Mediocre Tomatoes Explained!

Jacob Schor, ND, FABNO

July 29, 2012


American tomatoes have little flavor. Anyone who has eaten food outside the United States will rave that foreign tomatoes taste better. Our tomatoes, to paraphrase a recent Science News description, taste like wet paper towels.


The June 29th issue of the journal Science finally tells us why.  It turns out that losing the flavor was something of an accident.  For the last 70 years plant breeders have striven to create tomatoes that are uniform in color; the goal has been to eliminate ‘green-shoulders’.  This refers to the green collar near where the fruit attaches to the stem, which once upon a time tended to linger, staying green, even when the rest of the tomato had reddened up nicely.  Consumers prefer uniformly red tomatoes and purchase them rather than their green-shouldered neighbors while shopping. 


Check out the tomatoes in the store.  The plant breeders have clearly succeeded.   The tomatoes look beautiful.  The problem is that in weeding out the green shoulders they messed with a gene called SlGLK2 that is important for flavor.


Common wisdom among tomato biologists had been that chloroplasts in the leaves of the plant supply the fruit with sugars as it ripens. The authors of the Science paper, all researchers from the University of California at Davis, explain that this isn’t exactly true.  Chloroplasts that remain in a tomato’s ‘green-shoulder’ continue to perform photosynthesis as the tomato ripens and actually add about 20% more sugars to the tomato.  Eliminate the shoulder and you eliminate that extra’ sweetness.  Eliminate the shoulders and you also eliminate a host of volatile chemicals made by these chloroplasts that we recognize as tomato flavor. 


Thus the secret to finding a good tasting tomato is to look for a ripe tomato with green shoulders.  A tomato that is uniformly red from pole to pole will probably disappoint you.





Powell AL, Nguyen CV, Hill T, Cheng KL, Figueroa-Balderas R, Aktas H, et al.

Uniform ripening encodes a Golden 2-like transcription factor regulating tomato fruit chloroplast development. Science. 2012 Jun 29;336(6089):1711-5.