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OK... My first and only attempt at bleu cheese (gorgonzolla) ended in abject failure due to some kind of infection. The bleu developed but the finished cheese tasted STRONGLY of BANANA. (I hate banana.) I know this is a flaw that sometimes develops during brewing endeavors due to the formation of a type of esther called (unsurprisingly) Banana Oil... I'm just wondering if any of you fermented foods cross-discipline types can tell me what kind of contamination occurred and how I can avoid it on my next attempt. There were too many odd variables here for me to really pinpoint what happened, other than pinning this on the 'cheese sitter' that watched my cheeses while I was away on Christmas Vacation. I have since spent hours DECONTAMINATING all of my cheesing supplies, just in case, but... Whoa. Is there a specific kind of yeast that causes this, or is it the normal yeast that may populate my home (or the cheese sitter's) in combination with certain conditions like too much moisture/oxygen/temperature... I'd like to avoid any further bananification of cheese if I can!

Jesse-very strange in deed. What other types of home made activities are you interested in? It sounds like a contaminant but I have never personally seen it in my blue's. I did find an interesting article online that I have attached to this email that may shed some light-it is a reach for sure. It was an article on banana's and possible microbial contaminants and there associated off Oder's. I is a reach but the link given lists some of the critters that we use in cheese making and some that are now to be problematic for us.

I sent the cheese to the cheese-sitter's house in tupperware, (normally they live in my cheese fridge with no tuppers) and when I got them back, I noticed a STRONG alcohol scent inside the containers. Did this happen because there wasn't enough oxygen to prevent the yeasts from taking off? I bake in my kitchen and make plenty of other fermented foods like kraut and mead, but I'm pretty solid in my cleaning and bleaching of all my equipment between endeavors so as to avoid cross contamination. I do know that my cheese sitter is a pretty heavy brewer, which is why she was willing to babysit my cullenary endeavors in the first place... She knows what it means to have food-pets...

QuoteEster formation depends on the amount of fusel alcohols and organic acids in the wort, but also on the activity of alcohol acetyltranferase enzymes (ATAase I and II), which in turn depends greatly on the yeast strain. Esters in the fermentation can be classified into two groups: The acetate esters (acetate+alcohol) and the ethyl esters (ethanol+fatty acid). The acetate esters are usually formed in greater amounts, but the ethyl esters can be very aromatic even in low concentrations. Common descriptors for the aromas of esters are listed in the table below. The short chain fatty acid esters (C6, C8) are formed early in the fermentation, the medium chain esters (C10,C12) quite evenly throughout the fermentation and the longer chain esters (C16) mostly at the cell-death phase. Increased cell growth usually results in lower levels of esters, due to lower levels of free fatty acids in the wort, as fats are used to build cell walls. Organic acids are formed throughout the fermentation and at high levels they produce notes of vinegar, vomit and barnyard. The right proportion of fusel alcohols and free fatty acids or acetate is crucial when producing estery wort and avoiding the solventy off-notes from the excess alcohols and on the other hand the rancid aromas from the excess free fatty acids. An estery, fruity wort can be produced with warm long fermentations, high original gravities, high pitching rates with aerobically grown yeast and low nitrogen barley. Increased glucose levels tend to produce more short chain esters, for example isoamyl acetate with a typical banana aroma. High fermentation temperatures usually produce more acetate esters with mainly fruity aromas, but also medium-long chain ethyl esters, which can give an oily and waxy texture to the flavour.

Ester Name* Odor or occurrence

Ethyl butyrate* banana, pineapple, strawberry
Ethyl hexanoate* pineapple, waxy-green banana
Isoamyl acetate* pear, banana (flavoring in Pear drops)
Amyl acetate (pentyl acetate)* apple, banana

I wonder if this is from late blowing? It might be the milk, if the cows were fed silage. Here's a quote from http://www.cskfood.com/ingredients/307.html

QuoteContamination of cheese milk with spores of clostridia, especially Clostridium tyrobutyricum, originates mainly from the use of silage in the feeding of dairy cattle. Spores of the bacteria are ingested by cows from contaminated silage and subsequently arise in the dung. Contamination of milk with even very small quantities of the dung (for example from the utter) leads to the presence of Clostridium tyrobutyricum in milk.

Spores of Clostridium tyrobutyricum have been found to survive the normal heat treatment of milk during the production of cheese and later propagate to cause late blowing. During the ripening of salt brined, semi- and hard cheeses Clostridia ferments lactate into butyric acid and large quantities of gas (CO2 and H2). The formation of gas produces undesirable effects in texture (cracks and irregular eyes) and the acids cause unacceptable tastes and smells.

Could the formation of butyric acid form ethyl butyrate?

a lot of times you will see reference to ammonia smell in the aging area if there was not enough air exchange-don't know about alcohol smell. Dthelmers might have the connection...

Propanoic acid is used commercially to make fruity-smelling esters - perhaps this is the culprit? (possible sources include propionibacteria from sweaty hands or Swiss/Gruyere-type cheeses in your cave?)

In homebrewing, you can get this ester from fermenting at too high a temperature - I don't know if the same can be said for cheese.