I found this forgotten bar of soap after winter at my home in northern Sardinia. It had grown a coat of mould (pictured). What is the mould and how did it grow on soap, which is supposed to keep your hands clean?Patrizia Figoli Turcheteti, Bellaire, Texas, UK
Like many other people I like the 'blue cheese'. I am also not afraid of mould on soap.I think that the mould grown on the soap could grow because usually mild soap contains unconverted fat or oils.... but not only fatty acids. So there is no surprise that in wet and warm environment mould may grow on parmesan or mild soap... I would just scrape the mould from parmesan and eat it. I also would scrape the mould from the soap and use it.It would be interesting to check if the mould on soap might be having any new specific fragrant? You never know when new discovery would be made!
There is a distinction to be made between 'clean' and 'sterile'; soap helps to remove dirt from your hands, but as many school pupils have discovered in simple microbiology experiments, there are still plenty of bacteria left on your skin afterwards.As long as it is adapted to alkaline conditions, there's no reason why the mould should not grow.
probably not enough lye was added to the oils to completely saponify them, and the unconverted oils were food for the fungus. A good bar of soap that was fully saponified doesn't go bad, it'll last a hundred years