110

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?

CHANGES

IN THE PH

OF

COFFEE

Valeria Bustamante

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 & Ph In Coffee." LIVESTRONG.COM . N.p., n.d. Web. 25 Apr. 2013.

<http://www.livestrong.com/article/305252-caffeine-ph-in-coffee/>.

"Características Químicas de la Leche y el Yogurt | Textos Científicos." Textos Científicos | Química,

física, ecología, informática y otras áreas de la ciencia. N.p., n.d. Web. 25 Apr.

2013. <http://www.textoscientificos.com/alimentos/yogur/caracteristicas-

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 Help, Periodic Table. N.p., n.d. Web. 25 Apr. 2013.

<http://chemistry.about.com/od/foodchemistryfaqs/a/Is-Milk-An-Acid-Or-A-

Base.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.coffee-

mate.com/Products/Original.aspx#cb8c631a-bf1c-461e-8ccf-9fb0969f2dcc>.

"Sweetened Condensed Milk." Food.com . N.p., n.d. Web. 25 Apr. 2013.

<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-of-

Cornstarch>.

"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 (Café Minerva™ brewed coffee, time the pH measuring stick is left submerged (10 min.)

Materials: 1) 3 ¾ cup of boiling water (100°C) 2) 1.5 cups of brewed coffee (Café Minerva™) 3) ¼ cup plain, flavorless yogurt (Kiosko™) 4) ¼ cup low-fat milk (Vita™) 5) ¼ cup non-diary coffee creamer (Coffee-Mate™) 6) ¼ cup sweetened condensed milk (La Lechera™) 7) 15 pH measuring sticks 8) Measuring cups 9) Post-its for labels 10) 5 ceramic cups

Procedure: 1) Boil 3 ¾ cups of water 2) Serve ¾ cup of water in each of the 5 cups

3) Add 3⁄8 cup of coffee in each cup 4) Label each cup according to the substance that will be added to

it 5) Add ¼ cup of Coffee-Mate™ in the corresponding cup 6) Add ¼ cup of sweetened condensed milk in the corresponding

cup 7) Add ¼ cup of low-fat milk in the corresponding cup 8) Add ¼ cup of plain, flavorless yogurt in the corresponding cup 9) Leave the 5th cup only with the coffee and water that were

added previously 10) Submerge three pH measuring sticks inside each cup 11) Allow the pH measuring sticks to remain submerged for 10

minutes 12) Remove one pH measuring stick from each cup 13) Observe the color on the pH scale it resembles the most while

the stick is still moist 14) Record pH level for each 15) Remove the second pH measuring stick from each cup 16) Observe the color on the pH scale it resembles the most while

the stick is still moist 17) Record pH level for each 18) Remove the last pH measuring stick from each cup 19) Observe the color on the pH scale it resembles the most while

the stick is still moist 20) Record pH level for each

Results

Changes in the pH of coffee when added different substances

Substance added to coffee (Independent Variable)

Ph

(Dependent Variable)

Measurement1 Measurement 2 Measurement 3 Average

Plain brewed coffee Control

5 5 5 5

Non-diary coffee creamer

(Coffee-Mate™)

8 8 8 8

Sweetened condensed milk 7 7 7 7

Low-fat milk 6 6 6 6

Plain, flavorless yogurt 4 4 4 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 coffee’s pH changed the most, from 5 to 8, with the addition of the non-

diary creamer Coffee-Mate™, 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