Student Projects in Chemistry Today
(912-006-94)
Winter 1996 - Winter 1997

Several different projects were undertaken by different members of the class; some were pilot projects which will be followed up in subsequent years while others obtained results that can now be reported.

A. Fluoride in Toothpastes: Isabelle Dancause and Karyn Belanger (1996)

Acids in our mouths, sometimes produced by bacterial fermentation of carbohydrates from the foods we eat, chip away at the enamel on our teeth, even though it is the most durable substance present in our bodies. Fluoride helps stop this dental decay in one of three ways: (1) It replaces the usual hydroxyapatite in the enamel with fluorapatite which is less likely to react with the acids in our mouths. (2) It inhibits the production of enzymes that convert the sugar we eat into the harmful acid. (3) It stops the bacteria from sticking to our teeth. Too much fluoride, however, can cause teeth to become stained and easily breakable. This project examined the effect of Crest and Aquafresh toothpastes and of dentist fluoride treatment on the loss of mass of two types of teeth when they were subjected to treatment with acid or with sugar. The two types of teeth were baby teeth (from one of our researchers!) and adult teeth obtained from a dentist.

Crest and the dentist's fluoride had about four times the concentration of available fluoride as Aquafresh, as determined using a fluoride electrode. Teeth were pre-treated for four days either with or without fluoride and then dried and weighed. After fours days treatment with either acid or sugar solutions, the teeth were again dried and weighed. The mass loss was determined.

Although the study suffered from problems of sample size (in some cases, the sample size was one tooth), some general points become evident:

1. Crest gives the best protection against tooth loss due to acid, being two to three times as effective as Aquafresh.

2. Baby teeth seem to be more susceptible to damage by acid than adult teeth (except for one case: another experiment next year!).

3. Sugar does not cause much tooth loss, at least with a four-day treatment; in fact in some cases, there was a gain in mass (perhaps due to the formation of plaque by the bacteria present on the teeth).

The researchers recommend that subsequent studies be more limited in scope and use larger sample sizes to overcome the problem of heterogeneity of the samples. It would also be recommended to carry out the treatment with acid or sugar for a longer period of time to increase the precision of the mass differences.

B. Sodium Content in Different Kinds of Soup: Sonia Beaulieu (1996)

Salt, or more specifically sodium ion, is one of the suspected bad-guys in our diets, perhaps leading to high blood pressure in later life. The purpose of the experiment was to determine the content of table salt in different kinds of commercial soups. To do this, a sodium ion-specific electrode which measures voltage as a function of sodium ion concentration was used. The voltages of solutions whose sodium ion concentrations were known were compared with that of soups made up ready to eat. The results obtained are summarized in this table which shows the milligrams of salt (in terms of sodium ion) per bowl of soup for the different types of soup:

Brand
Aylmer
Aylmer
Aylmer
Heinz
Heinz 		Soup
Beef broth
Cream of tomato
Chicken noodle
Cream of tomato
Chicken noodle 		[sodium], M
0.110
0.286
0.044
0.251
0.126 		mg sodium/250 mL
633
1640
253
1440
724

These results are quite surprising. The tomato soup, which tastes the least salty, turns out to have the highest concentration of salt, amounting to more than half the recommended upper limit of daily sodium consumption in a single bowl. An explanation for this high salt concentration might be that the soup makers wanted to counter the acid taste of tomatoes by adding salt. On the other hand, the soup that one might think as the most salty, chicken noodle, actually has the least. The different brands of the same soup also differed, with Aylmer having a higher salt concentration than Heinz for tomato soup but less for chicken noodle soup.

C. Determination of Unsaturation in Fats: Marie-Pierre Jolibois (1996)

Unsaturated fats have long been recognized as being better for our health than saturated fats, given that saturated fats contribute to the atherosclerosis that can lead to high blood pressure, heart attack and stroke. Shifting our fat intake from sources of saturated fats to unsaturated fats results in a decrease in cholesterol level in the blood. It is the cholesterol that deposits on the artery walls, along with other debris, to cause the narrowing that can block the artery. The purpose of this project was to determine the relative amounts of unsaturation of some common fats, using a method of determining the iodine number. Each double bond between adjacent carbon atoms in the fatty acid chains is capable of reacting with one molecule of iodine. Thus by reacting the fat with a solution with excess iodine and then titrating the excess against thiosulfate, by difference one can determine the amount of iodine used by the fat. The iodine value is reported as "g of iodine/g fat": the higher the value the greater the amount of unsaturation in the fat.

The results obtained were:

Fat Source

Olive oil
Butter
Crisco oil
Crisco solid 		Iodine Number
g iodine/g fat
172
37
46
97


Olive oil is a monounsaturated fat from a plant source, so it is expected to contain considerable unsaturation. Butter is from an animal source, so it is not surprising to find its value lower. Crisco oil has surprisingly little unsaturation, while Crisco solid has more unsaturation than butter, as expected. The experiment requires repetition to verify these findings, but if they are correct, it would seem that olive oil is a good choice of fat.

D. Fat Content of Weiners: Jeff Delisle (1996)

Our preoccupation with fat leads us to be concerned with the total fat content of even the humble hot dog weiner. Since chicken (without the skin) is lower in fat than beef and pork, one would expect chicken weiners to be lower in fat than ordinary beef or pork frankfurters. Some manufacturers even claim to produce weiners with reduced fat. In order to test these hypotheses, the fat was extracted from different types of weiners using ether as the solvent in a Soxhlet apparatus. The difference in mass before and after extraction corresponded to the amount of fat originally present in the weiners.

