Percentage of Sugar in Soft Drinks
Too Much Dietary Sugar
are a major source of energy for all living things. Plants produce
and convert that and other
(table sugar) or convert it into starch to store it more easily. Animals
which eat these plants can make use of this energy source and also are
attracted to the sweet taste and smell.
We humans have gone a step farther. We frequently add sugar
to foods that normally and naturally do not have it (or have it only in small
quantities) just because we crave the taste of it for its own sake. We have
fought whole wars because of sugar — there are sources that suggest that
the Boston Tea Party was caused not by the British tea regulations, but
because of their molasses regulations (Dufty, 1975). As our sugar
consumption has risen in western nations, so have our rates of the
heart and circulatory problems, dental caries, malnutrition, decreased
resistance to infections, etc. (Fredericks and Goodman, 1969; Fredericks,
1985) which are not nearly as prevalent (if at all present) in the Third
World nations. An increasing number of nutritionists and other medical
people are now in agreement that refined sucrose (or any sugar) is a
mind-altering, addicting drug (if you don’t think so, try doing without, and
you will probably experience the same withdrawal symptoms as any drug
Around 100 years ago, the average American consumed about
40 lb. of sugar per year (Robertson, et al., 1976). As of 1986,
Americans were averaging a third of a pound of sugar per person (including
children) per day, which comes to about 127lb. per person per year
(Robertson, et al., 1986). As of 1982, 25% of the average American’s
intake of cane and beet sugar came from soft drinks (Lappé, 1982). Soft
drink consumption in the U. S. rose from 1.6 drinks per person per year in
1850 to 620 drinks per person per year in 1981 (Robertson et al.,
1986). As of 1998, the average American sugar consumption has risen to
148 lb. per person per year, which is over ⅓ lb. or 600 KCal per day
(Guest, 1998)! In this experiment, we will analyze a number of types of
soft drinks to see how much sugar they contain.
Determining Percent Sugar in Sugar Solutions
We will be able to determine the amount of sugar in any given
soft drink by comparing the
of that soft drink to the density of distilled water (dH2O) at
the same temperature (20° C).
The density of pure water ranges from about 0.997 to 0.998 g/mL between 20
and 25° C (room temperature). If any
are dissolved in the water, the weight of a given volume of the
increases — the solution becomes more dense. People who have done a lot of
swimming probably have heard that a person floats higher in ocean water
and especially in very salty water like the Dead Sea or Great Salt Lake.
This is because relative to the density of our bodies, these salty waters are
more dense. When sugar is added to water, it also makes the solution more
dense. Thus, the weight of a known volume of solution can be correlated to
the amount of sugar in it. The
of a substance is defined as the density of that substance divided by the
density of water at the same temperature, and thus is a unitless quantity.
In the metric system, for all practical purposes, density and specific
gravity are equal (but in the English system, this is not true). Thus, by
weighing equal volumes of water and soft drink, we can determine the specific
gravity of the soft drink, and
|wt. of soft drink/100 mL
||wt. of soft drink
|wt. of dH2O/100 mL
||wt. of dH2O
because the 100 mL/100 mL cancels out. We can, then, look
up the percentage of sucrose from a chart or graph of specific gravity
versus percent sucrose. From this, it is possible to calculate how much
sugar is in a can of soft drink. Note that we are assuming that the other
solutes in soft drinks do not occur in large enough amounts to affect the
density of the solution very much.
Abrahamson, E. M. and A. W. Pezet. 1951. Body, Mind, and Sugar. Avon Books. New York.
anon. 1969. Betty Crocker’s Cookbook. Golden Press. New York.
Dufty, William. 1975. Sugar Blues. Warner Books. New York.
Fredericks, Carlton. 1985. New Low Blood Sugar and You. Perigree Books. New York.
Fredericks, Carlton, and Herman Goodman. 1969. Low Blood Sugar and You. Charter Books, New York.
Guest, Donna K. 1998. Test yourself: natural sweeteners. Better Nutrition. 60(7): 62.
Horwitz, William (Ed.). 1975. Official Methods of Analysis of the Association of Official Analytical Chemists, 12th Ed. Assn. Official Analyt. Chem., Washington, DC.
Lappé, Francis Moore. 1982. Diet for a Small Planet, 10th Anniversary Ed. Ballantine Books. New York.
Lappé, Francis Moore. 1991. Diet for a Small Planet, 20th Anniversary Ed. Ballantine Books. New York.
Lange, Norbert A. 1944. Handbook of Chemistry, 5th Ed. Handbook Publishers, Inc. Sandusky, OH.
Robertson, Laurel, Carol Flinders, and Bronwen Godfrey. 1976. Laurel’s Kitchen. Nilgiri Press. (Bantam Books Ed. 1978)
Robertson, Laurel, Carol Flinders, and Brian Ruppenthal. 1986. The New Laurel’s Kitchen. Ten Speed Press. Berkley, CA.
