Why does milk separate

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Image: iStock. Ink and solutions of soap and detergents are some common examples of a colloidal solution. This is why milk appears to be white.

Subscribe to Weekly Newsletter :. Donate Now. Post a Comment. Please Sign In to post a comment. Is this cheese? Well, it all comes down to science.

Milk is made up of bunch of different things including fat, protein and sugar, and even has good bacteria in it. Curdling happens when a few of those things interact in the milk. However, the premise of creating cheese starts a similar way. In essence, kappa casein normally keeps the majority of milk protein soluble and prevents it from spontaneously coagulating. Chymosin proteolytically cuts and inactivates kappa casein, converting it into para-kappa-casein and a smaller protein called macropeptide.

Para-kappa-casein does not have the ability to stabilize the micellar structure and the calcium-insoluble caseins precipitate, forming a curd. Casein molecules can also be separated from the whey by precipitation of the casein with acid similar to what happens in the stomach when milk is consumed or by disrupting the micellar structure by partial hydrolysis of the protein molecules with a proteolytic enzyme.

In the stomach of the young of many species is an enzyme called rennin which specifically hydrolyzes part of the casein micelle resulting in formation of a curd.

A classic precipitation method for casein in cow milk which is done in the laboratory is to slowly add HCl 0. The casein will gradually form a precipitate while relatively little of the other milk proteins will precipitate. Different combinations of controlled acid precipitation and enzymatic hydrolysis of casein are the foundation of the cheese industries.

Often specific bacterial cultures are used to establish the conditions for lowered pH and secretion of proteolytic enzymes which form the different types of cheese. Whey is the liquid remaining after milk has curdled and been strained.

Whey protein is a high-quality protein naturally found in milk products. Whey proteins , also called serum proteins, do not contain phosphorus and do not coagulate at pH 4. Traditinally the whey from sheeps milk is cooked down until it is soft fluffy curds. As the pH drops and becomes more acidic, the protein casein molecules attract one another and become "curdles" floating in a solution of translucent whey.

Curds are a dairy product obtained by coagulating milk in a process called curdling. The coagulation can be caused by adding rennet or any edible acidic substance such as lemon juice or vinegar, and then allowing it to sit.

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What Proteins are contained in milk? It is found in milk as a suspension of particles, called casein micelles, Casein contains a high number of proline residues, which do not interact.

It is found in milk as a suspension of particles, called casein micelles, Image: Casein micelle, kappa cassein in blue, alpha casein in red, beta casein in magenta, oxygen from water in cyan. Enter chymosin Chymosin proteolytically cuts and inactivates kappa casein, converting it into para-kappa-casein and a smaller protein called macropeptide.