The results obtained were the following:

Brand of Weiner
Lafleur
Maple Lodge Farm
Metro
Hygrade
Metro 		Type of Weiner
Chicken
Chicken
Frankfurters
All-beef frankfurters
Light "30% less fat" 		% fat by mass
16.6
17.8
21.5
23.4
19.1


It is surprising that the chicken weiners are not very much lower in fat than the regular beef frankfurters, but what is perhaps more worrisome is that the supposedly "light" (30% less fat) weiners actually were only 11% lower in fat than the regular frankfurters. Does Metro know about this?

E. Fat Content of French Fries: Colin Shattler & Annie Claveau (1997)

The Soxhlet apparatus was used to determine the fat content of French fries from five different restaurants: Chez Ashton, St. Lawrence Cafeteria, Valentine, A & W, and McDonald's. The results obtained were the following:

Restaurant
Valentine
Chez Ashton
St. Lawrence Cafeteria
McDonald's
A & W 		% fat by mass
20.8
22.1
12.4
11.9
8.0 		% of calories from fat
52.2
50.0
32.6
33.2
25.8


It is noteworthy that all the French fries except for the two that had the highest fat content have a lower mass percent fat than the frankfurters whose composition is reported above. Given that we are advised to consume less than 30% of our calories as fat, the logical choice of restaurant for French Fries might be one of A&W, Valentine or our own St. Lawrence Cafeteria, the French fries to be eaten with a healthful fat-free salad of course! Perhaps we should forgo the hot dog!

F. Acidity of White Wines: Marie-Noelle Tanguay & Amelie Billette (1997)

The acidity of wine can be assessed on several different levels. The pH is determined by the amount of free hydrogen ion in the wine: the lower the pH, the greater the amount of hydrogen ion. The pH can be converted into a concentration of free hydrogen ion. But pH may indicate only a part of the acidity of the wine: some acids do not give up their hydrogen ion easily, being weak acids, and other acids may be in the solution as the salts of the acids. We can therefore measure the "total acidity", the "fixed acidity" and the "volatile acidity", each determined in this communication in terms of "mmol acid/L of wine": the higher this value, the greater the amount of acid. Two different wines were studied: an inexpensive Canadian wine, Plaisir d'amour, and an expensive French wine, Chateau Tanesse. The results obtained were the following:

Acidity
Free Hydrogen Ion
Total Acidity
Fixed Acidity
Volatile Acidity
Plaisir d'amour
1 mmol/L
80.0 mmol/L
73.2 mmol/L
6.8 mmol/L
 Chateau Tanesse
0.4 mmol/L
58.8 mmol/L
54.8 mmol/L
4.0 mmol/L


By all measures, the expensive wine is less acidic than the cheaper wine. Since the volatile acidity is usually acetic acid (vinegar), clearly the more expensive wine has less vinegar in it. The lower level of acidity in this wine is consistent with its having been produced from grapes which had matured in a sunny climate. Given the shorter growing season in Canada, Canadian wines often contain more acid. This in fact is the case here: by all four measures, Plaisir d'amour is more acidic than Chateau Tanesse, ranging from 34% greater fixed acidity to 70% greater volatile acidity.

G. Sulfur dioxide Content in White Wines: Miguel Friede and Thierry Richard (1997)

Sulfur dioxide is used as an antiseptic in wine making. Since residues often remain in the wine after processing, the sulfur dioxide contents of three white wines from different sources were determined using potentiometric titration with iodine. Both free sulfur dioxide and total sulfur dioxide (called "free and combined sulfur dioxide") were determined. The results obtained were the following:

Wine
Plaisir d'amour
Caballero
Chateau Tanesse
Free Sulfur Dioxide
0.288 mmol/L
0.500 mmol/L
0.682 mmol/L
 Total Sulfur Dioxide
1.34 mmol/L
2.88 mmol/L
2.20 mmol/L


Plaisir d'amour is an inexpensive Canadian wine, Caballero an inexpensive wine from Chile and Chateau Tanesse a fairly expensive French wine. While it is normal to find some sulfur dioxide in all wines, it is noteworthy that both of the wines that were grown in warmer climates have more sulfur dioxide than the Canadian wine (grown in our cooler climate). Since northern grapes are more acidic than those grown in warmer climates, these wines are often subjected to a secondary fermentation called malo-lacto fermentation in order to reduce the acidity. The organisms that accomplish this process are inhibited by sulfur dioxide. It is important to avoid this compound as much as possible if the wine is to undergo this step. It is therefore not surprising that the Canadian wine has less sulfur dioxide, both in the free and in the combined form, than either of the others. Thus, if the consumer is sensitive to sulfur dioxide, he or she should drink only Canadian wines! Could this be a new marketing strategy?

H. Tannin Content of Wines: Genevieve Briere, Melanie Lefrancois and Genevieve Caron (1997)

Tannins are polyphenolic polymers found in wine, grape juice and tea. These compounds are responsible for the astringency and bitterness of wines. Red wines normally have higher tannin contents than white wines, in the range of 600 to 900 mg/L. The tannin contents of two white wines were determined by potentiometric titration with potassium permanganate, using a carmine indigo indicator. The two wines were a Canadian wine, Plaisir d'amour and a more expensive French wine, Chateau Tanesse. In each case, it was found that the tannin content was 270 mg tannin per liter of wine. Thus these white wines have between one half and one third the tannin of red wines, as is to be expected given the lower tannin content of the white grapes from which the white wine is made. Since tannins are antioxidants, it may thus be better to drink red wines.