CHANGES IN THE PH OF
COFFEE
How does the pH of brewed coffee change when creamy substances such as nondiary coffee creamer, sweetened condensed milk, low-fat milk, and flavorless yogurt are added to it?
Valeria Bustamante 110
Objective To observe the changes in the pH of brewed coffee when creamy substances such as non-diary coffee creamer, sweetened condensed milk, low-fat milk, and natural yogurt are added to it.
Background Information pH is the quantitative measure of the acidity or basicity of a liquid. It is commonly used in chemistry, biology, and agronomy. It is the concentration of hydrogen ion range between 1 and 10-14 gram-equivalents per liter, but is translates it into a more simple scale of 0-14. When the pH is 7, it means the liquid is neutral, like water. If it is below 7, the substance is considered acidic and above 7 is considered basic (“pH”).
Coffee, for example, usually has a pH of 5, but it can vary slightly in different kinds of coffee. Even though a pH of 5 does not mean that coffee is very acidic, it is still considered an acidic substance. Because of this, coffee sometimes causes heartburn and stomach pain (“Caffeine & Ph In Coffee”). In fact, 2 out of 10 people experience stomach irritation because of coffee (EurekAlert! - Science News”.
Even though many people think differently, milk is actually an acidic substance because it contains proteins that make it acid. Milk has a pH of 6.5 to 6.7, but most sources claim that it is a neutral substance because its pH is so close to 7.0 (Helmestine).
The pH of yogurt can vary depending of the fruits and flavor that has been given to it. However, once the yogurt has been fermented, its pH should be somewhere around 4. (“Características Químicas de la Leche y el Yogurt”). It is an acidic substance because, like milk, it contains lactic acid, which increases during the process of fermentation ("Lactic Acid"). Coffee- Mate™ from Nestlé is a non-diary coffee creamer. Although its pH is not given, if contains no dairy products of any kind, so probably its basicity is higher; its pH is above 7, or above milk’s pH at least. Coffee-Mate is made out of the following ingredients: corn syrup solids, vegetable oil (partially hydrogenated coconut or palm kernel, hydrogenated soybean), sodium caseinate (a milk derivative yet nor a source of lactose), and less than 2% of dipotassium phosphate (moderates coffee acidity), mono- and diglycerides (prevents oil separation), sodium aluminosilicate, artificial flavor, and annatto color. Instead of being diary-based, it is based on corn syrup, which is a type of sugar made from cornstarch (“Nestlé’s Coffee-Mate”). Cornstarch has a neutral pH level, meaning 7 (“pH of cornstarch”). Sweetened condensed milk is a mixture of whole milk and sugar. The mixture is heated until 60% of the water evaporates, leaving a sticky, sweet cream. Condensed milk is 40% sugar. Its pH is not given with exact numbers either, but it is slightly above neutral, probably somewhat over 7. Even though it is still milk and contains lactic acid, the large amount of sugar that is added to it causes the acidity to drop (“Sweetened Condensed Milk”).
Works Cited Bernstein , Michael. "Brewing up a gentler java: Dark-roasted coffee contains stomach-friendly ingredient." EurekAlert! - Science NEWS. N.p., 21 Mar. 2010. Web. 20 Apr. 2013. <http://www.eurekalert.org/pub_releases/2010-03/acs-bua030810.php>. "Caffeine
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quimicas>. EurekAlert! - Science News. "Brewing up a gentler java: Dark-roasted coffee contains stomach-friendly ingredient." EurekAlert! - Science NEWS. N.p., 21 Mar. 2010. Web. 25 Apr. 2013. <http://www.eurekalert.org/pub_releases/2010-03/acs-bua030810.php>. Helmestine, Anne. "Is Milk an Acid or a Base? - pH of Milk." About.com Chemistry - Chemistry Projects, Homework
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<http://chemistry.about.com/od/foodchemistryfaqs/a/Is-Milk-An-Acid-Or-ABase.htm>. "Lactic Acid." Encyclopædia Britannica. Encyclopædia Britannica Online School Edition. Encyclopædia Britannica, Inc., 2013. Web. 25 Apr. 2013. <http://www.school.eb.com/eb/article-9046770>. "Nestlé© Coffee-Mate." Nestlé© Coffee-Mate. N.p., n.d. Web. 25 Apr. 2013. <www.coffeemate.com/Products/Original.aspx#cb8c631a-bf1c-461e-8ccf-9fb0969f2dcc>. "Sweetened
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<http://www.food.com/library/sweetened-condensed-milk-146>. "PH of Cornstarch ." Ask Jeeves. N.p., n.d. Web. 25 Apr. 2013. <http://uk.ask.com/beauty/PH-ofCornstarch>. "pH." Encyclopædia Britannica. Encyclopædia Britannica Online School Edition. Encyclopædia Britannica, Inc., 2013. Web. 24 Apr. 2013. <http://www.school.eb.com/eb/article-9059549>.
Scientific Question: How does the pH of brewed coffee change when creamy substances such as non-diary coffee creamer, sweetened condensed milk, low-fat milk, and flavorless yogurt are added to it?
