Measuring Fruit & Vegetable Quality


This instrument is called a refractometer. When measuring fluids it gives us a way to measure the specific gravity of the fluid or the “weight” of all the complex elements that are within it.

This weight can be measured on different scales, for example on a scale called specific gravity (SG) or on another called Brix. Whether SG or Brix, the refractometer measures the same thing – the “weight” of the fluid,


Let’s say you place water in a cup. When a pencil is dipped into the water, the tip appears bent.  Now put concentrated sugar water into another cup and try the same thing. The tip of the pencil should appear even more bent. This is the phenomenon of light refraction.


Refractometers are measuring instruments in which this phenomenon of light refraction is put to practical use. They are based on the principal that as the density of a substance increases (e.g. when sugar or minerals are dissolved in water, or fruits, or vegetables), it’s refractive index rises proportionately.

The more concentrated a solution is with dissolved solids, the more the light will bend. A refractometer measures the degree the light has been bent. This is known as the angle of refraction. An index value has been established for each of these angles of refraction and this “refractive index” can be used to evaluate a given liquid.

The Brix scale, due to its flexibility of use among nearly every industry, is the most common scale found on refractometers today. The Brix scale is named after its inventor, the German scientist, Adolf Brix. It directly correlates to the Refractive Index (nD) scale and is calibrated to the number of grams of cane sugar (sucrose) contained in 100 ml. of water. Therefore the Brix reading equals actual sucrose concentration.

In the medical arena Brix is not used as a measurement scale but instead it would be specific gravity for testing the specific gravity of urine for example to note hydration levels among other things.

You can get a refractometer, such as the type we sell and use at Biomedx, that has both scales side by side.

Refractometers all work the same. Here is one sitting on the table with the prism cover lifted up.


If we took a drop of distilled water and dropped it on the prism glass, then closed the lid and held it up to the light to look inside at the scale, we would see a line at the 0 level (or if not we would calibrate our refractometer to make it read 0 with distilled water.)

Distilled water is devoid of mineral so with no mineral to add weight to the water, 0 is all we get.






Here is a look at the idea of what is going on inside. The example circle on the left is what the scale might look like with little mineral and on the right a lot more mineral. The line between blue and white raises or lowers on the scale depending on how much mineral is in the liquid you are testing. You see this when you look into the refractometer and focus the lens.

So the question is; where do we want the weight of the juice we squeeze out of our fruits and vegetables that we might be testing to be on the scale?

Answer; as high as possible.

When we look at soil, the better the mineral content, the microorganisms, the pH balance and the dynamics of polarity between anions and cations (negatively and positively charged ions) that are in the soil, the better the plant that grows in it will be able to pull up mineral. This makes for a stronger and healthier plant that is less prone to disease, bugs, and rot. And it makes much healthier food.

Here is another question; if you have two tomatoes in front of you, which is the better, healthier tomato? Is it the one that is bigger? Or redder? Or the one with the organic label?

Answer; you don’t know until you check the Brix. The one with the higher reading wins. You might be surprised. Just because a label says organic and you paid more money, it does not mean that the soil had what it needed or the farmer knew how to get the most mineral into the plant. It just means the produce qualified with the USDA to use the organic label.

With your handy dandy little refractometer, you can check out the quality of your fruits and vegetables. Squeeze out some juice (use a garlic press for drier types) and take a look. Here is a chart of the refractive index of various plants as originally developed by Dr. Carey Reams and how their measured Brix level might rank.


What are you shooting for? Good to Excellent.

Arden Anderson, in his text “Real Medicine, Real Health” explains it this way:

“Nutrient density means the quantity of nutrient per quantity of food. Typically, the USDA analyzes how many milligrams or how many micrograms of nutrients there are per 100 grams of food. With nutrient density, we want to increase the amount of nutrients-calcium, magnesium, selenium, chromium, iodine, whatever there might be-per 100 grams of that food. If you eat an apple and it is highly nutritious, highly nutrient dense, you get a lot more nutrients out of that single apple than if you pick up another apple which has half that nutrient density.”

When you look into your refractometer when making a measure, you see a distinct separation of color, white on the bottom and blue on top. Sometimes the line of demarcation is not sharp, but a little fuzzy or blurry or diffuse. This is thought to be related to a greater mix of minerals leading to more atom distribution, hence the fuzzy nature of the line. If it is a sharp line, it would be an indication of increased simple sugars alone and of less quality mineral. For a Brix reading of a fuzzy line you would read it in the middle. Usually the more blurry, the better the taste and overall quality.

A refractometer is a great tool to have in the health conscious kitchen.

And with a dual scale refractometer, you might find it also comes in handy to check and see what’s going on with your urine!

Is your SG (specific gravity) too high? Not drinking enough water, or maybe retaining too much mineral in your system leading to cardiovascular stress, or too catabolic?

Or is your SG too low? Drinking too much water, or maybe losing your mineral and fatigued, or too anabolic.

It’s a dual purpose tool, get a quick check on certain aspects of your produce, and other aspects of your own body’s health.