PLEASE NOTE: THIS INFORMATION SHEET HAS NOW BEEN UPDATED AND THE
RESULTS ARE PRESENTED IN FOOD SURVEILLANCE INFORMATION SHEET NUMBER 144.
Number 103 March 1997
MAFF UK - SURVEY OF CAFFEINE AND OTHER METHYLXANTHINES IN ENERGY DRINKS AND
OTHER CAFFEINE-CONTAINING PRODUCTS
Index to MAFF UK Food Surveillance Information
Sheets, 1997
See also:
21: MAFF UK -
Caffeine in Guarana Products (December 1993)
144: MAFF UK - Survey of Caffeine and Other
Methylxanthines in Energy Drinks and Other Caffeine-Containing Products (March
1998)
Summary
MAFF has recently completed a survey of caffeine and two other
methylxanthines (theobromine and theophylline) in a range of "energy"
drinks and other soft drinks, teas, coffees and chocolate products. Caffeine
levels in standard cola drinks ranged from 33 to 213 mg/l, while those in low
caffeine colas were less than 0.2 mg/l. Energy drinks had a broad range of
caffeine contents (0.5-349 mg/l), but most contained more than 110 mg/l.
Caffeine concentrations in standard tea products ranged from 95 to 630 mg/l,
when prepared according to a standard method, with the highest levels being
found in instant teas, followed by tea bags. Instant coffees contained caffeine
at between 210 and 340 mg/l, while lower levels of 105-215 mg/l were found in
filter and percolated coffees. As expected, the two decaffeinated instant
coffees analysed contained low levels of caffeine (10 and 11 mg/l) and complied
with the relevant statutory limits. Of the chocolate products analysed,
powdered drinks contained caffeine at 5.5-41 mg/l, while milk drinks contained
8-20 mg/l and two chocolate mousses, 21 and 50 mg/kg. Theobromine levels were
generally low, with the exception of chocolate products which contained up to
651 mg/l, while theophylline was undetectable in most products.
Background
Caffeine (1,3,7-trimethylxanthine) is one of a group of chemicals called
methylxanthines which occur naturally in a range of plant-derived foodstuffs
such as coffee, tea, cola products and chocolate. Caffeine also occurs in soft
drinks due to the addition of flavourings containing natural extracts such as
cola nut which may contain caffeine and, more frequently, due to the addition of
caffeine as such. Although there is no statutory limit for caffeine in soft
drinks, its use is subject to the general provisions of the Food Safety Act
1990.1
A number of studies have been carried out to determine the levels of
caffeine in coffee, tea, chocolate products and soft drinks.2-10 However, details of the products analysed and the
sample weights used in their preparation have often not been reported, thus
limiting a comparative evaluation of the data and their usefulness. Moreover,
as these studies were generally undertaken over five years ago and most were
carried out in the USA, they do not provide an up-to-date picture of the
caffeine content of products currently sold in the UK.
In addition to the more traditional caffeine-containing soft drinks such as
colas, a new range of drinks, known as "energy" drinks and marketed as
"revitalising", "stimulating" or providing some sort of "pick-me-up",
has entered the market over the last 2-3 years. Some of these contain extracts
of guarana (Paullinia cupana), a South American plant which has been
shown to contain caffeine,11 and many have
caffeine added as such. These products typically contain caffeine at higher
levels than cola drinks, with concentrations of up to 350 mg/l being reported on
the labels of some canned drinks. However, as the majority of these drinks were
not available until relatively recently, there is a lack of data on their
caffeine content.
MAFF has recently carried out a project to provide a reliable quantitative
assessment of the caffeine content of a wide range of soft drinks, including
energy drinks, and other caffeine-containing products currently available to
consumers in the UK. Products have also been analysed for two other
methylxanthines, theobromine (3,7-dimethylxanthine) and theophylline
(1,3-dimethylxanthine), which are often found along with caffeine and for which
data in the scientific literature are generally lacking. The information
obtained will expand and update the data generated by MAFF on the composition of
food in the UK and can be used to estimate dietary intakes of caffeine. In
addition, data obtained on the caffeine levels of energy drinks will not only be
used to inform any future EC discussions on these products, but will also assist
the European Commission's Scientific Committee for Food (SCF) in its on-going
review of these drinks.
