Heirloom Cultivar Evaluation Study

[amideutch]

I came across this study performed by the University of Illinois in 2004. The interesting thing about the evaluation was they not only documented production but the Brix and PH of each cultivar tested. What was surprising was the PH swing of all the varieties was not that great as people assume an acidic tasting tomato would have a lower PH than a sweet tasting one which was not really indicated by the results in this study.
The Brix tests was also of interest and the following exerpt below describes what Brix actually measures.

• BRIX is a measure of the percent solids (TSS) in a given weight of plant juice---nothing more---and nothing less.
• BRIX is often expressed another way: BRIX equals the percentage of sucrose. However, if you study the contents of this book, you will soon enough understand that the "sucrose" can vary widely. For, indeed, the BRIX is actually a summation of the pounds of sucrose, fructose, vitamins, minerals, amino acids, proteins, hormones, and other solids in one hundred pounds of any particular plant juice.
• BRIX varies directly with plant QUALITY. For instance, a poor, sour tasting grape from worn out land can test 8 or less BRIX. On the other hand, a full flavored, delicious grape, grown on rich, fertile soil can test 24 or better BRIX.

For tomatoes the following Brix levels indicates the quality of the fruit.

4=Poor
6=Average
8=Good
12=Excellent

I plan on buying a "Refractometer" for next year to measure the Brix on my tomatoes to get an idea as to how well my growing/fertilization regimen is working and being able to tweek that regimen to better the quality of my produce. For those growing in the ground it will definately give you an indication as to the quality of the makeup of your soil.

Here is the link to the study. Ami

http://www.hort.purdue.edu/fruitveg/...mato_il_04.pdf

[carolyn137]

Ami, I'm so glad you posted that b'c maybe folks will no longer refer to low and high acid tomatoes as regards taste. Ph is indeed about the same for almost all varieties/

And Brix values also can't be totally associated with taste either b'c it measures just soluble sugars and there's much more to taste than sugars.

I know I've mentioned here before that over 400 different organic compounds as measured by mass spectroscopy have been associated with taste and I think only one of those compounds has been associated with a specific gene.

I don't necessarily agree with some of the poundages they got/variety, but is oft said....the mileage may vary for anyone growing a specific variety in any given season.

There's a few other studies that have been done on fruit pH's but I like this one b'c it includes the other data as well.

In the early 90's I had an SSE friend who wanted to measure pH of fruits of different varieties and he set out several hundred plants of different varieties and he too found no appreciable difference in fruit pH values, but he never collated all the data in a form that could be posted.

The positive result of his study for me was that he sent me seeds, almost all were purchased, for about 200 different varieties. Some I had already, but many were a welcome addition to my tomato collection.

[TZ-OH6]

Odd thing about the data presentation is that it is a total for two plants, except for the asterixed (asterized?) values which are single plants. Once I figured that out the # of fruit per plant came within range of what I have gotten for some of them.


pH is a Log scale so one full point is 10X increase/decrease in number of acidic ion equivlents (H+), so there is a decent amount of total difference in the amount of acidic ions among those tomatoes (Amana Orange has twice the amount of acidic ions of Big Rainbow). Luckily our taste buds do not seem to taste on a log scale so the values are close from that perspective, but I would have liked to see the range or standard deviation for their values. Without that the comparative data is pretty meaningless if one interprests the pH and Brix values as being close. This year my mouth seems to be sensitive to acidity and I seem to be getting a wide range in acidic "bite" for a given cultivar from fruit to fuit, and I wonder if that translates into among fruit variation in pH value or if it is just me from day to day.

There is a website where a guy is testing pH and brix for the cherry tomatoes he grows, he is getting wider differences. Wide enough to think about the effect on taste.

[carolyn137]

Some good points TZ and yes I know that pH is based on a log scale.

But I've seen other pH data that is quite similar and really, it depends on the way that the pH is done in terms of the number of fruits used for each variety and the exact method used for pH and whether just juice was used or the whole squeezed glop.

I didn't see the asterisks until I'd already posted here. I suppose I should go back and take another look at the Materials and Methods section to see if they specified exactly how they did the pH's as to juice or glop.

First comes reading the AM paper.

[Douglas14]

Ami,
None of the tomatoes trialed had a brix above 6. So does that mean they were all below average?

[carolyn137]

However, if you study the contents of this book, you will soon enough understand that the "sucrose" can vary widely

****

Ami, what book are you quoting from?

I ask b'c I just reviewed a lot of links on Brix measurements via Google and didn't see anything much higher than 6 and that for some of the hybrid cherry tomatoes.

Just curious and I've never seen anything approaching 24 and I'm not sure how one associates Brix levels with soil quality.

There's lots of links showing that higher Brix levels are associated with dry farming of processing tomatoes.

[amideutch]

Here's the site I got my information on Brix from.

http://www.tandjenterprises.com/brix_equals_quality.htm

Douglas, according to the table they were a little below average. But if you look at the website above there seems to be two or three standards. Interesting stuff. Ami

[feldon30]

See, and I don't think there's anything a handheld computer can tell me about the taste of a tomato.

[Douglas14]

Ami,
I skimmed through that second article you linked. It seems very interesting. I hope to read it in full later. Thanks!

[habitat_gardener]

Regarding tomato taste, I've seen a couple articles about tomatoes having lots of umami, the "fifth taste," recently. (The other four tastes are sweet, salty, sour, and bitter.) I haven't seen different varieties tested against each other, though.

The main point of the article below is that tomato sauce made with seeds has more umami than sauce made without seeds.

http://www.umamiinfo.com/science_of_...of_vegetables/

[TZ-OH6]

Inner vs outer parts of the tomato is a bit confusing to me. What I think they mean by inner parts is the seed gel, which is often carries more flavor than the flesh.

Now I have a reason to be a lazy cook and just use chopped up toms, skin and all, for sauce