Every once in a while, five of us get together and do some blind tasting of rum. As part of this tasting, we try to evaluate the rum and place it into the category of sweet/dry and simple/complex. Describing how sweet a rum is compared to other rums can be quite tricky, so we talked about using a more scientific approach and measuring the amount of sugar in the rum. This would make it easier to classify where the rum fit into the overall picture.
Not so long after this discussion, Richard Seale from Foursquare distillery on Barbados, wrote some posts on Facebook about rum producers adding sugar to rum and not admitting to it. As part of the discussions that followed, a simple way of measuring the sugar content was described.
The method is as follows:
After fermentation and distillation, there are no sugar left in the rum. If you measure the alcohol level of the rum with a hydrometer/alcoholmeter. The measurement will be identical to the actual alcohol level of the rum. When sugar is added to the rum, the density of the rum changes, causing the measurement with the hydrometer/alcoholmeter to change as well (even though the alcohol content of the rum remains the same).
So knowing the real alcohol percentage of the rum (written on the label of the rum bottle) and the alcohol percentage measured with the hydrometer/alcoholmeter, it is possible to do a rough estimate calculation of how much sugar that has been added to the rum. According to EU law, the %abv listed on the label must be within a tolerance of +-0,3% ( http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31987L0250:EN:NOT )
Using some tables that describes the density of rum at different alcohol levels (% abv (Alcohol By Volume)) and another table that describes how the density changes as a function of how much sugar that's added in a water solution (measured in Brix), a map was created that maps sugar added in g/L (Lookup based on actual %abv and hydrometer/alcoholmeter measured %abv).
Note: The table for density change as a function of Brix level (sugar added) is not completely linear. In these calculations the assumption is made that the increase is linear within the brix range of 0 to 10. This is one of the reasons why the end result is a rough estimate. Also the table for density change is based on sugar in water solution and not sugar in alcohol/water solution.
Well then, what about aging in the barrel, that must add some compounds to the rum that will affect the hydrometer/alcoholmeter measurements. Yes, it does but according to Foursquare Distillery, this only contributes with a miniscule amount resulting in a misreading of up to 0,6% abv with the hydrometer depending on the amount of time the rum has been aged. The longer the aging, the more impact the wood extract and possible caramel will have on the measured number.
A question was also raised if aging the rum in sherry casks would have a larger impact on the measurements. Foursquare (Richard Seale) provided a calculation that included the size of the barrel, the amount of sherry left in the wood and the amount of sugar in the sherry. The conclusion was that the amount of sugar added to the rum from the sherry cask is also miniscule in the overall picture. So this would not have a large impact on the hydrometer/alcoholmeter measurements. Any misreading's on the hydrometer/alcoholmeter must be due to sugar added by the rum producer/blender.
So is it good or bad that the producers add sugar to the rum. Well, I guess that's up to each individual to make that decision. Some of the rums I really like, have sugar added to them. So why the lie about not adding sugar to the rum, when a simple hydrometer/alcoholmeter measurement can show that there clearly has been added sugar?
Why all the fuzz then?
If you take a cheap rum, not aged very long, add some caramel colour plus sugar, and market it as a premium rum. The consumers end up with a rum that's just sweet due to the sugar added and the underlying complex rum flavours are gone because its a young rum that's missing most of the aging process that will add complexity and smoothness to the rum. This will have an impact on the producers that spend a lot of effort/time and money in producing a premium quality rum.
Adding sugar to rum, is that bad then?
I would say it depends. if the producers use the sugar to adjust the flavour of a premium product, that's not a problem to me. At the end of the day, you still buy a premium product so there's a correlation between the money you pay and the product you get. My problem arises when you pay for a premium rum and in reality you buy a cheap rum that has been flavoured and coloured so it appears to be a premium rum. My concern is that these "premium" rums will push some of the other real premium rums out of the market, leaving behind fewer of the brands that I over time have come to appreciate more and more.