Percentage of Sugar in Soft Drinks

Background Procedure Submit Data

Background — Percentage of Sugar in Soft Drinks

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 127 lb. 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 1/3 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.

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 mLwt. 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

Activity — Determination of Percentage of Sugar in Soft Drinks

Materials Needed

Procedure

  1. Pour about 125 mL dH2O into a clean 250 mL beaker and insert the thermometer to check temperature. 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 way 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 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 will 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. 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 H2O 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 (medicine dropper) to adjust the volume and dry off any excess water droplets.
  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.
  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 the 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/or 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 bubbles and excess 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 H2O99.72 
  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
    1.000000.0 1.014903.8 1.030107.6 1.0458211.4
    1.000390.1 1.015303.9 1.030507.7 1.0462511.5
    1.000780.2 1.015704.0 1.030907.8 1.0466811.6
    1.001170.3 1.016104.1 1.031307.9 1.0471111.7
    1.001560.4 1.016504.2 1.031708.0 1.0475411.8
    1.001950.5 1.016904.3 1.032118.1 1.0479711.9
    1.002340.6 1.017304.4 1.032528.2 1.0484012.0
    1.002730.7 1.017704.5 1.032938.3 1.0488212.1
    1.003120.8 1.018104.6 1.033348.4 1.0492412.2
    1.003510.9 1.018504.7 1.033758.5 1.0496612.3
    1.003901.0 1.018904.8 1.034168.6 1.0500812.4
    1.004291.1 1.019304.9 1.034578.7 1.0505012.5
    1.004681.2 1.019705.0 1.034988.8 1.0509212.6
    1.005071.3 1.020105.1 1.035398.9 1.0513412.7
    1.005461.4 1.020505.2 1.035809.0 1.0517612.8
    1.005851.5 1.020905.3 1.036219.1 1.0521812.9
    1.006241.6 1.021305.4 1.036629.2 1.0526013.0
    1.006631.7 1.021705.5 1.037039.3 1.0530213.1
    1.007021.8 1.022105.6 1.037449.4 1.0534413.2
    1.007411.9 1.022505.7 1.037859.5 1.0538613.3
    1.007802.0 1.022905.8 1.038269.6 1.0542813.4
    1.008192.1 1.023305.9 1.038679.7 1.0547013.5
    1.008582.2 1.023706.0 1.039089.8 1.0551213.6
    1.008972.3 1.024106.1 1.039499.9 1.0555413.7
    1.009362.4 1.024506.2 1.0399010.0 1.0559613.8
    1.009752.5 1.024906.3 1.0403210.1 1.0563813.9
    1.010142.6 1.025306.4 1.0407410.2 1.0568014.0
    1.010532.7 1.025706.5 1.0411610.3 1.0572314.1
    1.010922.8 1.026106.6 1.0415810.4 1.0576614.2
    1.011312.9 1.026506.7 1.0420010.5 1.0580914.3
    1.011703.0 1.026906.8 1.0424210.6 1.0585214.4
    1.012103.1 1.027306.9 1.0428410.7 1.0589514.5
    1.012503.2 1.027707.0 1.0432610.8 1.0593814.6
    1.012903.3 1.028107.1 1.0436810.9 1.0598114.7
    1.013303.4 1.028507.2 1.0441011.0 1.0602414.8
    1.013703.5 1.028907.3 1.0445311.1 1.0606714.9
    1.014103.6 1.029307.4 1.0449611.2 1.0611015.0
    1.014503.7 1.029707.5 1.0453911.3 1.0615315.1
    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 drink355 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. If this is the case, 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. Record the (corrected) manufacturer’s reported number and comment on how close this is (or is not) to your measurement. For example,
    The can says it contains 43 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. Many 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. 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. 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.
    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 would be roughly equivalent to 72.5 lb of sugar. Packaged in typical 5-lb sacks, that would be 14.5 sacks of sugar from “only” 2 cans of soft drink a day!
  19. To compare your data to those collected by other students here at UC, you may submit your data via the World Wide Web, filling in all the required blanks. View class data here.
  20. 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.
  21. 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.
  22. As you compare the class data, which soft drinks had the most sugar? You may wish to comment on the implications, healthwise, for someone who drinks a lot of soft drinks.
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