The BIG PIZZA SAUCE EXPERIMENT - Measure Acidity & Sweetness

[petef]

Everyone, in another thread.. http://www.pizzamaking.com/forum/index.php/topic,12647.0/topicseen.html
a few of us decided to take on an experiment where we will attempt to accurately measure the ACIDITY and SWEETNESS of our pizza sauce recipes hoping to find some new ways to communicate and determine the taste and ingredients of our pizza sauce.

So far it has been determined that we will need some relatively lost cost measuring devices:

ACIDITY
* Litmus Test Strips or a PH meter.
Not sure about the pH range but suspect it will be pH 7 and lower.

SWEETNESS
* Sugar Scale Hydrometer
* Hydrometer Jar


Hopefully we will come up with some basic pizza sauce recipes & procedures were we will correlate various degrees of taste (related to acidity and sweetness) quantified by measured levels of acidity and sweetness.

If you already have the devices needed to measure Acidity or Sweetness, you are welcome to join us in this experiment. The first phase is to determine which devices work best and what range of pH and Sugar we need to measure accurately.

---pete---

[Jackie Tran]

That's great Pete.  I'll provide some readings in the next several days. 

Chau

[petef]

That's great Pete.  I'll provide some readings in the next several days. 

I performed my first experiment yesterday, I wrote it up in detail and lost the entire post when my attached pic produced an error due to it being too large. Darn!!! Anyway, I'll summarize now quickly.

I opened a can of Cento brand, San Marzano peeled tomatoes, crushed them down and measured pH 6 using litmus test strips.

I then cooked my favorite sauce which included about 4 ts of vinegar and 3 ts honey and measured pH 5 or less. Problem is, my test strips only range pH 5 thru pH 9 which I feel is inadequate. I probably need a pH meter or litmus strips that can accurately measure in the 3 to 7 pH range.  So I need to improve my ability to measure pH in the 3 to 7 range and repeat my experiment.

See pic below to better understand the measurement problem.

[petef]

I'm just shopping for pH & sugar testing equipment.
Here's what I found.

PH meter $50
http://www.eckraus.com/WIDE_RANGE_PH_PAPERS_(2/Page_1/PH410.html

PH test strips accutate in the 2 to 6 range. Two different kits required. $7.50 each
http://www.eckraus.com/Page_1/PH110_____2844.html

Sugar Hydrometer $14
http://www.eckraus.com/WINEMAKING/Wine_Making_Equipment/Hydrometers_-and-_Testing/Hydrometers/Page_1/HY120.html

Hydrometer Jar $9
http://www.eckraus.com/WINEMAKING/Wine_Making_Equipment/Hydrometers_-and-_Testing/Hydrometers/Page_1/HJ110.html

[PizzaHog]

Thought I might try to establish a baseline this morning for comparison and calibration since I have some raw Super Dolce and a pH test kit handy.  Unfortunately, my kit is a liquid reagent and not paper type so the red color of the sauce is an issue.  I figured I would try anyway just because and am attempting to filter out the tomato solids to see what happens.
These look interesting and not much more than litmus paper:
http://www.amazon.com/HM-Digital-TDS-EZ-Tester-Purity/dp/B002C0A7ZY/ref=sr_1_21?ie=UTF8&qid=1293979330&sr=8-21  
http://www.amazon.com/Milwaukee-Instruments-pH-Pen-PH600/dp/B001DTQJ8O/ref=sr_1_26?ie=UTF8&qid=1293979330&sr=8-26
I have, or used to have, a hydrometer but the problem is finding it after so many years, so I will start searching...
Keep in mind for this to be as useful as possible everyone needs to be on the same page to be able to compare from afar.  So a potential lauching point might be to compare readings on unaltered tomato products each has access to.  This will show if each testers results are consistent/accurate and provide a baseline of "taste" that relates to those numbers.  
I also had a thought that pet stores with fish usually have pH and specific gravity testing stuff, not sure what ranges are typical for those environments though.
My schedule is such that I will be over the top occupied for a while but still hope to participate as I can.

[petef]

Keep in mind for this to be as useful as possible everyone needs to be on the same page to be able to compare from afar.  So a potential lauching point might be to compare readings on unaltered tomato products each has access to.  This will show if each testers results are consistent/accurate and provide a baseline of "taste" that relates to those numbers.  

Excellent point! We may have to select a few brands of canned tomato product to get more people involved. My Acme grocery store in NJ only has one brand (CENTO) of San Marzano tomatoes, so I'll be testing using that and also some liquid tomatoes I now have frozen from my garden.

