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pH test strips to measure range of pH 3 to 6?

I posted on the Cookware board asking for a way to test pH for home canning purposes. Fritter suggested test strips for the mildly acidic range between pH 3 and 6.

Problem is I need them by friday morning. I've checked with a couple pharmacies and the type they stock are for pH 5 to 9 range.

Any ideas where I can get my hands on some NOW?

Cookware board:
pH test kits for home canning tomatoes?

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  1. The Master Food Preservers at your local Cooperative Extension Office could probably sell you a roll or "give" you a piece. There's one in Sacramento County - (916) 875-6913, and also one in El Dorado County.
    I would imagine grocery chain stores would have some, especially meat departments. Or, try food products vendors or culinary schools.

    1. Try calling Oak Barrel Winecraft in Berkeley. Rationale: vinegar pH about 3, they have supplies to make vinegar ergo perhaps they have testing equipment.

      Oak Barrel Winecraft
      1443 San Pablo Ave, Berkeley, CA

      1 Reply
      1. re: wolfe

        I spoke to the folks at Oak Barrel Winecraft. They have beer strips and wine strips, $6.50 per 100. The wine test strips measure from 2.8 to 4.4 and the beer strips measure from 4.6 to 6.2. For my range, I'd need to purchase a pack of each, but it could be a handy solution for someone nearby.

      2. Hydroponic supply stores sell pH meters which are more expensive but presumably would also supply a full range for other errr... projects.

        1 Reply
        1. re: little big al

          I wanted to report on what I've learned so far. The cheapest from hydroponics stores, about $7.50 for a kit, is General Hydroponics pH test indicator, which measures from 4.0 to 8.5. However, it does not have a fine gradation at the lower end that I need. Here's what it looks like.

        2. I canned some san marzanos from mariquita two weekends ago and I happen to have access to some pH paper (4 to 7, don't tell my boss) from work. If you're curious, the sauce ended up right at 4.4, which is the cutoff point for safe canning. I added 0.25tsp of citric acid/pint to a pint and conducted a taste test (see Well Preserved by Eugenia Bone). People really couldn't tell the citric acid was there, aside from one mildly positive comment about "brighter flavor." The strip said the sauce was about 4.3-4.4. So... to be on the safe side, I added the citric acid to all the jars. Some recipes say to add vinegar or bottled lemon juice, but I much prefer citric acid b/c it doesn't add any extra flavors.

          Anyhow, if you're desperate for some, I could give you some strips. I'm in SF, drop me a msg at the address in my profile.

          12 Replies
          1. re: sfbing

            Thanks so much for the info and your kind offer. Our San Marzanos from Mariquita are being delivered today. It will be very interesting to see what the numbers turn out to be for our batches compared to yours.

            Would I be able to buy citric acid at Rainbow or where did you purchase yours? You can tell I've never done this before . . .

            1. re: Melanie Wong

              I got my citric acid for cheesemaking at BBE in bulk section if Rainbow fails you but I doubt it.

              1. re: Melanie Wong

                Just in case Rainbow doesn't have it, I got my citric acid at 22nd and Irving on the bottom shelf where they have all their spices. (I tried Andronico's, Safeway, and Whole Foods but no dice.)

                I took the tomato canning class that happy girl kitchen offers, and Todd Champagne mentioned that different batches from the same farmer are usually very consistent with regard to pH but that batches from different farmers can differ.

                1. re: sfbing

                  Great, that works for me. I'll be in the Sunset tomorrow and can swing by.

                  Consistency from a single farm makes sense to me. It will be interesting to see if our later harvest date and presumably more ripeness after Saturday's heat wave makes much of a difference. I've asked one of my canning partners to get a lab notebook for us to record our info!

                  22nd & Irving Produce
                  2101 Irving St, San Francisco, CA

                  1. re: Melanie Wong

                    I have San Marzanos from Mariquita from last Saturday and am not canning them. But juice from the seeding is in the low 4's. My pH paper is full range so not as exact.

                    1. re: wally

                      I had emailed Julia to ask if she had a pH range for Mariquita's tomatoes. No data available, so I'm sure she'll be happy to get all this info.

                    2. re: Melanie Wong

                      Have fun! (I am also doing a canning party, hence my obsession with pH.)
                      I should also mention that I asked Andy of Mariquita about tomatoes for sauce. He said that the Early Girls are also popular for sauce, partially because they are more acid and therefore seem to taste more tomatoey to some people. However, the drawback is that they have a lot more water than the San Marzano, so take longer to cook down. Apparently some people also use his heirlooms to make sauce--the end result is orange rather than red. (I would definitely be concerned about pH with the heirlooms, though.) Like you, we went with the San Marzanos, but maybe we'll try another tomato in the future.