Determination of Percentage of Sugar in Soft Drinks
- Pour about 125 mL dH2O
into a clean 250-mL beaker and insert the
to check the temperature of the water. Please be careful with glass
thermometers — they break easily. Obtain the balance which has been
assigned to you.
- While the thermometer is equilibrating,
weigh a clean, dry 100-mL volumetric flask to the nearest 0.01 g. Record its
weight in your lab notebook. You must use the same flask each time (each
flask weighs a different amount), so if the flask does not already bear any
identifying code number, mark the flask in some non-permanent way (on the
glass, not in the white spot) BEFORE you weigh it (any markings you add will
also add weight to the flask). THIS IS THE ONLY CHANCE YOU WILL GET TO
OBTAIN A DRY WEIGHT FOR YOUR FLASK. For example,
|wt. of empty flask = 61.83 g
- Read the temperature of the
dH2O. If it is not right on 20° C, use the ice bath to adjust it.
Set the beaker briefly in the ice bath, and while constantly moving it, also
stir the contents with a stirring rod (temporarily remove the thermometer so
it doesn’t break). Monitor the temperature frequently because it may change
rapidly. If the original temperature of your water was close to 20° C, it
may probably need to be in the ice bath for only a few seconds, and if you let
it get too cold, you’ll have to wait for it to warm up to the right
temperature. Remove the beaker from the ice bath when the temperature is
just above 20° C, and keep stirring it. As the cold beaker absorbs heat
from the water inside, the water will continue to cool.
When the water is at exactly 20° C, pour 100 mL into the volumetric flask.
To avoid getting air bubbles trapped in the flask, pour the water gently down
the side of the flask. Any air bubbles in the flask or excess water drops
will change the weight. Remember that in a correctly-filled volumetric
flask, the BOTTOM of the
should touch the TOP of the calibration line on the neck of the flask. Use a
Pasteur pipet or plastic dropper to adjust the volume and dry off any excess
- Using the same balance as before
(and without any further adjustments to it), weigh the flask plus water.
Record the weight in your lab notebook. Subtract the weight of the flask
alone to determine the weight of the dH2O. For example,
|wt. of flask + H2O:
| wt. of empty flask:
||– 61.83 g
|wt. of H2O alone:
- Pour your used dH2O into
the designated container for “recycling”. Invert the flask to drip dry,
supported in a test tube rack in a location where it will not get knocked
over or in one of the dish-drying racks.
- Pour about 125 mL of your favorite
soft drink into the 250 mL beaker. If possible, recap the soft drink to
avoid contamination. Record the name of soft drink you are using. For
- “De-gas” the soft drink by heating it
to about 80° C (It may not get quite that hot, and temperataure reached is
not as important as lack of fizzing in determining if it is “done.”).
Place your beaker in the hot water bath and stir it occasionally with a
stirring rod. Periodically, monitor the temperature with the thermometer.
Do not boil your sample or water will evaporate and change the concentration
of the solution — you only want to get rid of the carbonation. Stirring
gently will speed things up. Heat and stir until there is no more “fizz”
left — until the soft drink is totally flat.
- Place the beaker of sample into the
ice bath. As before, gently swirl the beaker and stir the soft drink with
the stirring rod. Periodically monitor the temperature as before (CAUTION:
thermometers are fragile). When the temperature is a few degrees above
20° C, remove the beaker from the ice bath. Continue swirling and stirring
until the temperature reaches 20°.
- Place 100 mL of de-gassed soft drink
in the SAME volumetric flask you used before and adjust the level of the
meniscus as before. Remember to watch for air bubbles and excess water
- Using the same balance as before,
weigh the flask plus soft drink. Record this weight in your lab notebook
and subtract to find the weight of the soft drink. For example,
|wt. of flask + soft drink:
|wt. of empty flask:
||– 61.83 g
|wt. of soft drink alone:
- Determine the specific gravity of
the soft drink by dividing the weight of 100 mL of it by the weight of 100 mL
|wt. of soft drink
|| = 1.0463
|wt. of H2O
- Use the following chart to determine
the percent sucrose by weight in your soft drink. This chart was excerpted
from a much larger version in the chemistry handbooks (Lange, 1944;
Horwitz, 1975). What this number means is that your soft drink contains that
percentage of sugar, or for 100 g of soft drink, that number of grams out of
the 100 would be sugar. Record the appropriate number in your lab
|Specific Gravity of Sucrose Solutions at 20/20° C
|from this chart, a specific gravity of 1.0463 corresponds to 11.5% sugar.
- However, your 100 mL of soft drink
probably didn’t weigh exactly 100 g — it probably was around 103 or 104 g.
