Save Fuel Indicator Pasteurize Don't Boil

[DAN-Y]

Being able to save on fuel consumption intrigued me. Made this floating water pasteurization indicator. Instead of boiling, just bring water to pasteurization temperature 145*.
Here is what it looks like when used in a pot of water. Shows how it turns black in color once it reaches predetermined temperature of 145 degrees. Once cooled, the color blue returns.

No batteries, no gimmicks…just pure science 

 

[David Thomas]

I like that. A lot. It treats the water without wasting fuel. And if I’m making hot chocolate or soups that don’t need cooking, 145F is a lot closer to a drnkable temperature than 190F is.

A friend in college was working on third-world water treatment via thermal solar. He needed a way to show if, at the end of the day, the water had gotten over 140F or not (the villagers may have been in the field all day). He made an assembly of a metal washer sliding on a glass vial of high-temp oil/wax. When it melted, the oil would run down to the bottom from the top and, if it cooled later, would reharden into wax. But you could see that the wax was now at the bottom instead of at the top and know it had gotten to temperature.

[Steve M]

Good information.  I never could understand the fuel wasting adage “Boil your water for 5 mintues”… that is STILL being posted.  In the US Navy we ‘made’ our potable water with an 8K Evaporator.  It boiled seawater at lower than normal temperature/pressure to maximize efficiency and thus save Uranium :o.  I believe the minimum temperature was 166F….to insure all bacteria was killed.

[Anonymous]

Nice.

[Rex Sanders]

The Wikipedia article on pasteurization for milk says 161° F (72° C) for 15 seconds (with good mixing), or 145° F (63° C) for 30 minutes.

https://en.wikipedia.org/wiki/Pasteurization

Maybe 161° F @ 15 seconds is a good target for backpackers?

There are lots of DIY or low-cost Water Pasteurization Indicators (WAPIs) designed for developing countries, many target ~150°F for multiple minutes.

— Rex

 

[DAN-Y]

Here is some additional info copied from Equip2Survive:

(quote)
So how much heat? And for how long?
Great questions! Depending on your source, “conventional wisdom” has told us for decades that bringing water to a rolling boil at the very minimum and holding it there for a period of time is what is required to kill these microscopic pathogens.

For example, let’s take a look at what the Boy Scouts of America say about treating water:
“The surest means of making your drinking water safe is to heat it to a rolling boil—when bubbles a half inch in diameter rise from the bottom of the pot. While this is a simple method, it does require time and fuel.”

Now let’s take a look at what the United States Marine Corp. recommends for treating water:

“Purify all water obtained from natural sources by using iodine tablets, bleach, or boiling for 5 minutes.”

So are the Boy Scouts of America and the Marines wrong? No. Bringing your water to a full boil will absolutely kill all common pathogens that we have all learned to take so seriously because can make us sick with illnesses like Giardia, Cryptosporidium, E. coli and the rest. The problem with bringing your water to a boil, as you are about to learn, is that doing so is actually complete overkill when it comes to treating water for harmful microbes! Boiling your water, while completely safe and will absolutely kill those nasty pathogens, is actually a waste of precious fuel/firewood resources in a survival situation!

<b>OK, so how much fuel are you wasting exactly?
Did you know that heating your water from 200° F to 212° F… just that last extra 12° to get your water to it’s boiling point… actually uses TWICE as much fuel as it does just to get your water to that initial 200°?? Well… it does. TWICE as much fuel! That is nothing to scoff at!</b>

So now that we know what the Boy Scouts of America and the Marines say about purifying water (and we love both of these organizations!), let’s see what science tells us about using heat to purify water.

Important Temperatures to Factor In to this Equation:
212° F = Temperature at which water boils
160° F = Temperature at which milk is generally pasteurized
149° F = Temperature at which Hepatitis A is quickly killed
140° F = Temperature at which bacteria (V. cholerae, E. coli and Salmonella typhi) and Rotavirus are quickly killed
131° F = Temperature at which worms & protazoa cysts (Giardia, Cryptosporidium and Entamoeba) are quickly killed

As you can see from the temperatures listed above, the pathogens that we are primarily concerned about when it comes to safe drinking water are ALL killed (quickly) at temperatures much lower than 212°, the temperature at which water boils. That being the case… why would you unnecessarily waste any more fuel than you need to heating up your water those additional 63°? Great question, isn’t it?

