How Is Coffee Decaffeinated? Is Decaf Safe To Drink Regularly?

What is Decaffeinated Coffee?

Decaffeinated coffee, regularly called decaf coffee, is coffee with most of the caffeine content removed. Decaf coffees generally have 97-99% of the caffeine removed. Both regular and decaffeinated coffee are produced from seeds from Coffea plant fruits. These seeds are what we know as coffee beans, and at this stage, the seeds naturally contain caffeine, which is present to deter insects. Before they are processed and roasted, the coffee beans are green and hard in texture. To remove the caffeine, specialist companies are usually used, as the process requires complex chemistry and equipment. [1]

Decaffeinated coffees have traditionally lacked the same flavour profile as a regular coffee. This is because the roasting of the coffee beans plays a key role in determining the final taste and chemical constitution of the final drink, and decaffeinated beans are not easy to roast properly.

Another reason for the taste difference is because the taste of a coffee is determined by the balance of many hundreds of different compounds in the drink. The decaffeination methods extract the caffeine, but depending on the process used, some of the aromatic compounds can also be removed in the process. Various decaffeination processes have been developed to attempt to improve the quality of the coffee produced.

When Should You Drink Decaf Coffee?

The demand for decaffeinated coffee has been increasing in recent years, with many people finding that the caffeine in regular coffee can lead to jittery feelings and difficulty in sleeping. Caffeine consumption even 6 hours before bedtime can have important disruptive effects on both objective and subjective measures of sleep. Heart palpitations can also be triggered by regular coffees when large quantities are consumed or in individuals particularly sensitive to caffeine. [2] [3]

Decaffeinated coffees are also a good option for expectant mothers, who should avoid drinking caffeinated beverages when pregnant. The consumption of caffeine has been associated with adverse gestational outcomes. It has been found that ‘caffeine exposure during sensitive windows of pregnancy may induce epigenetic changes in the developing foetus to cause adult-onset diseases in subsequent generations’. [4]

Some people find that regular coffees trigger the onset of heartburn or acid reflux. Decaf coffees can present a solution to this problem, as they have been found to be significantly less likely to trigger gastro-oesophageal reflux than a caffeinated coffee. [5]

How is Decaf Coffee Decaffeinated?

There are many methods used to decaffeinate coffee in the modern world. Coffee can be decaffeinated by using solvents, pressurised carbon dioxide, or even just using water and a carbon filter. All these methods result in a slightly different flavour, and there are significant cost differences associated with each one. All of the methods of decaffeination use unroasted green coffee beans, as decaffeination processes applied to coffee beans that are already roasted tend to ruin the final product. The four main methods currently used to decaffeinate coffee are the direct solvent method, the indirect solvent method, the water process, and the supercritical CO2 method.

The first commercially successful decaffeination method was invented around 1905, by German coffee merchant Ludwig Roselius. Two years prior, is is said that a shipment of coffee beans had been submerged in seawater during transit. The seawater had the effect of leaching out the caffeine, yet the final product apparently still retained it’s flavour. Regardless of whether this event is fact or fiction, coffee decaffeination took hold, and has grown into a complex and specialised industry in the modern world.

During the first half of the 20th centuary, Roselius’s company used the solvent benzene to create his companies decaf coffee on a commercial scale. After major health concerns surrounding benzene became apparent, this was replaced with a variety of safer methods. We will now look at the four most commonly used methods as the industry stands today.

You can view a short summary of the situation in our video here, or continue reading to learn about each process in more detail.

Decaffeinating Coffee Using Solvents

The most common method used to decaffeinate coffee is to use solvents such as ethyl acetate, a natural fruit ether usually made from acetic acid, or the industrial solvent methylene chloride. Both of these solvents are able to draw the caffeine out of the beans, and into the water medium. These solvents can be applied either directly to the beans, or indirectly through a separate tank. Let’s quickly have a look at the difference between these two methods.