Methodology
A total of 156 samples, comprising 36 cola drinks, 26 energy drinks, 12
miscellaneous drinks (mainly soft drinks), 26 tea products (mainly loose, bags
and instant), 30 coffees (mainly percolated, filter and instant), 24 chocolate
drinks (powdered and ready-to-drink milk drinks) and two chocolate mousses, were
obtained for analysis by MAFF Central Science Laboratory (CSL) Food Science
Laboratory, Norwich, between June and December 1996. The majority of these were
purchased from retail outlets in and around London, although a small number of
energy drinks not yet available in the UK were obtained direct from the
manufacturers. Details of the ingredients listed on the product label and,
where appropriate, manufacturers' instructions for preparation, were recorded on
receipt.
Tea and coffee infusions were prepared according to a standard method
involving 200 ml of boiling water and either: one teaspoonful (1.6 g) of instant
tea, instant coffee or loose tea; 2.6 g of filtered or percolated coffee; or one
tea bag. Loose and bagged teas were allowed to brew for 5 minutes, while
percolated coffees were prepared by refluxing the coffee under simulated
percolator conditions for 10 minutes. Filter coffees were prepared using a
domestic coffee filter apparatus. Powdered chocolate drinks were prepared using
a reduced sample weight (1 g) in 200 ml of boiling water in order to maintain
product solubility on cooling, with the results subsequently being expressed in
terms of the portion size recommended on the packet. All samples were analysed
for caffeine, theophylline and theobromine using liquid chromatography with
ultraviolet detection (LC-UV), with Beta-hydroxyethyltheophylline as an internal
standard. Confirmation by liquid chromatography-mass spectrometry (LC-MS) was
carried out in cases where peak purity data were outside the quality control
limits of 95 percent purity. Further details of the methods used are given
elsewhere.12
Samples were analysed using a batch procedure, with each batch comprising 8
test samples, together with 4 quality control samples (an in-house reference
material, a duplicate test sample, a spiked sample and a blank) to determine
accuracy and precision. In-house reference materials were chosen to
matrix-match the respective sample types as closely as possible. In batches of
colas, energy and miscellaneous drinks, a cola drink which had previously been
analysed as part of the Food Analysis Performance Assessment Scheme (FAPAS) and
which had an assigned value of 104.4 mg/l for caffeine,13
was included. Batches of teas and coffees contained an instant tea material and
batches of chocolate products contained a chocolate powder material, with both
reference materials having been tested for homogeneity prior to the start of the
survey. Spiked samples were fortified at levels similar to those already
present in the products.
Between-batch analyses of the in-house reference materials and other control
samples showed excellent agreement, being well within the specified acceptance
criteria. For example, precision values for replicates of the test samples and
in-house reference materials were well within 15 percent of the mean value and
recoveries of the internal standard and spiked samples all met the acceptance
criterion of greater than 70 percent, with most being above 90 percent .
Caffeine concentrations obtained for the cola reference material (mean, 105.9
mg/l; standard deviation, 2.8 mg/l; n=12) were also very close to the FAPAS
assigned value of 104.4 mg/l. The survey results were calculated relative to a
recovery of 100 percent for the internal standard, with no other recovery
adjustment being made as the recoveries of the methylxanthines relative to the
internal standard were close to unity.
Limits of detection of 0.2 mg/l for caffeine and 0.1 mg/l for theobromine
and theophylline were obtained for colas, energy drinks, teas, coffees and
chocolate infusions, while for chocolate milk drinks, the corresponding
detection limits were 1 mg/l and 0.5 mg/l, respectively. Limits of 2 mg/kg for
caffeine and 1 mg/kg for theobromine and theophylline were obtained for the
chocolate mousse samples.
Results
A summary of the concentrations of caffeine, theobromine and theophylline
found in the cola, energy and other miscellaneous drinks is given in
Table 1, with the results for teas being summarised in
Tables 2a and 2b, coffees
in Table 3 and chocolate products in
Table 4. Individual results for each product are
listed in Annex A.
