Mould growth in fermenter

[mattco353]

In spite of a number of mistakes on my first all grain brew (a sweet stout) it has turned out very drinkable (if somewhat low in alcohol and slightly lacking in carbonation). My problem is that I have a completely new set of issues with my second batch (a bitter ale) just bottled and I'm anxious not to repeat them. Fermentation was slow on the 1st batch and i decided to use a brew band heater for the ale to eliminate temperature issues. Owing to a spill during wort transfer the volume collected was nearer to 4 gal than 5 so there was a gap of about 7-8 inches between wort 7 lid. After two weeks in the fermenter (thermometer in the cupboard read 23 dec C anytime I checked it) there were spots of green mould and a foul chemical smell. Starting gravity was 1.046 and final gravity 1.012. I bottled it anyway just in case there's a miracle! I have read somewhere about fusel alcohols but don't know enough about them to know that this was the odour in question.

1) Is the large air gap likely to have lead to the mould growth?
2) If yield was low again for any reason, would it be better to top up to the recipe volume using cooled boiled water?
3) Any thoughts on glass carboys vs plastic in terms of being able to see a problem developing before it's too late to do something about it?
4) Any reason to hope that secondary fermentation will improve the brew? (be honest!)

All help appreciated

 

[arch1tect]

Did you santize it properly?

You may just be seeing the krausen ring/debris. I wouldn't worry about the smell too much as every fermentation is different.

 

[Kaz]

Are you sure it was mold and not hops floating etc? Green beer can have some pretty funky odours, especially while its still in the fermenter.

1....I don't think the air gap had anything to do with the mold formation...poor sanitation and a long lag time before the yeast get going could have.

2....topping back up to 5 gal. would work, but it may give you a weaker watery final product depending on the specific gravity.

3....If you had been able to see the mold start growing, what would you have done? Once its in there, its there.

4....secondary conditioning could lessen the chemical smell/taste, so could leaving it in the primary longer. Did you rack to a bottling bucket before bottling? I've read that other guys have gotten mold growths and just siphoned the beer from underneath the pellicle and had fine beer in the end. Good Luck!

 

[mattco353]

Thanks for that, you may be on to something with long lag time for yeast to get going. I've only done two AG batches but yeast action has been slow on both (48 hrs +!) which is why I'm planning to move to yeast starters. I'm not sure why this is as I have tried to follows best practice re aeration of the wort and I've used two types of liquid yeast (activator and white labs). The cupboard where I place the fermentation bucket is in a room with underfloor heating and is typically 19-20 deg C, but in case this was a little low I used the heater on the last batch....so I guess I need to fix a yeast lag problem somehow. On the last point, I did rack before bottling so it will be interesting to see what it's like. Thanks