What is the Difference Between Pasteurization, Boiling and Distillation?

Categories: In the News.


There is discussion on the internet about pasteurization of water in an emergency situation. In this article I want to clear up any confusion between boiling and pasteurization, because they are not the same thing, and I want to compare both methods to distillation.

Water boiling

Water boiling in a clear glass pot.

Let’s start by comparing boiling and pasteurization. While there are some similarities, they are not at all the same. One similarity is that they both involve heating water, but the difference is the temperature to which water is heated and the length of time it is held at a specific temperature.

Mankind has been boiling substances much longer than we have been pasteurizing substances. To my knowledge, no one person has been given credit for discovering the process of boiling though many have studied it. Let’s just give credit to early man or God since there are some examples of boiling in nature. The process of pasteurization, on the other hand, is named after a famous French Chemist, Louis Pasteur. He did much of his research pasteurizing wine and is also famous for anthrax and many other germ-related research. He is the one most responsible for the germ theory for infectious disease.

We shall continue here by defining the word boiling. According to Wikipedia, boiling is defined as the process of heating a liquid substance until there is a rapid vaporization of a liquid. This occurs when a liquid is heated to a specific temperature referred to its boiling point. At this temperature, the vapor pressure (tendency to evaporate) of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere to not evaporate.

When the pressure exerted on the liquid is decreased, such as is the case at higher altitudes, the boiling point is lower. Example: Water boils at a lower temperature in Denver than it does at sea level. When the pressure exerted on the liquid is increased, as is the case in lower altitudes such as in Death Valley, the boiling point is higher. In other words, the boiling point of a water and any other liquids much be defined at a specific atmospheric pressure. For standardization purposes this is usually defined as 760 millimeters of pressure on the metric barometric scale or 30.0 inches of mercury on the English barometric scale. This is referred to as standard pressure.

It is quite fascinating to carefully observe the side view of water boiling. As the water warms up, tiny bubbles of steam will begin forming at the bottom of the flask (closest to the heat source.) The size of the bubbles increases as the bubbles rise and eventually burst at the surface to release the invisible steam. Faster and faster it goes until big bubbles are forming and bursting simultaneously at the surface of the water. In other words, it is boiling! Tada!

There are actually three types of boiling. The first is called nucleate boiling, as was just described above. This is where small bubbles of vapor form at discrete points. The second type is critical heat flux boiling where the boiling surface is heated above a certain critical temperature and a film of vapor forms on the surface. Transition boiling is an intermediate, unstable form of boiling with elements of both of the two main types. The boiling point of water at sea level is 100 °C (Celsius) or 212 F° (Fahrenheit), but as was stated earlier, is lower with the decreased atmospheric pressure found at higher altitudes.

Boiling water is a very useful method for making water sterile and therefore more potable. It does this by killing virtually every microbe that may be present. Because the sensitivity of different micro-organisms to heat varies, it is possible to kill many, but not all germs or organisms by heating water to 70 degrees C (158 Fahrenheit) and holding it there for ten minutes. This is defined to as Pasteurization of water.

The process of pasteurization does destroy some biological contaminants but it does not remove them. It also evaporates some gases and liquids with low boiling points but it, like boiling, concentrates some of the inorganic chemicals such as heavy metals and nitrates. Here is a big one…pasteurization does virtually nothing to deal with viruses.

Pasteurization is a very useful process for substances other than water. It most commonly applied to milk, beer and other alcoholic beverages, vinegar, eggs, even almonds are sometimes pasteurized as well as several other food products. Pasteurization is not guesswork however. There are specific procedures and temperatures involved for each product.

survival stillPasteurization of water is a step in the right direction but it is simply not adequate treatment for most tap water today and here is yet another reason why. Some micro-organisms are more resistant to heat and require heating for at least one minute at the boiling point of water. The destruction of viruses requires the boiling of water for at least 20 minutes! Clostridium spores can even survive this treatment, but because this infection is caused a microbe in milk and is not water-borne, this is not a water problem. (Fortunately there are antibiotics that kill clostridium spores.)

I want to mention two more significant differences between pasteurization and boiling. First, and this is a significant point, boiling is recommended by FEMA and the Red Cross for treating biologically contaminated water in an emergency while pasteurization is not. Second, from a more practical perspective, it’s much easier to tell when water is boiling than to take it through the pasteurization process.

One of the problems of both boiling and pasteurization is that while these processes can kill biological contaminants, other types of contaminants such as chemicals and metals such as lead will actually become concentrated in the boiling water. Why is this?

Survival StillSimple. The steam is pure water, and it’s leaving. Which means that the water that remains in the boiling pot gets increasingly contaminated with inorganic and most organic contaminants. This brings us to distillation, because in distillation we are boiling the water and then capturing the pure steam and then cooling it back down into high-purity, liquid water. So, in effect, distillation is the opposite of boiling water, because the boiling water actually is what we want to throw away.

The process of distillation (assuming that the distiller is designed properly) is the single most effective water treatment process that there is. This is why the Survival Still is the best emergency water purifier on the market today.

In summary, if you are only concerned with biological contaminants in water, boiling is an effective method and is definitely better than pasteurization. I recommend that you simply drop pasteurization of water from your thought process. Definitely the best process is distillation.

I recommend the AquaNui Brand of water distillers for everyday drinking water, and the the Survival Still water distiller for emergency situations, or any other off-grid situation.


  1. Thank you for this information Glenn.
    It clarifies a lot for us and clarifies the advantages of distillation.
    Many will realize how perfectly pure water can be achieved and that is why I bought and continually use your distiller which only has two stainless steel parts and a silicon hose.
    It can be sued even over an open fire.

    Thank you again


  2. richard schwartz

    I found your article to be well done and technically correct. Especially important is the fact that boiling of water is no guarantee of its safety.

    However, there are some volatile contaminants that may be present that will still be present in distilled water. At West Basin Municipal Water District, we destroy those molecules by ultraviolet radiation before the water is purified by reverse osmosis. (By California law, that water is for industrial and irrigation use only and may not be fed into the domestic supply, even though it is superior in purity.) Some of those contaminants are toxic at levels too low to measure!

    • Hi Richard. Thanks for the response. I’ve received a few questions about the VOCs. It’s an important point, so I will write a separate article on it soon.

  3. carolynbahr

    Thanks for this! I think most of us are aware of the importance of this information on a much more basic level, but because we have access to drinking water right now…we don’t understand the threat of not having access to clean water in an emergency.
    I actually unsubscribe to many sites, but haven’t unsubscribed to your site because you share so much information that I actually can use! Thanks for staying on the cutting edge!

  4. Garry Gleeson

    Glenn, thanks for all the excellent info shared. One concern I haven’t seen adequately covered is if water contains solvents with a lower boiling point then water and your using a distiller, surely the solvent will boil off and also be condensed out and back into the distilled water by the distillation process. How is this problem to be avoided or dealt with?

  5. Charles Wainwright

    I first heard about your distilling units on a summit I was listening to.I’ve been going back and forth~get one,you can’t avoid bad water.Please send info.Cost of differing units,shipping,etc.I am on a very limited budget so it would be a major investment.Will it help the all?~through me?

  6. Wow, this was so interesting and informative. I understood the difference between these methods at least superficially, but I couldn’t explain how the actions actually differ. Great information, thank you very much for sharing.

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