Computing water activity without having to spend $500

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geostriata

Meat Mopper
Original poster
May 18, 2021
236
126
California
My understanding is that a snack stick with a 6.0 ph (and in general > 4.5 ph) will require a water activity (aw) level below 0.85. Meters to measure this run around $500, and I'd rather not spend that amount if I can avoid it.

So my question is: Does anyone know how to measure water activity on the cheap? Looking at this FDA thread, it looks like inspectors actually can use a hair-hygrometer for a sort of spot-check water activity measurement. Presumably they have a known sample with pure water and they measure that in a sealed container, and the meat product in a sealed container (after waiting 5 hours or so). So my thinking is that I could do one of two different approaches:
1. Have two meat samples. One is commercial of high ph, and the other is my own. Put both in a sealed container and measure with the hygrometers. If mine is less than or equal to the humidity, I should have sufficient water activity for shelf stable.
2. Go with the FDA approach, and try to compute the actual AW figure using pure water/known samples.

I also ordered a meat moisture sensor from AliExpress, but I don't have much faith in that (and it doesn't measure AW in any case).

Here are some of the links, if you're curious:
* FDA inspection guidelines: https://www.fda.gov/inspections-com...tion-technical-guides/water-activity-aw-foods
* Example Hair Hygrometer: https://www.amazon.com/3B-Scientific-U14293-Precision-Hygrometer/dp/B00KWZ6DCC
* DM300R meat moisture meter: https://www.aliexpress.us/item/2255800105046875.html

Or perhaps there might be another way I don't know about? Possibly leveraging my protein % and measuring weight loss? Any thoughts?
 
Easiest way is to weigh one of the sticks just after stuffing and record the weight. Weigh the stick daily ( or every 2 or 3 days). Write the weight down. Then divide that daily weigh by the starting weight. Then subtract your answer by 1. The number will be negative, but that will give you a percentage of water lost. A rough estimate is that 30% weight loss is Aw 0.90....

You do not need a Aw meter....and I do not recommend drying snack sticks with a pH of 6 in a drying chamber at temps, of 55*F. You need the acid drop as one of the safety hurdles to keep the bad bacteria at bay. high pH sticks can be dried at refrigerator temps., but acidifying down below pH5.3 and above pH5 will offer a better safety profile without any noticeable tang (sticks will also dry much faster). I do not recommend trying to replicate a stick with a pH of 6 like a commercial producer, they have much better systems in place that a home producer.

Once the stick has lost 30%, dry continue drying to your liking. I dry mine to 45% weight loss which is about Aw 0.85......but I acidify my sticks down to a tangy pH of 4.7~4.8....
 
Easiest way is to weigh one of the sticks just after stuffing and record the weight. Weigh the stick daily ( or every 2 or 3 days). Write the weight down. Then divide that daily weigh by the starting weight. Then subtract your answer by 1. The number will be negative, but that will give you a percentage of water lost. A rough estimate is that 30% weight loss is Aw 0.90....

You do not need a Aw meter....and I do not recommend drying snack sticks with a pH of 6 in a drying chamber at temps, of 55*F. You need the acid drop as one of the safety hurdles to keep the bad bacteria at bay. high pH sticks can be dried at refrigerator temps., but acidifying down below pH5.3 and above pH5 will offer a better safety profile without any noticeable tang (sticks will also dry much faster). I do not recommend trying to replicate a stick with a pH of 6 like a commercial producer, they have much better systems in place that a home producer.

Once the stick has lost 30%, dry continue drying to your liking. I dry mine to 45% weight loss which is about Aw 0.85......but I acidify my sticks down to a tangy pH of 4.7~4.8....
Wow, that's so much simpler than I expected. Thanks for the explanation. I'll aim for 45% weight loss accordingly. However, I also thought that the ratio of fat to protein also had an impact in AW.. If you have anything available to help establish the basis of that rough-estimate calculation, I'd be eager to dig into it.

As for the PH, I had a strong distaste for the 4.5 or below PH snack sticks, so that didn't work for me, and since I knew that a commercial producer could do it, I sought to replicate their approach. I've been trying to find out how they accomplish this, but haven't had much luck other than what's available in this forum and a few other forums. If I'm able to understand their approach, then I should be able to reproduce that...

