Strong, bitter, metallic taste after a week bottled

[Paulus]

Hi all, I have done a fair few kits over the last 8 months.
I have pretty good temperature control for fermenting and post bottling (in summer here it gets HOT).
In the last 2 months (December-January) I have done 4 kits which have all been bottled in a mix of 450-500ml flip tops and 1l capped types.
I mix the LME from the kit with 3.5l of boiling water and add in chilled filtered water to 22.5l.
After that I add a Pure Brew tablet and powder then pitch and seal the fermenting bucket.
Once fermented (no bubbles +1 day), going from fermenter to another bucket with 120g DME in 200ml of boiled water using a siphon it then gets siphoned again to the bottles.
I store the bottles at the recommended temperature (18-20C) for 2 days then leave them in a cupboard at about 17C.
When I try a bottle after the 2 day initial bottling it tastes good. 2weeks later they all seem to develop an almost over powering bitter, metallic flavour. After 6 weeks in bottle this reduces quite a bit but is still in the background.
Any ideas where this is coming from?

 

[MmmBeer]

A metallic taste / aroma is usually caused by ferrous sulphate, which results from the presence of iron in either your equipment or your water.

Off flavours Metallic is no. 9

If you are making kits, I'm assuming everything that comes into contact with the wort or beer will be plastic or glass, but have a check over your process to assess whether anyfhing metallic (other than a high grade stainless steel) came into contact with the wort or beer.

As for the water, try to find a water quality report for your area on your water supplier's website and see if there is any significant level of iron in the supply.

Other, less likely sources could include the LME from the kit, your water filter, any additives or even the bottle caps.

 

[Paulus]

A metallic taste / aroma is usually caused by ferrous sulphate, which results from the presence of iron in either your equipment or your water.

Off flavours Metallic is no. 9

If you are making kits, I'm assuming everything that comes into contact with the wort or beer will be plastic or glass, but have a check over your process to assess whether anyfhing metallic (other than a high grade stainless steel) came into contact with the wort or beer.

As for the water, try to find a water quality report for your area on your water supplier's website and see if there is any significant level of iron in the supply.

Other, less likely sources could include the LME from the kit, your water filter, any additives or even the bottle caps.

Hi MmmBeer, thanks for the link that is a very useful reference. I can't find any other off taste in the links that matches.
I don't have any metal components in the fermentation or bottling steps.
The water could have metal ions,though it tastes OK (slight chlorine which I will get campden tablets for soon).
The thing is the taste lessens after 6 weeks or so. Just seems strange it is fine 2 days after bottling, then really bad at one week, getting better at 6 weeks ( so far).
Again thanks for the reply, very useful.