How to use a refractometer when growing grapes
Hi friends,
I hope you are having a wonderful week!
With this article, I want to reply to an email I received from Suzanna, one of the subscribers of My Grape Vine. Suzana became a member way back in 2007 when I first started the website and blog and established a great looking vineyard. Her question is about the use of a refractometer to determine the ripeness of grapes.
With the help of the Complete Grape Growing System, Suzana and her friends at St Mark’s Presbyterian Church will be collecting the fruit of their labor soon!
To listen to an interview with the ladies, just click on the link below
http://www.stmarkspresby.org/archive/032509_ladiesvine.html
Well done ladies!
Now, Suzana is thinking of buying a refractometer to help them determine the ripeness of their grapes, but she is not sure how to use this instrument.
Okay, so before I tell her how to use one, I am sure there are some readers that don’t know what a refractometer is and how it works.
A refractometer is an instrument that measures the amount of sugar in an aqueous solution. There are various models available on the market - from digital to the traditional analog one’s. It works on a basis of critical angle principle where light goes through a lens and prism, projecting a shadow on a glass reticle inside the instrument.
Without getting too technical - A sample of grape sap is pressed out on the prism and covered with the cover plate (the small perspex like thing on top of the refractometer).
VERY IMPORTANT: Ensure that there are no solids, like pips on the prism when you close the cover plate, otherwise it will break and you can throw away the refractometer.
The amount of sucrose in the sap, either reflects the light or pass it through the prism, and then shines the amount of light coming through on a scale inside refractometer.
IMPORTANT: Because temperature plays a big role in this process, it is advisable that you get a refractometer that automatically compensate for the difference in temperature. Although they are a bit more expensive, I really do recommend you get one of these. For those who buy from Amazon.com, here is a link where you can order yours online -
Hand Held Refractometer with Automatic Temperature Compensation
When looking through the eye-piece you will see a white and blue (some black) area on the scale. The line between these two areas on the scale is what the sugar contents of the sap is.
This scale is measured in Brix (°Bx)- 1 degree Brix corresponds to 1 gram of sucrose in 100 grams solution. In the picture below, the reading is just below 17 on the scale. This means that there are +- 17 grams of sucrose in every 100 grams of sap. In other words; the higher the number, the more sugar there is in the sap.
Now, the question is: At what Brix reading should I pick my grapes?
Mostly, it depends on what you will do with your grapes. For making wine, a reading of 22 and above is the best as this will ensure enough sugar for good fermentation and flavour. As for eating, I would say round about 17 to 19 degrees is more than enough.
The problem when waiting too long for the Brix reading to get higher, is that the berries become softer and loose it’s crispiness and chances of rotting becomes bigger as the sugar increase as well.
The old trustworthy method of tasting the grapes alongside using the refractometer, will help you decide when to pick your grapes.
I hope you enjoyed this article and you will now know how to use a refractometer.
Take care and enjoy the rest of the week.
Danie
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Suzana had some trouble with kids picking their grapes before they are ready. Here is a sign she put up in her vineyard - LOL 
Loved it …….
Tags: how do i grow muscudine grapes, best places to grow flame seedless grapes, grapes you can grow in ontario, how to grow grapes, growing grape vines
Dear Danie
I can not avoid my comment on your instructions of use of a refractometer
Never put any solid material on the glass of the refractometer.
any scratch will destroy the accuracy of measurment and the refractometer.
Also, the measurment os a single berry does not represent the sugar content of the grapes on a vine, and is meaningless.
for a single vine, take a plastic glass of about 200 ml and put at least 20 berries.
for a real vineyard take about five berries from each 6-7 vines up to about 200 ml.
crush the berries with a clean plastic rod or a clean wooden piece.
draw a little amount of the juice and put it on the glass without toucung the glass, and read the sugar concentration.
sincerely
Aharon Yerushalmi
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Helloo Danie
Thank you very much for such an informative topic. Refracometer can easily be handled.
Regards,
Mohammed
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If you know you have planted them to close, when is the earliest i can prune and move them? I didnt get a good crop this year, Thanks
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keith nahdee Reply:
July 29th, 2010 at 2:23 pm
My name isn’t Danny but I have a ‘partial answer’ to your question. I pruned mine in February and moved (transplanted) mine in early April and they are thriving. I don’t know if it is good to (move) them in the fall but I will try. Again, I am not Danny, but your vines probably won’t produce until their “second year” as mine did. Another thing when pruning Bill: When you prune in early spring make sure to cut only that part of the vine which is “pencil thickness” to about 10 inches. Shove this in the ground three inches and you will get a young vine that takes three years to produce. I did this with 80 cuttings in various parts of my yard and 15 started growing using this technique. You could also put these cuttings in water and they will start to sprout roots which can be put in a pot to grow until it is time to put them in the ground. I just started three years ago and the experiments continue, my crop is looking divine for just 3 years of loving care.
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This year in Southeastern Ontario, Canada we had two days of late spring “almost freezing rain” which killed my tiny grape clusters. They did not ‘rebound” but the pruned vines are doing extremely well (at least in my yard). That’s Mother Nature for you, always “throwing a curve at you”. Just a little reminder that we can’t always rely on any crops to produce under these conditions. One more thing, there are these ‘beatles’ with a shiny blackish green shell which are feasting on my young vines/leaves. I grab a jar and slowly, yet quickly push them in the jar with my fingertips (they won’t move if you ’sneak’ up on them) where they will die a slow death. Anyone else out there see these bugs, that’s it for today? Happy vining everyone!
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Danie,
Thank you so much for writing the article about refractometers. I was hoping you’d suggest a model under US$100, and you did! You answered all my questions.
Blessings,
Suzana Rockhold
St. Mark’s Centennial Vineyard
Lomita, CA
[Reply]
hi danny,
i’m living in a tropical country,(surinam— south america) i’ve only one grape plant, my questions is will this plant give me fruits?is is it possible to grow grapes in tropical countries?
is someone who has experiments growing grapes in a tropical country.
please, let me at my mail adress. gire…@hotmail.com
have nice day.
yours girdhari c.
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Hi Danie
Great blog on the refracometer,very simply wrote but very informative.
Originally from the wine capital of south africa, i have some knowledge of wine making.I now live in the U.k and am pasionate about growing and making wine.
Do you have any info on where and who to contact in the uk to study to degree level.
Great work
Regards
Ian Hardie
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Hi Danie
How are you?
I am not fine because my Grapes tree is seek. Maximam grapes Leaf are burn, but I dont know what can I do this protection?
Please Suggest me
Thanks
[Reply]
thanks danie, for the great info on how and what a refractometer,is and does. all is well here in tx really warm now. had my first clusters of grapes this year. hope to have bigger turn out next year. vines are this years plantings. thanks julie
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