---pete---

[Bill/SFNM]

One important flavor component of tomatoes are the free glutamates which can vary widely depending on the variety of tomato used, handling, canning, preparation, etc. Measuring this may be out of the scope of your experiment, but it is factor that should not be overlooked.

 

[scott123]

As this device works by bouyancy and actually measures the relative density of a liquid it would take some gyrations to use it with a sauce (no chunks, no air whipped in, etc) and how accurate the measurements would be is in question.  Hydrometers are used in making sorbets though, which as pureed fruit in a semi thick liquid, sounds a lot like pizza sauce so who knows.  If nothing else it might prove to be accurate enough for some comparitive experiments.

I hate to rain on everyone's sugar measuring parade, but there's not a chance in heck a hydrometer will reliably measure sugar content in tomato sauce.  There's too little sugar and far too much extraneous matter. The only thing a hydrometer will tell you is density- which might actually be good if you feel like a manufacturer might be inconsistent with their puree consistency.

As far as measuring pH in tomatoes... now that I'm interested in seeing. I'm not a big believer in adding acid to sauce, but if the pH numbers revealed high fluctuations from batch to batch, season to season, I might consider standardizing my pH levels with a naturally occurring tomato acid such as citric (or scaling back my added sugar based on pH). 

[Jackie Tran]

I have some sauce from 3-4 days ago.  Check the pH with strips and the closest I got is a pH of 5.8.   Sauce always seem to become more acidic as it sits in the fridge.  Had to add a bit of stevia to this to get it back to where I like it.

Next time I make "fresh" sauce, I'll do another set of readings.

Chau

[petef]

I hate to rain on everyone's sugar measuring parade, but there's not a chance in heck a hydrometer will reliably measure sugar content in tomato sauce.  There's too little sugar and far too much extraneous matter.

I may be wrong, but I'm thinking if a human can taste a difference in sweetness then it must be measurable using some type of device. In my typical pizza recipe I'm cooking down to about 18 ounces of sauce and adding 2 to 3 teaspoons of honey, so going from raw tomatoes to final cooked, I hoping to measure a difference in sugar level. Do you think it's feasible?

---pete---

[petef]

Some info about measuring sweetness...

Source:
http://www.physicsforums.com/showthread.php?t=105311

Measuring sweetness
There are no laboratory instruments to perform the task, no absolute or even arbitrary units of sweetness. Instead we have to rely on the human tongue and the hope that if we average the findings of large numbers of tongues we can obtain useful data. The data scientists obtain will still not be in absolute units but will be expressed relative to some arbitrary standard, usually sucrose.

A typical way a panel assess sweetness is to make a dilution series of the solution. (10:1, 100:1, 1000:1 etc...) At some dilution, the entire panel will no longer taste any sweetness. A relative scale is constructed based on this taste test. (similarly Scoville Units were developed to measure heat (spicey) units).

[dms]

I may be wrong, but I'm thinking if a human can taste a difference in sweetness then it must be measurable using some type of device. In my typical pizza recipe I'm cooking down to about 18 ounces of sauce and adding 2 to 3 teaspoons of honey, so going from raw tomatoes to final cooked, I hoping to measure a difference in sugar level. Do you think it's feasible?

See, for instance, http://dx.doi.org/10.1007/s00217-007-0743-4 for an example of how measuring glucose in tomato can be done.  Probably beyond the abilities of most home kitchens.

[shuboyje]

Most home winemakers who want to measure residual sugar use clinitest tabs.  Here is a link about how they are used in that application

http://www.101winemaking.com/residual_sugar_test_using_clinit.htm

I second the notion that a hydrometer will be useless.  You also should be able to find pH strips that range from 3-4+ at most wine supply stores, and my gut feeling is pizza sauce may end up in the top end of that range.  I would also think about measuring titratable acidity like we do in wine making.  pH is controlled by buffers in the solution as well as the acidity, titratable acidity will tell you more about the amount of acid you actually have.

[norma427]

I don’t know if this will be of any help, but I measured the pH of Saporito Super Heavy Pizza sauce yesterday before I added any herbs, garlic, or other ingredients I mix into my sauce.  The pH was 4.50, right out of the can.  This afternoon I measured the pH again and it was 4.46.

Norma

[petef]

I second the notion that a hydrometer will be useless. 

Yes, I agree now too. I originally saw a "Sugar Hydrometer" on a wine making site and I thought it was a simple measurement, but I see now that the same techniques used for measuring sugar level in wine making  are not applicable to pizza sauce. Therefore, I'll be focusing on pH measurements for this pizza sauce experiment.

---pete---

[petef]

I don’t know if this will be of any help, but I measured the pH of Saporito Super Heavy Pizza sauce yesterday before I added any herbs, garlic, or other ingredients I mix into my sauce.  The pH was 4.50, right out of the can.  This afternoon I measured the pH again and it was 4.46.