Direct Solvent Method

The direct application method is perhaps the easiest and cheapest way of decaffeinating coffee. To begin, hard green coffee beans are initially soaked in hot water, with the temperature of the water just below boiling point. This soaking softens the beans and makes them spongey. Next, the beans are rinsed continuously with a solution containing one of the two solvents for 10-12 hours. The soft and spongey beans absorb the solvents, which draws the caffeine out of them. Once this step is complete, the beans are rinsed with clean water to remove the solvent. After this hosedown with water, they are left to dry, and the end result is decaf coffee beans ready to be roasted.

Unfortunately, this method is heavy handed in removing aromatic and flavour compounds from the beans. Coffees processed in this way tend to have a poorer taste, and are lower in the beneficial antioxidants and flavonoids that a regular coffee contains.

The rinsing process also rarely removes 100% of the solvent used, as the long exposure to the solvents allows them to penetrate deeply in to the beans. This is a big issue when the solvent used is methylene chloride.

Indirect Solvent Method

The indirect solvent process is named as such because the solvents do not come into contact with the beans in this method. It requires a few more steps, but similarly begins with the beans being being soaked in hot water. In the indirect method, this is done to extract the caffeine out of the beans and into the water medium, as caffeine is water soluble.

The caffeine and various compounds, are all separated from the coffee beans and moved to a holding tank. The isolated concentrate in this tank can then be mixed with a solvent solution, allowing the caffeine to bond to the solvent. The mixture is then heated, evaporating the caffeine and solvent together.

After the caffeine and the solvent have been removed, the beans are reintroduced to the concentrate in an attempt to restore the many compounds lost in the extraction process. As a result, the indirect solvent method tends to retain more flavour than the direct method, and generally produces a higher quality coffee than the direct application, because the beans are essentially soaked in a concentrated coffee essence. It is also seen as a healthier option as the solvent used is less likely to become deeply absorbed into the beans, and therefore is less likely to end up in your morning coffee.

To understand why both the direct and indirect solvent decaffeination methods may be a less than ideal choice for the consumer, we should take a closer look at the two most common solvents used in coffee decaffeination.

Solvents Used In Decaffeinating Coffee

Methylene Chloride

The chemical structure of methylene chloride allows it to bond with caffeine. This feature of chemistry has led to it’s use as a replacement for benzene in commercial decaffeination techniques.

Decaffeinating coffee with solvents is a low cost option for the manufacturers, but the use of Methylene chloride makes this process undesirable for consumers. Methylene chloride is an industrial solvent used in commercial paint strippers and degreasing agents, and is highly toxic to human health. [6]

Although manufacturers are held to strict limits about how much methylene chloride can be present in the final coffee product, it nonetheless remains a valid health concern. In 2023 however, the process is still used, and coffee companies are not legally required to state on the label whether or not methylene chloride was used to create the product.

Ethyl Acetate

Due to the fact that it is derived naturally from microbes in acetic acid, coffees decaffeinated using ethyl acetate are often marketed as being ‘naturally decaffeinated’. As we have discussed, coffee beans naturally contain caffeine, so this terminology is vague at best, and deliberately misleading at worst.

That said, ethyl acetate is a superior solvent to use when compared to methylene chloride. Furthermore, most of the ethyl acetate remaining in the coffee should be evaporated off by the boiling and roasting processes. However, poor manufacturing processes may lead to some of this solvent remaining in the final product.

For this reason we should take a look at a 2023 study to discern the toxicity profile of ethyl acetate, in which concentrations of around 400 ppm were given to volunteers. It was found that ethyl acetate was rapidly absorbed where enzymes called carboxyesterases converted it into ethanol. Most volunteers experienced mild irritation for 4-8 hours, but no lasting effects. [7]

Decaffeinating Coffee Using A Water Process

There are also methods that have been devised that only use water. The most famous of these processes is the Swiss Water Process, which since it’s first use in the 1970s, has grown into a trademarked brand and a name that is famous in the coffee industry. Whilst the Swiss Water Process is perhaps the best known method of decaffeination using water, it is not the only game in town. Other methods exist, including the French Water process.