In any case, for the time being, I'll certainly try at a ph of 5.3 and see if that works for me. I'll also conservatively set my drying chamber at 38F instead of 52F (given the promising initial results of a room temp "extended bloom" at 70F for one day, I was thinking 52F-55F was a good compromise for 4 days or so as an intermediate measure).
 
However, I also thought that the ratio of fat to protein also had an impact in AW.. If you have anything available to help establish the basis of that rough-estimate calculation, I'd be eager to dig into it.
If you shoot for 25%fat/75%Lean then the correlation is very close to what I posted. Fat is about 15% water, meat is about 75% water, but it does vary slightly depending on the animal and where on the animal it comes from.
 
If you shoot for 25%fat/75%Lean then the correlation is very close to what I posted. Fat is about 15% water, meat is about 75% water, but it does vary slightly depending on the animal and where on the animal it comes from.

As it so happens, I'm on my next Mariansky book (Green one) and I just got to the part where he mentioned water-holding capacity. Beef meat is apparently on the top of the list in terms of water-holding capacity, with "Bull Meat" on the top of the top at up to 100%? (Which is strange and has me curious about bull meat now, but I digress...)

Given I'm trying to make an all-beef product using brisket, and I see Mariansky says "Shank Meat is up to 70%", I think that's the figure I'd estimate.

indaswamp indaswamp In any case, I think your advice was spot on (again). I was fortunate to find a non-fermented salami recipe in the Green Marianski book, and his target was 35% weight loss. So your figure of 30% weight loss for 0.90AW seems consistent.

However, I often hit the 35% weight loss, sometimes going beyond 40%, and it still seems my sticks aren't dry enough... I think I'll have to try the Salami Krakowskie recipe in the green book to get a better feel for this...


As for the low-cost AW test solution:

I tested a version of the FDA approach out of curiosity, and because I always like to use numbers where possible for guidance. I wasn't able to get a solid and repeatable reading on the denominator for water activity (using pure distilled water vapor), but it does seem I was able to get a somewhat good relative reading.

Here's my approach:
1. Purchase 10 hair-hygrometers ($3 on aliexpress) and pick the two with the best accuracy and the same reading. Unless you spend $400 on one of these, they can be imprecise. Comparing against my fancy reference hygrometer, the best two seem to be +/- 2%.
2. Take the same volume of product from your sample sausage and your target sausage
3. Cut in half place in the vacuum bag and line up both bags in your chamber vac at the same time. Turn it on and press "STOP" after two seconds. This way, you have the same amount of ambient air in both bags.
4. Leave and wait for 5 or so hours, and you get a rough approximation of whether your AW is less then or greater than your target.

1712258483245.png


What you see above is each sample in the bag after 5 hours of rest and the reading on the hair-hygrometer. Under each bag is me taking a reading from by meat moisture meter (also ordered from AliExpress).

Technically this is a misuse of the meat moisture meter since it's meant for portions of meat that aren't fat. However, I tested at many locations on each stick and each reading was within 2% of each other. So I think taking repeat measurements and averaging it out is a good approach for sausages. Nevertheless, this extra data point help lends credence to the relative hair-hygrometer data.

So although I don't have the AW for my sausage, I do know the following:
  1. My target sausage is under 0.85Aw (by law). Unfortunately, I don't know if my target is 0.85 Aw or 0.80 Aw or even lower. Given my sausages with 35%+ weight loss still don't pass the bend test, I actually think this sausage is below 0.80Aw.
  2. My sample sausage is definitely less dry than my target sausage.
  3. A meat moisture meter of 36.7% correlates with an AW value of 0.85 or below (but this is just guidance. I'm not saying 36.7 means it's definitely below 0.85). This is a target for me to hit, then once I hit this target, I can do another hair-hygrometer test.
So there you have it! A rough way to measure relative aw using $6 in materials (as long as you also have a chamber vac or really good bag sealer technique).

I suppose the next step is to buy some reference non-fermented polish salami (or make my own) and run the same test for that, as I imagine that sausage would be closer to 0.85 Aw...
 
You do you.
But for me it's

Way too much....GL on your quest.
Thanks.

Yeah, I can't explain it. I feel the sausage I make might hit that dryness level, but it's the bad sort of dry (which is why I'm experimenting with 'seeding' flakes of hard fat into the mix).

