Is anyone still wondering if any two vegetables are created equal? In 2013 International Ag Labs conducted a competition to see who could grow the best Butternut Squash, and the data is openly available. For each fruit that was submitted we can see a nutrient analysis and a Brix reading. I was able to copy the data into a spreadsheet and pulled out some interesting information.
First, lets look at the Brix readings. Let us assume that a low Brix value is bad, and a high Brix value is good in this way:
6 - Poor 8 - Average 12 - Good 14 - Excellent
If we then sort the available data by Brix, lowest to highest, we have a graph that looks like this:
If we can now apply the same scale as established above but instead graph out the various mineral nutrients from the data, we find that:
There does seem to be a correlation between Brix and mineral nutrients.
In the 1953 Yearbook of Agriculture (USDA), it is proclaimed that the “Lack of fertilizer may reduce the yield of a crop, but not the amount of nutrients in the food produced.” In essence, they’re saying that a Squash is a Squash is a Squash.
For the testing of these squash, 100 gram samples of each fruit are taken and scientifically dried. Once all the water has been removed, the leftover material is carefully weighed and we have what’s called the Dry Matter, the sum of all the material of the plant: minerals, proteins, lipids, etc. More dry matter means more nutrients. If it is as the USDA say’s it is, and a Squash is a Squash is a Squash, then all samples should be equal. Lets see what the graph says.
As Brix increase there is a doubling of the Dry Matter!
If you have been looking carefully at the charts, you will see some variations in the data. The sample to the very right serves as a good example of this. In a detailed explanation of the results, Jon Frank of IAL says that particular variety was called Honeynut and “it was genetically patterned to make more sugars but it didn’t back it up with more minerals.” This exposes itself to us with its high Brix value but a lesser Nutrient profile. A lot of factors come into play to produce a nutrient dense product, and in this particular case it appears that the selected variety is genetically predisposed to be higher in sugars, thus giving a strong Brix reading. This means that relying solely upon Brix by itself is not a sure fire way to identify a top of class product, although it is a very strong indicator.
There are two more bits of information in our data we haven’t looked at yet and that’s the Protein content and the Free Nitrates. Here they are:
What is the significance of this? Reviewing the Nitrates chart, notice that the first half of the graph the free Nitrates (Nitrogen) are very high and erratic, but then stabilize in the middle. Now look at the peaks and valley’s in both charts, there is a matching pattern in there, again more so on the first half of the graph while the Brix is still low. Nitrogen and Protein relate, and this takes us to our first small lesson on plant physiology.
Nitrogen is a required element for protein construction. A sick plant however doesn’t do a good job of this, and the protein synthesis can fail at any point. This can give you a large number of partially completed proteins, the degenerative kind that are unstable and decay rapidly, leaving a lot of extra Nitrogen floating around inside the plant. At the same time, all farmers and gardeners know that in order to get lots of green leafy growth you should add lots of Nitrogen, making an already bad situation worse. Further, in the laboratory setting when the Protein content is analyzed, it’s only tested for crude protein, and that’s only done by adding up all the Nitrogen found. What it does not tell us is how much functional protein is actually in the plant. Look at that last chart again, and drop the protein content even further downwards on the left side, because the free nitrogen is excessive and the proteins are not any good.
For gardeners, there’s no need to send a plant sample to the laboratory for an expensive count of the Protein and Nitrogen, just test your Brix and look for Aphids instead. These little bugs, and other sap-sucking insects, have a digestive system specially designed for processing low sugar sap and incomplete proteins. The excessive Nitrogen then becomes a signal to the insect, one that can be detected at a distance, and says “I am a plant in poor health, come eat me.” If however the Aphid inadvertently feeds upon the sap of a healthy plant, the high sugar and complete proteins can actually kill the poor little bug. Thus not only is a healthy plant more difficult for Aphids to identify, but the plant can effectively protect itself from attack. The digestive system of insects does not work the same as they do in animals, who obtain health from consuming healthy plants and illness consuming sick one.
One more small tidbit about identifying nutrient dense food. Some people can get a digestive upset consuming salad lettuce, my wife being one of them. This can be due to the presence of excessive free nitrates in the lettuce leaf. The farmer, organic or not, is spreading the nitrogen thick on these crops to get good leaf growth as rapidly as possible to take to market. Your lettuce should never give you a stomach ache, it should always be very crisp and free of decay, and should last for many months in the refrigerator.
Brix testing is one of the most powerful tools you can use to measure both the health of your plants, and the quality of your food. As you saw here, there are some pitfalls to be aware of, but that’s for another day. For now, get a refractometer.