How Much Caffeine Is In Coffee?
We examine how much caffeine, sugars, oils and acids are extracted in an espresso shot to better understand what a ristretto is, and how to capture the tastiest part of a coffee shot.
Google “What is ristretto?”
You will find a plethora of definitions for what a ristretto, in fact, is and the many opinions on the function of a ristretto circulating in coffee society, but from all of our digging only one thing can really be agreed upon by all members:
A ristretto is an espresso that has been restricted or limited in some way for the purpose of capturing the tastiest part of the shot, and leaving the bitterness behind.
The methods for restricting espresso, the reasons why those methods are chosen and the results they anecdotally produce are varied. As with our previous caffeine study, this variety of information led us to ask questions about the ristretto and explore those reasons more thoroughly.
To do this, we have had the continued privilege of working with the University of Newcastle’s Chemistry Department, including Dr Ian van Altena, and Dr Steve Beveridge (retired Associate Professor of Chemistry). With their help, we have analysed the rate of caffeine and TDS (Total Dissolved Solids like sugars, oils and acids) percentages being extracted over time in a 60ml double espresso to learn whether the methods outlined to produce a ristretto are achieving the desired goal.
The experiment was completed using three different types of coffee beans from different origins and different continents, including a Colombian, an Ethiopian and a Sumatran, and involved taking samples of the espresso as it dropped in 3-second intervals.
We discovered that caffeine drops consistently – really consistently – across all three origins, which is reflected in the TDS as well, with the highest concentration of caffeine and dissolved solids being extracted in the first 3 seconds.
The TDS percentage of the double espresso shot over time measured at the same intervals as the caffeine content and levels dropped in the same proportions as the caffeine as well.
This means that we are able to provide baristas and coffee drinkers with a concrete foundation to choose methods that get exactly what they want out of their ristretto.
But before we go deep into the data and science of the ristretto, let’s first answer the following questions:
- What is ristretto?
- How do we make one?
- Why do we make it that way?
What Is A Ristretto & Why Drink One?
The term ‘ristretto’ has become quite the coffee buzzword that some consumers and baristas feel signals a discerning palate and deeper knowledge of coffee, while others suffer debilitating eye-rolls at its mention.
Joe Le Mura, Accredited International World Syphonist Championship Judge and Product/Technical Manager at Bombora Coffee & Water Supplies, weighed in on this polarising topic for us. “The word ristretto means restricted. I drink them because I like the intensity, boldness and flavour profiles that it brings out in some single origins.”
Delicious as they may be when properly executed, there is a lot of confusion out there regarding how they should be made. “For me,” continues Le Mura, “I stick to the 1-1 water to coffee ratio. I run 22g VST baskets, I also like a longer extraction time, so I tend to find that sweet spot when tamping to keep the flow rate down enough for a slow run without it over extracting.” But there is no one right way to produce a ristretto, according to Le Mura, “It all comes down to personal preference as well as the baristas experience, skill level and knowledge.”
If there’s no single correct method, is it really that important to know? “Of course,” says Le Mura, “I think that, like variance in espressos during barista training, [baristas] should be taught the differences of what to look for, if a blend or origin that they are serving will suit [a ristretto]… There is a fine line between getting it right and wrong, more baristas need to learn how to ‘get it right’.”
In saying that, before we can get it right, we need to know how it’s done and the result of each method for flavour and caffeine intake.
How To Make A Ristretto
All the methods of making a ristretto – each purported to be the true version – produce different taste and caffeine outcomes. There might have at one stage been an ‘original’ ristretto, but the history of it has been lost over time. In saying that, we are of the opinion that it is time to embrace the variations of ristretto, each developed for their specific functions, rather than stay stuck on questions of origin.
After an immense amount of research and time spent determining the concept of a ristretto, we’ve concluded that there are THREE absolutely agreed upon and prevalent ways of making a ristretto. The first two are the more commercial version, which we’ve coined the Cut-Off Ristretto and the Selective Ristretto:
1) The Cut-off Ristretto:
To achieve a single or double ristretto, a basket is dosed normally and cut off before its natural endpoint (typically the halfway point of the espresso) either manually or automatically using the volume settings on your machine.
This is the most commercially practised version of the ristretto due to its simplicity and ability to be automated by a volumetrics espresso machine, but there are also some very compelling reasons why it is preferred.
What Does the Data Say: According to the results of our research, this version of the ristretto gives the best bang-for-buck on both caffeine content and flavour strength.
2) The Selective Ristretto:
To achieve a single or double ristretto, only the middle portion of the espresso shot is captured in the cup.
As the reader can imagine, this is a difficult method to make as the standard ristretto recipe in a high-volume commercial setting due to the undivided attention required by the barista. However, it is easily accommodated by request and there are certainly valid reasons for ordering it.
