It is a fairly common question Del and the forum search at the bottom of the page will pull up some of the prior discussions about it. Just search "pH testing" and "pH meter".

But I fear you won't like the results. Not only is doing your own pH testing not recommended when it comes to home canning, it is strongly recommended against.

Primary reason, aside from meter accuracy issues etc., is because pH doesn't remain stable during shelf storage. It rises. So an item which might test safe at processing time may easily become unsafe within a relatively short time period.

We here advocate the use of tested and approved recipes only and you need not find them "limiting" as there are numerous sources of 100's of tested and approved recipes we happily share. And basic ingredients can always be safely canned and then mixed together at serving/preparation time.

A cardinal rule of home canning is that cooking recipes and canning recipes are two very different things. Cooking is an art, canning is a science. So you cannot safely can your own made-up recipes. The "rigorous guidelines" exist for your and your family's safety and are based on extensive lab testing. You can always choose to ignore them but it is done at your own risk.

Dave

First path to take may be that to your bank. Willing to do diligence on the science isn't the same as being able to do it in a home kitchen - PH is only one of the factors to be considered, along with density, others.

"If you want to explore private testing of your recipes for canning, it most likely will require an investment through private companies. You could contact your local Cooperative Extension office to see IF they have names of testing companies in your state, and/or if they could contact the Food Science Department at their state land-grant university to obtain help. You can find your local Extension office contact information by going to (the link below).

That office may also have someone on staff to help you with canning advice, although they do not do product testing and development there. Not every county has such a local person, but many county offices do have publications and/or faculty able to help you with your canning questions. "

Here is a link that might be useful: Links to state extension offices

is that if there is absolutely no safe method of developing new canning recipes, then there would be no new recipes published - no Blue Chair Jam cookbook, or any number of other new books making space on the bookstore shelf.

Please don't assume that just because someone publishes a book it means their recipes were tested or that their recipes are safe. That is far from the case and canning books are definitely "Buyer Beware". Look for things like USDA seal of approval, references to NCHFP, discussions about the importance of food pH, author's education and credentials, etc. before using.

Just as with online sites, there are numerous books out there with so-called canning recipes in them that have never been tested or only marginally tested, or are based on the "no one has died yet" philosophy. Some recipes have been proven unsafe to use and many others have borderline safety issues and advocate unapproved practices.

As to developing "new canning recipes", the issue only arises if one is talking about so-called niche foods, convenience, or artisan specialty items, etc. That isn't the primary purpose of home food canning. Preservation of the basic foods when in season or available so they can be used to create dishes when no longer available is the goal. And detailed instructions already exist for doing that - fruits, vegetables, nuts, meats, seafood, and poultry as well as basic mixes already exist.

On the off chance that you aren't familiar with NCHFP you might want to check out all the great info there. The extensive Publications list is especially informative.

Dave

Here is a link that might be useful: NCHFP

It takes between $10,000 and $50,000 to test one new recipe in a lab. That is not a typo... it does cost that much.
Such great comments here about not relying on testing your own recipes. No way to determine if the ph and density are exact matches for safety in a recipe. You have no way of knowing what the correct density should be for a recipe for safety.
Please, leave all of this to the scientists.
I work for a county extension office as a Master Food Preserver, so for what it is worth, that is the advice we give.

My state Dept of Consumer Protection Food Safety division, who is in charge of enforcing the new law allowing farmers to make and sell acidified foods without a commercial kitchen or filing a scheduled process with the FDA (or so the law says), actually recommended to me that I get a pH meter and test each batch, even after the first batch ("must be tested after the recipe has been completed") had been tested at a lab. Lab told me cost to pH test a jar of canned food was $7.50. From what I've read, they should do it within 24 hours b/c if it takes any longer than that for pH to come *down* to safe level (DCP says 4.2, not 4.6), botulism can start growing.

Of course, they're still trying to figure out how to implement the new law.

Now, if pH can *rise* after it's found to be safe initially, isn't it anyone's guess on how long a food can be stored, or if a recipe is safe at all? Do you keep pulling jars off the shelf and testing pH periodically? For a year? Two? Three? If it's still got below 4.6 (or whatever margin of safety the DCP/FDA, etc. put on it) after a year, is the recipe then approved?

