Why Grapes Don't Mold: Exploring the Mystery

[Victor Frankenstein]

I left some strawberries for a little over a week in the refrigirator and I noticed some white fungus like stuff on them, what is that stuff, how come this doesn't seem to happen to other fruits like grapes ?

 

[misskitty]

Interesting question. It might be the same mold that we were discussing in the Mold thread. You might want to check out the links in that thread. They were posted by Ouabache in the sixth post. They might be able to tell you what kind of mold is growing on those strawberries.

I'm not sure why this doesn't happen to grapes. Come to think of it, grapes are the only food that I know of that doesn't mold like other kinds of food. I'm beginning to wonder why grapes don't mold.

 

[Goodie]

What is the difference between mold, fungi, yeast and bacteria?

 

[iansmith]

Mold, fungi and yeast are eucaryotic cells. These type of cell are similar to animals cell. They have a nucleus and organelles. Bacteria is group of organism that lack a nucleus and compartmental struture (no organelle). The bacteria also have different type of ribosomal DNA than eukaryotes.

Mold and yeast are both fungi. Mold form multicellular filamentous colonies whereas Yeast are unicellular organism. Fungi are a group of organisms that lack chlorophyll and cellulose.

People often use mold and fungi i interchangeably.

 

[Victor Frankenstein]

Can consuming fungi be hazardous to ones health ?

 

[Math Is Hard]

Can consuming fungi be hazardous to ones health ?

Gosh, I hope not. I had some really yummy sauteed mushrooms for dinner!

 

[iansmith]

Can consuming fungi be hazardous to ones health ?

It will depend on the species. As MIH pointed out, some mushrooms are safe to eat. Yeast strain that are to ferment food are usually safe.

Several pathogenic and toxic species do exist. This is a quick description of some toxic species that are commonly found on food.

http://www.toxic-black-mold-info.com/moldtypes.htm

 

[Monique]

Ever eaten moldy cheese? The blue ones are my favorite :tongue:

To answer the question why strawberries rot so quickly: that is because they're very fragile, their skin is only very thin. Grapes have very thick skins so they are well protected from the outside environment.

 

[DocToxyn]

While the affects of bruising surely have an impact of fruit longevity, I might guess that there could be native yeasts and molds that discourage the colonization of the grapes by "bad molds". Part of my reasoning behind this follows.

Certain grape species, especially those used in the production of sweet wines, have a mold species specific to them, Botrytis cinera which facilitates the winemaking process. Also called "noble rot", this fungus causes the grape to shrivel, increasing acidity and sugar content to produce wines like Sauternes. It doesn't affect all grapes in the vineyard and the accompanying reduction in water content further limits yield, thus the higher price for these wines. Whether this mold is found on all grapes and it only "takes over" on limited bunches, or if it is only found on those bunches that it affects, I don't know.

 

[Ouabache]

VF , the white fungus you saw on your strawberries is most likely Botrytis cinerea. (same fungus that DocToxyn made reference too found on some grapes)

When the mycelia (fine filimentous hyphae) become dense enough, the colour is generally more grey. This one is also the major cause
of strawberries rotting in the field during especially wet seasons.

see ---> http://strawberry.ifas.ufl.edu/plantpathfiles/PP-bot-32.JPG
and ---> http://www.extension.umn.edu/yardandgarden/YGLNews/images/strawberrybotrytis-dpp.jpg

Upon ripening, all fruits (including grapes) will become colonized by fungi. That's why they taste the best at peak maturity. Their sugars are fully developed and lots of other tastey biochemicals are present. Strawberries have an especially pleasant fragrance and flavour. :tongue2: They chose a
fitting Family name Fragaria. Straw is often used as a mulch on strawberry beds. Which is one etymology in naming the fruit. Reason for the straw? To keep the fruit dry so they don't get moldy.

