AW, water activity

Tom
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AW, water activity

Post by Tom » Wed Dec 30, 2015 17:03

AW has been mentioned numerous times throughout the forum; can someone explain exactly how you would measure this activity? Lets say your making jerky and you want it safe but not overly dry or you have a whole meat muscle and you want to know the AW of the meat. Any information would be helpful. Tom
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Bob K
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Post by Bob K » Wed Dec 30, 2015 17:16

This was discussed recently here: http://www.wedlinydomowe.pl/en/viewtopi ... sc&start=0

To Sum it up:

The Regs:
https://www.gov.mb.ca/agriculture/food- ... lationship


Rich wrote:
Is it possible to duplicate without moisture, ph, etc, meters by following your your times, etc to the letter ? If not, where do I get my hands on those types of measuring devices ?

Bob K wrote:
The real answer is no, but you could probably come close :neutral:

Butterbean wrote:

I was hesitant about touching this subject so thanks Bob for putting it so well.

Since the door is now cracked, I'll put it another way - a definite maybe. Not because you couldn't do it and come out fine but because there are just so many factors that come into play.

Making a shelf stable product and being able to prove its shelf stable are two different things. Both could be but you will only have proof that one is and sadly we now live in a time where paper proof is valued moreso than quality.

But putting things in perspective, people have been making shelf stable products for years and have got along fine without all this equipment. While I wouldn't put a cocked pistol to my head to see if it was loaded I wouldn't have any real hesitation eating a sausage that had been processed in a known and proven manner.

What could happen? Take a snack stick for instance. You've removed the risk of botulism by using the cure so you are not going to die from that. You've removed the other risks through the fermentation, smoking and the baking processes so you have all that going for you. So what happens if you don't dry it as completely as you should have and it was placed in an airtight sealed environment? What organisms are left? I think the spoilage organisms would be the only ones and they will tell you by sight and smell. If not, I imagine the taste would be horrid but it would not be anything like having a bullet in the chamber.

I don't mean to downplay the importance of any of these safety concerns its just I think we need to sometimes put things in perspective and I hope I don't catch grief for posting this but this is how I understand things and I apologize if I'm wrong because the last thing I want to do is give erroneous information on this board. I'm here to learn as well and I know there is a lot I don't know.

But like I say, there is a big difference between being able to prove something is shelf stable and it actually being shelf stable. I think life was much simpler when we didn't know so much and question ourselves so frequently. In those days, we had many more more sausage shops and better selections to choose from but it is what it is.
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Post by Butterbean » Thu Dec 31, 2015 05:25

To test the AW you have to have an instrument which they are very proud of.

Before they came out with the water meters, the moisture protein ratio (MPR) was used. This sounds simple enough. You divide the percent moisture by the % protein and this ratio is used to determine if it meets the conditions. How you come up with the numbers to plug into this equation I haven`t a clue but now the USDA no longer likes this method even though I've read where one meat scientist has proven it is still a valid method and has never been wrong but in fairness to the USDA I did also read where there is a minute glitch where it could be wrong in certain unique situations. Maybe someone could explain how this is done because I'd love to know how to do this.
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Post by Rich » Thu Dec 31, 2015 08:54

Me too !
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Post by Bob K » Sat Jan 02, 2016 14:42

Butterbean wrote:Maybe someone could explain how this is done because I'd love to know how to do this.
Its actually quite simple: :grin:

Per the FDA-
Send 2 samples a year to the laboratory to be tested one in the dry winter months and one in the humid summer months.
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Post by Butterbean » Sat Jan 02, 2016 15:04

Bob K wrote:
Butterbean wrote:Maybe someone could explain how this is done because I'd love to know how to do this.
Its actually quite simple: :grin:

Per the FDA-
Send 2 samples a year to the laboratory to be tested one in the dry winter months and one in the humid summer months.
Ok. So this is not something you could do yourself. I misunderstood this. I've read something about sending the two samples each year but thought this figure was something you could do between tests.

If I'm understanding this right then between tests you simply base your figures on % shrink based on your approved process. So the aW meter will allow you to test more frequently to be doubly sure something didn't go wrong.
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Post by Bob K » Sat Jan 02, 2016 15:25

Sorry I meant the simple FDA simple method to be a bit of humor. :cry:

But from what I did read yes you get you method approved and send out the samples for verification.