Dave - you wrote
"Preservation of the basic foods when in season or available so they can be used to create dishes when no longer available is the goal. "

I have actually seen you write this before. I'm curious - is that your personal philosophy? Or is that the philosophy of USDA, NCHFP, Ball?

Thanks

delairen, there is a small scale, gourmet commercial jelly/jam/sauce factory in town, and they follow all the necessary guidelines for packing/canning acidic foods for national sale. They do the hair net thing, stainless steel everything, and what ever else the law requires.

They use a pH meter to check acidity, then fill as a hot pack the sterile jars and lids, then the center-snap lids are screwed on tightly. No further processing.

Linked is a .pdf article from Cornell about considerations of purchasing the necessary quality of pH meters for this kind of operation. I thought it had some good suggestions.

Here is a link that might be useful: link

Now, if pH can *rise* after it's found to be safe initially, isn't it anyone's guess on how long a food can be stored, or if a recipe is safe at all? Do you keep pulling jars off the shelf and testing pH periodically? For a year? Two? Three? If it's still got below 4.6 (or whatever margin of safety the DCP/FDA, etc. put on it) after a year, is the recipe then approved?

You can find this discussed in detail in several NCHFP publications on their website. But yes, tested and approved recipes have undergone multi-staged testing of their pH (ie: 6 weeks, 3 mos., 6 mos., 1 year, etc.) Based on those results adjustments can then be made in the initial acid level required or the ingredients allowed in the recipe to insure long term safe pH levels.

An example of this that has been discussed here in the past is with pickles. The pH of the fresh brine rises as the water in the cucumbers leaches out into the brine and dilutes it. Based on those tests many recipes now call for a much higher ratio of vinegar to water for safe shelf storage of pickles.

Dave - you wrote
"Preservation of the basic foods when in season or available so they can be used to create dishes when no longer available is the goal. "

I have actually seen you write this before. I'm curious - is that your personal philosophy? Or is that the philosophy of USDA, NCHFP, Ball?

Yes, we may call it canning but it's just another form of food preservation, preservation being the operative term. And preservation as the primary goal is clear from the history of the subject. Canning, like all the other forms of food preservation, came into being as an effort to achieve a balance between glut and famine.

Historical Origins of Food Preservation Has a great bibliography.

It is also discussed in the USDA Guide to the Principles of Home Canning and is one of the underlying principles behind many of the safety and cost effectiveness issues associated with home canning.

Do I subscribe to it? Yes, mostly In part because of my age and long personal canning history, my concerns for primo canning safety, high food quality without additives and preservatives, and my general lack of interest in artisan or niche foods. They are not cost effective to produce and are best when made fresh anyway.

Dave

Something to consider about pH meters (and other types of chemical testing equipment), not only must they be standardized with buffers before making a measurement but they also need to be calibrated at regular intervals. And the buffers should be of the appropriate range (bracketing the range you expect the result to be within) and the buffers need to be within expiry, stored properly and from a reputable source. The efficiency of the pH meter should also be considered. I know it helps confirm the readings are accurate but I'm not exactly sure how. Temperature also influences the reading. Testing should be done in a relatively small temperature range but the question would be what that temperature range is supposed to be used(maybe 20 - 25 deg. C?). I'm just trying to say that accurate pH measurements (and such) could potentially be done at home, but it wouldn't necessarily be easy.

Does anyone know if there are published (in scientific journals) articles about how recipes were tested? It would be a very interesting read for me. It would also help us (me) understand what was truly needed to test a recipe. I'm wondering if they test the pH of the liquid, the solid separately, the liquid and solid homogenized and/or the solids only homogenized? And would it matter if the center of the solids met the pH requirements or only the homogenized mixture? What would the pH of the liquid need to be in order to compensate for an upward trend? And how long would it take to equilibrate?

Sorry for all the questions but I'm terribly curious about this kind of thing.

~Cindy

Ajsmama & Dave52

Thank you very much for the information, especially the .pdf. I will definitely be researching this more, and this will be an excellent resource.