In the Swiss Water Process, a batch of green coffee beans is first cleaned and then soaked in hot water. Much as in the indirect solvent method, this water medium becomes saturated with water soluble components found in coffee, including caffeine. Instead of using a solvent however, in this process, the caffeine is filtered out with an active carbon filter. This filtering creates a caffeine free liquid that is mostly water, but retains a strong flavour profile. This completes step one of the process.

For the second step, new green coffee beans are once again cleaned and soaked. At this stage, these new coffee beans still have caffeine in them. These beans are submerged in the ‘flavour charged’ water from step one. When mixed in this way, physics dictates that the beans and green coffee extract seek an equilibrium, and the imbalance causes the caffeine in the beans beans to diffuse out into the water.

Importantly, because the compounds responsible for flavour are already in the water, no such imbalance exists for these compounds. With no imbalance, there is therefore minimal diffusion of flavour compounds from the beans.

This water then passes through the active carbon filter, again removing the caffeine, and a partial evaporation takes place. With the caffeine removed from the water, it can cycle back around and draw even more caffeine out of the beans. This process cycles and repeats for around eight hours, until the beans are up to 99.9% caffeine free. The beans are then dried and cleaned, and the process is complete.

The French water process is similar to this, though uses coffee solids in the water medium to retain the closest possible profile to the original coffee bean. The differences between the two can be seen in the diagram above.

The advantages of decaffeination using a water process are numerous. Most people tend to find decaf coffees made with this method to be much better in flavour than those created using solvents, as the flavourings are retained during the mixing process.

Another significant advantage of this method is that it completely avoids the use of chemical solvents, producing a cleaner and healthier final product. For these reasons, companies that sell decaf coffee made using this technique often proudly display this fact on their label.

Decaffeinating Coffee Using Supercritical Carbon Dioxide (CO2)

In the first step of the process, coffee beans are moistened in a pressure tank using hot water and steam, resulting in the coffee beans swelling up. In a separate tank, carbon dioxide (CO2) is brought to a supercritical state – meaning it has the low viscosity of a gas, yet also has the high density of a liquid. To achieve this, carbon dioxide is heated to 70°C, and is highly pressurised with 162 bars of pressure (2350 psi) – a higher pressure than the primary loop of a nuclear reactor! The CO2 is then pumped through a water bath, before passing through to the coffee beans. This liquid acts as a selective solvent, and draws the caffeine out of the beans.

In the next step of the process, the supercritical carbon dioxide is cooled to 25°C, and the pressure is lowered, resulting in the CO2 turning back into a liquid. In this liquid state, it is run through an activated carbon filter, which captures the caffeine. At this point, the process is nearly complete, but the coffee beans are wet and need to be dried.

In the final step, dry supercritical carbon dioxide flows through the mixture, absorbing the moisture from the beans and completing the process. After it passes through the filter, many modern devices recycle the clean CO2, which can be pumped back in to the high pressure tank and the cycle can repeat.

This method was developed almost by chance by a scientist called Kurt Zosel, who noticed in 1967 that caffeine dissolved in supercritical carbon dioxide. After working further on the matter, in 1970 his “coffee decaffeination process” was registered with the patent office. This is the latest method in the decaffeination industry, but also requires the largest capital investment due to the machinery used. Kraft Foods are known to use this method, and in a strange synchronicity, their decaffeination plant stands on the same site used by Roselius’s old company.

Not only does this method eliminate the use of potentially harmful solvents, but it may also positively impact the coffee’s chemical profile. Decaffeinating Coffee Using supercritical Carbon Dioxide has been found to produce compounds called melanoidins. Melanoidins are brown polymers that are formed by the combination of sugars and amino acids, and are responsible for the brown colouration of a coffee bean.