I think the only home method ( unless you have an Aw meter) is experience and common sense, as most of us go by feel or weight loss. :shock:
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Post by Butterbean » Sat Jan 02, 2016 16:35

Sorry. I'm slow this morning and didn't pick up the humor.

Just thinking aloud here but if you take the formula % moisture/%protein, I would think these numbers could easily be calculated if you knew what the initial percent moisture of the meat. I don't know if they had rules of thumb or if they used a moisture meter like this.

http://www.conservationhut.com/p-231-am ... oCA1rw_wcB

But if you knew this number then I think you could subtract the amount of water loss from your shrinkage this would give you both the water remaining and the protein remaining and the rest would be easy enough to calculate.

I've dug around on the net a fair amount looking for information on how this is done but all I've found are just articles referring to these numbers but haven't found an actual example of the process to go about calculating it.

My hunch is, it will all boil down to the shrinks we are already using as long as no water binding agents are used. In the latter, I think the aW would be the only way to know for sure but that is only speculation on my part.
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Post by Tom » Sat Jan 02, 2016 19:07

Butterbean and Bob your responses along with my research pretty much answers all my questions and concerns. In curing meats, to make shelf stable or just plan safe, several goals much be achieved. I'm sure you are well aware of these. The problem is with beginners, such as me and others just starting out, we lack the most important component experience. Yes we can follow a recipe but it will be trial and error before we may know what we are safely doing. My point is without two key testers, ph and aw meter plus experience, you can not make a cure meat product safely. Tom
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Post by Bob K » Sat Jan 02, 2016 20:12

Tom wrote:My point is without two key testers, ph and aw meter plus experience, you can not make a cure meat product safely. Tom
You are changing the subject from a shelf stable product to a cured product. I am not sure what you mean.

For example: To be safe for a dry cured commuted, fermented product, you only need to test the Ph, and use weight loss for Aw.
Last edited by Bob K on Sun Jan 03, 2016 13:30, edited 1 time in total.
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Post by Butterbean » Sat Jan 02, 2016 21:37

Tom wrote: My point is without two key testers, ph and aw meter plus experience, you can not make a cure meat product safely. Tom
I disagree. If you have followed a proven process like those given in Marianski's books or posted on this board and replicated them with due diligence and a measure of common sense then they will be safe. What you cannot do is PROVE its shelf stable which is not a real concern for someone not selling the meat. On the other hand, if you buy into this belief that nitrates are man made poisons and refuse to use them you will probably end up killing yourself and Darwin's rule will again be proven true and some might argue this a good thing.

Another thing you cannot do is test to see when you need to stop the drying process if it reaches shelf stability before the target shrink is reached. 10% more drying is nothing to the home producer but this loss could mean a lot to a commercial producer.

If you happened to cryovac some meat before it reached the threshold the worst that would happen is the meat would spoil and spoilage in and unto itself under these conditions is not something that is "unsafe". Assuming you could get it past your nose it might make you nauseated or vomit.

On the other hand, if you didn't cryovac the meat and simply wrapped it in paper it would simply continue to dry just as it would if it were left hanging in your drying room. From personal experience I can attest if left this way for nearly a year you will no longer have salami but jerky. Miserable tasting jerky but safe nonetheless.

IMO, the best thing about being able to know its reached the point of shelf stability is your ability to stop the drying process when its at it peak of texture and flavor. IMO, drying it too long reduces the quality but if you have doubts, just wrap in paper and don't cryovac.

To experience what I'm talking about, assuming you've haven't already done this, try cutting a slice of salami that hasn't quite reached the target shrink but when it has that nice cheesy aroma. The mouth-feel, the aroma, the flavor is heavenly and it just might be ready to go in a cryovac bag to preserve this flavor profile but you just don't know for sure without testing it. Some might frown at this but its safe. Just think of Metka.
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Post by Tom » Sat Jan 02, 2016 22:54

Butterbean it's nice we can disagree. I also disagree. Guess I missed the comments about nitrates. The rest of your comments appear to speak of your experiences which I'm sure are extensive. I do appreciate your input. Thanks Tom
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Post by Butterbean » Sat Jan 02, 2016 23:27

