Building a House of Straw — With Brix!

Before I get into the meat of this issue I wanted to mention that, a couple of weeks ago, Purdue came out with a statement which basically supported a post that I had previously written – one where I stated that there’s not a lot of good evidence that using Roundup leads to sudden death syndrome in soybeans. Yeah me! Well, not really – that’s not the way science works. While it is nice that other scientists agree with my conclusion, that doesn’t mean that Round-up isn’t affecting soybeans – it just means that there’s no evidence of it right now. Science doesn’t stop because a few scientists agree.

Same with compost tea – Linda and I have both posted about compost tea and we agree that, at this point, there’s no reason to use it. But science doesn’t stop, and it wouldn’t be completely surprising if, someday, someone comes up with a compost tea type product which is actually reliably useful.

Now on to the flavor of the day! Brix. So, what is brix you ask? Brix is a measurement of solids in a water (usually these solids are sugars). It’s easy to test brix by using something called a refractometer which measure how light bends when it passes through a thin film of water. We use brix in foods to tell how sweet they are. We just take a little sample of sap or juice, put it on a refractometer and bang, we know about how much sugar we have (actually, as I mentioned earlier, any dissolved solid, not just sugar, can alter measurements, as can non-solids, like alcohol. But the dominant thing affecting the brix measurement is usually sugar content).

Though it isn’t exactly mainstream, there is something out there called brix based gardening. Basically, the goal of brix based gardening is to increase the brix of the food we eat. Increasing the brix means increasing the sugar. The theory is that the higher the brix of a food the better it is – in terms of taste, resistance to insects, resistance to disease, healthiness.  The list goes on and on.

The biggest problem with arguing that gardening based on brix is a bad idea is that there is a nugget of truth in brix based gardening. Moreso than compost tea (in my opinion), brix has proven itself useful in certain situations.  Particularly in wine making, brix is used to quantify the sugar content of your grapes so that you can predict the sweetness of the wine you will produce (it will also help tell what level of alcohol you’ll get). As time goes on at the end of the season grapes increase their sugar content, so grapes are picked according to when the brix is right for the wine you want to produce.  Another grain of truth is that with higher brix you’ll get less insect pressure. This stands to reason, at least to some extent, because insects are usually looking for nitrogen rather than sugar.

But along with the little grain of truth comes some BS. For example, the idea that eating a food with a higher brix reading means that you’re eating a healthier food is just silly. It just means that you’re eating a sweeter food. The idea that higher sugar levels mean a healthier plant is also silly. In fact, one of the most significant things which can make brix go up is putting the plant under drought stress. Under drought stress, with less water, the concentration of sugars in sap naturally increases (because there’s less water to dilute it). Raisins are sweeter than grapes! Furthermore, the variety of the plant which you grow has an extreme effect on brix. Chardonnay grapes may have a low brix (around 21), a late harvest Riesling may have a brix of 42!

I have seen an inordinate amount of gobbledygook about mixing different fertilizers to get the perfect ratio of nutrients to increase brix. First, it’s important to realize that fertilizers can alter sugar content. For example, fertilizing heavily with nitrogen will increase growth of the plant but will usually decrease sugar concentration (hence brix). Indeed, from what I’ve seen, nitrogen seems to be the biggest player in sugar content.

That said, calcium and phosphorus based fertilizers seem to be the favorites among brix based gardeners – but from what I can find research hasn’t actually shown that these fertilizers increase brix on anything approaching a reliable basis. Another common recommendation is a molasses based fertilizer – once again, research on molasses doesn’t seem to show that it can do much to increase brix. Honestly, it looks to me like those recommending high brix as necessarily a good thing for us and our plants and then offering methods to do it are putting a scientific veneer on witchcraft – at least until further research comes along. I am sure that those favoring brix-based gardening will disagree with me – if you do and you read this I would welcome seeing some published papers which support your claims.

12 thoughts on “Building a House of Straw — With Brix!”

  1. I see what you mean about a disquieting grain of truth. I think it’s accepted that plants are healthier (in growth and to eat) when they aren’t deluged with excess water and nitrogen, so striving towards that doesn’t seem like a bad goal, and it seems brix kinda-sorta measures that…but not completely. Very interesting. Thank you.

  2. The argument that higher brix always equals tastier food is suspect, too. Here in Virginia, we had a brutal summer in 2010 – many, many days over 90 degrees and little rain – and it had a huge impact on the harvest for vineyards. The average harvest was a good two months earlier than usual, because the brix of the grapes were off the charts. The concern wasn’t just the resulting sweetness or higher alcohol (depending on ferment), but the fact that as brix went up, pH went down. Winemakers had to get the fruit in or risk having to do a ton of manipulation with acids in the winery.

    Point being, too much sweetness at the expense of other flavors isn’t going to do food any favors either.