Thanks Norma, did you also taste the sauce for acidity at each measurement? I'm curious if, with some practice, we will be able to correlate certain levels of acidic taste to measured pH level.

In other words, say a few of us taste test the same brand of raw canned tomatoes and we all agree it's high in acidity. Then we each measure the pH and come up with similar pH readings. We successfully repeat the process with another product deeded as "low acidity". Then we will be able to use those standards when talking about our sauce recipes with good assurance that we are all on the same page.

---pete---

[norma427]

Thanks Norma, did you also taste the sauce for acidity at each measurement? I'm curious if, with some practice, we will be able to correlate certain levels of acidic taste to measured pH level.

---pete---

pete,

I did taste the sauce both times, but couldn’t taste any difference in the acidity at each measurement.  The only things I could taste were the added herbs, garlic, and other ingredients.  I am sorry I couldn’t taste the acidity.  I don’t know if other members might be able to taste the acidity or not.

Norma

[petef]

pete,

I did taste the sauce both times, but couldn’t taste any difference in the acidity at each measurement.  The only things I could taste were the added herbs, garlic, and other ingredients.  I am sorry I couldn’t taste the acidity.  I don’t know if other members might be able to taste the acidity or not.

Norma

Norma, your before & after readings of 4.5 pH & 4.46 pH indicate to me that you didn't add any ingredients that changed the acidity level significantly. On the other hand, if you had added vinegar, you would increase the acidity level and the sauce would have a "sharper" taste. The big question is, will we be able to accurately measure that difference in pH level.

I received my pH test kits in mail so I hope to do some more experiments soon.

---pete---

[norma427]

The big question is, will we be able to accurately measure that difference in pH level.

I received my pH test kits in mail so I hope to do some more experiments soon.

---pete---

petef,

I don’t know if we will be able to accurately measure the difference in pH in different sauces.  Each member adds different ingredients to different tomato sauces, (whether they are fresh or canned).   Right now I don’t understand how we can come up with sauces that taste about the same by just using pH readings.  In my opinion, measuring pH’s of sauces is like taking all the variables that can go into pizza making.  They are just too many variables to come up with good conclusions.  Time will tell.

I understand if I had added vinegar to my sauce the pH would have changed more, but I don’t like vinegar in my sauce.  That is just a personal taste opinion.  I added herbs and garlic infused with olive oil that was done in my microwave, a little sugar, Parmesan cheese, a little more dried oregano, water (which I didn’t take the pH of), and fresh grated pepper.  Even when adding water, I would have thought that would have changed the pH more. I even added much more water at market before I took the second pH reading, because my sauce I used was like a paste.

When I defrost some of Les’s sauce I make, I will measure the pH of that.  I used fresh tomatoes in Les’s sauce in combination with the Walmart Great Value Brand of Crushed tomatoes.

Good luck with your readings you get with your pH meter.

Norma

[petef]

petef,

I don’t know if we will be able to accurately measure the difference in pH in different sauces.  Each member adds different ingredients to different tomato sauces, (whether they are fresh or canned).   Right now I don’t understand how we can come up with sauces that taste about the same by just using pH readings.  In my opinion, measuring pH’s of sauces is like taking all the variables that can go into pizza making.  They are just too many variables to come up with good conclusions.  Time will tell.

Norma, this idea of testing PH came from the notion that there is no perfect pizza sauce recipe that can be duplicated with consistency due to the varying amounts of acidity and sweetness in the base tomato product used. This notion also suggests that the cook must sharpen their skills of tasting first and adding certain ingredients (vinegar and/or sweetener) to compensate for the variations in the base tomato product used. That's what this experiment is all about.

As for all the other ingredients such as salt, basil, olive oil, and other spices, I don't believe they will have any significant impact on the PH readings and therefore they can be relied upon to produce a consistent taste and used in precise amounts per recipe.

So the PH and taste tests will be used in this experiment mainly to determine how much vinegar or sweetener to add to a pizza sauce recipe with some folks preference being low acidity and other folks preference of high acidity.

Since sweetness cannot be accurately measured we may have to rely upon taste testing, but perhaps the PH tests can also be used as a rough guide for how much sweetener to add for a specific target taste.

At this point in time, I'm not even sure if adding white sugar or honey will affect the PH test.

As for WATER, I just did some initial research and drinking water is ideally PH 7 which is considered neutral, so adding drinking water should not affect the PH levels unless it is far off from PH7/neutral. TAP water is supposedly PH 6 to PH 8, so it might make for a good a reason to use bottled water known to be PH 7/neutral for our sauce recipes.

---pete---