點解檸檬汁加入奶會有d凝結物??

奶入面有隻protein成份叫casein, 本身是不太溶於水. 一加檸檬汁, 就更加唔肯溶, 跑晒出來, precipitation 凝結.
casein含有ca+ 成分, 係一隻含phorsphorus的protein,
佢既amino acid chain 入面都冇sulphur, 所以冇可能有disulphide bond, 即係冇可能被denatured [by heat or by pH].
Casein precipitation係可以用加入alkaline來還原.
參考資料:
http://en.wikipedia.org/wiki/Casein
Casein (from Latin caseus "cheese") is the most predominant phosphoprotein found in milk and cheese. When coagulated with rennet, casein is sometimes called paracasein. British terminology, on the other hand, uses the term caseinogen for the uncoagulated protein and casein for the coagulated protein. As it exists in milk, it is a salt of calcium.
Casein is not coagulated by heat. It is precipitated by acids and by rennet enzymes, a proteolytic enzyme typically obtained from the stomachs of calves. The enzyme trypsin can hydrolyze off a phosphate-containing peptone.
Casein consists of a fairly high number of proline peptides, which do not interact. There are also no disulphide bridges. As a result, it has relatively little secondary structure or tertiary structure. Because of this, it cannot denature. It is relatively hydrophobic, making it poorly soluble in water. It is found in milk as a suspension of particles called casein micelles which show some resemblance with surfactant-type micellae in a sense that the hydrophilic parts reside at the surface. The caseins in the micelles are held together by calcium ions and hydrophobic interactions.
The isoelectric point of casein is 4.6. The purified protein is water insoluble. While it is also insoluble in neutral salt solutions, it is readily dispersible in dilute alkalis and in salt solutions such as sodium oxalate and sodium acetate.

十分詳盡!thx

chemical reaction take place
奶的ca2+和檸檬汁產生reaction

檸檬汁加入奶..........係造芝士的方法.........
果d凝結物就係芝士啦~
原因不明............