Interestingly, the melanoidins produced using the supercritical CO2 method are unique to the process, and possess biological properties distinct from those formed during the regular roasting process. Interestingly, the melanoidins created in this process appear to have anti-inflammatory properties. [10]

The supercritical CO2 process is the most high tech process, and with that comes an increased cost. The decaf coffee beans produced in this way are said to be of the best flavour when compared to the alternatives, and research suggests it may provide best outcome in terms of preserving the beneficial compounds in the beans. However, due to it’s high cost in building and running the facilities, this method is not commonly used. With increasing consumer demand for high quality decaf coffee, and an increased awareness of the downsides of other processes, the supercritical CO2 technique may be the future star of the industry. [11]

How Much Caffeine is in Decaf Coffee?

The final volume of caffeine in a decaf coffee very much depends on the decaffeination process used. Decaffeination using solvents generally removes around 97% of the caffeine content from the coffee, and these coffee beans are used primarily in cheaper decaf coffee brands. Supercritical CO2 and Water processes are reported to remove up to 99.9% of the caffeine from the beans, though results in a more expensive final product. Regardless of the method used, it is certain that some caffeine ends makes it into the final beverage, with the average 240ml cup of decaf coffee containing around 2-15 milligrams of caffeine.

This is considerably lower than a standard coffee, which contain around 80-100 mg of caffeine for the same 240ml serving.

How Much Caffeine Should People Consume per Day?

In 2015, the European Food Safety Authority published a report stating that caffeine intake of up to 400mg per day is generally considered to be within safe range. However, it is best to avoid doses of above 200mg at one time. Having more than 200mg in one sitting is more likely to produce some of the unpleasant effects of caffeine intake, such as headaches, feelings of anxiety, or heart palpitations. By spreading out caffeine consumption through the course of a day, these side effects are far less likely, and you are also less likely to experience a ‘caffeine crash.’ [12]

However, with many high caffeine coffees on the market, avoiding high doses of caffeine may be easier said than done for coffee drinkers. For context, we should compare these recommended daily values with the caffeine content in popular UK coffee shops.

Caffeine Content In Popular UK High Street Coffees

Brand	Single Shot Espresso	Cappuccino	Filter / Brewed Coffee
Caffè Nero	45mg	110-115mg	N/A
Costa Signature Blend	100mg	325mg	N/A
Greggs	75mg	197mg	225mg
Pret	180mg	180mg	271mg
Starbucks	33mg	66mg	102mg

Data From: Which? [13]

When we consider that a medium cappuccino (362ml) from Costa contains 325mg caffeine, it becomes clear that just one cup will far surpass the recommendations for caffeine intake in a single sitting, and nearly reach the recommended value for the whole day! Decaf coffees can therefore play a role in allowing coffee lovers to keep caffeine consumption within the recommended limit.

Does Decaf Coffee Have Health Benefits?

Whilst caffeine is the most famous of the compounds in the drink, regular coffee isn’t just a hot, flavoured caffeine solution. In actuality, coffee is highly rich in polyphenols and flavonoids, and contains over 2000 different compounds! Among these compounds are, quercetin, quinic acid, caffeic acid, and ferulic acid. These compounds are much of the reason that coffee consumption has been associated with reductions in the risk in the development of several chronic diseases. Many of these compounds are potent antioxdants, and also responsible for coffee’s amazing ability to reduce the absorption of mercury from fish and seafood meals. [14] [15]

Two of these compounds, quinic acid and caffeic acid are able to form an ester together, to create Chlorogenic acid (CGA), which constitutes a major polyphenol in coffee. Chlorogenic acid and its derivatives (CGAs) account for approximately 3% of the roasted coffee powder, and a single cup of coffee contains 20–675 mg of CGAs. [16] [17] [18]

Chlorogenic acid reacts with saliva in the mouth and various chemicals in the stomach to produce a variety of secondary compounds. CGAs have been linked with numerous health benefits, and studies have revealed that CGAs show protective effects against various toxins and metals. [19] [20]

Upon ingestion, both caffeic acid and chlorogenic acid form “an intricate antioxidant network” with glutathione, and the compounds work together scavenging free radicals and toxins. Interestingly, research also suggests that coffee consumption can increase the levels of glutathione present in the body. [21] [22]

