From your descriptions so far this sounds like something unrelated to your vorlaufing (or your have a couple of different things going on). The high pH of your mash prior to the correction could extract tannins, but again I would expect that to be evident in the pre-boil taste. Given that this occurred in both an extract brew and an all grain brew I'd look for something in your boiling process/equipment. And it's not a metallic taste. Right?

I'm thinking in my extract brew I steeped my grains for like 90 minutes... so relating the taste I get to a grain tannin flavor. My extract used totally different equipment. The only common thing is my wort chiller really...

Plan on doing the centennial recipe again sat and will taste the wort after it boils for 45 minutes, then also after flame out then once again after cooling. I should be able to rule out the coil.

 

[TheSlash]

After even more reading it seems a lot of people don't even vorlauf and some deco, so maybe I'm back to looking at my sparge and copper IC?

So sick of all the RDWHAHB whatev!!! I can't they all suck! lol

 

[Homercidal]

Honestly, if your sure your pH was in the right range during the whole sparge process, then I'd look at your water make up. Everything else you've said probably wouldn't cause more than a very slight astringency if at all.

But your water may affect how the hops are perceived, even if the water itself doesn't taste very unusual.

I've vorlaufed and I've skipped it either on purpose or on accident, and other than adding a small amount of protein in the kettle, I doubt it had any real flavor impact on the beer.

 

[luke2080]

Slash - on your next batch, take some samples during the boil, and post-boil but pre-chilled like you are saying. But, I'd take the next step and vorlauf better. On of the brewing rules is to vorlauf so as to not get grain husks in the boil, which will extract tannins. I've had a few husks in the boil, but we are talking 1/4 of a handfull. The way you keep describing it, lots of pieces are flowing through.

So in that respect, I'd get a new braid. (Go a step further, braids suck, build a copper manifold. I did it with some copper tubing, some copper elbows, and an angle grinder to cut slits)

At least this way you can reliably test multiple steps on one batch.

Personally, I suspect your water is out of whack. A lot more to the water then pH. And I won't pretend I know what I'm talking about on the topic. But if your Mg, Na, etc are far out of line, it can cause extreme bitterness and off flavors. I know you've different waters, and I wouldn't change your water habits in the next batch if you don't think thats it (too many variables changing) but if you still get the taste next time, buy 10 gallons of distilled water, then brew.

Good luck to you.

 

[TheSlash]

Slash - on your next batch, take some samples during the boil, and post-boil but pre-chilled like you are saying. But, I'd take the next step and vorlauf better. On of the brewing rules is to vorlauf so as to not get grain husks in the boil, which will extract tannins. I've had a few husks in the boil, but we are talking 1/4 of a handfull. The way you keep describing it, lots of pieces are flowing through.

So in that respect, I'd get a new braid. (Go a step further, braids suck, build a copper manifold. I did it with some copper tubing, some copper elbows, and an angle grinder to cut slits)

At least this way you can reliably test multiple steps on one batch.

Personally, I suspect your water is out of whack. A lot more to the water then pH. And I won't pretend I know what I'm talking about on the topic. But if your Mg, Na, etc are far out of line, it can cause extreme bitterness and off flavors. I know you've different waters, and I wouldn't change your water habits in the next batch if you don't think thats it (too many variables changing) but if you still get the taste next time, buy 10 gallons of distilled water, then brew.

Good luck to you.

That is plan number 1. Taste EVERY step of the way, all through the boil etc.
I have a hard time believing it is the water just because I have used multiple types and they have the exact same astringency. I'm picking up a nice PH meter for this weekends brew, that should help on that front.

What would happen if I did an all grain with distilled?? Assuming would taste bland, but might tell me if PH was the issue right? If it comes to that

Thanks for the tips. I think I'll also make a copper manifold, I always assumed the braid would be a finer filter, but learning it's the grain that makes the filter. Plus I wont knock a manifold around.

 

[Denny]

What would happen if I did an all grain with distilled?? Assuming would taste bland, but might tell me if PH was the issue right? If it comes to that

You don't want to use distilled water for AG brewing. It lacks the minerals the yeast need for health and the wort needs for beer flavor. In addition, it won't guarantee you a proper pH. You need to work through this methodically, changing only one thing at a time.

 

[metal850]

Honestly, if your sure your pH was in the right range during the whole sparge process, then I'd look at your water make up. Everything else you've said probably wouldn't cause more than a very slight astringency if at all.

But your water may affect how the hops are perceived, even if the water itself doesn't taste very unusual.

I've vorlaufed and I've skipped it either on purpose or on accident, and other than adding a small amount of protein in the kettle, I doubt it had any real flavor impact on the beer.

+1

Could it be a result of very high sulfates affecting the perception of hop bitterness? Seems like it's a boil problme so my first guess would be hops. Do you have the profile for the water you use for brewing? It seems like it might not be very good brewing water considering you initial ph is 6-7.

 

[bob1852]

AZ IPA... You said this 2 years ago
"I forgot to vorlauf an IPA - tasted great to me; but in a contest all 3 BJCP judge noted astringency. I couldn't detect it, but they could -- not saying that it was the result of not vorlaufing, but it could have been.

oh, extreme Coleman MLT with SS braid...."

LOL

Nice find!

(but I did isolate the problem as water, not not vorlaufing. )

 

[Homercidal]

You could vorlauf longer/better and it certainly wont' hurt the beer. However, a having grain husk in the boil isn't necessarily going to give you tannins, if we believe brewing history where German brewers use decoction mashing as the ONLY way to brew.

Portions of the thick mash are boiled and added back to the mash tun. Grains and all. The difference is that the pH of the boiling grains is fairly low.

Also consider that you will have an almost microscopic amount of husk in your wort if you do even a small vorlauf. I'm talking a few pieces.

In the interest of getting to the bottom of this, I suggest looking elsewhere for what you describe as an astringency. My bet is on the water.