Now let’s take another look at that milk pasteurization temperature above: 160° F.
Pasteurization is a process invented by French scientist Louis Pasteur during the early nineteenth century. Pasteur discovered that the pasteurization process made it possible to heat the milk to high enough temperature to kill all harmful microorganisms without “cooking” the milk causing it to curdle.

Now of course you never have to worry about your water curdling, but an important lesson can be gleaned from this milk pasteurization process that can be extremely beneficial: Water, like milk, does not have to be boiled to be safe to drink!

Temperature + Time = Pasteurization
Pasteurization is a process that occurs based on two variables: temperature and time. You see… you can actually pasteurize water at lower temps if you do it for a longer duration. This is extremely helpful in situations where A) you aren’t able to effect fire for heating your water, or B) you can make fire but you do not have a suitable container for boiling that can withstand the intense heat of your fire. Lower temperature/longer duration pasteurization can actually be done with discarded plastic 2 liter bottles set in the sunlight for longer periods of time (typically 6 hours). This method of disinfecting water is known as the SODIS (Solar Water Disinfection) method. You can even put something black or reflective behind your bottle to speed up the process!

So Why Do So Many Advocate Boiling Your Water?
Great question with a very simple answer: When those bubbles start to roll in your container of water, that is nothing more than a clear VISUAL INDICATOR that your water has become hot enough (actually MORE than enough) to have killed all of those little nasties. It works. It’s effective. But is it ideal? Or can we do better?

So if the bubbles from boiling water gives us that terrific visual indicator to let us know that our water has reached 212° F… but now we know that boiling our water to make it safe to drink is actually a waste of precious fuel resources (fuel, wood, candles, etc.)… how can we then determine if our water has gotten hot enough to have been properly pasteurized without those rolling bubbles? Great question again! We could certainly use a thermometer… but most of these are glass and very fragile. Too fragile to keep from breaking inside your kit. We need something small, light, compact, durable and can be used over and over again to let us know that our water has reached that effective pasteurization temperature.

Here is what David was referring to:

 

[Diane Pinkers]

Ok, so what did you use to make it? I have those ointment containers.

I suppose using a stick-on thermometer on the outside of the pot, like baristas use, while heating on the stove, doesn’t give you the temperature of the liquid inside.

[DAN-Y]

Diane, thermochromic ink was used to silkscreen print on polyester decal film and then laminated with polyester clear sheet to encapsulate it. Then it was die cut to fit inside watertight container.

[Mario Caceres]

Nice gadget.  I normally pre-treat water before using it for re-hydrating my meals.  When not using my own dehydrated meals I like “Good-to-Go” meals.  They specifically recommend to bring water to rolling boil before pouring it into their packages, I think this has more to do with the starting temperature of water for the recommended “rehydrating/cooking” times.  It would be interesting to make a comparison of those times under different starting temperatures.

[Diane Pinkers]

Wow, did you just have the materials sitting around?  A quick search on thermochromic ink reveals mostly stuff that changes at 88 F, you have to really poke around to find ink for higher temperatures.

 

[Jerry Adams]

Thanks for the info, nice little device

Pasteurization of milk only kills enough of the bacteria common in milk so it will keep longer.  It’s hard to equate that to what you have to do for the organisms commonly found in drinking water and how many you have to kill to not cause a human to get sick.

I wish there was a little more science about this.  Like count the number of Giardia before and after heating to different temperatures and hold times.  Except there probably isn’t enough need for this.  Few people care about saving a little fuel.

Amount of fuel required is proportional to temperature increase, up to the boiling point.  If you raise the temperature 180 degrees instead of 200 degrees, you save 10% of your fuel.  Ignoring the fact that inefficiency increases with temperature, for example conduction or radiation of heat from the pot to the air.

If I’m low on fuel, I’ll heat it up to 195 F or so, when it starts getting noisy, then turn it off with lid on and let it sit for a minute.  That saves about 10% of fuel.  And run it fairly low and it’ll save another 10%.