                      1. re: sfbing

                        I grew Big Rainbows this season which is a potato leaf heirloom. The fruit is orange. Very tasty but I'm not sure I would want to can an orange mater. I have some black from Tulas that might be an interesting option though.

                        1. re: Fritter

                          Where did you get the black from Tulas?

                          1. re: wally

                            I'm in greater Detroit and a local Organic farmer had the plants this spring.
                            A delicious tomato if you get a chance to try or grow them in the future.

                            1. re: Fritter

                              Oh ,well. I had them here a couple of years ago, but not lately.

                      2. re: Melanie Wong

                        Back in the City today, stopped by 22nd & Irving, no citric acid left. I even asked an employee to help me, and he was surprised that it was all gone, so must be a recent occurance. Not wanting to find an empty bin marked "citric acid" at Rainbow tomorrow morning, on my way down to Menlo Park, I stopped at Aladdin in San Mateo (on Hillsdale, just off 101) and bought some there.

                        Aladdin Deli & Market
                        224 E Hillsdale Blvd, San Mateo, CA 94403

                2. Depends where you are. I'm 95% certain the ph strips I buy from SF Brewcraft on Clement street cover the mildly acidic range you mention; they're always around and would answer the phone. I think they come out around $0.25 each, sold as how ever many you want.

                  Oak Barrel also probably carries them. I think there are also home brew stores up in Santa Rosa.

                  Places is cranky, so here's the info:
                  1555 Clement St.
                  San Francisco

                  12 Replies
                  1. re: SteveG

                    Yeah, I feel really dumb that I didn't know this when I was in wine country two days ago, would have been so easy.

                    The guy at San Francisco Brewcraft answered the phone even though the store doesn't open until noon. The beer or wine test strips, for the range I noted above, are 50¢ each.

                    I also called More Wine (aka Fermentation Frenzy) in Los Altos. There's a second local store in Concord. It has test paper to measure the 3.0 to 6.0 range, 10 sheets for $1.80. One of our canners is coming from Palo Alto, so I'll have her pick it up for us.


                    95 Detroit Ave. Unit G
                    Concord, CA 94518
                    Phone: 925-671-4958
                    Fax: 925-671-4978
                    Mon - Fri 9am to 6pm
                    Sat & Sun 10am to 5pm

                    991 N. San Antonio Road
                    Los Altos, CA 94022
                    Phone: (650) 949-BREW (2739
                    )Mon - Fri 10am to 6pm
                    Sat & Sun 10am to 5pm

                    San Francisco Brewcraft
                    1555 Clement Street, San Francisco, CA

                    1. re: Melanie Wong

                      I have a PH meter for soil which measures from 3 to 8, its new so not dirtied up. Can you use this????

                      1. re: celeryroot

                        You're a gem! But I won't be back to Healdsburg to get it until after the canning party in SF. I had checked garden supply places and the range the simple kits measured bottomed out at 5.0. Thanks for the offer.

                        1. re: Melanie Wong

                          Melanie, I've been reading all your posts..I assume you got the citric acid by now at Rainbow. I also picked up SM's today. I was curious if you are using a pressure canner or a water bath. Acidity is more a concern with a water bath as more bacteria survives a water bath method. Are you doing hot pack or raw?

                          1. re: cakebaker

                            With a pressure canner you usually don't have to worry about acidity, if you follow directions.

                            1. re: cakebaker

                              I'm not back in the City yet. The plan is to cook sauce then process it in a water bath. We are descending on a friend's new condo on friday for the project. I've not canned before and will show up with a borrowed food mill and tomato press, plus 10.875 qts worth of canning jars I scrounged from various households this week. Others are more experienced than I, fortunately, but the Italians are aghast at the thought of adding acid. I was happy to read sfbing's finding with Mariquita's product and look forward to hearing about yours.

                              Here's a thread on the Home Cooking board about pressure canning tomatoes that might be the more appropriate place to comment.

                              Here are the guidelines for home canning that raised the acidity concerns for us.
                              The section on acidity says: "Researchers at USDA and at the University of Minnesota have found that most underripe to ripe, cooked tomatoes have a pH below 4.6. Unfortunately, a few varieties may have a pH above or close to 4.6. These include Ace, Ace 55VF, Beefmaster Hybrid, Big Early Hybrid, Big Girl, Big Set, Burpee VF Hybrid, Cal Ace, Delicious, Fireball, Garden State, Royal Chico, and **SAN MARZANO**. Some of these are grown for commercial purposes and are not found in home gardens. However, safely canning these varieties requires additional acid for water bath processing or a pressure canning process similar to low acid vegetables." (emphasis added


                              P.S. would you believe that I'm roasting my last 2#s of raw Hatch chiles now?

                              1. re: Melanie Wong

                                How about new canning jar lids? The rubber seals aren't intended for reuse, and while they're fine a time or two, I find they pick up odors and it's best to use new. My noccino has a subtle but present fermented garlic pickle note...

