Isoamyl Acetate

[DaveC73]

So I've been gathering apples from around my neighbourhood and making cider with them for the past couple of years. These apples tend to be low ph (< 3.4), high acid (> 8g/L malic), and some are also high gravity (sg > 1.070). Tough conditions, yes, but not impossible. I stick with champagne (DV10 and EC1118 mostly) for the most part, but also dabble with other yeasts.

I've been getting strong banana esthers (isoamyl acetate) late in primary fermentation more and more as of late. I sulfite the juice to 100ppm, wait 24 hours, add pectinase, wait 24-48 hours, aerate & pitch properly rehydrated yeast, and feed 2-3 g/L of Fermaid O (1/3 at pitch, 1/3 after 24 hours, 1/3 after another 24 hours). About 1/3 of the time I get the banana explosion.

Anyone have any ideas why this happens and how to prevent it?

 

[Maylar]

It's not common in cider. It's a signature characteristic of certain beers, and a possible fault in wine -

Isoamyl acetate is formed by yeasts during fermentation. The concentration formed is yeast-dependent. Carbonic maceration, must aeration, and must clarity also play a key influence on the amounts formed. The compound contributes a banana-like note and complexity to neutral white wines and to red and white premier wines. When present in excess it can mask key varietal characters.

High fermentation temps and stressed yeast can be factors. The yeasts you listed are notoriously clean fermenters, but you need to keep temperatures controlled.

 

[DaveC73]

Fermentation temperature is kept between 60-64F (15-18C). I've had DV10, Renaissance Fresco and a wild fermentation go "bananas" on me so far. EC1118 has been steady as usual.

The only other common thing between the three "bad" fermentations is that they were all from different yellow skinned apples. No idea if there's a connection there, but I've fermented straight rhubarb and grapefruit juice with no problems. Wondering if there might be some kind of precursor in the yellow apples? So far the internet hasn't been helpful on that correlation.

I'll keep looking though. Thanks!

 

[gregbathurst]

I have had that when using some dessert apples. It always tended to age out in a month or 2. Now that I use wild ferments I don't get it at all.