How many times have you purchased a cantaloupe and cut it open, only to discover a watery and tasteless flesh? Or a tomato, or a peach? The list could go on and on, but it need not be that way. Produce quality can be measured, telling us how much nutrition and taste is available; it is easily done with a hand held device called a refractometer. A refractometer is an optical device that refracts (bends) light passing through a liquid. Refractometers will measure Brix (technically, they measure degrees Brix, written °Bx) which is the ratio of sugars (carbohydrates) to water in a liquid. Actually it is more complex than just sucrose being measured, but that basic information works here in an introduction to Brix.

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Place a drop of juice on the lens
Look through the refractometer
Read the scale

Example of using a Brix measurement: Suppose you find a new cantaloupe vendor who will a cut melon for you to take a taste. Squeeze that cut piece, put a drop of the melon juice on the handheld refractometer and look through it to the light. You will get a numerical reading of ºBx on the scale in the refractometer. Published Brix charts have values for many fruits and vegetables; cantaloupes measuring 8ºBx are Poor, 12ºBx are Average, 14ºBx are Good, and 16ºBx and above are Excellent. Chances are the tasteless, watery cantaloupe you bought last week measured far less than 12ºBx, and if this new vendor has some cantaloupes that measure 14ºBx or better, you will be in seventh heaven eating that melon. There is a direct correlation between Brix and taste… you CAN taste Brix! Your taste buds will not be able to tell you the Brix degree, but they will surely tell you whether there is any good taste or not. Nutritional values in foods can be measured, of course, but that requires sophisticated equipment and higher costs, plus time to get test results back. Brix readings are something you can do on the spot, and the literature is full of scientific reports of high-tech testing that correlate higher ºBx to more nutrition in the food.

What makes good Brix? Good soil. Soil that is high in the nutritional elements and the microbial activity needed for good plant growth will produce plants that are high in Brix, which in turn produce fruits and vegetables high in Brix. You cannot grow plants in poor soil and expect to produce 14ºBx vegetables and fruits.

Why do I even have a refractometer? When I moved here in the fall two years ago, there were some old grape vines and I decided I wanted to make wine. A pocket optical refractometer is used to test grapes and determine when to harvest them, by measuring the sugar levels in the grapes. Higher sugar equals more alcohol and flavor. So, I bought a basic Zeiss Pocket Refractometer on eBay for under $50. Newer refractometers are available with a built-in LED light, which could be quite useful. My refractometer cannot be calibrated, but I am familiar with the reputation Zeiss has for great optics and I don’t think for my garden use it’s necessary to calibrate to a hundreth of a degree. For testing fresh fruits and vegetables, the refractometer should measure from 0 to 32ºBx. Others are available with different scales for concentrates and thick liquids like molasses. Some refractometers automatically adjust for temperature; some are dust and/or waterproof, and some are digital.

My grapes turned out not to be good wine grapes, and I no longer want to make wine anyway, but I still had the refractometer. Then research opened a new door for me, showing that my refractometer would be ideal in my garden to measure the quality of the fruits and vegetables I grow. Last year I didn’t have much of a garden, so the refractometer remained unused until now.

A refractometer isn’t just useful for testing harvested crops; it is invaluable in testing during growth. Plants, as they grow, can be measured for ºBx, giving you time to add more amendments if needed before the plant even flowers, and if necessary, again long before the crop grows to maturity. This testing is best done in the morning after the sun has driven off the dew and warmed the plant for two hours or more. Take several youngish leaves (without thick stems) and crush them through a garlic press, dropping some juice on the lens of the refractometer. Close the cover plate and look through the eyepiece at a strong light like bright clear skies. Do not look directly at the sun, which can damage your eyes! You will see a dark line indicating the ºBx. The higher the Brix, the better.

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Refractometer lens cover closed
Squeezing leaves for a drop of juice
Refractometer with lens cover open

If the Brix is low, now is the time to side dress with compost, or a foliar spray of fish emulsion… or whatever your gardening practices dictate. I suggest you keep a chart of dates and measurements including harvest measurements, and what--if any--amendments you add. It will become very helpful data year after year.

Not all fruits and vegetables are listed on the charts, but you can sometimes select from the same family. For example, Brussels sprouts are not on most charts, but they are in the Brassica family like cabbage, which is on the charts. Most Brix charts are public domain and there is a link at the bottom of this article where you can download one. Keep in mind the Brix chart numbers were determined from a huge selection of fruits and vegetables, including those commercially grown with better properties for shipping and handling rather than taste and nutrition.

Yesterday I walked around what little is still growing in my garden this middle of September. I was aghast (and ashamed) that my few remaining 'Black Krim' tomatoes in straw bales only measured 4ºBx, which equals Poor. Obviously I didn’t feed them enough of the right things! In contrast, my 'Kentucky Wonder' green beans growing in composted soil measured 14ºBx where 12ºBx is "Excellent" for green beans. No wonder they tasted SO good! However, most of my other readings indicate a huge need to improve my soil for all future crops.

You can begin to test your homegrown produce, as well as store-bought. The grocery store pear I ate for breakfast this morning measured 10ºBx which is "average" for pears. It tasted only okay, but not what I would expect from “average”. I can only imagine how wonderful a pear testing “good” or “excellent” might taste! Keep a record comparing taste to Brix. Good Brix is like money in the bank!


Download a Brix Chart:

Video on Brix

Photo Credits:
Many Thanks to Rex Harrill for permission to use his graphic of the Brix scale as seen through a refractometer lens. I first learned of Brix testing for foods two or more years ago from his terrific efforts.
Savings Growth, #6992529, © Alex Slobodkin, Used by Permission
All other photos are by the author.