I noticed the formation of e red pigment on a typical Arabic cheese, this cheese is prepared by Bedouins from the goat milk and conversed in a hyper-saline water, the pigment is formed only when the cheese is exposed to the air (out of water), is it a microbial metabolites? Is this phenomena known for other types of cheese?
In addition to Micrococcus roseus. Also may be due the growth of Serratia marcescens on cheese surface. It produce a red pigment. I found it in Domiatti cheese (Biodiversity of Bacterial Ecosystems in Traditional Egyptian Domiati Cheese., Appl. Environ. Microbiol. February 2007 vol. 73 no. 4 1248-1255 )
Thanks,
more microbial were red pigment production e.g micrococci , Serratia marcescens. but in high level salt were found some Bacillus spp. red pigment production in aerobic condition
In terms of other types of cheeses, one event was reported in 2010 on Mozzarella cheese contaminated with Pseudomonas fluorescens. Please refer to the following links:
http://www.europarl.europa.eu/sides/getDoc.do?pubRef=-//EP//TEXT+WQ+E-2010-5176+0+DOC+XML+V0//EN
http://www.ingentaconnect.com/content/iafp/jfp/2013/00000076/00000003/art00016?token=0056170d77b42bd6e586546243163425b6b675d7e7846242c5e4e26634a492f253033297694ff96906d1cf
This red stain is usually due to native and contaminant microflora composed of bacteria and yeasts. Most such cases is Micrococcus roseus. Yeasts are easily determined by microbiological analysis are indicators of practices and hygiene status of cheesemaking.
They can also interact with other bacteria that give this kind of pink or red pigments.
It is important for microbiological analyzes that are polluting ????
Anyone have a simple microscope? Simply streak a little of the red stuff on a drop of water on a slide, add a drop of crystal violet just to stain the cells (not trying to perform a Gram stain), and see if they are bacteria (cocci/Micrococcus vs. rods/Serratia) vs. large yeast cells (Rhodotorula, Monascus). Should provide likely candidate simply from the cell morphology. Easy start to the answer.
I agree that the above answers are all very plausible and most likely correct. However, your mention that the cheese is in hypersaline water leads me to another suggestion. The red pigment could be from a member of the halophilic archaea, Bacillus halobius ruber, or another halophile. Similar red pigments were a common 'problem' back when fish were commonly transported across the seas without refrigerated compartments and were packed in salt for preservation. In the early 1900s a microbiologist named Henrich Klebhan was asked to determine what the red pigment was that was forming on the fish in transit. His eventual answers can be found here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2912921/. It's not directly related but might be similar to what is going on with your cheese.
Hi Ammar: All colleagues have provided interesting contributions. I would also explore, like James has pointed out, the presence of hallophilic bacteria. We used to work with Halobacterium and Halococcus in the past. The carotenoids they produce in foods, such as salted-dried cod, are quite similar to the pigments in your cheese.
Brevibacterium linens group (Brevibacterium linens and Brevibacterium aurantiacum sp. nov.) is also able to produce pigments and to colour cheeses.
Most likely a pigment made by an obligate aerobic organism like Pseudomonas. I have investigated a similar problem observed in Mozzarella cheese (usually soaked in Salt saturated water before packing in a plastic film). The film used usually has low oxygen penetration coefficient and the cheese lasts for the expected length of shelf-storage time. However, in that specific case the film supplier ran out of the regular film so he substituted it with a film material that was more permeable to Oxygen. Guess what! Oxygen interned the package and allowed the obligate aerobic organism to grow and produce the red pigment.
We were able to isolate the organism and show it will not grow or produce the pigment in absence of air (20% Oxygen). But upon exposure to oxygen the pigment was produced. It is a Phenazine Pigment.
This defect was repeated many times in the last few years in Egypt, most apparent on the surface of Domiatti cheese (high salt white soft cheese) due to a mold called Monascus ruber, the defect is characterized by diffuse red pigment on the cheese surface without apparent growth of the mold, the defect was recorded for the first time at 1996.
Moawad, A. A. (1996). A problem of red color defect in raw milk soft cheese
in Egypt. Alex. J. Vet. Science, 12: 73-79.
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