Blue milk

In the first half of the nineteenth century milk was found to have all kinds of different colours, mainly, it was thought, because of the cows eating plants which stained the milk. In my last message of 11 september 2013 I cited the ideas of Vallot about the colour, and other alterations, of milk. This message of today is about blue milk.

Vallot stated that the cause of blue milk is unknown but suspected that the eating of hyacint plants could be involved. Alexander Numan (1780-1852), director and teacher of almost every subject to be taught at the the Dutch Veterinary School, thought more about it. In his lecture notebooks, preserved in the library of Utrecht University, he mentions a list of plants that may be the cause of blue milk; what those plants had in common is that they contained indigo-like compounds that may have an effect on milk, Numan lectured, when the digestion of the animal is incomplete and when those compounds are not “decomposed and equilized”. He wondered why it is that the colours are not transferred to the butter but stay dissolved in the whey[1].

Almost two decades later, in 1841, C.J.Fuchs published the results of a study in which he showed that the blue colour of milk could be attributed to a contagium of which Fuchs was of the opinion that it was an infusorium of the genus Vibrio, observed by him in the milk. As long as milk was normal no infusoria were observed. Fumigation with chlorine was not sufficient to fight the Vibrio: Fuchs prescribed treatment of utensils, udders and milker’s hands with boiling lime [2]. With regard to the hygienic measures for preventing mastitis, to be applied several decades later, I consider this an interesting prescription.

The discussion about blue milk was brought to a new phase by Friederich Mosler, professor of (human) internal medicine (and other disciplines) in Greifswald (Germany). Mosler published a paper[3] in 1868 about blue milk, because he was confronted with a family of which some of the members became ill with gastritis after having consumed milk with a blue colour. In his paper Mosler gives an overview of the many plants that may give the milk this colour (hyacints were not mentioned, but some of Numan’s plants were) and then starts to describe what really matters when people are drinking blue milk. The difference between milk stained blue by plants and blue milk as a cause of gastritis was that when the latter was left standing for several days it became covered with a thick blue skin. Mosler studied this layer with the microscope and found blue-stained fungi in it, which he compared to known fungi and of which he made some drawings which he included in his paper (see below).

So instead of resolving the problem of blue milk, Fuchs and Mosler added a new problem, that of contaminated milk. This latter became much more important, because of food safety and food hygiene. The problem of the milk becoming blue by plants silently disappeared from the academic interest.

  

Drawing by Mosler (1868) of fungi in blue milk.

A: partly stained fungus; B and C: stained casein particles; D: unstained butter droplets

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[1] A.Numan, Kort zamenstel der algemeene veertsenijkundige ziektekunde strekkende tot een leidraad der voorleezingen over dezelve (Short composition of general veterinary pathology meant as a guide to the lectures about it) HS 13 A 1 (1823), par. 124, p. 126.

[2] The original publication was abstracted by Wellenbergh from a paper in a German journal edited by Gult and Herwig of 1841: F.H.J.Wellenbergh, ‘Uitbreiding der Veertsenijkunde in de jaren 1841, 1842 en 1843.’ Numan’s Veeartsenijkundig Magazijn V, II (1846) 81-281.

[3] F.Mosler. Ueber blaue milch und durch deren Genuss herbeigeführte Erkrankungen beim Menschen. (On blue milk and the diseases of man caused by its consumption). Archiv für pathologische Anatomie, 1868, 43, 161-181.