Off Flavour - Brown Beer

[AzzaR25]

Hi All, I’m new to the forum and while I’ve done a lot of reading I wanted to post my specific experience to see if the brewing brains can assist in identifying the culprit of my off flavour.

I have brewed this beer twice now and the first batch was fine for the first few days but quickly went off having what I could only describe as the wet cardboard flavour commonly associated with oxidation. After a week this flavour got drastically worse as well as the colour going from a nice golden to a hazy dull brown. This batch was dumped down the drain as the flavour was too disgusting .
After reading multiple forums I decided to revise some equipment. Got RO system to rule out water issues. Closed transfer from fermenter to keg.
So I brewed a very similar version of this and kegged last week and tasted last night and have tasted a subtle characteristic of this off flavour coming through again! But with the adjustments to my process I can’t see where this is coming from if oxidation. Could it be an infection in my plastic fermenter? The only difference so far in this beer is absolutely zero hop flavour is coming through and is incredibly bitter. My hops were from a 500g bag opened and then reseated in just a ziplock andstored in freezer. These are a year old so wondering if the issue could be caused from the poor storage?

Further background to assist in feedback for recipe and equipment/process:
23L batch
78% Golden Promise
8% Vienna Malt
8% Wheat Malt
3% Carapils
3% Crystal Light

20g Galaxy 60min
20g Tettnang 60min
90g Galaxy Hopstand
80g Galaxy 7 Day Dry Hop

Water additions to suit IPA style

US-05 yeast

Brewed with Brewzilla. 60min Mash, Mash Out, 60 min boil lid off

In temp controlled fermentation fridge in HDPE fermenter. 7 days 18 degrees, dry hopped, 7 days 21 degrees.
The airlock had just a tiny bit of activity when I removed lid for dry hop so though safe that co2 would push out any oxygen but maybe this was where it became oxygenated?

Anyway I don’t know what’s causing my issue or if my issue is in fact oxygen. Any advice is appreciated as I’m still fairly new as this my 10th home brew.
TIA

 

[AzzaR25]

A couple points I forgot to include:
My immersion chiller is rubbish and it’s bloody hot so couldn’t get temp down so the beer sat in my fermentation fridge for a couple hours to get down to temp 27 degrees for yeast pitch.
Also as briefly mentioned I did set up a closed transfer from fermenter to 10L keg that I’m fairly confident worked well. I bottled the remaining 13L but will have to wait another week to try these.

 

[Malchizedec]

Hi AzzaR25

Unfortunately, I cant nail your issue but I can provide some thoughts of my own experianced.

US-05 should be a clean ferment at 18c
I've used hops a year old before which have been stored in a freezer & ziplock bag without an issue (other than a decrease if flavour profile).

As you have already stated, cardboard flavours mean oxidation at some point, when the yeast doesn't need oxygen anymore.
If you have ruled out everything else then my next thought would be the few hours of standing above 26c exposed to oxygen.
While my gut says this shouldn't be an issue as yeast need oxygen to ferment (at the beginning), maybe it's too much for the short fermentation time of beer versus mead and wine?

18 Common Off Flavors In Beer (And How They're Caused) (item 16)
http://howtobrew.com/book/section-4/is-my-beer-ruined/common-off-flavors
Improving your hot to cold transfer time might be a good way to test if this is where the issue is coming in?

At this point, I have had Metalic, cardboard, green apples, and butterscotch. slow learning