                                1. re: SteveG

                                  De rigueur at the kitchen where I volunteer and jar food weekly. A new lid for every jar.

                                  1. re: SteveG

                                    Yep, I've got new canning jar lids, both sizes. Bought them at Ace hardware, marked down a little (~10¢) until 9/7. Also have quart-size freezer bags and some squarish containers to freeze sauce.

                          2. re: Melanie Wong

                            I'll be waiting to see your results. An excellent expiriment.
                            Will you be testing different methods? Lime Juice Vs Vinegar Vs Citric acid Vs Au natural?

                            1. re: Melanie Wong

                              Cool, thanks for researching everything! I'll check out the place in Los Altos, that's a better price than SF Brewcraft. The nerd in me wants to check the PH of my grain mash constantly at different temperature rests, but it seems wasteful at $0.50 a shot, especially if I have to adjust the ph and retest.

                              You can definitely buy citric acid at Rainbow Grocery. It's near the bulk refrigerator with the individual mason jars above the bulk nut butters/behind the bulk oil spigots. Comes in a small jar that looks like a vitamin jar, from the same vendor as some of their vitamins and supplements.

                              1. re: SteveG

                                You might want to get a pH meter, then you can take as many measurements as you want. I think I remember the description saying that it would calculate the effects of temperature on pH. The place in Los Altos has a handheld one for $90. My canning partner bought the only two pH 3 to 6 strips in stock. They measure in 0.5 increments.

                                To nerd out myself, I did pick up a few strips from SF Brewcraft today. The ones for wine measure 2.8 3.1 3.4 3.6 3.8 4.0 4.3 4.6

                          3. I have about 100 strips that measure pH 0-6 in 0.5 increments that I could give you. cjones8434@sbcglobal.net.

                            1. I wanted to add some notes to this thread that might be of help to others who are planning to preserve some of this season’s local tomato bounty.

                              First off, the San Marzano tomatoes from Mariquita Farms were just gorgeous. Evenly ripe and full of flavor.

                              I’d had every intention of doing a few experiments, taking many measurements, and writing a lot of notes. But I started canning day exhausted and hadn’t created the mindspace for any thought experiments, then the crush of canning activity started and I abandoned my scientific aims.

                              I had purchased pH test strips from both SF Brewcraft and MoreWine, and “sfbing” was kind enough to share her stash with me. Lucky thing, as the ones I bought turned out to be worthless. The MoreWine strips only measured to 0.5pH accuracy and the colors on the comparison sheet were too similar to each other to judge the difference between 4.0 and 4.5. Trying the ones from Brewcraft, the color for the sample didn’t look like ANY of the colors for the range of pH. One thing I’d not considered was the effect of the sauce’s red pigment, making it difficult to judge color distinctions. By wiping some of the sauce off with a white tissue, we could kind of tell, but that contact might affect the measurement somewhat. The strips that sfbing provided made by E Merck used color coding that was more distinct and easy to judge differences as well as being non-bleeding. I was most relieved when the unintentional blue stain I’d left on my friend’s white corian counter did come off after using some dish soap (water was not enough).

                              Crushing/massaging with the hands to release some initial juice for the bottom of the pot

                              Cooked down and quite saucy after just 25 minutes of simmering and occasional stirring.

                              The raw juice measured somewhere less (more acidic) than 4.4 pH. After cooking, the sauce looked to be right on 4.4pH, same as sfbing’s result for Mariquita Farm’s San Marzano tomatoes. Using the other strips, the cooked sauce came in higher than 4.3 pH and less than 4.5 pH, but again, those strips were hard to read with the same certainty.

                              We did some taste testing of citric acid vs. lime juice (Santa Cruz organic from Rainbow Grocery). I didn’t set these up for blind tasting since we were pressed for time, but I did have the four tasters (including me) start with the no-addition control sample and then end by retasting it again after trying the other two. All four of us were in agreement that the lime juice changed the flavor too much. We liked the taste with citric acid, adding some brighter treble notes, and especially after going back to the control sample we agreed that the sauce benefited from a little acidification.

                              Adding ¼ teaspoon of citric acid per pint, the pH came in close to 4.0 for a test batch. We decided to use half this amount for the lots we canned resulting in a pH reading higher than 4.0 and less than 4.4.

                              We also played around with equipment for removing skins and seeds. First we tried the food grinder attachment on the Kitchenaid. This went really slowly and stripped off too much of the pulp. We were basically left with juice. But it was amusing to watch it in action, as shown here with the tomato skin and seed turds squeezing out of the attachment.