What Does the Data Say: Taking the middle section of the espresso provides an even distribution of caffeine and dissolved solids for a deliciously smooth flavour most people will enjoy, however, the total amount of caffeine and TDS is lower – much lower than the Cut-Off Ristretto. This means you could drink many more of them in a day without exceeding your comfortable caffeine intake. This type of ristretto would generally be drunk as is or black, but milk coffee drinkers may opt for this to lower their caffeine consumption.
The third method is a more individualised and varied method, more along the lines of what our friend Le Mura describes which we have coined the Syrupy Ristretto:
3) The Syrupy Ristretto:
The last method focuses on restricting water flow which is achieved by increasing the dose normally used for espresso, tamping a normal dose harder OR by using the normal dose but grinding the coffee finer. The result is a slower extraction and the shot is run for the same time frame an espresso shot would normally take (although there is the odd coffee lover like Le Mura who prefer a longer extraction as well as altering the dose, tamp or grind). This style of ristretto is similar to the Selective Ristretto in that it requires extra attention to produce and monitor, and is less likely to be the main method used commercially. This type of ristretto should be drunk as-is, without being mixed with milk or water, because the syrupy body of this ristretto is the main reason it’s produced this way. That being said, there are no rules with coffee – drink it how you like it!
What Does the Data Say: Based on our understanding from our previous caffeine study that espresso extracts more caffeine because of the restricted water flow, it is likely that increasing the restriction on water flow will result in a higher extraction rate of caffeine and dissolved solids (per mL) across the recorded intervals. In saying that, the Syrupy Ristretto is commonly run for the same time as a regular espresso, which means two things:
- A Syrupy Ristretto method produces a thick syrup-like drink with more body, a denser mouthfeel and punchy flavour that some coffee drinkers live for;
- It likely has a lower total caffeine and TDS content because it tends to be a much smaller drink, i.e. a double espresso is usually 60mL, the other ristretto methods can range between 20-40mL and the Syrupy Ristretto could be as little as 10mL depending on how slow the extraction is. The only instance this wouldn’t be the case is if, like some coffee drinkers like our friend Joe, you like a Syrupy Ristretto method AND a longer shot time, in which case you will likely end up with a higher total caffeine and TDS content than the other ristretto methods. However, without studying this method and its specific variables, we can only speculate.
Ristretto Data
The info graphs seen below show the research we have done to corroborate our ristretto claims. It should be acknowledged that the content claims made about the Syrupy Ristretto have not been formally tested, but are an educated hypothesis based on the data and trends we have analysed in both this study and previous ones.
The choice to examine a 60ml shot was based on the knowledge that most Australian cafes exclusively use double baskets to produce both 60ml and 30ml espresso shots. The single basket is no longer commonly in use. We used coffee beans from Columbia, Ethiopia and Sumatra, and a 21g dose of coffee each time, with the extraction time sitting around 28-31 seconds (inclusive of a pre-infusion time of 5-6 seconds).
The particle size of the grind differed between single origins, as each bean cuts differently through a grinder. As the 60ml shot poured, a sample was collected every 3 seconds and analysed for caffeine and TDS %. In this way, we are able to see how the concentrations change over time.
The total amount of caffeine for each single-origin double espresso and their average caffeine content can be seen in the graphs below.
We’ve also graphed the TDS (Total Dissolved Solids) percentage over time and compared to the average rate of caffeine extraction over time for comparison:
Conclusions
It’s comforting to know that our reasons for drinking a ristretto in different ways, depending on the desired outcome, are backed by science.
So whether you feel like a caffeine hit or are wanting to take it a little easier without sacrificing flavour, our graphs will help you see at what point during the espresso shot you should catch your brew.
We can see from the results that there is a slight uptick in caffeine towards the end of the 60ml shot, which does not correlate with the TDS value, but without further testing, it is difficult to make a statement on whether that trend continues. It may do or it could be a short burst of extra caffeine that may be connected to a breakdown in the coffee beans organic structure after being exposed to high heat and pressure and may taper off again after that.
It’s worth acknowledging that the ristretto is no magic bullet – not all coffee is going to perform better in a ristretto than as an espresso. An espresso extracted correctly should be a balanced cup of acidity, sweetness, body (oil) and bitterness.
Some coffee blends and origins will require a longer, less restricted extraction to produce that balance and may end up tasting sour or under-extracted when used to produce a ristretto. Whether you’re a ristretto drinker or not, it’s really all about experimenting with different coffee and different methods to find the beverage that makes you excited to drink it.
You can use our infographics above as a guide at home or in your café for which part of your espresso shot to catch for the type of ristretto you want to make.
To view the caffeine content of other brewing methods from our previous research on caffeine content, read our CAFFEINE STUDY
If you have questions or would like to request further information, email us: [email protected]
THANK YOU - Thanks to Dr Ian van Altena from the University of Newcastle's Chemistry department for assisting in analysing the data. Thanks to Dr Steve Beveridge, retired Associate Professor of Chemistry, for his assistance in designing and executing the experiment. Thanks to Ravelle King, Crema Coffee Garage's Cafe Support Manager, for acting as Project Manager and executing the experiment.