Cola drinks
As shown in Table 1, caffeine concentrations in
the 32 samples of standard (diet and regular (non-diet)) cola ranged from 33 to
213 mg/l (mean, 69 mg/l) and were similar to those reported previously by other
workers such as Galasko et al.8 (27-146
mg/l), Scott et al.9 (50-90 mg/l) and
Sanchez et al.10 (58-147 mg/l). It is
interesting to note that in both diet and regular drinks, levels appeared to
fall into three distinct sub-ranges, at around 35 mg/l, 75 mg/l and greater
than 100 mg/l, perhaps reflecting the different flavouring blends available to
manufacturers. In contrast to the standard cola drinks, caffeine was not
detected (less than 0.2 mg/l) in the four colas labelled as caffeine-free or
decaffeinated or not listing caffeine on the label. Theobromine and
theophylline levels were generally below the limit of detection of 0.1 mg/l in
both caffeinated and decaffeinated products.
Energy drinks
Caffeine concentrations in the 26 energy drinks analysed ranged from 0.5 to
349 mg/l (mean, 240; median, 293 mg/l) (Table 1), with
all but one sample containing over 110 mg/l and most having significantly higher
levels than cola drinks. Caffeine concentrations in individual products (such
as Red Bull, Virgin Energy, XTC and X-Plosiv) were similar to those reported
previously10,14 and, where given, to those
stated on the can label (see Annex A). Caffeine
levels in drinks containing guarana extract but with no added caffeine (range,
167-188 mg/l) were also similar to those reported in an earlier survey of these
products.11 Lower levels of theobromine (less
than 0.1-6.2 mg/l) and theophylline (less than 0.1-1.3 mg/l) compared to
caffeine were found in energy drinks.
Miscellaneous drinks
Table 1 also includes data for 12 miscellaneous
drinks, comprising two alcoholic drinks and 10 assorted soft drinks. Caffeine
concentrations ranged widely (less than 0.2-123 mg/l), with the highest levels
being found in the diet and regular varieties of Mountain Dew, a
citrus-flavoured drink. Bunker and McWilliams4
reported a similar caffeine concentration (152 mg/l) for this product, while in
a later survey by Galasko et al.,8
caffeine was not detected. Detectable concentrations of theophylline (1.2 and
1.4 mg/l) were found only in these two products, while none of the samples
contained detectable levels of theobromine (less than 0.1 mg/l).
Tea products
A summary of the levels of caffeine, theobromine and theophylline in the 26
tea products analysed is given in Table 2a. Caffeine
concentrations in tea infusions made from standard (non-decaffeinated) bags
(n=14) ranged from 245 to 430 mg/l (mean, 326 mg/l) and were similar to those
reported previously by Blauch and Tarka6
(171-381 mg/l) and Scott et al.9
(214-344 mg/l). Lower theobromine levels of 10-31 mg/l (mean, 22 mg/l) were
found in these samples which were also consistent with previous reports6,9 (6.8-25 mg/l and 5.5-22 mg/l, respectively).
Theophylline levels in these products were generally low, at up to 2 mg/l.
Table 2a shows that caffeine levels in infusions
made from loose leaf teas (n=3) were lower (range, 95-105 mg/l; mean, 102 mg/l)
than those made from tea bags. Comparison of the caffeine levels in these
products in terms of mg per g tea (means of 22 and 12.4 mg/g, respectively) (Table 2b) suggests that this difference cannot be
explained simply in terms of different sample weights. Theobromine levels in
loose leaf teas (6-7 mg/l) were also lower than in tea bags. It is known that
bagged teas have a stronger flavour than loose leaf teas to overcome any
adsorption to the bags and, thus, it may be possible that these teas also have
higher caffeine and theobromine levels. Scott et al.9 reported higher caffeine and theobromine levels of
258-316 mg/l and 14.5-18.5 mg/l, respectively, in loose leaf teas but this
difference may be due to a different sample size.
