---

 

 

Do you know what Litmus paper is for? It is a special kind of paper that is used as an acid-base indicator. Placed in an acid medium, it turns pink, placed in a basic medium it turns blue.

 

Have you ever seen the plant called milflores? It produces small flowers in large clusters. The color of the flowers may be pink or blue. Like Litmus paper, this living pH indicator produces blue or mauve flowers in acidic soil and pink ones in basic medium.

 

 

Did you know that you can tell the temperature of the environment without a thermometer? Can you guess how? Well, all you need is a cricket! Male crickets make chirping sounds by rubbing together little teeth in their wings. This sound is called stridulation taken from a Latin term “stridulus” that means “squeaky”. At very low temperatures, crickets feel too cold to make these squeaky sounds. As temperature rises, the frequency by which a cricket chirps also increases.

 

According to A. E. Dolbear (1837-1910), a physicist who served as a professor at Tufts College, the number of chirps of a cricket in 15 seconds plus 40 can be a pretty accurate measure of temperature in Fahrenheit.

 

If a cricket chirps 40 times in fifteen seconds, what is the temperature of the environment in Fahrenheit?

Give the temperature reading in degrees Celsius using the formula below:

 

⁰C= (⁰F-32) x 5/9

 

 

More Topics

 

Code No. ______________

 

            Milk is important for everyone’s health and survival. It is necessary to keep bacteria out of milk so that people don’t get sick from food poisoning because of spoilage. Milk in its natural form, directly comes from a cow. It is an extremely versatile product from which a myriad of commercial products are derived. Varying amounts of fat are removed from the raw milk, resulting in different kinds of fresh milk. Skim milk has only about 0.5 percent milk fat. It is also called nonfat, even though it has this small amount of fat in it. One and two percent milk is milk with either one or two percents of fat and it is called low-fat milk. Whole milk has about 3.75 percent of fat in it.

            The purpose of this experiment is to determine whether skim, 1 percent, 2 percent and whole milk would develop the most bacteria after 1 hour, 2 hours and 4 hours of incubation. Different types of milk are tested and evaluated; the results of the experiment are that the normal (not inoculated) skim milk and one percent milk grow almost no bacteria. Milk with two percent fat and whole milk grow so many bacteria within four hours and they are too many to count.

            The findings are useful to families, nutritionists and institutions like schools for providing information on which type of milk easily get spoiled. It is important to keep bacteria out of milk so that we can’t get sick from food poisoning due to spoilage.

 

The researchers express their sincere gratitude to their energetic research adviser, Mr. Jaime S. De Vera Jr., for his concern and encouragement extended, prodding the researchers to finish their investigatory project.

The researchers also wish to express their appreciation to Dr. Brian E Ilan, the pro-active principal of the Valenzuela City Science High School, for his valuable suggestions and objective criticism made after reading the original draft, and unselfishly gave the researchers the permission to work using the school facilities during weekends.

For the assistance in the conduct of this project the researchers are grateful to their parents who allowed them to work on their project and gave their full support; Ms Clarissa M. Olavidez, the researchers’ computer teacher who gave the permission to use the computer for further research; to all the subject teachers who allowed the researchers use their class hours just to finish the research; to Mr. Jean Francis V. dela Cruz, the Physics teacher who expresses his confidence that the usefulness of this project will go a long way; and to the researchers’ Technical Writing and English teachers, Mr. Darwin M. Guianan and Ms. Jasmin B. Gaa, who edit and w check this manuscript.

Lastly love and gratitude to the Heavenly Father for giving the researcher rich ideas, principles, materials, and the people whose patience , tolerance, steadfast cooperation, and most of all, unflagging support, finally made possible for the completion of this project.

