Why doesnt mold grow on baguettes

Straight Dope Message Board > Main > General Questions > Why doesn't mold grow on butter the way it can on cheese?


View Full Version : Why doesn't mold grow on butter the way it can on cheese?


12-07-2000, 12:24 PM

Is there more water in cheese than butter? Is there any water mixed in with the fat in butte?


12-07-2000, 12:33 PM

You are mistaken. Mold most definitely **DOES** grow on butter.


12-07-2000, 12:50 PM

ok. Maybe I should describe the observation that lead to this mistake. I put some cheddar cheese in a zip-loc bag and it molded. The butter dish is out exposed in the air more often than that cheese was, and covered with plastic butter cover, but I had not seen it mold.


12-07-2000, 12:59 PM

I never saw butter mold until I bought one o' those nifty butter keepers where the butter is placed in a cup, which is then turned over onto a jar of water. This makes an air proof seal, which keeps the butter fresh.

Works really well, but I tend to put butter in it and forget about it for a couple weeks. Then I see mold grow on it.

When I used to just keep butter out in a normal butter dish, I never saw mold grow on it, but it may be that the "forget about it" factor wasn't a problem. I could see the butter, so I threw it away when it looked rancid.

The Devil's Grandmother

12-07-2000, 01:45 PM

Molds need nutrients and water to survive.

If there is lots of fat and little water (as in butter) mold does not grow easily.

If there is lots of sugar and little water (like jam or honey) mold does not grow easily.

In your instance, the cheese was probably room temperature when you placed it in the bag. The cheese began to “sweat” slightly when you put it in the fridge, and the cheese surface became a happy place with low taxes and an excellent school system in the Mold’s point of view. You can wipe off the mold with a paper towel dampened with vinegar and that will help your cheese be a dirt road, low-rent district for longer.


12-07-2000, 02:22 PM

When the fat in butter decomposes, it produces butyric acid, which inhibits (but does not prevent) mold growth. Pure butyric acid really REALLY stinks, but in butter the contentration is low enough to just slightly stink. Suffice to say, when you have rancid butter, you'll know it.

Doctor Jackson

12-07-2000, 03:50 PM

Butter molds are not as prevalent today as they once were, but they do exist. I like little butter flowers and hearts and such.


Oh. Heh. Nevermind!


12-07-2000, 06:19 PM

From Food Safety and Hygeine (http://www.dfst.csiro.au/fshbull/fshbull14.htm)

The following is about margarine but it looks like some of the same applies to butter. It looks like more salt inhibits mould growth to an extent. Also it appears that when mould grows in butter in margarine it is more likely to be smelled than seen.

"Margarine, like butter, is a water in oil emulsion in which the water is dispersed in tiny droplets generally a few micro-metres only in diameter. The microbiological stability of these products depends on proper moisture distribution. Most contaminating microorganisms are restricted in growth by either space limitation within a small water droplet or by exhaustion of nutrients available in the droplet in which it is present (ICMSF, 1998).

While lipolytic yeasts occasionally cause spoilage problems in margarine, moulds are usually the cause of any off flavour problems which develop as a result of microbial growth. Unlike yeasts and bacteria, moulds can grow through the fat matrix of margarine (or butter). The composition of the aqueous phase is seldom such that it will in itself inhibit mould growth. This is particularly true of low salt margarines.

Low salt margarines containing approximately 1% salt are susceptible to mould spoilage because their water activity (aw) is higher than that of margarine containing the regular amount of salt - approximately 2 per cent. These low salt margarines have a water activity in the range 0.915 - 0.93 compared to 0.865 - 0.89 for regular salt products. They are thus susceptible to spoilage by a wider range of moulds.

Spoilage of margarine by moulds is usually only detected by microbiological investigation undertaken after off-flavour complaints are received. Such an instance was reported recently by Hocking and co-workers from this laboratory (Journal of Food Mycology 1 (1) 1998 23-30).

Samples of low salt margarine were submitted to the laboratory following consumer complaints of a 'crushed ant' flavour in the margarine. A pure culture of the mould Penicillium solitum was isolated from the affected margarine and a range of aliphatic ketones were identified as the cause of the unpleasant odour and flavour associated with the spoiled product.

Attempts to reproduce the off-flavour problem under laboratory conditions by the inoculation of low salt margarine with P. solitum and incubation at 10°C and 15°C were unsuccessful. There was no discernible mould growth in the margarine after six weeks incubation.

However a similar range of odour compounds could be produced by inoculating P. solitum into laboratory media supplemented with margarine. Two conclusions can be drawn from this work. P. solitum is best known as a post-harvest pathogen of pome fruits although it has been reported as a spoilage species in packaged cheese (International Journal of Food Microbiology 16 1992 123-130). Changing the formulation of standard food products in such important characteristics as water activity and pH will almost certainly introduce the risk of spoilage by a different range of microorganisms from those normally associated with the product. Secondly, the spoiled margarine had been stored at around 10°C for four to six months. While margarines, including polyunsaturated margarine, are relatively robust with regard to chemical change when stored up to 10°C (Lebensmittel Wissenschaft und Technologie 16 1983 198-199), if mould contamination of the margarine has occurred, storage at such a high temperature will increase the risk of the product becoming unacceptable before its nominated use-by date has expired."


12-08-2000, 06:30 AM

Many moulds which grow opportunistically on food produce toxins, whose effects when ingested range from the humourous to the lethal.

