Carrageen off flavour?

[JAMC]

I brewed batch number 5 today (following this recipe). In preparation over the last couple of days I've been thinking about how to improve clarity in the finished beer, and it struck me that the sometimes-there, sometimes-not-there flavour I got for the first time in batch 4 might be because it was the first batch I experimented with whirlfloc tablets.

I know these are just the concentrated active ingredient in Irish moss compressed down into tablet form, but would using too much impart an off flavour? I used a whole tablet for a five gallon batch last time, but having read in a couple of places that this would be overkill (suggested ratio was 1 tablet / 10 gallons), I only used half a tablet in today's brew. Half the dose still seemed to have the same effect. I also went back to using a hopbag this time, to avoid having to deal with the hop trub as well as the protein gunk in the bottom of the kettle.

I ended up with about 3 litres of gunk left behind from about 25 litres total at the end of the boil, which I was pretty pleased with.

 

[Nosybear]

I use the Irish Moss in my "clarified" beers - never a problem with off flavors. The stuff smells like dead fish in the bottle but either there is so little of the aroma or it boils off. Never a problem.

 

[JAMC]

Hmm.... the other possibility then is that I seriously underpitched the yeast.

I'll keep an eye out for the tell-tale aroma as I work my way through the batch. I had a bottle this evening and couldn't detect it.