Frogsleap Farm

Frogsleap Farm

Thursday, April 7, 2011

Building with Brix

Although tomato fanatics will argue on relative taste of various tomato varieties, it is generally recognized that there are three major components to taste in tomatoes: sugar content, acidity, and volatile flavor compounds (reference).  The right balance of sweetness and acidity is crucial, but generally higher sugar content makes  for better tasting tomatoes (reference). Sugars are the predominant component of soluble solids in tomatoes.  Soluble solids content (Brix units) is easily measured with a hand held refractometer. 

Brix level in most tomato varieties varies between 4-6%, with popular cherry hybrids like SunGold and Sweet Million being notably higher.  To boost soluble solids content in tomatoes, breeders have recently incorporated genes from wild relatives.  This has resulted in a new generation of super sweet tomato hybrid cherry and grape types with reported >10% Brix.  Many of these new hybrids also contain the rin gene for longer shelf life, and have improved resistance to fruit cracking.  Seed for most of these is only available to commercial growers, so thanks to my various Tomatoville friends for helping us to access seed this winter.

This summer we are growing out F1 and/or F2 generation plants of several new super sweet grape/mini-plum hybrids for crossing to our best striped cherries, saladettes, plums, hearts and beefsteak types.  We hope to incorporate higher Brix, longer shelf life and improved disease resistance from the commercial hybrids to our “heirloom derived” breeding lines.
TGRC photo
A particular TGRC accession of S. galapagense (L.cheesmanii minor) from the Galapagos Islands has been reportedly widely used as a breeding source for high soluble solids.  In this research study (publication link) LA530 tips the scales at 13% Brix, more than double any of the commercial cultivar checks.  We are also growing this beast this summer, probably making a few crosses, but mostly out of curiosity.  Note the strikingly different fruit type.  Seedling vigor is also unique, and not in a good way.  An interesting side note is that LA530 also has high salt tolerance and under salty conditions gets even a little sweeter!

Taste is not all about Brix, but we are betting high Brix is a good building block for improved flavor (pun intended).  We should have F2 populations from these new crosses to taste test in 2012.