Why does the Milk Curdle when I add Vinegar?

Well, I knew that I had to answer this question, but seriously, the chemical bonds and everything look so complicated. Seriously, I went on this site: http://www.itisacqui.it/sitob/formagette/curdling.htm to find out what happens, but it's so hard to understand. ;-;
Anyway, I might ask Ms Zhang for help on it ^^''
Until then, I have a diagram. Of casein.

I'm not gonna lie, I have NO IDEA as to what the labels on the picture are.
All will reveal itself in the due course of time... 

Anyway, I went on yahoo answers and google to try and find out the answer to the question that is on the title of this post.
I'm not even sure if we're allowed to use yahoo answers. LOL.
Ah well, I'll just trust the people with a professional looking profile picture. AHAHAH.


One person said "The hydrogen ions from vinegar (5% water solution of acetic acid) react with -NH2 groups of lysine and asparagine to clot the milk and drive proteins out of solultion."
Um, yeah, so what is lysine, asparagine (related to asparagus?) and MINUS NH2? I understand the NH2 part but why the minus?!! There was also a typo in 'solultion'. Now I know why teachers don't like yahoo answers.

On to the next website. A cooking website. Don't you just love my variation in sources. Not. I should be using books or something shouldn't I? Too bad, it's the 21st century
According to Shirley Corriher on  http://www.finecooking.com/why-vinegar-curdles-milk.aspx "Acid on protein causes the protein to coagulate, because the acid is actually "cooking" the protein strands. When vinegar curdles milk, what you get is a dairy version of scrambled eggs." and that "When in doubt, a little cornstarch is always good insurance to prevent curdling."
Well, at least I can understand this answer... No, I still don't know what "coagulate" is. Why isn't this taught in school? -cries- Anyway, next time I am going to do the following because I'm really tired right now and need a shower:

• Find out why milk curdles when I add vinegar? (what I should have answered here)
• Learn what coagulate is
• Ask Ms Zhang for help
• Try and find more stuff on what happens when I add more vinegar to my milk (there are seriously NO websites with this!!!)

Different Types of Milk

So, for my experiment, obviously I'm going to do more than one experiment, because otherwise it would be too easy and I wouldn't be able to make very many conclusions. I think I said that first I'll do experiments where the independent variable is how much vinegar is added to the milk. My second "lot" of experiments is going to be with a fixed about of vinegar but with different types of milk. So this is research on the the second experiement.

It's said that whole milk is recommended for children, teenagers and body builders, and people trying to lose weight should drink skim milk which is actually funny . This is because, according to differencebetween.net (http://www.differencebetween.net/object/difference-between-skimmed-milk-and-whole-milk/) whole milk has all of the fat from the original cow milk, and usually, there is 3.5% of milk fat** for every cup of milk. However, in skim milk, there is a skimming process where as much fat as possible is taken out. This leaves the skim milk with 0.5% of milk fat, because obviously, not all of the milk fat is taken out.

The fat from skim milk is taken out by centrifuges. (http://www.answerfitness.com/tag/whole-milk-versus-skim-milk/) (hmm. this term seems so familiar. oh yes, year 8 FTW) Based on personal knowledge, centrifuges spin a liquid around and the excess solid is taken away. I'm pretty sure this is also how blood is put into a centrifuge and thats how you can see the plasma, red bloods cells and white blood cells.

 The fact that whole milk has more fat in it than skim milk means it's tastier. Obviously. I hate skim milk. It already smells, so curdling it will make it even worse.

I should really start my experiment.

**is the fatty portion of milk. wikied the definition....^^ (http://en.wikipedia.org/wiki/Butterfat)

SRP update...

I feel so bad, I haven't updated this in so long. I had to read over my posts to see what I had done in relation to my experiment... and realised why I got such a bad mark D: Anyway, I'll try harder from now on.

Ok, so I did a little more research and I found out some really interesting stuff. I might repeat some stuff but it's worth repeating.

Well, from the mixing of the vinegar and milk, you get casin as I've said before, and it occurs when the protein in the milk meets the acid in the vinegar. True plastics, called polymers, are a different in the way that they can be solids or liquids, and the molecules can chain themselves together, which is why you can get stuff like slime.
I got this information from:
http://www.sciencebob.com/experiments/polymer.php

On this website (http://pbskids.org/zoom/activities/sci/plasticmilk.html) it says that the chemical reaction separated the milk into two parts, the curds which is the solid and the liquid which is the whey. Also, on this website, kids as young as 6 did this experiment, which made me feel really bad. But they said that it felt like "wet playdough" and "smelt really bad". Something in my research with variables finally came up and a person said "
The skim milk smelt the worst, the 1% was the best we thought, 2% and whole milk produced the most, but was the bumpiest. " I have no idea what they're going on about with the percentages but I can conclude that whole milk might create more casein. I am seriously wondering why. Another thing to research.

Another thing I found out was that Little Miss Muffet was really eating this, in her nursery rhyme. This is because curds and whey as mentioned above can be made from milk by the help of a coagulant (something that helps cause a transformation of a liquid for example into or as if into a soft, semisolid, or solid mass). I saw the pictures of it and it looks seriously gross...

Um yeah. I'm SO glad I live in the 21st century, because people actually had to eat that stuff back in the day when their milk spoilt. O_O''
Casein was also manufactured into buttons, crochet hooks and knitting needles between the World War 1 & 2.  After World War II advances in technology made casein plastics obsolete.