[James Marco]

At 55F ambient temps in the ADK’s of NY, I need a full boil to cook rice&beans, beef & rice, fish, etc. Full boil, into a cozy for a half hour and done. While most Pasteurization works pretty well, it requires about a 6-7 minute wait period to insure that anything bad for you is killed off. So, you have to HOLD that 150F temp for the full time. A cozy won’t work.

[Rex Sanders]

I found a bunch of science on water pasteurization. Here’s one reference published in 1984 and frequently cited:

Pasteurization of Naturally Contaminated Water with Solar Energy
http://aem.asm.org/content/47/2/223.full.pdf

They heated river water on a hot plate and pulled samples for coliform counts as the temperature rose.

“No coliforms were recovered at 61 or 63°C.”

 

Worried about hard-to-kill Crypto? Many studies available, here’s two

Effect of pasteurization on infectivity of Cryptosporidium parvum oocysts in water and milk
http://aem.asm.org/content/62/8/2866.short

“In this study, oocysts were suspended in either water or whole milk and heated to 71.7 degrees C for 15, 10, or 5 s in a laboratory-scale pasteurizer. … No mice (0 of 177) given 10(5) oocysts pasteurized for 15, 10, or 5 s in either water or milk were found to be infected with C. parvum …”

Effect of high temperature on infectivity of Cryptosporidium parvum oocysts in water
http://aem.asm.org/content/60/8/2732.short

“These data indicated that when water containing C. parvum oocysts reached temperatures of 72.4°C or higher within 1 min or when the temperature was held at 64.2°C or higher for 2 min of a 5-min heating cycle, infectivity was lost.”

Google Scholar is your friend:
https://scholar.google.com/scholar?q=water+pasteurization

Yes, for cooking, you’ll often need or want higher temperatures.

But if you just need water clean enough to drink, boiling is overkill, but easy to see in the field. That’s why you can find so many WAPIs.

— Rex

[Anonymous]

Not so much for backpacking, but more survival situation, a vacuum insulated tumbler with extra insulated top might be a good combination for more energy efficient cooking.

I’m holding out hope that someday, some company develops a 7075 or better Al alloy vacuum insulated tumbler and hard anodizes the liquid/food contact surface. That could be light enough to justify bringing on an extended and/or more extreme cold weather trip for folks that do more traditional cooking (of non cooked, non dehydrated meals).

I wouldn’t know where to begin in building one of those myself.  If anyone here has that capability, I’d pay a decent sum for same. 40 oz tumbler would be pretty sweet, if it’s possible.

Meanwhile, I’ll keep an eye out for larger and wider silicone bottles, which I can insulate pretty well, at fairly low weight, but definitely more bulk and less convenience than a vacuum insulated tumbler.

[DAN-Y]

Justin, how about using Vargo Bot or the Keith Ti6300 Titanium 256g 900ml Cooking Pot Nonstick Rice Cooker. Insulate with Neoprene gaiter material.

Rex, thanks for the great links. I have to read that info again this morning when I’m wide awake ,-)

Something I read recently is viruses are not common out in locations frequented by hikers. Years ago I read the book “how to shit in the woods” written by a doctor?, had some good info in it. I’ll see if I can find some quotes from it.

 

[Jerry Adams]

yeah, thanks Rex

73 C for one minute, that would be 163 F, that’s not that hot

let’s say I heated 32 F water to 172 F (hard to measure exactly, better to go a little hotter).  That would be 140 F temp increase vs 180 F if I heated to boiling.  That would be about 20% less fuel.

[Colin Krusor]

I taught general biology and intro to microbiology (“baby micro”) to undergrads in the University of California system for several years while I was a grad student, and we isolated a spore-former (Bacillus sp) by heating a mixed culture to 80C. The bacilli formed spores and survived, and the rest of the bacteria in the mixed cultures died. I agree with those who have suggested that heating to 160 F and keeping it near there for a few minutes with insulation seems efficient and adequate for infection prevention.

[Jerry Adams]

but if the bacilli formed spores and survived, wouldn’t they then be able to infect a human?