      Milk is the white liquid that comes from lactating mammals. Humans often consume milk from dairy cows. It has water, minerals, fat, protein, and carbohydrates. A lot of people drink milk because it has almost all the vitamins and minerals needed to stay healthy. There is 87.4 percent water, 0.7 percent minerals, 3.5 percent protein, and 4.9 percent carbohydrates. It also has lots of calcium to help your bones grow and remain strong. This is why doctors and nutritionists recommend that people drink milk. Children should at least drink three glasses of milk a day at the least. Adults should have one orr more. Pregnant women and women who are nursing are encouraged to drink three to four glasses of milk each day, to keep the baby and herself healthy (Worthington et al, 2001).

      There are many products made from milk, like cheese and yogurt. Some others are ice cream, butter, cultured butter milk, cream, evaporated milk, and sour cream. The most common of course, is skim, low-fat, and whole milk.

     

 

 

 

 

      This study aims to determine which milk (skim, 1%, 2%, or whole milk) would develop the most bacteria after 1 hour, 2 hours, and 4 hours of incubation. Specifically, this study sought to answer the followingproblems:

a.       How the different milk (skim, 1%, 2%, or whole milk) is affected by different span of incubation.

b.      How will the number of bacteria differ in skim, 1percent, 2 percent and whole milk?

                       

            The following hypotheses were tested in this study, H_1: There is no significant difference on the number of bacteria in the different kinds of milk after a span of incubation. H₂: There is no significant effect on the percentage of milk in term of number of bacteria after a span of incubation.

 

      This study contributes to the improvement of the storage of milk.

      This helps the teachers in promoting experiments about incubation of milk in different temperature.

      The information gained from this experiment will help families on how to keep milk out of bacteria so that the members won’t get sick from food poisoning because of spoilage.

      This also help people because they would know whether to have a skim milk, one percent, two percent or whole milk for longer period of time.

 

      This study is limited only on comparing the number of bacteria in the different kinds of milk incubated. This will lead on determining which milk (skim, 1%, 2%, or whole milk) would develop the most bacteria after different span of incubation.

 

      Pasteurization is the process of heating a liquid, particularly milk, to a temperature between 55° and 70° C (131° and 158° F) to destroy harmful bacteria without materially changing the composition, flavor, or nutritive value of the liquid. The process is named after the French chemist Louis Pasteur, who devised it in 1865 to inhibit fermentation of wine and milk. Milk is pasteurized by heating at a temperature of 63° C (145° F) for 30 minutes, rapidly cooling it, and then storing it at a temperature below 10° C (50° F). Beer and wine are pasteurized by being heated at about 60° C (140° F) for about 20 minutes; a newer method involves heating at 70° C (158° F) for about 30 seconds and filling the container under sterile conditions

      Milk in its natural form, directly from a cow, is called raw milk. It is an extremely versatile product from which a myriad of commercial products are derived. Varying amounts of fat are removed from the raw milk, resulting in different kinds of fresh milk. If the fat content is lowered to 3.25 percent, the milk is sold as whole milk. Low-fat milk typically has 1 percent or 2 percent fat. Skim milk, or nonfat milk, is the liquid that remains after removing all the cream; it contains about half a percent milk fat (Marshall R. 1991).

      Food poisoning is an illness associated with eating food contaminated by disease-causing bacteria, viruses, or parasites; natural toxins in plants and animals, such as mushrooms and shellfish; or harmful chemical agents such as insecticides and heavy metals. The symptoms of food-borne illness develop within a period of several hours to two days after eating contaminated food and usually include nausea, abdominal and stomach cramps, vomiting, and diarrhea. Dehydration (excessive fluid loss from the body) may develop, leading to thirst, dizziness, or fainting (Worthington, R., 2001)

 

 

 

 

 

 

 

 

 

 

           

            The manipulated variables were the time the milk was left in the incubator and the percentage of fat the milk contained.

            The responding variable was the amount of bacteria that grew. To measure the responding variable, the researcher counted all of the colonies of bacteria (big red dots).