Do you know which moulds are safe and which may trip a biological trigger that results in your getting liver cancer in 20 years? I sure don't, mycology ain't my field. Bet you don't either (unless one of you is Ailsa Hocking!).

Xtal advised, humourously, to wipe the surface clean with an acidifying agent. Allow me to advise, seriously, that you don't.

Many mould-toxins can migrate through the cheese from the site of production, giving a graduated concentration from exterior to interior. If you absolutely must use the item, cut as much as possible of the exterior away, to a depth of several centimeters, and only use the interior. Even better, don't wipe the cheese clean, throw the blighted thing away.

How much does a new piece of cheese cost?


12-08-2000, 07:53 AM

Originally posted by funneefarmer
From Food Safety and Hygeine (http://www.dfst.csiro.au/fshbull/fshbull14.htm)
Samples of low salt margarine were submitted to the laboratory following consumer complaints of a 'crushed ant' flavour in the margarine.

So some consumers tasted the margarine and said to themselves, "Ew, this tastes like crushed ants"?


12-08-2000, 09:17 AM

It's even worse when your crushed ants begin to take on a buttery flavor. Trust me.


12-08-2000, 09:39 AM

Originally posted by AKAmame
If you absolutely must use the item, cut as much as possible of the exterior away, to a depth of several centimeters, and only use the interior. Even better, don't wipe the cheese clean, throw the blighted thing away.

How much does a new piece of cheese cost?

What you say about the migration of the bacteria or mold may be true, but I've read that all you need to do for hard cheeses is to cut away the mold. Now, perhaps in soft cheese there is the migration , but is that true for hard cheese, in view of what I've read previously?

The Devil's Grandmother

12-08-2000, 12:37 PM

Oh dear. Sorry for the bad advice about cleaning your cheese with vinegar. It's one of those things my grandmother did. I suspect she's one of the many who never got over the "there are hungry children in xxxx, so we must eat all this food".


12-08-2000, 01:42 PM

Do you have any cites for your views? Like many people, I've been eating moldy cheese and bread for many years without ill effect. I might re-consider if there's a real threat. I was always told, and my experience has so far verified, that the only threat from molds is the allergy threat.


12-08-2000, 07:58 PM

Do not read the following if you are squeamish about food.

Barbitu8, I'm not saying the microorganisms migrate(*), but that the chemicals they produce do.

Think about a soft, mould ripened cheese like a Brie or Camembert. Much of the ripening process and the flavour is due to the metabolism of the curd by the surface moulds with which the cheeses are innoculated, and the flavour chemicals they produce as byproducts. Cut the imaginary cheese in half - you can see how the edges, with a higher concentration of the various chemicals are "riper" under the mould "skin". Cut another imaginary cheese that has been aged a month longer in half - see how the chalky, unripe centre is smaller? The cheese interior has ripened as the chemicals migrated, with a diminuition in chemical concentration from the origin point. This is effectively 3 dimensional - chemical concentration will diminish with the cube of the distance.

(*) On relatively solid foodstuffs such as meat, microorganisms rarely migrate through the flesh, but remain as surface contaminants. When you mince meat, that not only increases the surface area, but distributes the contaminating microorganisms throughout the product. Thus, unless it has added preservative, minced meat goes "off" more quickly than hunks of meat, allowing for the same conditions of refrigeration and contact with pooled blood.

In a hard ripened cheese, there are zillions of microorganisms throughout the product, metabolising away and producing the physical and flavour changes we love so much. For commercial cheeses they are added as a starter culture (think yoghourt) to the milk or when the curds are formed and cut, which is why they are so evenly distributed.

Time for lunch, I think!


12-08-2000, 09:55 PM

Sorry, I don't have one on rate of mycotoxin migration through cheese - my comment was based on a combination of prior professional knowledge and conversations with mycology researchers (which was not my field, as I said in the previous post).

I am not suggesting you take my word for it in the absence of a researched article - mycology is not my field and I could be wrong. I have, if you will, reasonable belief but not knowledge on the matter. But walk with me through this if you would: Various moulds produce a range of chemicals, some useful (such as antibiotics), some long term lethal (such as aflatoxins). Most of the chemicals produced by moulds will migrate through the substrate on which they are produced, with the rate in that substrate likely to vary according to the concentration of the oil/water in which the chemical is soluble. You could reasonably expect migration rate to be lower in hard than soft cheese, for instance.

(Actually I found cite sort of on-topic, but I didn't think it was a known source that would carry any more weight than my unsupported word!) Plenty on mycotoxin production in foodstuffs, particularly grains, probably because the effect of mycotoxins, particularly aflatoxins, in animal feeds has a strong commercial impact.

The following cites give information on mycotoxins in foodstuffs, though not on toxin migration.

http://www.inform.umd.edu/EdRes/Topic/AgrEnv/ndd/health/MYCOTOXINS_IN_FEED_AND_FOOD_PRODUCING_CROPS.html (overview_of_mycotoxins_in_feed_,emphasis_on_aflatoxins)

http://www.fao.org/docrep/x0036e/X0036E08.HTM#Toxigenic aspergillus and penicillium species
http://www.omu.edu.tr/w2/akd/fenbilen/gidam_d.htm English abstract part way down page.

If this is not on point enough please advise and I'll have another whack at it.

And yes, I do eat brie and blue vein cheeses. A lot!

vBulletin® v3.8.7, Copyright ©2000-2020, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: [email protected]

Send comments about this website to: [email protected]

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Copyright © 2018 STM Reader, LLC.