                              The tomato press borrowed from my brother in law saved the day. It was much faster to hand crank. I was surprised at how little force was needed though I was grateful for the buffed guys who took their turn on this. The position of the handle makes it easier to operate than a food mill, and the hopper system with the waste squirting out the side allows it to be set up in continuous process.

                              The food mill borrowed from my sister did a clean and efficient job too. The smallest hold blade caught all the seeds and skins and broke up the pulp.

                              We canned pint-size jars of tomato sauce, good for small households. We used a water bath process, boiling for 40 minutes, measured from the time the jars went into the boiling water.

                              We also bagged pints of tomato sauce for freezing, using quart-size freezer ziplocs. Some of the bags leaked, so it’s a good idea to double bag several of the quart-size bags in gallon-size.

                              We had purchased 100 lbs of tomatoes and the three of us processed 80 lbs of them from 10:30am to 7:00pm. We had a brief lunch break, picking up food at Kitchenette down the street. Our 80 lbs of tomatoes yielded
                              14.5 quarts of sauce in jars
                              8 quarts of sauce in bags
                              2 quarts of cooked juice
                              .5 quarts of raw juice
                              totalling 25.0 quarts of tomato product. We cooked down our sauce a bit more than other reports I’ve seen. I have made a simple marinara (only adding salt, garlic and EVOO) with some of the frozen product and I am delighted with the taste. Now I’m wondering if I should make more to get me through the year.

                              Each of us took home some of the remaining case to play with for other things. I made tomato confit and added tomatoes to daal, salads, pasta alla Norma, and other dishes this past week.

                              Notes on tomato sauce project

                              5 Replies
                              1. re: Melanie Wong

                                The Mariquita San Marzanos were great! I processed just 50 lbs of tomatoes and 20 lbs of sweet pepper (roasted) all for freezing. We slow roasted san marzano halves and froze them in zip log bags (in a relatively thin layer). For the tomato sauce, we cook down more than most folks probably do, blend it up, and then freeze in silicon muffin tins. Pop them out and keep in ziplocs - 1/2 cup size preportioned tomato goodness year round. I don't bother seeding and skinning - the immersion blender does a good enough job with that for my purposes.

                                But since this is the bay area board, i do recommend the Ladybug buying club. we got great stuff for a good price. Then again, we are long time Two Small Farms members too.

                                1. re: jsaimd

                                  After a week's break, I did jump back in by turning 10#s of Roma tomatoes I bought from Healdsburg's Westside Farms into a fresh tomato bisque. The soup was delicious, but I couldn't help but think that it would have been much better made with Mariquita's San Marzanos.

                                  Hope we'll see you at the picnic this year!
                                  Ninth Annual Chowing with the Hounds Picnic! October 3rd, 2009, details and registration info

                                  Chowing with the Hounds Picnic, 2008 Report.

                                  Recipes from the 2008 Chowing with the Hounds Picnic!

                                2. re: Melanie Wong

                                  Thanks for sharing Melanie. A lot of very good info!

                                  1. re: Melanie Wong

                                    A couple questions came in by email that I'll respond to here.

                                    For acidification, we also had on hand tartaric acid and cider vinegar. We didn't even try the cider vinegar in a taste test, figuring that it would have too much flavor impact. We didn't use the tartaric either because no one had figured how much would be equivalent to the recommended amount of citric acid. For a moment, we were in dueling iPhone mode trying to look stuff up but just dropped the idea. Also, when my friend bought the tartaric acid crystals, the clerk warned her to be careful saying, "too much of this will kill you." If I get more tomatoes before the season is over, I'll figure out the equivalencies and play around with it.

                                    To sign up for the Ladybug Buying Club email alerts for buying opportunities, contact ladybugbuyingclub@gmail.com

                                    On Sunday I was a guest at a tomato party, La Quinta Sagra del Pomodoro, and the kitchenaid was set up with the grinder attachment to make fresh tomato juice for bloody marys. Later we used it to make a fresh sauce, and found that if we ran the extruded skins and seeds through a second time, we could extract more pulp and juice creating a sauce more to our liking. The skins and seeds were saved to add to the stockpot, and it does add a lot of color and flavor to stock.

                                    1. re: Melanie Wong

                                      A bottle of wine contains about one teaspoon of tartaric acid, so tartaric acid won't kill you. The lethal dose is about a pound.
                                      But it has a sharper, different taste than citric acid. I believe citric acid is naturally present in tomatoes, while tartaric acid (in nature) is the primary acid in grapes.

                                  2. I'm a day late and a dollar short joining this thread. But in future if you're stuck, you can find citric acid packaged under the name "sour salt" in the kosher foods section of many larger supermarkets.

                                    We've eaten our way through two cases of San Marzanos from the Peach Farm in Winters, only managing to preserve the tiniest bit. But I think their San Marzanos are done for the season. I'll ask in a separate post if anybody knows who else is harvesting San Marzanos worth putting up.