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Wake up to caffeine levels in your espresso, scientists urge
Some cups of coffee sold on the high street contain up to six times as much
caffeine as those produced by rival outlets, a study has shown.
Adams and Andrew
6:30AM GMT 01 Dec 2011
Researchers found large discrepancies in caffeine levels in espressos, contradicting the widespread belief that retailers follow a uniform set of guidelines.
Medical experts warned that the differences were potentially putting pregnant women at greater risk of miscarriage. They found that café customers were unaware of the wide variations in caffeine levels.
The findings suggest that the general assumption that a cup of strong coffee contains 50mg of caffeine is misleading.
The Food Standards Agency (FSA) advises pregnant women to restrict their daily caffeine content to 200mg.
In their study, Glasgow University researchers found a sixfold difference in caffeine quantities in cups of espresso.
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Their analysis, from 20 shops in the city, found that a cup bought from Starbucks contained the smallest amount of caffeine, 51mg. This compared with 322mg from an independent café, Patisserie Françoise. An espresso from Costa contained 157mg.
A further three shops, University Café, Café Cinnamon and Paperino’s, sold coffee containing more than 200mg.
The FSA warns that too much caffeine can result in a miscarriage or a baby having a lower birth weight.
The researchers warned that, without clear labelling, coffee shops were selling coffees with “substantial variations” in caffeine.
In 2008 American researchers found that women who drank more than 200mg of caffeine daily were at a 25 per cent greater risk of miscarriage in the first 20 weeks of pregnancy than those who drank none.
Alan Crozier, from Glasgow University’s School of Medicine, said: “Despite the increasing number of coffee shops on the high street and in airports, there appear to be no recent publications on the caffeine contents of the various types of commercially prepared coffees.
“This snapshot of high street espresso coffees suggests the published assumption that a cup of strong coffee contains 50mg of caffeine may be misleading.
“Our data represent only a snap-shot of the caffeine contents of espresso coffees, but the range and scale of the results is sufficient to demonstrate that there is a problem, unlikely to be restricted to Glasgow.”
Researchers analysed coffees ranging in cup size from 23ml to 70ml. Their findings are published in the Royal Society of Chemistry’s Food and Function journal.
Dr Euan Paul, of the British Coffee Association said: “Caffeine content does vary between different blends that are available.
“The overall advice for coffee drinkers is that 400mg to 500mg of caffeine per day is safe and may confer some health benefits but it’s important that pregnant women do limit their intake to 200mg per day, from all sources.
“For pregnant women that are concerned, switching to decaff coffee will ensure that they are drinking less caffeine whilst still enjoying their cup of coffee.”
Experts say the effects of caffeine usually last around five hours for adults but can be as long as 30 hours.
Scientists say caffeine stays in the body longer in females taking an oral contraceptive, pregnant women, young children and people with liver disease.
Responses to caffeine vary with frequent coffee drinkers suffering headaches when caffeine is withdrawn.
Figures quoted in the study show more than £730m was spent on coffee last year with an annual average of 500g of coffee consumed per person.
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Caffeine Myths: Espresso vs. Drip
Posted on December 10th 2013 by Maddie
We’re challenging caffeine myths once again; another juicy exposé to share with friends and family this holiday season.
Last week we learnt that given dark and light roasts of coffee , we will notice only a minimal change in caffeine depending on how we measure our brew.
This week we’re out of the Roasting Department and into the Café.
Can different brewing methods impact our caffeine consumption?
Common assumption seems to be that a shot of espresso has more caffeine than an average drip cup of coffee. I mean isn’t that why you only ever find hardcore coffee aficionados ordering straight up shots of espresso… and Europeans.
However, when you get down to numbers the amount of caffeine is greater in a drip cup of coffee.
One 2 oz double espresso shot has about 80 milligrams of caffeine.
Whereas a 12 oz brewed coffee has about 120 milligrams.
So actually there is more caffeine in an average cup of drip coffee than in espresso. But, that doesn’t seem like a fair comparison given the difference in volume.
Let’s examine caffeine concentration per ounce.
A single shot of espresso has an estimated 40 mg per ounce whereas a brewed cup only has around 10 mg in each ounce. By concentration we see espresso having more caffeine. The difference in the serving size is where the discrepancy lies; less caffeine in espresso from a beverage perspective.
By now we know caffeine affects us all in our own way. I even find different effects dependent on the day. My current mood can alter my reactions to caffeine. If I’m already in a good mood caffeine generally ups the ante. However, if I’m feeling edgy caffeine only leads to more anxiety. Maybe I’m a special case though, which my family would agree.
Along the same lines, espresso may have less caffeine, but how quickly do you consume a shot versus an entire mug of brewed coffee? You generally drink espresso much faster. Caffeine can be more rapidly assimilated when taken in concentrated dosages; hitting your central nervous system differently than if you sipped a drip cup over the course of an hour.
So there is some truth in the assumption when considering concentration and time of ingestion.
What causes the difference in caffeine levels with Espresso and Drip?
Since there is a finite amount of caffeine to extract in coffee, what can cause this difference in caffeine concentration? Moreover what does it take to extract caffeine from coffee?
We know from earlier entries that caffeine is water soluble. Caffeine is extracted into the brew by hot water acting as a solvent. Since all brewing methods don’t yield the same percentage of caffeine, let’s see what else can affect the buzz.
The grinds need to be 100% saturated to extract all the caffeine available.
Above we mentioned hot water acting as a solvent. The ideal water temperature is near-boiling, 95-105°C. Temperature is going to make a big difference in how quickly caffeine is withdrawn from the bean. A cold brew will take hours longer.
Roughly all of the available caffeine is released during the first minute of extraction. The brewing time of an espresso shot is from 20-30 seconds.
Grind can influence how quickly caffeine is extracted. With a finer grind you have the ability to extract caffeine faster. Water reaches the surface area and saturates the grind with ease, as there is a greater contact area.
Under-extraction will happen with espresso when the grind is too coarse; whereas you will have over-extraction if the grind is too fine.
All these factors influence how quickly caffeine is extracted from coffee. Essentially, you could take a whole bean and saturate it with water, eventually the caffeine will be removed, but how long do you imagine it will take?
Espresso is prepared using pressurized water, more ground coffee than used for drip, all of which result in a higher concentration of caffeine than drip.
Since caffeine is easily extracted from coffee, your best bet for obtaining more caffeine is simply to use more ground coffee.
Which roast has more caffeine?
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