How To Kill Germs With Violet Rays

This article is about removing germs from milk using ultraviolet radiation. That doesn’t sound very exciting on the face of it. Since I couldn’t decide whether or not milk germ eradication is a topic worth posting about, I did a little investigating. When I eventually found myself browsing through a 1917 book called City Milk Supply I decided that I didn’t want all my research going to waste. So here you have this fascinating post about milk, germs, and radiation.

In a nutshell, the main scientist in this article says:

“The pasteurization of milk has been followed by great improvement in conditions, but there is objection to the Pasteur treatment method, because it is claimed that the taste of the milk is changed. The effect of the ultra-violet rays on milk is different, and although it kills all the harmful germs the taste of the milk is not changed.

“So far as I have been able to determine the only noticeable change is that the milk in its new method loses its animate or ‘cowy’ odor, something that will not, in my opinion, cause people to object.”

But this other scientist says:

“It will destroy the micro-organisms without doubt. That has been positively proved. But what chemical changes would take place in the milk we have not yet entirely determined. This is to be found out only by lengthy experiments. There may be such a change brought about by the using of the violet rays that the milk would not be suitable for use. It might develop a disagreeable smell or taste, which would render it impossible to use. These are matters yet to be determined.”

And seven years later, here’s what the book City Milk Supply had to say on page 308 after further research:

When milk was exposed under conditions suitable for a satisfactory reduction of the bacteria by the ultraviolet rays there was also produced an abnormal disagreeable flavor that would render the milk unsaleable… On a commercial scale it would be difficult to control the factors which influence the bactericidal action of the rays and moreover the disagreeable flavor imparted to the milk renders the process impracticable.

So there you go.

HOW TO KILL GERMS WITH VIOLET RAYS: Dr. Frederick G. Keyes Tells of the Important Results of Experiments With Milk Made in the Laboratory of Brown University (PDF)

From May 29, 1910

2 responses to “How To Kill Germs With Violet Rays”

  1. I never gave pasteurization much thought until one day that I decided I wanted to try to make my own cheese.

    It turned out that all the milk my local grocery store sold was ultra-pasteurized which was unsuitable for proper cheese making.

    My local organic store had normally pasteurized milk. Which made decent cheese. But it got me to thinking about how much better the cheese would be if I could find some non processed milk.

    After a bit of research I was shocked to find that raw milk sales were illegal in most cases in my state. Further poking around on the net told me that raw milk sales were illegal or prohibited in most states and many countries.

    This got me thinking: What is in raw milk that people are afraid of? Is this why I have to eat pro-biotic yogurt now? Could I ever really believe a supplier that their raw milk was not dangerous?

    After much digging I still don’t have perfect answers to my questions.

    So yes, I think it was a topic worth posting. It gave me pause to re-visit some my old thoughts.


  2. @Unconfused Brain: That is unfortunately true. Traditional french cheese es made with raw milk, but in many countries it cannot be imported for that same reason. As far as I know, there are no health issues in France caused by this.

    @David: At first I thought the post title was “How To Kill Germans With Violet Rays”, which seemed even less likely to be published nowadays.


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