[Anonymous]

“Justin, how about using Vargo Bot or the Keith Ti6300 Titanium 256g 900ml Cooking Pot Nonstick Rice Cooker. Insulate with Neoprene gaiter material.”

Hi Dan, definitely could work, but those are some pricey pots.  I was thinking more like keep the Al ceramic non stick pot I already have, and use a combination of something like this:

with a couple of layers of 1/8″ Evazote foam, with some Al foil and some insulating fiber in between (I have some left over 650 down I could use). Contact cement weld the foam together and also weld some velcro at the top to open and shut the insulated, holding pouch.  Pretty light weight, fairly packable, and highly insulated at not much weight or price. Can also double as part of a low slip pillow system (instead of putting the silicone pouch in there, put in a shirt or the like. I’m going to make a prototype of this or very similar combo and see how it works.

You can buy other silicone “zip lock” pouches that are smaller and much cheaper than the above one. Like 4, 1 liter sized ones for 16 dollars.  I would prefer more of a screw on cap, large bottle type design myself, but all the larger volume capacity silicone bottles are still fairly small diameter and would be hard to clean for food use.  The pouches would be a lot more stable too, besides being much easier to clean.

[Anonymous]

I think that was the point that Colin was trying to make Jerry.  Err on the side of caution.  A little more heat and a little longer than earlier recommended.

[Colin Krusor]

Sorry, Jerry. I think I somehow left that piece out of my last post. The bacteria that we worry about in backcountry water are generally not spore-formers, so they die rapidly at 80C. I would expect less than 1% survival after 5-10 minutes at 60C for most pathogens, and none or negligible at 70-75C (about 160F) for 5-10 minutes. Anthrax and botulism (Bacillus and Clostridium) form spores, but those aren’t considered a major risk in most waters (for immunocompetent people). Under extraordinary circumstances, a Toxoplasma or Cryptosporidium oocyst might survive that treatment, but not in any condition to excyst and reproduce. I would filter the water beforehand if the water comes from a pasture pond, or if there is recently overturned soil in the water, like at the base of a rockslide.

[DAN-Y]

@ckrusor, thank you for your imput. If we disregard the pasteurization of milk temperature because we don’t deal with “water” coming directly from animals, can we be fairly confident in the heating temperatures listed quoted from above:

 

Important Temperatures to Factor In to this Equation:
212° F = Temperature at which water boils
160° F = Temperature at which milk is generally pasteurized
149° F = Temperature at which Hepatitis A is quickly killed
140° F = Temperature at which bacteria (V. cholerae, E. coli and Salmonella typhi) and Rotavirus are quickly killed
131° F = Temperature at which worms & protozoan cysts (Giardia, Cryptosporidium and Entamoeba) are quickly killed

 

 

[Jerry Adams]

good info, thanks

Giardia and Crypto are maybe the biggest risk in back country

I normally just boil my water and don’t worry about it, but if I was low on fuel for some reason this would be useful

[Colin Krusor]

Dan, if you want my opinion on that list, my only input would be to bump up the generalized temps for bacteria and protozoans. The diversity of microorganisms is challenging to neatly describe using the taxonomic rules that are used for animals and plants. Consequently, microbial taxa (like genus or species) tend to include things that differ a lot more from each other than in animal or plant taxa. So, among bacteria or protozoans in general, there are a lot more oddities and biological differences than you would see in a group of animals at that taxonomic scale. To include those unusual organisms, and to account for field conditions that differ from lab conditions, I would bump those temperatures up by at least 10F.

[Colin Krusor]

More than 10F for the protozoans. It takes hundreds or thousands of bacteria to infect a person who ingests them, in general. But it takes fewer than a dozen (sometimes only one) Cryptosporidium or Toxoplasma oocysts to cause an infection, so a larger proportion of them have to be killed to prevent infection. A Cryptosporidium oocyst is actually four little microbes (sporozoites) packed together like sardines in a heavily armored little can. In a Toxoplasma oocyst (also present in surface waters), there are eight passengers. Just one of those passengers has to survive and bust out of its capsule make you sick, so a generous safety margin for protozoan inactivation temperatures seems warranted, I think.

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