Science Buddies: "Ask an Expert"

I would like to do a science fair project on Milk and pasteurization but I can't decide what I would like my project or Hypothesis to be. I would appreciate suggestions!
Thank You!!!
Liesl

Hi Liesl,

Heating milk to kill harmful bacteria was discovered by Louis Pasteur in the 1860s and it is still in use today. The two most important things about pasteurization are the temperature and the length of time that the heat is applied. These are the two variables that you could change in a project.

The one problem I see is that the milk you buy in the store is already pasteurized. You really need to get unpasteurized milk to do a proper experiment. If you happen to know someone with a small dairy herd you might be able to get some raw milk to test.

Assuming that you can't get raw milk, I think you could 'unpasteurize' it by adding a bit of plain yogurt. This contains a culture of bacteria that grow in milk. As the bacteria grow, in a day or so they will turn the milk into yogurt. But, if you pasteurize it, the bacteria should be killed and the milk will not turn into yogurt. Does that make sense? Is that something that you might be interested in doing? You could try different temperatures and times of heating and see what it takes to kill the bacteria.

Let us know what you think and we'll try to help you make a good project.

Sybee

I have plenty of access to raw milk. one of the things that kind of interests me are the benefits of raw milk verses pasteurization. I don't understand what you're saying about the yougurt

Hi Liesl,

Pasteurization kills the bacteria in milk, so i was telling you to add yogurt which contains live Lactobacillus bacteria so that the milk you used would be like it was unpasteurized. But, since you do have raw milk, just forget about the yogurt.

Heat treatment in the pasteurization process is only supposed to kill bacteria. It is not supposed to affect the nutrients in milk. I don't know if this is 100% true and it would make a good project if you could figure out a way to test the milk. A calf drinks unpasteurized milk and does just fine, but I wonder what would happen if it drank pasteurized cow's milk instead. Do you have access to cows and calves as well as raw milk?

What I am thinking is that the best way to compare raw to pasteurized milk is to feed the two types to baby animals and measure their weight gain and development. That's why I was asking you about calves. However, such an experiment might not be practical for you. First you would need two (preferably six--three for each test) animals of exactly the same age--twins would be perfect--and then you would have to bottle-feed one while the other was allowed to nurse normally. Calves are usually fed twice a day and can drink 2-3 liters at a time so it would take you a while. And the milk feeding has to be continued daily for about three months until they are developed enough to eat fodder (http://animals.mom.me/bottle-feed-newbo ... 11101.html)

How are you thinking of comparing pasteurized to raw milk? You could try analyzing the proteins, fats and vitamins to see what affect heating might have on them, but such tests usually require expensive lab instruments, equipment and reagents. Heating may partially break down proteins and vitamin A but whether this changes the nutrient value of cow's milk I don't know. Some people think raw milk is more nutritious, but others point out that pasteurization prevents human diseases like tuberculosis and undulant fever: http://www.realmilk.com/health/pasteuri ... real-milk/

Let us know more about what question you were thinking of asking and we can help you design a project around your hypothesis.

Sybee

Thank you so much for lending me some of your time! I will let you know when I decide my final project