Percentage of Sugar in Soft Drinks


Too Much Dietary Sugar

Sugars, especially glucose, are a major source of energy for all living things. Plants produce glucose by photosynthesis and convert that and other monosaccharides into various disaccharides such as sucrose (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 “stress” diseases: diabetes and hypoglycemia, 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 addict).

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 density 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 solutes are dissolved in the water, the weight of a given volume of the solution 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 specific gravity 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.


Bibliography

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

    thermometer thermometer close-up
  1. Pour about 125 mL dH2O into a clean 250-mL beaker and insert the thermometer 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.
  2. 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

  3. 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.
    4. 100-mL volumetric flask
  4. 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 meniscus 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 water droplets.
    5. meniscus
  5. 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:   161.55 g
     wt. of empty flask:   – 61.83 g
    wt. of H2O alone:   99.72 g
  6. 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.
  7. 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 example,
    I used JunkPop
  8. “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.
  9. 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°.
  10. 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 droplets.
  11. 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:   166.17 g
    wt. of empty flask:   – 61.83 g
    wt. of soft drink alone:   104.34 g
  12. Determine the specific gravity of the soft drink by dividing the weight of 100 mL of it by the weight of 100 mL of dH2O.
    wt. of soft drink   =   104.34   = 1.0463 
    wt. of H2O 99.72
  13. 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 notebook.

    Specific Gravity of Sucrose Solutions at 20/20° C
    Specific
    Gravity    		 Percent
    Sucrose    		 Specific
    Gravity    		 Percent
    Sucrose    		 Specific
    Gravity    		 Percent
    Sucrose    		 Specific
    Gravity    		 Percent
    Sucrose
    1.00000 0.0 1.01490 3.8 1.03010 7.6 1.04582 11.4
    1.00039 0.1 1.01530 3.9 1.03050 7.7 1.04625 11.5
    1.00078 0.2 1.01570 4.0 1.03090 7.8 1.04668 11.6
    1.00117 0.3 1.01610 4.1 1.03130 7.9 1.04711 11.7
    1.00156 0.4 1.01650 4.2 1.03170 8.0 1.04754 11.8
    1.00195 0.5 1.01690 4.3 1.03211 8.1 1.04797 11.9
    1.00234 0.6 1.01730 4.4 1.03252 8.2 1.04840 12.0
    1.00273 0.7 1.01770 4.5 1.03293 8.3 1.04882 12.1
    1.00312 0.8 1.01810 4.6 1.03334 8.4 1.04924 12.2
    1.00351 0.9 1.01850 4.7 1.03375 8.5 1.04966 12.3
    1.00390 1.0 1.01890 4.8 1.03416 8.6 1.05008 12.4
    1.00429 1.1 1.01930 4.9 1.03457 8.7 1.05050 12.5
    1.00468 1.2 1.01970 5.0 1.03498 8.8 1.05092 12.6
    1.00507 1.3 1.02010 5.1 1.03539 8.9 1.05134 12.7
    1.00546 1.4 1.02050 5.2 1.03580 9.0 1.05176 12.8
    1.00585 1.5 1.02090 5.3 1.03621 9.1 1.05218 12.9
    1.00624 1.6 1.02130 5.4 1.03662 9.2 1.05260 13.0
    1.00663 1.7 1.02170 5.5 1.03703 9.3 1.05302 13.1
    1.00702 1.8 1.02210 5.6 1.03744 9.4 1.05344 13.2
    1.00741 1.9 1.02250 5.7 1.03785 9.5 1.05386 13.3
    1.00780 2.0 1.02290 5.8 1.03826 9.6 1.05428 13.4
    1.00819 2.1 1.02330 5.9 1.03867 9.7 1.05470 13.5
    1.00858 2.2 1.02370 6.0 1.03908 9.8 1.05512 13.6
    1.00897 2.3 1.02410 6.1 1.03949 9.9 1.05554 13.7
    1.00936 2.4 1.02450 6.2 1.03990 10.0 1.05596 13.8
    1.00975 2.5 1.02490 6.3 1.04032 10.1 1.05638 13.9
    1.01014 2.6 1.02530 6.4 1.04074 10.2 1.05680 14.0
    1.01053 2.7 1.02570 6.5 1.04116 10.3 1.05723 14.1
    1.01092 2.8 1.02610 6.6 1.04158 10.4 1.05766 14.2
    1.01131 2.9 1.02650 6.7 1.04200 10.5 1.05809 14.3
    1.01170 3.0 1.02690 6.8 1.04242 10.6 1.05852 14.4
    1.01210 3.1 1.02730 6.9 1.04284 10.7 1.05895 14.5
    1.01250 3.2 1.02770 7.0 1.04326 10.8 1.05938 14.6
    1.01290 3.3 1.02810 7.1 1.04368 10.9 1.05981 14.7
    1.01330 3.4 1.02850 7.2 1.04410 11.0 1.06024 14.8
    1.01370 3.5 1.02890 7.3 1.04453 11.1 1.06067 14.9
    1.01410 3.6 1.02930 7.4 1.04496 11.2 1.06110 15.0
    1.01450 3.7 1.02970 7.5 1.04539 11.3 1.06153 15.1
    For example,
    from this chart, a specific gravity of 1.0463 corresponds to 11.5% sugar.
  14. 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,
    11.5% = 0.115.
    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 sample.
    decimal form of percentage × weight of soft drink
    = grams of sugar per 100 mL of soft drink
    For example,
    0.115 × 104.34 g = 12.00 g of sugar
    in 100 mL of that soft drink.
  15. 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,
    measured grams of sugar  =    X grams of sugar  
    100 mL of soft drink 355 mL of soft drink
    can be used to determine the grams of sugar in your can of soft drink. Solving for X gives:
    3.55 × measured grams of sugar = X grams of sugar/can of soft drink.
    For example,
    3.55 × 12.00 g = 42.60 g of sugar per can.
    Calculate the grams of sugar in a can of your soft drink and record this number in your lab notebook.
  16. 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,
    29 g of sugar per 8-oz. serving × 1.5 = 43.5 g per 12-oz. serving
    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,
    The can says it contains 43.5 g of sugar.
  17. 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
    For example,
    42.60 g × 0.22433 tsp./g = 9.56 tsp. sugar 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?
  18. How often do you drink soft drinks? How much sugar does soft drink consumption add to your diet?
    1. 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
    2. Since 1 C = 48 tsp., divide the number you just obtained by 48 to convert to cups of sugar per day.
        tsp./da    = C/da
      48 tsp./C
    3. Multiply this number by seven to calculate cups of sugar per week
      C/da × 7 da/wk = C/wk
    For example,
    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
    If you wish to go one step further, there are 52 weeks in a year, thus
    2.79 C/wk × 52 wk/yr = 145 C/yr
    By the way, my Betty Crocker’s Cookbook says that 1 lb. of sugar is approximately equal to 2 C. That would mean that
    145 C/yr × 1 lb/2 C = 72.5 lb/yr
    Packaged in typical 5-lb sacks, that would be
    72.5 lb/yr × 1 sack/5 lb = 14.5 5-lb sacks/yr
    from “only” 2 cans of soft drink a day!
  19. 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,
    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
    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. That means,
    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
    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 drinks!
  20. 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 students).
    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
    Hmmm. . . anybody looking for a good way to lose some weight?
  21. 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 dries.
  22. 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 glassware.
  23. 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 here.
  24. 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:


fankhadb@uc.edu
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 Counter times since 14 Mar 2001.