To calculate how much of your soft drink was actually sugar, first convert
your percentage number to its decimal form. For example,
Multiply the decimal form of your percent sucrose times the weight of your
soft drink to calculate the weight (number of grams) of sucrose in your
|decimal form of percentage × weight of soft drink
= grams of
sugar per 100 mL of soft drink
in 100 mL of that soft drink.
|0.115 × 104.34 g = 12.00 g of sugar
- Did you notice when you first poured
your soft drink that there was still soft drink left in the can? A can of
soft drink contains more than 100 mL. In fact, if you look at the side of a
can, a 12-oz. can of soft drink is equivalent to 355 mL. The ratio,
can be used to determine the grams of sugar in your can of soft drink.
Solving for X gives:
|measured grams of sugar
|| X grams of sugar
|100 mL of soft drink
||355 mL of soft drink
|3.55 × measured grams of sugar = X grams of sugar/can of soft drink.
Calculate the grams of sugar in a can of your soft drink and record this
number in your lab notebook.
|3.55 × 12.00 g = 42.60 g of sugar per can.
- How does this compare with the number
of grams reported on the side of the can of soft drink? How close did you
come to what the manufacturer is reporting? One note of caution here: if
your soft drink is in a 12-oz. can, the manufacturer has calculated the sugar
content based on one “serving” of soft drink equaling 12 oz. However, if
your soft drink came from a larger container (like a 2-L bottle), then the
manufacturer probably reported the sugar per serving based on an 8 oz.
“serving.” That is true, even if it is the same soft drink! For
example, one “serving” of Coke in a can is listed as 12 oz. but one
“serving” of the same Coke from a 2-L bottle is listed as only 8 oz.
Because it is difficult to evaluate and compare the sugar content of one
“serving” of the various brands of soft drink unless we’re dealing with the
same serving size for all (and considering that very few soft-drink
consumers will drink only 8 oz. at a time) for purposes of this lab,
we want to compare all soft drinks tested on the basis of a 12-oz.
“serving,” regardless of the size of container in which they were packaged.
Thus, if the bottle in which your soft drink was packaged says that one
serving is 8 oz., remember that 12 is 1.5 × 8, so however much sugar the
manufacturer reports in 8 oz. should be multiplied by 1.5 to convert to a
“normal” 12-oz. serving. For example,
Similarly, if the container reports anything other
than 12 oz. as one “serving,” the amount of sugar listed will need to be
converted to a per 12 oz. basis. Record the (corrected) manufacturer’s
reported number in your notebook and comment on how close this is (or is not)
to your measurement. For example,
|29 g of sugar per 8-oz. serving × 1.5 = 43.5 g per 12-oz. serving
|The can says it contains 43.5 g of sugar.
- However, for most of us who don’t
really have a visual idea of how big a gram is, a more useful comparison
might be teaspoons of sugar per can. Some people put one or two teaspoons of
sugar in a cup of coffee or tea. How many teaspoons of sugar do you think
are in one can of your soft drink? This can be calculated based on the
following information. Knowing that one cup (1 C) equals 48 tsp., a cup of
sugar was weighed. The weight of this cup of sugar was found to be 213.97 g.
Thus, if 48 tsp. of sugar weigh 213.97 g, then each gram of sugar is
equivalent to 0.22433 tsp. (48 tsp. ÷ 213.97 g = 0.22433 tsp./g). To determine
the number of teaspoons of sugar in your can of soft drink, multiply the
number of grams you calculated per can by 0.22433 tsp./g. Use your number,
not the manufacturer’s number.
|calculated grams per can × 0.22433 tsp./g = tsp. per can
Keep in mind that 3 tsp. = 1 Tbsp. (1 T), so 9.56 tsp. is just over 3 T of sugar.
Note that there are 16 T in 1 C, so that means 4 T = ¼ C. Would you put that
much sugar in a cup of coffee or tea?
|42.60 g × 0.22433 tsp./g = 9.56 tsp. sugar per can.
- How often do you drink soft drinks? How much sugar does soft drink consumption add to your diet?
- You now know how many teaspoons of sugar each can contains.
Multiply that times the number of cans you drink each day to figure
out how much sugar you get per day.
|tsp./can × cans/da = tsp./da
- Since 1 C = 48 tsp., divide the number you just obtained by 48 to
convert to cups of sugar per day.