This commercial sausage represents the sausage of my childhood and after purchasing literally every beef stick on amazon, I can't find any other source. So I'm literally worried this sort of beef stick will disappear. Hence the mission to replicate it.

I do think that maybe if you try it, you'll see what I'm talking about. If you're on this thread and curious, feel free to PM me your address, I'll send you a sealed bag so you can try. Or you can get them here: https://www.ajaysmontanabananas.com/shop. Or maybe you have similar in the gas stations of your state, where they sit unwrapped and unsealed with deep wrinkles in a tall plastic tube. I just can't find those anymore where I'm from. All slim-jim-type floppy crap.
 
Easiest way is to weigh one of the sticks just after stuffing and record the weight. Weigh the stick daily ( or every 2 or 3 days). Write the weight down. Then divide that daily weigh by the starting weight. Then subtract your answer by 1. The number will be negative, but that will give you a percentage of water lost. A rough estimate is that 30% weight loss is Aw 0.90....

You do not need a Aw meter....and I do not recommend drying snack sticks with a pH of 6 in a drying chamber at temps, of 55*F. You need the acid drop as one of the safety hurdles to keep the bad bacteria at bay. high pH sticks can be dried at refrigerator temps., but acidifying down below pH5.3 and above pH5 will offer a better safety profile without any noticeable tang (sticks will also dry much faster). I do not recommend trying to replicate a stick with a pH of 6 like a commercial producer, they have much better systems in place that a home producer.

Once the stick has lost 30%, dry continue drying to your liking. I dry mine to 45% weight loss which is about Aw 0.85......but I acidify my sticks down to a tangy pH of 4.7~4.8....
This ^^^^^^^^
Is the best answer.

To the OP, G geostriata
These are snack sticks. They dry very fast and are simple. Don’t make to much out of it. Acidification of a sausage ( lowering PH) is a hurdle for bacterial growth, necessary so the sausage can dry properly, however, snack sticks in those small 15-20mm diameter dry very fast. So low PH is an option and it does make the drying process faster, however it is not necessary. Snack sticks are very close to jerky in terms of food safety. You thermally process them and that is your safety. From there it is a matter of drying for texture. I smoke my sticks then cut them and brown bag them and into the fridge for a few days to harden them up for texture. They are sticks and very safe and not rocket science. The rocket science comes in when drying a sausage in 50mm plus. Then you can apply all the science but 20mm and below not so much, just roll with it and have fun. It’s safe.
 
This ^^^^^^^^
Is the best answer.

To the OP, G geostriata
These are snack sticks. They dry very fast and are simple. Don’t make to much out of it. Acidification of a sausage ( lowering PH) is a hurdle for bacterial growth, necessary so the sausage can dry properly, however, snack sticks in those small 15-20mm diameter dry very fast. So low PH is an option and it does make the drying process faster, however it is not necessary. Snack sticks are very close to jerky in terms of food safety. You thermally process them and that is your safety. From there it is a matter of drying for texture. I smoke my sticks then cut them and brown bag them and into the fridge for a few days to harden them up for texture. They are sticks and very safe and not rocket science. The rocket science comes in when drying a sausage in 50mm plus. Then you can apply all the science but 20mm and below not so much, just roll with it and have fun. It’s safe.
To clarify, I absolutely agree it's the best answer for ensuring safety and it's also what I'm doing for safety.

However, the weight-loss approach doesn't work for me because what I am trying to do here is ensure that my sausage is as dry as another sausage. Without the original weight of the target sausage, it won't work. That's why I created this thread and why I felt that it would be good to share my approach (e.g., if anyone else wanted to do a comparative dryness test with an unknown sausage).

Using my rough measure of relative dryness, it shows that, although I hit the weight loss %, I still have a bit further to go before my sausage is a match.

So SmokinEdge SmokinEdge , I may have to disagree on the rocket science bit. Even though you're right in that small diameter snack sticks dry faster, they're still not drying sufficiently. I've tried every approach mentioned, including the brown bag approach in any ways you can think of. So if you try every non-rocketscience approach and still nothing works, and have gone back to fundamentals and checked your work and still nothing works, then I think you've got to get more technical and hit the books. Try to find out why it's still not working, and one good way to do that is to experiment and to ground your experiments in actual measurable results, even if it takes a little bit of rocket science to get those measurements. It continues to be a fun challenge for sure!
 
Last edited:
To clarify, I absolutely agree it's the best answer for ensuring safety and it's also what I'm doing for safety.

