No aroma after dry hopping

[HT Shen]

We are kegging the NEIPA today.
But we found that the hop aroma is not as good as before. (Not just a littlie bit, it is really big different)
Please check the information as follows which we change for this batch of IPA.. Other than that, everything is the same. Any idea what's going on?

1. Malt bill
@Changed mattis otter to pale ale
@Increased 100g of flaks oak
@added 100g of melano castling malt

2 Mash PH
@This time : PH 5.4
@last time:No measurement

3. Water profile
@This time Ca+:119 ; Mg2+:10 ; Na+:13 ;Cl-:163 ;So42-:124 ;Hco3-: 0
@Last time Ca+:85 ;Mg2+: Na+:6 ;Cl-:102; So42-:66 ;Hco3-: 0

4. Fermentation processes
It is limitation for my cooling equipment. (The highest temperature which I can control is 18C)
In this way, I just can do it in this method.

@ This time
1-5 days:
Control 18C and free rising temperature to 22.8C and back to 18C
(In order to get more ester and remove diacetyl)
6 days : Decrease temperature to 15 degree C
7 days : dry hops
10 days cold crashing to 7 degree C
14 days: kegging
@ Last time
6-14 days : Keep temperature at 18 degree C

5. Dry hop hop
@ This time: No bag or stainless hop tube
@ Last time: Used stainless hop tube

6 Hop schedule

@This time
*No bitter and aroma hops
*Whirlpool (85C 25 min) 49g Citra, 28g El dorado, 28g Azaaca
*Dry hop ( 15C dry hop, 10 days cold crashing to 7C) 119G Citra, 56g El dorado, 56g Azacca
@Last time
*No bitter and aroma hops
*Whirlpool (80C 20 min) 49g Citra, 28g El dorado, 28g Azaaca
*Dry hop ( 18 degree C) 119G Citra, 56g El dorado, 56g Azacca

7 Final Gravity
@This time: 1.013
@ last time : 1.007 (Hop creep)

Footnote
1. I did notice the hop burn for this batch of beer. However, after reading some article,
I think that it should not the problem after storage the beer after couple weeks, right? Does the aroma something related to hop burn?
2. I read the Janish article Examination of Studies: Hopping Methods and Concepts for Achieving Maximum Hop Aroma and Flavor - Scott Janish It looks like that dry hop stay in the wort is too long. (Now, I leave it for 7 days. So, I will reduce it to around 4-5 days)

 

[Bobby_M]

No need to read the post. The answer is oxidation.

 

[HT Shen]

No need to read the post. The answer is oxidation.

Tks! But, I have no idea which processes cause the oxidation.
When we do the dry hop for last and this time batch, we did do purge the CO2 into the fermenter first, and then do the dry hop.

The only different for this batch is that we didn't use any bag or stainless hop tube.
But, it should not make the oxidation.

5. Dry hop hop
@ This time: No bag or stainless hop tube
@ Last time: Used stainless hop tube

According to the Janish information, it can dry hop loosely can increase 50% of hop extraction.
So, it should be had more aroma?

 

[Bobby_M]

I probably should have read it. That's what I get for being lazy. Yes, you can definitely compact hops too much in a small container to the point where the center doesn't even get wet, let alone extract the oils into the beer. Free floating is always best.

 

[HT Shen]

I probably should have read it. That's what I get for being lazy. Yes, you can definitely compact hops too much in a small container to the point where the center doesn't even get wet, let alone extract the oils into the beer. Free floating is always best.

Hi Bobby !
However, the issue now is the batch used container is more aroma than the batch used free floating.

 

[bailey mountain brewer]

That's where oxidation comes into play, how are you dry hopping, oxygen free? Purging with co2? Are you doing closed transfers when kegging?

 

[HT Shen]

That's where oxidation comes into play, how are you dry hopping, oxygen free? Purging with co2? Are you doing closed transfers when kegging?

Yes, I did do close transfer when kegging.
Yes, I purging CO2 before and after when doing the dry hopping.

 

[Panderson1]

Are you doing a starsan CO2 purge?

Also. I would recommend buying a stainless mesh dryhop container and drop it in the keg. Skip the fermenter hops. Cold extraction in 3-5 days. Swirl the keg every day a bit to circulate the hops. Scott Janish talks about this a lot.