- Multiply this number by seven to calculate cups of sugar per week
If you wish to go one step further, there are 52 weeks in a year, thus
|9.56 tsp./can × 2 cans/da = 19.12 tsp./da
19.12 tsp./da ÷ 48 tsp./C = 0.398 C/da
0.398 C/da × 7 da/wk = 2.79 C/wk
By the way, my Betty Crocker’s Cookbook says that 1 lb. of sugar is
approximately equal to 2 C. That would mean that
|2.79 C/wk × 52 wk/yr = 145 C/yr
Packaged in typical 5-lb sacks, that would be
|145 C/yr × 1 lb/2 C = 72.5 lb/yr
from “only” 2 cans of soft drink a day!
|72.5 lb/yr × 1 sack/5 lb = 14.5 5-lb sacks/yr
- Another, better way to convert to
pounds is to use the conversion factor, 1 lb = 453.6 g (or,
1 g = 0.002205 lb.). Thus, for example,
That’s a lot of sugar. . . 14 sacks a year, just from two cans of soft drink
a day! Some of you who are concerned about diet and Calorie-counting may
know that 1 g of carbohydrate stores/is equivalent to 4 Cal. of energy, and
1 g of fat stores/is equivalent to 9 Cal of energy.
|42.60 g/can × 2 cans/da = 85.20 g/da
85.20 g/da × 7 da/wk = 596.4 g/wk
596.4 g/wk × 1 lb/453.6 g = 1.31 lb/wk
1.31 lb/wk × 52 wk/yr = 68.4 lb/yr
68.4 lb/yr × 1 sack/5 lb = 13.7 5-lb sacks/yr
Thus, if consumed along with an otherwise adequate diet, two cans of soft
drink a day could, theoretically, contribute to gaining 30+ lb of body fat
over the course of a year. . . and our fictitious “JunkPop” that we’ve been
using as an example is actually a bit lower in sugar than most “real” soft
|596.4 g/wk × 4 Cal/g = 2385.6 Cal/wk
(2385.6 Cal/wk × 1 g of fat/9 Cal × 1 lb/453.6 g = 0.58 lb of body fat/wk)
2385.6 Cal/wk × 52 wk/yr = 124051.2 Cal/yr
124051.2 Cal/yr × 1 g of fat/9 Cal × 1 lb/453.6 g = 30.4 lb of body fat/yr
- For comparison, according to what the
manufacturer states on the side of the can, Mt. Dew has about 50 g of sugar
per 12-oz. can. Suppose someone drinks a 2-L bottle (67.61 oz) of Mt. Dew
per day (which, from what I’ve been told, is not that unusual for some of our
Hmmm. . . anybody looking for a good way to lose some weight?
|67.61 oz/da × 50 g sugar/12 oz = 281.72 g sugar/da
281.72 g sugar/da × 4 Cal/1 g = 1126.9 Cal/da
(1126.9 Cal/da × 1 g of fat/9 Cal × 1 lb/453.6 g = 0.28 lb of body fat/da)
1126.9 Cal/da × 7 da/wk = 7888.3 Cal/wk
(7888.3 Cal/wk × 1 g of fat/9 Cal × 1 lb/453.6 g = 1.93 lb of body fat/wk)
7888.3 Cal/wk × 52 wk/yr = 410191.6 Cal/yr
410191.6 Cal/yr × 1 g of fat/9 Cal × 1 lb/453.6 g = 100.48 lb of body fat/yr
- CLEAN UP AFTER YOURSELF!!!
Using hot water, thoroughly rinse all soft drink off thermometers and
stirring rods. Thoroughly rinse out your volumetric flask by gently
inserting the water supply tubing up into the flask so clean water will
“push” the sticky soft drink out. Thoroughly rinse all soft drink out of the
beaker. Check you work area and clean up any spilled soft drink. Any soft
drink that gets left on glassware or table tops makes a sticky mess when it
- Make sure that you have recorded all
data and observations as indicated in the procedure into your lab notebook.
Take any other notes you feel are important. Draw any new equipment so you
can better remember what it looks like and how to use it. Make an effort to
illustrate markings on glassware exactly as they appear on the
- To compare your data to those
collected by other students here at UC, you may
submit your data
online, filling in all the required blanks, and
view class data
- As you compare the class data, which
soft drinks had the most sugar? You should think about and comment on the
implications, healthwise, for someone who drinks a lot of soft drinks.
Other Things to Include in Your Notebook
Make sure you have all of the following in your lab notebook:
- all handout pages (in notebook or separate protocol book)
- all notes you take during the introductory mini-lecture
- all notes and data you gather as you perform the experiment
- all requested calculations based on those data
- print-out of class data (available online)
- (if not drawn as part of the pH lab) drawing (yours!) of
thermometer used with detail of the actual markings and
range (that looks like a thermometer, not like a worm)
- drawing (yours!) of stove used with detail of markings on
any important knobs or dials
- answers to all discussion questions, a summary/conclusion in your
own words, and any suggestions you may have
- any returned, graded pop quiz
Copyright © 1997 by D. B. Fankhauser and J. Stein Carter. All rights reserved.
Based on printed protocol Copyright © 1982 D. B. Fankhauser
and © 1988 J. L. Stein Carter.
This page has been accessed times since 14 Mar 2001.