Tom, if you don't mind my asking, why do you think you can't make cured meat safely?
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Post by Bob K » Sun Jan 03, 2016 17:18

Please guys no personal comments. Some posts have been moved. See disclamer container http://www.wedlinydomowe.pl/en/viewtopic.php?t=5839
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Post by redzed » Mon Jan 04, 2016 00:23

OK, let me weigh into this discussion. I think that all of you made some good points and observations, but also all of you are missing one thing or another. Making dry cured products requires a bit of a learning curve, and as you progress you realize that the more learn, you realize you've barely scratched the surface. It is an art and a science and it requires time and patience as well as failures and successes. So let's go into this with an open mind and not with the stand that we have read all there is to it, or that the way we have been making our salame is the only correct way and we have mastered the craft.

There exists a considerable amount of risk when we make sausages that are essentially raw when consumed. For the most part, it is impossible to eliminate 100% of the risk, but there are well established methods to mitigate this risk. The best way to practice risk mitigation is to adopt what is known as hurdle technology developed over 40 years ago by a German scientist, Lothar Leistner. Stan Marianski explains it very well here:
http://www.meatsandsausages.com/sausage ... ty-hurdles
An informative and easy to digest slide presentation is here:
http://www.slideshare.net/pallvidhotra/ ... technology
And a summary by Leistner himself is here.
https://openagrar.bmel-forschung.de/ser ... -181ff.pdf

If you read the above documents you will have basis from which to develop good practices and applications when making your salami. In almost everything you do, you will be looking at whether you have created enough hurdles to eradicate or slow down various pathogens and unwanted bacteria from growing and multiplying in your salami.

Now to answer the original question whether it is possible to make a safe product without a pH meter and an aW meter? I would venture to say yes, but without that 100% certainty. That is why our government agencies implement standards and regulations that are higher than what might be just adequate. That is also why Stan Marianski's recipes ask for 3% salt when 2.5% is quite satisfactory, and 156ppm nitrite when 120ppm will do. That is why Ruhlman, Cairo, Weiss and Butcher & Packer tell you to dump in half the package of culture into a 5lb batch of salami when a couple of grams could do the trick. And many recipes also ask for more sugar than is necessary so that the lactic bacteria have lots of food to drop the pH. So be careful in selecting recipes as there are many dangerous ones out there. But if you follow one from a credible source, have fresh cultures, use clean very cold or frozen meat, ferment and cure in an appropriate environment, you will probably succeed each time. And like all things that are learned over time, you will come a point when you will recognize wonky recipes and feel comfortable with formulating your own. If you are making the same thing all the time and in the same environment, you will probably get away without checking the pH. When my electrode failed last year I made a few batches of salami without pH readings which turned out well. And I also had a couple failures even though the pH was where I wanted it to be. But it's not what I would recommend for anyone just starting out or trying new products. I advise investing in a meter, or at the very least, using test strips. Lowering the pH is an important hurdle and can be tricky, so we need to know what the heck is going on. Even in Italy they check the pH, and look for that drop even though they don't use starter cultures. We simply don't have that flora in our environment, so we inoculate. I totally believe in using cultures not only for safety reasons but for flavour and aroma that will be similar to that found in Europe. And if you use bioprotective cultures such as B-LC 007 and F-LC you raise a hurdle even higher.

Now, let's look at water activity, the final hurdle. Note that in erecting all the earlier hurdles we already had been slowing down the water activity. (salt, sugars, nitrite and nitrate, fermentation bi-products and even some spices.) The rest we leave to osmosis and dehydration. Fresh meat has a water activity level of .99 and we need to drop it to <.86. At an aW of .91 all pathogens will have been prevented from growing with exception of Staphylococcus aureus. In a perfect world we would have the means to test aW, but the cheapest meter the PaWkit is $2,000 and apparently it's not that accurate. To test accurately we need a laboratory quality unit, running at $6-8k. So for most of us hobbyists, this is not an option. 35% weight loss is considered by many as the safe point, but there is the need to make adjustments for the amount of fat, the type of meat and whether it might have been frozen before or not. But even small producers are allowed to make fermented sausages without continually testing for water activity. So my conclusion is that if you follow the first steps of the hurdle technology, you can succeed without an aW meter, (inasmuch as I would love to have one :lol:) .
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