                  The constant variables in this study were:

§      The amount of milk sample

§      The temperature it was stored at

§      The freshness of the milk ( the same expiration date)

§      The test method

§      The brand of milk

§      The way of counting the bacteria

§      The method of measuring the milk samples

§      The place where the milk was stored before and during the experiment

§      The location the test took place

§      The type of agar plates used

§      The type of vials used

 

 

      The researcher gathered and set out all the materials, the skim, low fat milk (1% and 2%fat milk), whole milk, 28 vials and 29 Petri film plates. The first 4  vials were labeled with skim 1hour inoculated, 1% 1 hour inoculated, 2% 1 hour inoculated and w.m. (whole milk) 1 hour inoculated. The other 4 vials were labeled same with the first 4 vials with 2 hours inoculate and the rest 4 vials with 4 hours inoculated. The inoculated 12 vials with different span of inoculation were set up in a rack. Another 12 vials were gathered based on the previous procedures; these 12 vials were labeled with 1 hour, 2 hours and 4 hours, not inoculated. The remaining 4 vials were labeled as skim (control), 1% (control), 2% (control) and w.m. (control).

      The same procedure was also followed in preparing the plates, the first twelve plates were labeled with inoculated, and the other twelve plates were labeled with not inoculated. The last 4 plates were labeled as control. Finally the extra plate was placed with water (control).

      Thirty milliliters of each type of milk were poured into the vials with corresponding label on it. The vials that were not labeled with control were placed in the incubator and stick them in a 33-35°C (85°F).The vials labeled as control were plated, to plate the milk, the researcher took the pipettor and a pipe to sucked up 1ml of milk into the pipe. The agar flap was lifted to squirt 1ml of milk into the middle of the plate. A plastic spreader was used to spread and pressed the milk onto 20 squares (the spreader was placed in the middle of the milk sample and pressed down).

After the researcher had plated the milk, the plates and vials were placed in the incubator.

      After an hour, the 1-hour vials from the incubator were plated and placed in the incubator. The 2-hour vials of milk were brought out from the incubator and lined up with their matching plates and sucked up with 1 ml of milk and squirted it into 100 ml of sterilized water. The researchers turned the plates upside down twice to mix it up. After this, the group drew up 1 ml of control water and 1/10ml of the inoculated water (the water with milk in it). This water was also plated and placed in the incubator.

      On the 4-hour milk the same process were used based on the 2-hour vials milk procedure. Finally the plates were placed in the incubator and were left over night.

      On the next day the plates were took out from the incubator and the big red dots or the colonies of bacteria were counted. The researchers did not count the small dots because they have not yet grown into colonies of lacto bacillus. The number of dots or colonies was recorded on the data sheets. Some colonies were hard to count so the researchers just recorded TNTC which stands for “too numerous to count”.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Graph 1, shows the different types of milk that used by the researchers in this experiment. There are four lines for each type of milk, one each for the different amounts of time the milk was incubated (either 0, 1, 2, or 4 hours). The skim milk (the first four lines), grew almost no bacteria. The 1 percent milk grew very little bacteria, and the 2 percent and whole milk grew so many bacteria that it went off the charts and to much to count (TNTC).

 

 

Graph 2. shows the different types of milk that used by the researchers in this experiment. There are four lines for each type of milk, one each for the different amounts of time the milk was incubated (either 0, 1, 2, or 4 hours). This milk was introduced to bacteria meaning this milk was inoculated. The milk with higher fat content and with longer incubation period produced more bacteria. The 2% milk (#3) and whole milk (#4) grew so many bacteria that it went off the charts. Some colonies were hard to count so the researchers just recorded TNTC which stands for “too numerous to count”.

 

Milk is perishable commodity and it spoils very easily. Its low acidity and high nutrient content make it the perfect breeding ground for bacteria, including those which cause food poisoning (pathogens).The pH level, oxygen availability, temperature and the initial concentration of pasteurization-surviving bacteria are the factors that influence bacterial growth in milk. Milk with higher fat content allows bacteria to produce in greater numbers. Bacteria are one-celled organisms that live almost everywhere. They are usually 0.3 to 2 microns in diameter and very microscopic. They may cause disease that may result to fatality.