Dave - I am, actually interested in Artisan and Niche foods, so I think we're approaching this from very different perspectives.

Del

Del - please don't take me wrong. I too love many of the so called Artisan and niche foods. To make and eat. They just aren't for canning in my book. Flavor changes while sitting on the shelf and cost effectiveness aside, they just contain far too many variables to make many of them safe for canning.

It isn't as much a matter of what goes into the jar. It may fine to eat right then. It is what happens inside that sealed jar while it sits on a shelf somewhere for months that determines if it is safe to eat when it comes out. ;)

Dave

Dave, you brought up a good point about the safety of the jars of food. Some of it depends upon how it is stored. If in a hot environment it will deteriorate. Same if it is stored in a light environment. There are factors to safe storage, I agree.
Also, the recipe for the lemon curd from NCHFP still concerns me. If it is only shelf stable for 2 or 3 months it make me very leery of canning it at all. It is rather surprising to me it is even in the books as I sent that same, exact recipe to our food specialist at the university and she said NO, it was NOT safe to can. Then, a few years later it came out in the So Easy to Preserve from the Univ. of Georgia. I was shocked.
I would can most all of the recipes with confidence from USDA or Ball, but the lemon curd is sure one exception for me.

Dave - could you provide a link for the pH testing schedule? I couldn't find anything. I thought once a food reached final pH equilibrium, by definition that wouldn't change? I *was* surprised to find that 'some foods may take as much as ten days to reach finished equilibrium' - wow! You'd have to be a food scientist to know what foods/combos would take how long (larger particles of low acid food take longer, so things like cucumber or melon pickles?), which is why we shouldn't just make up our own recipes and figure if we test them right after cooking, they'd be OK (temperature matters too, and of course the meter must have the correct range and accuracy, be calibrated, etc.). Not as simple as DCP made it sound - but it makes me wonder how we can even home-can acidified foods at all.

From www.foodsafetysite.com:

'Processors of acidified foods are required to register and file a scheduled process with FDA. The process needs to be scientifically established to ensure that the final pH is always below 4.6. Processors need to test each lot of finished product for equilibrium pH. That means a natural pH balance has been reached by all ingredients -- which can take as long as 10 days in foods with very large particulates. Foods that require several days to reach equilibrium pH might need to be refrigerated during that time to prevent the growth of C. botulinum or other pathogens. In order to speed up the testing process, the product can be blended to a uniform paste. When a food that contains oil is blended, the oil should be removed before blending. Another way to do this is to measure the pH before the oil is added to the product because the oil does not affect the final pH.

Measuring pH
If a processor is using acidification, they must measure pH. A pH meter is what most food processors use. Food processors can also use indicator solutions, indicator paper, or titration as long as the finished pH is below 4.0. If a pH meter is used, it must be calibrated properly.
The pH meter can be a two electrode or a single combination electrode, where both functions are combined into one electrode system. One is the reference electrode and one is the measuring electrode. When not in use, the electrodes are stored submerged in distilled water or other solutions as recommended by the manufacturer. The instrument must be checked each day of use with two different buffer solutions -- one on either side of the expected equilibrium pH. After calibration, the electrodes should be rinsed off with distilled water and then they can be used for testing. The operation and calibration of the pH meter must follow the meter manufacturer�s instructions.

Direct Acidification and Bath Acidification
There are several different methods of adding the acid to the product. One is direct acidification, where predetermined amounts of acid are added to individual finished product containers during production (adding vinegar to home canned tomatoes is an example of this). With this method, one must control the acid to food ratio. This is probably the most common method used for acidified vegetables. Another method of acidification is batch acidification. Acid and food are combined in large batches and allowed to equilibrate. The acidified food is then packaged.
The necessary frequency of monitoring the finished product for pH would be less for batch acidification than for direct acidification. This is because there is variability from jar to jar with direct acidification that one does not have with batch acidification.'

By frequency, I'm not assuming every week, month, etc. for a particular batch to see how (if?) pH changes over time, but testing of each batch/lot for batch acidification vs testing on each individual jar for direct acidification?

Here is a link that might be useful: Acidified foods course intro on FoodSafety site