  3. We’ve been doing brix testing as part of our tomato variety trials and comparing with the subjective evaluations the public gives us in the blind tomato taste day and believe it or not, there’s only minimal correlation between high brix and high scores in our public taste tests.

  4. I agree with everything you said before and after this statement: “the idea that eating a food with a higher brix reading means that you’re eating a healthier food is just silly”. Consider that many antioxidants are long chains of 40-something carbons or carbon rings. Then consider that all this carbon originally formed in the plant as a simple 6 carbon sugar which is what we are measureing with a refractometer. It would make theoretical sense that, within the same cultivar, the more simple sugars the plant has, the more antioxidants the plant can create. The biochemical pathways go in that direction. To me it wouldn’t make sense that a plant grown in a manner that produced more simple sugars is going to form less antioxidants. Or that a fruit containing more antioxidents managed to do it with less simple sugar building blocks. The researchers haven’t proven this point yet, but I have talked with some PH.ds who certainly believe that to be the case. And it matches my observations that low brix fruit such as tomatoes and watermelons will have less antioxidants (you can tell this from the color because lycopene reflects red.)

  5. David, unfortunately plant biochemistry is not this straight forward. Simple sugars are often stored in fruit, because that attracts fruit-eaters which then disperse seeds. But in the rest of the plant, simple sugars may be transformed into more complex storage sugars such as raffinose and stachyose, and starches, or into structural carbohydrates like cellulose and pectins. Then there are all the other biochemicals (proteins, fats, nucleic acids, and so-called secondary compounds) that must be manufactured from carbohydrate precursors. Antioxidants are only one of many biochemicals that plants might manufacture with their “extra” sugar. Which of these compounds are produced depends on the demand of various plant tissues, the species, the life stage, environmental conditions, etc. etc. (If you want to blow your mind with the sheer number of different biochemicals plants manufacture, take a look at T. Robinson’s book “The Organic Constituents of Higher Plants.”)

  6. The scientific understanding might be off but that’s OK. The brix hoopla starts with concern with both conventional agricultural methods and conventional home landscape schemes that employ maximum water and nitrogen for the empty calories of green green lawns and maximum yealds of watery tasteless produce, both increasingly susceptible to insects and disease.

    The theories may be an oversimplification or even incorrect, but if it motivates people in the west to garden with less water and people everywhere to be more conservative with their use of nitrogen it’s not too bad.

    But this blog is about the scientific basis of garden practices and your article is a very nice contribution.

  7. Would this process also be contributing to the rise in diabetes in our culture? Seems to me that the amount of sugar we consume is very high & our health is poor. Eating vegetables should be a healthy thing, not contribute to a problem!

  8. Lynn, I don’t think sweeter fruit or vegetables has any causative affect on national health, although our hyper corn sweetened diet may alter our tastes for ever more sugary food. That may leave us craving for ever sweeter fruit as well. I strongly doubt that the piece of fruit Americans might eat in a day competes with their sugar drinks at every meal as a cause for epidemic diabetes.

    As far as high brix improving the flavor of produce, just because too much isn’t always better doesn’t mean people don’t generally prefer higher brix produce.

    I have no idea how those tomato trials came out as they did but in fruit breeding the trend is strongly to push up the brix to produce winners.

    The Zeigers and there many plum and apricot crosses have come on very strongly in commercial production because consumers love their off the charts brix levels- some of their pluots capable of surpassing 25%.

    High brix doesn’t always mean sweeter, however, as my favorite apple is Goldrush which has brix as high as Fuji (sometimes above 18%) but as grown in southeast NY is usually quite tart off the tree.

    I love apples with exceptionally high brix if there’s plenty of acid to go with that sugar. Around here, it is well understood that drought years produce the highest quality tree fruit whatever the woes of Virginia grape growers. They don’t eat their grapes!

  9. “For example, fertilizing heavily with nitrogen will increase growth of the plant but will usually decrease sugar concentration (hence brix). ”
    What is your source for this? Could this apply to citrus? The question, “How do I sweeten up the oranges on the tree?” comes up frequently on the radio show. The standard answer: leave the fruit on the tree longer, you impatient gardener.

  10. Fred, my source for this is probably from faulty information in popular literature or perhaps a faulty memory. I searched around for confirmation but found only research that indicated no relationship between N. fertilization and levels of soluble solids.

  11. Reference Linda’s reply to my previous comment. I wasn’t talking about different species. I specifically stated “within the same cultivar”. I can easily see how it wouldn’t hold true outside the same cultivar. It would seem to be a simple thing to study but I don’t find any research on it. I am not saying it is true, just objecting to the adjective “silly” when there is a reasonable theory of why it could be true.

  12. David, you know — I agree with you. I strongly doubt that higher brix would mean more antioxidants — and in fruits higher sugar does not usually correlate with higher antioxidants — but you’re right, I may have overstated — let’s go with unlikely instead.

Leave a Reply to Linda Chalker-Scott Cancel reply