Understanding Oechsle

Whilst understanding the definition of Oechsle (the number of grams over 1,000 that a litre of must weighs), I have been trying to understand what makes up those extra grams and how the interplay between sugar and acid works.

I’m hoping some of our resident experts like @Lars_Carlberg (part way through your book and really enjoying it) or others with a mix of technical and practical experience can help.

I presume the majority of the extra weight is made up of sugar and acid and that these vary from vintage to vintage.

If there is a low acid vintage (and hence less material in the must that is heavier than water), is the resulting must generally lower Oechsle or is there typically more sugar to make up the “missing” weight.

If that is the case, would you usually expect that higher acid vintages to have relatively higher Oechsles?

As you can tell, I’m fumbling for the right words here!

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Thanks, I’m glad you’re enjoying Mosel Wine.

I don’t really understand your question. You might be better off asking someone else to answer it.

Sorry for the delay. Most of the day, I work in the vineyards.

@Lars_Carlberg - I have added two simplified example tables below to try to illustrate my question. I have included only major components of the must and both tables give an Oechsle of 75. I’ve tried to set the acid levels to be indicative of a cold vintage vs a hot vintage. I have seen @Robert_Panzer post a bit about tartaric and malic acid so maybe you could help?

Assuming the table makes sense, the hot vintage would have about 6.5g more sugar per litre of must. My question is really about what options are available to the winemaker in a hot vintage? I presume those are:

  1. Pick earlier while malic acid levels are higher and sugar is lower
  2. Make a final wine with lower acid and higher residual sugar
  3. Longer fermentation which means the wine will have higher alcohol, lower acid and lower residual sugar

Cold vintage

Material g/cm3 grams volume
Sucrose 1.59 97 61.0
Glucose 1.54 96 62.3
Tartaric acid 1.79 6.5 3.6
Malic acid 1.59 6.5 4.1
Citric acid 1.66 0.2 0.1
Water 1 868.8 868.8
Total 1075.0 1000.0
Total sugar 193 123.3
Total acid 13.2 7.8

Hot vintage

Material g/cm3 grams volume
Sucrose 1.59 101 63.5
Glucose 1.54 98.5 64.0
Tartaric acid 1.79 4.5 2.5
Malic acid 1.59 2.5 1.6
Citric acid 1.66 0.2 0.1
Water 1 868.3 868.3
Total 1075.0 1000.0
Total sugar 199.5 127.5
Total acid 7.2 4.2
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Thanks for the tables. All three options make sense.

I’ve spent a lot of time analyzing musts and wines for their respective components, and densities (of which Oechsle is a direct description), and your tables, while not quite right in the details, essentially illustrate the point: the density difference between two musts can be assumed to be almost purely a result of sugar differences.

Ripeness is not determined only by sugar content, so the biggest difference in a hot vs cold vintages is the sugar content of the grapes when they are picked. Total acid may vary by a few g/L, but total sugar can vary by tens of g/L.

Really helpful, thanks Ben. If the sugar vs acid ratios in my table (as you’ve pointed out, they’re wrong but demonstrate the point) are in the vicinity, the extra sugar in the warm year would be ballpark 0.5% extra alcohol (assuming 17g of sugar to 1% alcohol) if fermented.

As an interesting observation, I was drinking a 2021 Dönnhoff Hermannshöhle Spätlese, 2021 Max Kilburg Ohligsberg Spätlese and 2021 Falkenstein Niedermenniger Herrenberg Spätlese (Palm) over the past week, as noted the Dönnhoff and Kilburg were 8% and the noticeably steelier Falkenstein was 9%.

Another factor that’s important is the yield. In 2021, the Webers of Hofgut Falkenstein could pick fully ripe grapes earlier than many other growers who have much higher yields per vine. That’s also why some of these growers had extremely low must weights even when they harvested their grapes late. A number of producers chaptalized their wines, including high-end GGs.

As for the difference in alcohol, the 2021 Herrenberg Spätlese Palm has about 30 g/l residual sugar, whereas the 2021 Ohligsberg and 2021 Hermannshöhle probably have higher residual sugar. We would need to know the ripeness and residual sugar levels for these three wines to compare them.

According to MFW, the 2021 Kilburg Ohligsberg was harvested at 85 degrees Oechsle and had 65g of residual sugar, so the relative flavour profiles make sense. I haven’t been able to find info on the much sweeter and less acidic Hermannshohle. Could you let us know the Oechsle of the Palm?

The Palm had outstanding structure and persistence with its sweet and sour fruit. I thought it needed a lot of air (the bottle held up very well in the fridge over a couple of weeks) to show its best.

The Ohligsberg was my first Spatlese from Max and another positive sign of where he is heading. Dense, dark and brooding.

The Donnhoff went between looking simple, sweet and clumsy to then having fantastic red toffee apple and orange mouth perfume.

Re chaptalization in 2021, which I presume is a touchy subject, is there any way for consumers to find out who did what?

The legal minimum must weight for Mosel Riesling Spätlese is 80 degrees Oechsle, which is very low. With the exception of 2021, most Mosel Riesling Kabinetts are above 80 degrees Oechsle. The 2021 Palm was harvested at 85 degrees Oechsle. This indicates that Max Kilburg has higher yields than Hofgut Falkenstein. My guess is that he has two canes per vine, whereas the Webers have one cane per vine.

Any wine with a Prädikat (Kabinett, Spätlese, Auslese) has no sugar added. Otherwise, there’s really no way to know. But, in 2021, a dry non-Prädikat Mosel wine with over 11 percent alcohol has surely been chaptalized.

Apologies, I have corrected to 85 degrees Oechsle and 65g residual sugar.

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No problem. That makes more sense based on your tasting note.