Brix reading predicts food flavor

Tuesday, January 1, 2008 | 5:12 p.m. CST; updated 5:53 a.m. CDT, Tuesday, July 22, 2008

A month of experimenting with the taste of foods and a refractometer has convinced my friends and me that a high Brix reading of plant juices does directly correlate with a satisfying, flavorful fruit or vegetable, and a low reading accurately predicts little flavor.

For the gardener, then, the message is clear: To grow the most satisfying produce, use gardening practices that grow high Brix foods.

And there all clarity and certainty ends.

There is a BrixTalk Yahoo group and a HighBrixGardens site on the Web, and there you will find enthusiastic discussions of various dimensions of “high Brix gardening.”

An instinctive aversion to “true believers” of any creed or code is perhaps making me a little more skeptical of Brix gardening potential than I ought be, but I am dedicated to flavor, above all things, from my garden and am always searching for ways to achieve it. So let us look a little further.

If you read last month’s column, you may recall that the Brix reading of a liquid, such as fruit juice, is the percentage of dissolved solids — these dissolved solids being almost entirely sucrose (glucose and fructose) — it contains. This measurement is very easy to get with a refractometer.

I am satisfied by direct experience that a high Brix reading goes with more satisfying taste and flavor. But I have been unable to find any peer-reviewed research that shows that higher Brix also means healthier food, a higher presence of minerals, longer storage and less appeal to destructive garden pests. All of these attributes are frequently asserted by high Brix adherents, referencing garden gospels they take from a now deceased Carey Reams, who may indeed have undertaken valid research in this unfamiliar (to me) field. I have not been able to find any citations of it. One claim, that high sugar, which can convert to alcohol that pests cannot metabolize, thus making high Brix plants unappealing to them, is interesting. Any or all of these claims could be true even if I am unable to find proof of it. I am personally satisfied that growing high Brix foods in my garden is a valid way to focus gardening practice to both a specific measurement of each crop that can be made, and, much more importantly, to improved taste.

Various strategies are applied by high Brix gardeners, among them foliar feeding of plants and the use of fish emulsions applied to the soil, along with the full use of compost and other standard good gardening practices, including, of course, reliable soil testing. Here these gardeners appear skeptical that standard testing of garden soil informs the gardener of what does surely matter most: plant-available nitrogen, phosphate, potash, calcium and then magnesium and other trace minerals. That is, the presence of these in your soil in appropriate amounts is not enough if, for whatever reasons, they are not plant-available; too low a soil pH is a familiar barrier to fertilizer availability, but a soil test always reveals this. Their further efforts, beginning with more refined soil testing, toward insuring availability seem to me useful, and you may learn more about this on the Web. I cannot help but wonder, however, if foliar feeding does anything more than increase the Brix reading in juices crushed from the leaves without necessarily making the fruiting produce any better. Best to try it and see, I suppose.

As I spent many largely interesting hours on the Web over this month of cold evenings, learning more of high Brix gardening, their goal of sufficient calcium in the plant impressed me most, for calcium follows right behind NPK and carbon in the spectrum of nutrients plants most need, being essential for the construction of cells and the development of root systems and growing points (meristems).

Many gardeners know, for example, that blossom end rot is a “disease” of insufficient calcium uptake, and thus we do at times in our gardens have evidence of calcium deficiency in a plant (not necessarily in the soil). One typically applies lime to increase soil calcium, but this is no free lunch. For one thing, lime is slow to become plant-available, and for another, lime alters pH. Too much lime can make soil too alkaline, creating a new problem while treating an old.

The significant point about calcium is that it has low mobility — it isn’t easily taken up by the plant, nor does it move around much in the plant to where it is needed. For this reason calcium deficiency will appear first in new upper growth of the plant — such as the tomato or pepper with blossom end rot. The short version of the calcium story is this: A plentiful supply of soil calcium is not enough unless the plant is itself constantly producing new root stems that grab the calcium for transport to new visible growth. This calcium must be in ionic form that plants can use immediately. Beyond this, calcium use in plant-available form is a focal point of the nexus of photosynthesis, soil structure and soil nutrient balance, including soil sodium, and more topics well beyond the limits of this column.

High Brix gardeners lean to the use of gypsum (calcium sulfate) to provide calcium. Gypsum has the additional advantages of supplying sulphur in the immediately available form of sulfate — an essential trace mineral especially used by garlic and onions — and, more importantly, gypsum does not alter soil pH. And the calcium in gypsum quickly dissolves with soil moisture into calcium ions that plants can use immediately, without waiting for soil acids to produce these ions from other calcium forms, such as lime. I am looking forward to seeing how calcium via gypsum shows itself in my garden this summer.

Dennis Sentilles, MU professor emeritus of mathematics, is a Missouri Master Gardener and a member of Katy Trail Slow Food International with a love for working outdoors and eating simply and well every day. He can be reached at

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