Hello Nabil, great to see your first post.
Excellent question, I believe the common term is like you say Slip Skin or Toad Skin or Peau De Crapaud. I have had the same problem on my last two batches where I also added Geotrichum candidum. My pictures of
dramatic #7 here and
less dramatic #8 here. So I am also very interested in this. Fellow member Likesspace had
similar problem here, I'm 99% sure he uses Geo. Fellow member Captain Caprine had a
good post on it here.
I've done some reading in "Cheese Problems Solved", to summarize:
1) "Toad-skin" defects originate from uncontrolled development of specific strains of Geotrichum candidum and is characterised by a web of ridges at the cheese surface.
2) This organism is able to produce arthrospores which form chains, which when present at high density, join together and create ridges by pushing one against the other, causing the development of "toad skin".
3) Very soon after manufacture, yeasts grow on the surface forming a dense layer about 200 um thick; G. candidum appears just after these yeasts but its growth is very sensitive to salt.
4) In the past, G. candidum caused concern to cheese technologists because of its proteolytic activity which is associated with the "toad skin"-like surface of the cheese. However, it is now known that through its enzymatic systems, it also plays a major role in the development of flavour.
5) Now, selection of strains of G. candidum that do not cause "toad skin", and use of low inoculum levels (down to 25 spores/ml), have led to a widespread use of this species. In order to improve the organoleptic quality of Camembert made from pasteurised milk, selected strains of G. candidum, yeasts and coryneform bacteria are generally added to the cheesemilk, giving a product closer to traditional Camembert, and closer to the expectations of most consumers.
6) The use of dry salting may stop the growth of G. candidum for a while. Geotrichum likes quite high temperatures (25C), and low ripening temperatures may hinder its growth.
7) If Geotrichum is added to the milk for its positive effects, the choice of the strain and the level of inoculum have a major impact on the properties of the resulting cheese. The inoculation of G. candidum should be about 25 spores/ml in the milk, that is to say about 100 times less than the level of inoculation of Penicillium camemberti.
So in summary:
1) G. candidum adds beneficial taste, colour, odour and feel properties to cheese.
2) "Toad skin" is formed by unwanted G. candidum strains.
3) Manufactured G. candidum is made to minimalize the bad strains, but inoculation is best below 25 spore/ml (1/100 of P camemberti).
4) Dry salting and ripening temperatures <25C/77F will hinder G. candidum growth.
5) As an aside, you will get better taste, colour, odour and texture properties is als add years and corymeform bacteria.
Where I had this problem:
1) I used G candidum, about the same amount as P. camemberti (few puffs of each directly into the milk), which looks like way way to much (I don't know the spores/gram concentration of either, but I think one to one is way too much).
2) I had ripening temperatures of 33>30C before adding rennet with G. candidum in the milk.
3) I dry salted (inhibits excessive G. candidum growth) my Camemberts in batches #7 & #8 by sprinkling directly on the top and bottom, not sides. My worst one in my batch #7 looked just like your picture with minimal slip skin on top and most around sides.
So I think those are my three major causes, ripening temp is function of recipe, but key is too much G candidum resulting in slip skin especially around sides where I didn't dry salt. This reasonably agrees with Caprine's post.
Questions to you, to help confirm this diagnosis:
- Did you use G. candidum?
- If so, did you use lots or little G. candidum?
- Did you dry salt?
- Your slip skin appears mostly around the sides, did you dry salt top and bottom but not sides?
- What was your ripening temperature?
Hope helps and looking forward to your reply . . . John.