Hypothesis: If creamy substances such as non-diary coffee creamer, sweetened condensed milk, plain milk, and natural yogurt are added to brewed coffee, then its pH will increase with the non-diary coffee creamer, the sweetened condensed milk, and the low-fat milk because they are less acidic substances.
Independent Variable: substance added to the coffee Dependent Variable: pH of coffee Control: plain coffee Constants: volume of water in the coffee (3/4 cup), volume of coffee (3/8 cup), type of coffee (CafĂŠ Minervaâ&#x201E;˘ brewed coffee, time the pH measuring stick is left submerged (10 min.)
Materials: 1) 2) 3) 4) 5) 6) 7) 8) 9) 10)
3 ¾ cup of boiling water (100°C) 1.5 cups of brewed coffee (Café Minerva™) ¼ cup plain, flavorless yogurt (Kiosko™) ¼ cup low-fat milk (Vita™) ¼ cup non-diary coffee creamer (Coffee-Mate™) ¼ cup sweetened condensed milk (La Lechera™) 15 pH measuring sticks Measuring cups Post-its for labels 5 ceramic cups
Procedure: 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16) 17) 18) 19) 20)
Boil 3 ¾ cups of water Serve ¾ cup of water in each of the 5 cups Add 3⁄8 cup of coffee in each cup Label each cup according to the substance that will be added to it Add ¼ cup of Coffee-Mate™ in the corresponding cup Add ¼ cup of sweetened condensed milk in the corresponding cup Add ¼ cup of low-fat milk in the corresponding cup Add ¼ cup of plain, flavorless yogurt in the corresponding cup Leave the 5th cup only with the coffee and water that were added previously Submerge three pH measuring sticks inside each cup Allow the pH measuring sticks to remain submerged for 10 minutes Remove one pH measuring stick from each cup Observe the color on the pH scale it resembles the most while the stick is still moist Record pH level for each Remove the second pH measuring stick from each cup Observe the color on the pH scale it resembles the most while the stick is still moist Record pH level for each Remove the last pH measuring stick from each cup Observe the color on the pH scale it resembles the most while the stick is still moist Record pH level for each
Results Changes in the pH of coffee when added different substances Substance added to coffee (Independent Variable)
Plain brewed coffee
Measurement1 5
Ph (Dependent Variable) Measurement 2 Measurement 3 5 5
Average 5
Control
Non-diary coffee creamer (Coffee-Mateâ&#x201E;˘) Sweetened condensed milk Low-fat milk Plain, flavorless yogurt
8
8
8
8
7 6 4
7 6 4
7 6 4
7 6 4
Analysis
Conclusions After having carried out the whole process of measuring the pH of coffee when different substances were added to it, I can conclude that the experiment was a success. Throughout the experiment, I was able to meet my objective, which was to observe the changes in the pH of brewed coffee when creamy substances such as non-diary coffee creamer, sweetened condensed milk, low-fat milk, and plain, flavorless yogurt are added to it. Not only was I able to observe these changes, but I was also able to understand why they happened. My hypothesis, which stated that if creamy substances such as non-diary coffee creamer, sweetened condensed milk, low-fat milk, and plain, flavorless yogurt are added to brewed coffee, then its pH will increase with the non-diary coffee creamer, sweetened condensed milk, and low-fat milk because they are less acidic substances, was completely supported by my results. After adding the substances to the coffee and measuring its pH, it became clear that there had been a change in the pH. When low-fat milk was added to the coffee, its pH increased from 5 to 6 as the acidity decreased. When the sweetened condensed milk was added to the coffee, its pH became level 7, making it a neutral substance. The coffeeâ&#x20AC;&#x2122;s pH changed the most, from 5 to 8, with the addition of the nondiary creamer Coffee-Mateâ&#x201E;˘, which probably happened because the creamer has no diary-products that contribute with lactic acid; instead, it is cornstarch-based. Unlike the other substances, the addition of the yogurt to the coffee caused an increment in acidy and its pH decreased from 5 to 4. Because coffee sometimes causes stomach irritation, mixing it with milk, condensed milk, or non-diary creamers will probably reduce the risks of experiencing discomfort because of acidity. Even though I tried to diminish the risk of mistakes by being organized and scrupulous, there might still be errors of some degree in the experiment. For example, I did not consider that leaving a pH measuring stick submerged in the substance for too long can alter results. The pH of substances like coffee do not require more that 3 or 4 minutes to be measured because caffeine can influence the color that the measuring stick acquires and therefore can cause an inaccurate interpretation of the pH scale. Because I did not take this into account, I left the pH measuring sticks submerged in each cup for 10 minutes. Also, after the pH measuring stick has been submerged, it has to be read, which can be slightly tricky and subjective because it depends on each person to interpret the color on the pH scale that the stick resembles the most. To avoid these mistakes, I would suggest to consider the amount of time that the pH measuring sticks needs to be left submerged depending on the substance and later have another person interpret the results too instead of only interpreting them oneself, like I did. However, despite the minor errors and improvements that I am sure the experiment could have, it was a great opportunity to practice the use of the scientific method, develop creativity, and gain knowledge about a topic of my interest.
Annex