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Old Feb 19th 2013, 01:00 PM   #1
Len351
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Lowering pH in food

I'm trying to make shelf stable chopped garlic packed in glass jars. I need to get the pH level between 2.8 and 3.8. This is what the majority of product on the shelves already is. I'm using a digital pH indicator that's used for the food industry. Most packers of this product use 85% food grade phosphoric acid, mixed with water. They partially fill jars with dehydrated garlic and then add the water/acid mixture to rehydrate the garlic and lower the pH level. Some companies heat this solution up to create a vacuum seal. Other companies that want to pack in plastic bottles pack it cold without a vacuum cap. So, here's what I'm trying to figure out....what pH level should the acid/water mixture be prior to adding it to the garlic? I've done multiple attempts now and I want to make sure I'm heading in the right direction. Here's a few of what I've done so far....

Garlic placed in jar with just water has a pH of 5.3.
The COLD tap water had a pH of 7.1.
This was a pH drop of 1.8.

I mixed some of the 85% phosphoric acid with HOT tap water to get a pH level of 5.6 thinking that the garlic dropped the pH from 7.1 to 5.3 that when added would drop it to 3.8 pH. That didn't happen. The pH was still 5.3.

I made a COLD water/acid mixture with a pH of 1.2. When I added this to the garlic and tested it, it was 1.6. Way too low.

I just made a COLD water/acid mixture with a pH of 2.0. I read somewhere that temperature can affect the pH level. I heated this water up (not boiling) and the pH dropped to 1.6. I now have a jar packed and I'm waiting for it to completely rehydrate and cool down before I test the pH.

Am I doing something completely wrong here? Can anyone shed some light on this?

I'm lost when it comes to chemistry but I'm willing to learn.

Last edited by Len351; Feb 19th 2013 at 01:04 PM.
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Old Feb 20th 2013, 12:14 PM   #2
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Hmm, I found something, which isn't exactly what I was looking for but might help a bit:



This is a graph of how pH changes when a base (or alkali) is added to a weak acid and is added to a strong acid.

The thing to note is that the pH doesn't change a lot between the initial pH and the pH of the solution you'r adding.

It's not like concentration where if you add two solutions of same volume but of different concentrations and you get the average concentration.

pH is calculated from the logarithm of the concentration of H^+ ions. The actual formula is:

pH = -log([H^+])

Phosphoric acid is a quite strong acid (moderately strong) and garlic is a weak acid. The net pH of adding the two is definitely not easy to get.

And yes, temperature affects the pH to some extent, which I can explain if you want me to. It returns to the normal when temperature comes back to normal.

What I would suggest is try adding a lot more of garlic water (10 times maybe? I never tried it) to your phosphoric acid.

Sorry for not being more helpful than that
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Old Feb 21st 2013, 07:01 AM   #3
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Thanks for the info. I'm going to try to make a 1.0 pH hot water/acid solution and then add it to the garlic. I think I'll let this one sit for a few days, then check the pH. The last one I made I waited 24 hours and opened it. 5.8 pH with a 2.0 pH water/acid solution. I'm so confused right now. I have no problems buying a food processing book covering this garlic/acid topic. I just can't find one.
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Old Feb 21st 2013, 11:44 AM   #4
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I hope you find what you're looking for

I wish I could help you more than that
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Old Feb 21st 2013, 03:39 PM   #5
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Did some more reading. I think there's an "acidification" period. Which means I have to wait for the garlic to acidify before checking the pH. I made 4 bottles with different pH levels. I'll check them in 3 days.
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Old Feb 25th 2013, 07:15 AM   #6
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Tested the 4 bottles with different pH levels.

bottle 1 - 2.1 pH after sitting 3 days.
bottle 2 - 3.6 pH after sitting 3 days.
bottle 3 - 5.1 pH after sitting 3 days.
bottle 4 - 5.8 pH after sitting 3 days.

I think I got it down but after further research, I need to be certified by a school that's recognized by the FDA in order to pack any low acid or acidified food products to sell. Found a school and registered yesterday.
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Old Feb 25th 2013, 11:04 AM   #7
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Awesome! Sounds like you'll be able to go forward with your project
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Old Feb 25th 2013, 07:36 PM   #8
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You need a pH buffer mixture KH2PO4/K2HPO4 adjusted to the pH you want by trial and error. You would be using more KH2PO4 than K2HPO4. You can get the equivalent of that by mixing diluted H3PO4 with dilute KOH which would involve even more trial and error. Only a buffered solution will maintain a relatively constant pH at the desired value. Good luck.
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Originally Posted by Len351 View Post
I'm trying to make shelf stable chopped garlic packed in glass jars. I need to get the pH level between 2.8 and 3.8. This is what the majority of product on the shelves already is. I'm using a digital pH indicator that's used for the food industry. Most packers of this product use 85% food grade phosphoric acid, mixed with water. They partially fill jars with dehydrated garlic and then add the water/acid mixture to rehydrate the garlic and lower the pH level. Some companies heat this solution up to create a vacuum seal. Other companies that want to pack in plastic bottles pack it cold without a vacuum cap. So, here's what I'm trying to figure out....what pH level should the acid/water mixture be prior to adding it to the garlic? I've done multiple attempts now and I want to make sure I'm heading in the right direction. Here's a few of what I've done so far....
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Old Nov 28th 2016, 09:49 AM   #9
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Garlic pesticide

Hi there i have a small farm in the west of ireland and i have 50 kg of spare garlic. I'm trying to find out what i must add to it to make a pesticicde concentrate.
I know the simple recipie which is Garlic , Water and Washing up liquid.
My problem is that i want to make a 500 bottles of concentrate to sell at the farmers markets and im worried that the product may spoil over time. Does anyone know what i must add , if anything , to stabilize the garlic?
So far my simple plan was to crush the garlic , add it to 250 litre of water , washing liquid, leave it for 24hrs then strain it into bottles, cap them and label them.
Surely its not that straight forward. Do i need to add some sort of acid to keep the ph level down? do i ferment garlic mash slightly ?
There are a few companies that sell this type of product but obviously they wouldn't share their secrets.
Hopefully someone out there may know the answers and be able to help.
Thanks in advance
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