The original purpose of this experiment was to determine whether skim, 1 percent, 2 percent, or whole milk would grow the most bacteria at 1 hour, 2 hours and 4 hours. The results of the experiment were that normal (not inoculated) skim milk and one percent milk grew almost no bacteria. Milk with two percent fat and whole milk grew so many bacteria within four hours that there were too numerous bacteria to count (TNTC).

The researchers would like to suggest that more trials should be done on this experiment. The researchers would like also to suggest trying other brands of milk rather than just one to have more insights.

 

 

 

 

 

§                  Facklam, Howard and Margery “Bacteria “ New York: Twenty first Century 

            Books, 1994 pp. 7-10

§                  Marshall, Robert. “Milk” World Book Encyclopedia 1991. pp 545-550

§                  Moore, Stephen. “Pasteurization” Microsoft Encarta, 2001.

§                  Puccio, Frank. “Nature’s Children Cows.” Danbury CT: Grolier Educational,  

            (1997). pp. 27, 28, 35.

§                  University of Texas Houston Medical School.“Lactobacillus” [Online] Available

http: // medic.med.uth.tmc.edu

§                  Worthington-Roberts, Bonnie. “Whole Milk, Low-Fat Milk and Skim Milk.”      

            Microsoft Encarta, 2001.

1. Bioremediation
2. Ecosystems Management
3. Environmental Engineering
4. Land Resource Management, Forestry
5. Recycling, Waste Management

1. Air Pollution and Air Quality
2. Soil Contamination and Soil Quality
3. Water Pollution and Water Quality

1. Climatology, Weather
2. Geochemistry, Mineralogy
3. Paleontology
4. Geophysics
5. Planetary Science
6. Tectonics

1. Disease Diagnosis and Treatment
2. Epidemiology
3. Genetics
4. Molecular Biology of Diseases
5. Physiology and Pathophysiology

1. Antibiotics, Antimicrobials
2. Bacteriology
3. Microbial Genetics
4. Virology

1. Agriculture/Agronomy
2. Development
3. Ecology
4. Genetics
5. Photosynthesis
6. Plant Physiology (Molecular, Cellular, Organismal)
7. Plant Systematics, Evolution

1. Development
2. Ecology
3. Animal Husbandry
4. Pathology
5. Physiology
6. Populations Genetics
7. Systematics

1. Clinical & Developmental Psychology
2. Cognitive Psychology
3. Physiological Psychology
4. Sociology

1. Analytical Chemistry
2. General Chemistry
3. Inorganic Chemistry
4. Organic Chemistry
5. Physical Chemistry

1. Bioremediation
2. Ecosystems Management
3. Environmental Engineering
4. Land Resource Management, Forestry
5. Recycling, Waste Management

1. Air Pollution and Air Quality
2. Soil Contamination and Soil Quality
3. Water Pollution and Water Quality

1. Atoms, Molecules, Solids
2. Astronomy
3. Biological Physics
4. Instrumentation and Electronics
5. Magnetics and Electromagnetics
6. Nuclear and Particle Physics
7. Optics, Lasers, Masers
8. Theoretical Physics, Theoretical or Computational Astronomy

1. Electrical Eng., Computer Eng., Controls
2. Mechanical Engineering,
3. Robotics
4. Thermodynamics, Solar

1. Bioengineering
2. Civil Engineering, Construction Eng.
3. Chemical Engineering
4. Industrial Engineering, Processing
5. Material Science

1. Aerospace and Aeronautical Engineering,
2. Aerodynamics
3. Alternative Fuels
4. Fossil Fuel Energy
5. Vehicle Development
6. Renewable Energies

1. Algorithms, Data Bases
2. Artificial Intelligence
3. Networking and Communications
4. Computational Science, Computer Graphics
5. Software Engineering, Programming Languages
6. Computer System, Operating System