However, the weight-loss approach doesn't work for me because what I am trying to do here is ensure that my sausage is as dry as another sausage. Without the original weight of the target sausage, it won't work. That's why I created this thread and why I felt that it would be good to share my approach (e.g., if anyone else wanted to do a comparative dryness test with an unknown sausage).

Using my rough measure of relative dryness, it shows that, although I hit the weight loss %, I still have a bit further to go before my sausage is a match. It continues to be a fun challenge for sure!
You are chasing texture, not per-se weight loss.

For instance, with a Umai dry bag you will get perfect weight loss but a soft not firm texture. So more drying is needed. The sticks though will dry very fast in red butcher paper or a plain brown bag. Giving you the mouth feel or texture you are chasing, because in reality that is what you are chasing. Don’t make it complicated.
 
You are chasing texture, not per-se weight loss.

For instance, with a Umai dry bag you will get perfect weight loss but a soft not firm texture. So more drying is needed. The sticks though will dry very fast in red butcher paper or a plain brown bag. Giving you the mouth feel or texture you are chasing, because in reality that is what you are chasing. Don’t make it complicated.
Oh. Awesome! I'll try Umai dry bag! Thanks!

I have tried dry bags and butcher paper in about 12 times now, so I'm still skeptical that the Umai dry bag will be different. But I'll certainly try it!

(I'm not trying to make it complicated! I just may go into the complex because there are simple solutions that I don't know about, but I'd certainly rather try the simple approaches first)
 
Oh. Awesome! I'll try Umai dry bag! Thanks!

I have tried dry bags and butcher paper in about 12 times now, so I'm still skeptical that the Umai dry bag will be different. But I'll certainly try it!

(I'm not trying to make it complicated! I just may go into the complex because there are simple solutions that I don't know about, but I'd certainly rather try the simple approaches first)
If you are chasing flavor and texture from a gas station stick, your next rabbit hole is GDL. Have fun. I don’t make gas station sticks so I’ll back out now.
 
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If you are chasing flavor and texture from a gas station stick, your next rabbit hole is GDL. Have fun. I don’t make gas station sticks so I’ll back out now.
Thanks! Yeah, in other threads I've heard about gas station sticks that were acidic. I guess it's a regional thing. Mine weren't that way, so looks like GDL isn't next on my list (I've also tried fermento, fermentation, ECA, and other similar acidifiers. The tang is a step in the wrong direction). Thanks for mentioning it though!

I'll definitely try to nuance texture vs. dryness and not just singlemindedly go for dryness. It's good advice. Although my target stick _is_ dryer, you may be right in that it could be more about the texture. I've also got a few batches in my drying chamber I can compare with the Umai bag approach, so fingers crossed that one of those will develop that texture over time.
 
Oh, it sounds like gas station sticks aren't viewed too well. For what it's worth, these aren't, they're just the closest thing I can find to match them (and probably a good amount better since it's been decades).

In any case, I appreciate all of your help so far.
 
I think you guys persuaded me to ramping Johnsonville brats140 -175 till 158 IT in 4 hours. Lol
 
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I think you guys persuaded me to ramping Johnsonville brats140 -175 till 158 IT in 4 hours. Lol
Oh, I don't know. Seems risky. Those brats are precious, you got to treat them right. No less than a 6 hour ramp. :P
 
Thanks.

Yeah, I can't explain it. I feel the sausage I make might hit that dryness level, but it's the bad sort of dry (which is why I'm experimenting with 'seeding' flakes of hard fat into the mix).

This commercial sausage represents the sausage of my childhood and after purchasing literally every beef stick on amazon, I can't find any other source. So I'm literally worried this sort of beef stick will disappear. Hence the mission to replicate it.

I do think that maybe if you try it, you'll see what I'm talking about. If you're on this thread and curious, feel free to PM me your address, I'll send you a sealed bag so you can try. Or you can get them here: https://www.ajaysmontanabananas.com/shop. Or maybe you have similar in the gas stations of your state, where they sit unwrapped and unsealed with deep wrinkles in a tall plastic tube. I just can't find those anymore where I'm from. All slim-jim-type floppy crap.
So I been doing things wrong since 1975 :emoji_astonished::emoji_astonished::emoji_astonished::emoji_laughing::emoji_laughing:
 
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