Quiz time: What is the only fruit that bears its seeds on its outside? :uhh:

The most common mould in grapes are yeast. Over a 100 species of yeast have been identified, naturally on grapes. That is why old-world cultures who made grape wine, didn't have to add anything to their ripe fruit. Just stomp around on them for awhile and put them up in barrels to ferment.
Today we also inoculate the mash using an isolate of Saccharomyces cerevisiae. (the genus Saccharomyces is well chosen, Latin Saccharum = sugar, and this yeast's primary food group )

iansmith rightly points out the phenotypic differences distinguishing moulds, fungi, yeast and bacteria. Though in mentioning eucaryotes, I thought he would also point out that bacteria are procaryotic.

I am not convinced of a distinction between "good mold" and "bad mold" that DocToxyn proposes. For myself and everyone else who happens to be allergic to fungi, all molds are bad molds. I am not familar with allelopathy (chemical inhibition of one species by another) between molds. Generally it is, first come first serve, which ever mold lands there first has first dibs at colonizing the fruit.

 

[iansmith]

[
iansmith rightly points out the phenotypic differences distinguishing moulds, fungi, yeast and bacteria. Though in mentioning eucaryotes, I thought he would also point out that bacteria are procaryotic.

I did point out that bacteria are procaryotic because it is not appropriate and not accepted term to describe bacteria anymore. Also, procaryotes should not be used to described either bacteria or archea because it is a classification based on not being an eucaryote.

If you want more info read, http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=2112744

 

[DocToxyn]

DocToxyn[/I] proposes. For myself and everyone else who happens to be allergic to fungi, all molds are bad molds. I am not familar with allelopathy (chemical inhibition of one species by another) between molds. Generally it is, first come first serve, which ever mold lands there first has first dibs at colonizing the fruit.

Perhaps the term "preferred mold" would be more acceptable , at least in the case of the wine makers. Are the different species of molds readily definable in terms of their appearance and/or effect on the grapes? One would guess that it can be done since it is a specific species the vintner is going for and they would selectively allow the Botrytis to remain and remove any bunches with unwanted mold species. This would then increase the chances of further propagation of the desired mold across the vineyard. As far as competition, I hadn't envisioned "chemical warfare", simply, as Ouabache stated, a foothold-type effect.

 

[Ouabache]

I did point out that bacteria are procaryotic because it is not appropriate and not accepted term to describe bacteria anymore.

Ian, that is very interesting about change of nomenclature and that distinction came about with the advent of genomic sequencing.
But as the term procaryote is embedded in the literature, it will take some time before folks stop using it

Are the different species of molds readily definable in terms of their appearance and/or effect on the grapes? One would guess that it can be done since it is a specific species the vintner is going for and they would selectively allow the Botrytis to remain and remove any bunches with unwanted mold species. This would then increase the chances of further propagation of the desired mold across the vineyard.

DocToxyn, I think you are right that vintner's selectively allow that species of Botrytis to remain.. One way they might accomplish that, is by allowing the pruned deadwood from the vines that yielded the preferred mold, to remain in the field.

Yes there are readily definable fungi that colonize grapes. Several that also cause disease, come to mind Melanconium fuligineum causes a disease called 'Bitter Rot'. Phomopsis viticola also infects grapes, and Guidnaridia bidwellii causes 'Black Rot' .If the berries are injured from mechical growth cracks or are punctured by insects, they can be colonized by any of the following: Aspergillus niger, Alternaria tenuis, Cladosporium herbarum, Rhizopus arrhizus, Penicillium sp. collectively causing 'Sour Rot'

 

[Ouabache]

Can consuming fungi be hazardous to ones health ?

In addition to the fungi that iansmith pointed to, there are many mushroom genera that are hazardous to your health

Aminita and a some species of Galerina produce a cyclopeptide poison. Gyromitra species produce monomethylhydrazine poison. Others can produce, coprine, muscarine, ibotenic acid - muscimol poisons. Many mushrooms will give you digestive déjà vu :yuck: and/or bad case of Motezuma's revenge.

ref ---> http://www.mv.com/ipusers/dhabolt/dad/mushroom/puffball/puffball4/poisonous.html

Older cultures including native American, used hallucinogenic mushrooms for religious practises. These included the genera Psilocybe, Conocybe, Stropharia, Panaeolus and Copelandia and Lophophora