There has been much research in to the benefits that caffeine can provide to the mind and cognition. However, it is not only caffeine in coffee that helps to produce these effects. Indeed, research has found that even decaffeinated coffee can produce feelings of increased alertness. [23]

Decaf coffee may be able to provide the same long term benefits to the mind that a conventional coffee does. The flavonoid Quercetin is thought to play a major role in the neuroprotective benefits of coffee, and . Can provide long term protection against degenerative neurological diseases such as Parkinson’s Disease and Alzheimers Dementia. It has been found that quercetin is potentially the most potent anti-inflammatory and neuroprotective component of coffee. In addition, quercetin has antioxidative properties, but caffeine does not. [24]

Both regular and decaf coffee are linked with lower diabetes risk in a dose-response manner. Coffee consumption is associated with widespread metabolic changes, among which lipid metabolites may be critical for the anti-diabetes benefit of coffee. [25]

Is Decaf Coffee Safe to Drink Regularly?

Whilst the many beneficial compounds in decaffeinated coffee may have you rushing to the kitchen to put the kettle on, we should first discuss the situations in which decaf coffee should be limited. As we discussed earlier in this article, cheap decaf coffees are sometimes decaffeinated using solvents, with methylene chloride being used in many cheap brands. Legally, coffee can contain no more than 10 parts per million of methylene chloride after decaffeination. However, brands are not currently legally compelled to state on the labels whether or not they have used methylene chloride during the production process, and “quantifiable amounts” of the solvent have been detected in many popular brands.

A 2019 report by the Clean Label Project analysed many of the leading decaf coffee brands. Disturbingly, methylene chloride was detected in 10 of the brands tested, including AmazonFresh, Keurig Green Mountain, and Maxwell House. The Clean Label Project opened up lawsuits against these companies for deceptive advertising, as many of these products were labelled as ‘Pure’. This event has a strange echo of the original decaf coffee, which Ludwig Roselius advertised as “Always harmless! Always wholesome!” despite it containing benzene from the extraction process.

It should be noted that methylene chloride is so highly toxic that the EPA has recently banned it’s use in paint strippers in the United States. It has been known to cause death in industrial settings and even limited exposure to the solvent is a known cancer risk. Choosing a decaf coffee that has been decaffeinated using Supercritical CO2 method or the Swiss Water process is therefore a sensible step for consumers to avoid exposure to methylene chloride. [26]

Prospective coffee drinkers should be aware that adding sugars, syrups, or sweeteners to the coffee will greatly reduce the potential health benefits of drinking it. High daily intake of sweetened beverages is a risk factor in the development of many health issues, such as type 2 diabetes and cardiovascular disease. Sugars and artificial sweeteners such as aspartame have both been linked with an increased risk of the development of cancers. [27] [28]

It is perhaps no surprise then that research has found that most of the health benefits of drinking coffee are more pronounced when the coffee is unsweetened. Studies have found that consumption of unsweetened decaf coffees is associated with a lower risk of death. [29]

Finally, we must remember that all coffees, including decaf coffees, stimulates colonic motor activity. In other words, drinking coffee produces a laxative effect which multiplies with the amount of coffee consumed. If you find yourself rushing to the bathroom after several coffees, this may be why! [30]

Conclusion

A cup of decaf coffee provides a rich blend of polyphenols, and many of these are known to be beneficial to human health. However, not all decaf coffees are created equal, and consumers must be vigilant to avoid purchasing brands that use methylene chloride in the decaffeination process. To ensure the health promoting qualities of the drink, the use of sugars or sweeteners should also be avoided.

Organic coffee without milk exhibits a higher level of almost all beneficial bioactive compounds compared to other types of coffee. A medium roast and a brewing time of 3 minutes has been found to be ideal for preserving these beneficial compounds. [16]

However you like your coffee, a high quality decaf can present a good option for many people to avoid the downsides of high caffeine beverages.

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