Caffeine concentrations in instant tea infusions (n=3) were in the range,
560-630 mg/l (mean, 585 mg/l), while theobromine levels ranged from 26 to 33
mg/l (mean, 31 mg/l) and theophylline levels were 2.5-3.5 mg/l. Levels of all
three methylxanthines were higher in instant teas than in teas made from bags.
Similar concentrations of caffeine (586-633 mg/l) and theobromine (25-41 mg/l)
were also reported by Blauch and Tarka,6
although Reid and Good5 found lower
concentrations (232 mg/l and 14.4 mg/l, respectively) in one sample of instant
tea.
As expected, caffeine concentrations in infusions made from the two samples
of decaffeinated tea bags were very low, at 5 mg/l and 20 mg/l (Table 2a and Annex A). A
caffeine content of 125 mg/l was found in the one "low caffeine"
product analysed which, in terms of dry tea (8.2 mg/g), was around two-thirds
that found in loose leaf teas (11.5-12.8 mg/g). Despite this, these tea bags
met the manufacturer's claim of containing half the caffeine of its normal bags
(17.2 mg/g). The levels of theobromine and theophylline in the decaffeinated
and low caffeine products were of the same order as those in the standard bagged
teas (15.0-26.5 mg/l and 1.0-1.5 mg/l, respectively).
Coffee products
Levels of caffeine, theobromine and theophylline in the 30 coffee products
analysed are summarised in Table 3. As shown,
caffeine levels of 210-340 mg/l (mean, 288 mg/l) were found in the standard
instant coffees (n=16), which are similar to the results reported by Reid and
Good5 (181 mg/l), Blauch and Tarka6 (315-455 mg/l) and Scott et al.9 (285-374 mg/l). The two decaffeinated instant coffees
analysed contained, as expected, very low levels of caffeine, at 10 and 11 mg/l.
As in the case of the teas, levels of theobromine and theophylline in standard
and decaffeinated instant coffees were similar.
Caffeine concentrations found in filter and percolated coffee infusions
(range, 105-215 mg/l; mean, 180 mg/l) (Table 3) are
similar to the levels reported previously by Reid and Good5
(164 mg/l) and Blauch and Tarka6 (187-330 mg/l)
but are significantly lower than those found by Scott et al.9 (601-2137 mg/l), assuming a sample weight of 1.6 g in
200 ml in the latter study. As with the instant coffees, levels of theophylline
and theobromine in the filter and percolated coffees were low.
Caffeine levels in the miscellaneous coffee products (n=4) ranged from 70 to
580 mg/l (Table 3), with the highest levels being
found in an instant espresso product and a coffee and chocolate powdered drink.
The concentration of theobromine in the latter sample was also significantly
higher than in other coffee infusions, at 60 mg/l, due to the presence of
chocolate in the product.
Chocolate products
Levels of caffeine, theobromine and theophylline in the 26 chocolate
products analysed (powdered drinks, milk drinks and mousses) are summarised in
Table 4. In the case of the powdered drinks, as noted
previously, determinations were carried out using a sample weight of 1 g due to
solubility problems on cooling. However, the concentrations reported in Table 4
are expressed in terms of the portion size recommended on the packet. As shown,
the concentrations of caffeine in the 18 powdered drinks analysed ranged from
5.5 to 41 mg/l. Previous studies6,9 have found
similar results for chocolate drinks and hot cocoa mixes. Higher theobromine
concentrations compared to caffeine (range, 85-590 mg/l; mean, 367 mg/l) were
found in the powdered drinks which are similar to those previously reported.6 Theophylline levels varied widely (<0.1-140 mg/l;
mean, 10.6 mg/l; median, 2.8 mg/l) but most samples contained less than 10 mg/l.
Table 4 shows that caffeine concentrations in
chocolate milk drinks (n=6) ranged from 8 to 20 mg/l, while theobromine levels
ranged from 141 to 371 mg/l. The two chocolate mousses had caffeine
concentrations of 21 and 50 mg/kg and theobromine contents of 386 and 651 mg/kg.
Theophylline was undetectable in the milk drinks and mousses.
Interpretation
As stated earlier, comparison of analytical data on caffeine levels in
various foods and beverages by different authors is not always straightforward.
