98 



In order to trace the microbes which render cocoa nut oil and 

 palm kernel oil rancid, as well as vegetable margarine prepared 

 from these oils, a number of samples of these oils and marga- 

 rine was subjected to a bacteriological examination. This 

 revealed that the oils themselves may turn rancid through the 

 action of moulds, when the oils contain small quantities of 

 water (0.2 — ^0.5 %). The origin of the oils or the methods of 

 preparing and refining them appeared to have no influence. 

 Rancid samples showed as a rule a higher percentage of fatty 

 acids. Sometimes however these percentages gradually diminish. 



Next a few samples of vegetable margarine, rancid as well 

 as fresh, were examined. This examination proved again that 

 rancidity coincides with a higher percentage of fatty acids and 

 further that rancidity first appears on the surface of butter, 

 where it is exposed to the atmosphere. Only later on does 

 this rancidity permeate the remainder. The number of microbes 

 found in one gram of vegetable margarine turned out to be 

 considerable (too. 000 — 18.000.000). Torulas, moulds and bac- 

 teria (mostly micrococci) were chiefly found. 



In this experiment the culture-plates of EykMAN 1) were 

 used, which through the presence of a thin layer of fat under- 

 neath the nutrient agar enable us to discover the fatsplitting 

 microbes at once. At the same time cultures were made on 

 agar-plates in which a mixture of cocoa nut oil and pressed 

 tallow had been emulsified. The latter culture media, after 

 being inoculated with rancid margarine, very soon showed 

 rancidity of the cocoa nut oil contained in them. 



Several microbes (isolated from fat- and margarine-samples) 

 including Torulas, Micrococci, Bacteria, Bacils and Moulds 

 were examined for their capacity to render cocoa nut oil ran- 

 cid. Only the following moulds were proved to have this 

 capacity: Pénicillium glaucum, Aspergillus spec, Aspergillus 

 niger, Clasterosporium spec, Hormodendron spec, Phoma spec, 

 Mucor spec, and Cladosporium butyri. We may mention that 

 Oidium lactis, though a strong fat-splitting organism, does not 

 cause rancidity. 



Especially Pénicillium glaucum and the yeastlike mould Cla- 



1) EYKMAN, C. Centralbl. f. Bakteriologie, i Abt., 1901, Bd. 29, S 841. 