There are many variables to consider including the sample weight and the volume
of water used in preparing some drinks, brewing time (tea) and also different
methods of detection, possible changes in drink formulations by manufacturers
over the years and use of different formulations to appeal to consumers in
different countries. Despite this, the levels of caffeine, theobromine and
theophylline found in this survey are generally consistent with previous
results.
The Coffee and Coffee Products (Amendment) Regulations 198715 state that the caffeine content of decaffeinated
instant coffee products should not exceed 0.3 percent of dry coffee matter
determined using the method of analysis laid down in Commission Directive
79/1066/EEC.16 The two decaffeinated instant
coffees analysed were found to comply with these Regulations, having caffeine
concentrations equivalent to around 0.1 percent in the coffee powder. There
are no regulations on decaffeinated tea products.
The information obtained in the survey will expand and update the data
generated by MAFF on the composition of food in the UK and can be used to
estimate dietary intakes of caffeine. In addition, data obtained on caffeine in
energy drinks will be used to inform any future EC discussions on these products
and will assist the SCF in its on-going review of these drinks.
References
- Food Safety Act 1990. HMSO.
- Gilbert, R.M., Marshman, J.A., Schweider, M. and Berg, R.
(1976). Caffeine content of beverages as consumed. Canadian Medical
Association Journal, 114, 205-211.
- Groisser, D.S. (1978). A study of caffeine in tea. American Journal
of Clinical Nutrition, 31, 1727-1732.
- Bunker, M.L. and McWilliams, M. (1979). Caffeine content
of common beverages. Journal of American Dietetic Association, 74,
23-81.
- Reid, S.J. and Good, T.J. (1982). Use of chromatographic
mode sequencing for sample preparation in the analysis of caffeine and
theobromine from beverages. Journal of Agricultural Food Chemistry,
30, 775-778.
- Blauch, J.L. and Tarka, Jr., S.M. (1983). HPLC
determination of caffeine and throbromine in coffee, tea an instant hot cocoa
mixes. Journal of Food Science, 48, 745-750.
- Terada, H. and Sakabe, Y. (1984). High-performance liquid chromatographic
determination of theobromine, theophylline and caffeine in food products. Journal
of Chromatography, 291, 453-459.
- Galasko, G.T.F., Furman, K.I. and Alberts, E. (1989). The
caffeine contents of non-alcoholic beverages. Fd Chem. Toxic., 27,
49-51.
- Scott, N.R., Chakraborty, J. and Marks, V. (1989).
Caffeine consumption in the United Kingdom: a restrospective survey. Food
Science and Nutrition, 42F, 183-191.
- Sanchez, S., Bodart, P. and Noirfalise, A. (1996). Taux
de cafeine dans des boissons non-alcoolisees. Cerevisia, 21(3),
58-61.
- Willetts, P., Buxton, P., Chapman, S., Brereton, P. and
Wood, R. (1994). Studies of the properties and xanthine composition of the
herbal supplement guarana. Proceedings of Euro Food Tox IV,
443-447.
- Ministry of Agriculture, Fisheries and Food (1997).
Survey of caffeine in energy drinks and other caffeine-containing products.
Report FD 96/39. Final Report submitted by MAFF Central Science
Laboratory, Norwich, February 1997.
- Ministry of Agriculture, Fisheries and Food, Central
Science Laboratory (1996). Food Analysis and Performance Assessment Scheme
(FAPAS) Report 0313, January 1996.
- Consumers Association (1995). Which?, September 1995.
- The Coffee and Coffee Products (Amendment) Regulations
1987 (S.I. [1987] No. 1986.). HMSO.
- European Community (1979). Commission Directive
79/1066/EEC laying down Community methods of analysis for testing coffee
extracts and chicory extracts. Official Journal of the European Communities
L327/17.
Contact Point
For further information please contact:
Dr A M Davies
MAFF,
Food Safety and Science Group
Additives and Novel Foods Division
Room
232 Ergon House
c/o Nobel House
17 Smith Square
LONDON SW1P 3JR
Tel:
+ 44 (0) 171 238 6217
Fax: + 44 (0)171 238 6263
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