CLASS 4

DAIRY PRODUCTS: MILK PROCESSING & CURDLING 

In the class we learned about dairy products.

To begin, the main proteins in milk are: 

• Casein
• Albumin 
• Globumin
• Other important aspects are sugar, water, minerals and microorganisms.
• The curd is formed when milk is coagulated with lactic acid or other acid
• organic or with rennet, subsequently removing the serum.

STANDARDIZATION OF MILK

To make milk products, milk with different fat contents is needed.

For this reason, it is sometimes used to standardize it, that is, to lower or increase its

fat content, by skimming or adding cream, respectively.

FILTRATION OF MILK

The filtrate of milk to prepare curd can be made with metal filters or with

very clean and disinfected canvases. By filtering the milk, the most impurities are eliminated

thick that she brings with her and to curd will be of better hygienic quality.

PASTERIZATION OF MILK

Milk to make curds should be pasteurized at 63 ° C for 30 minutes or at 72 ° C

for 15 seconds. The purpose of pasteurization is to obtain a curd with a

purer flavor and with the least amount of undesirable microorganisms.

These bacteria die by heating the milk at the following temperatures and times:

60 ° C for 60 minutes.

65 ° C for 4 minutes

68 ° C for 1 minute.

72 ° C for 12 minutes

Calcium precipitation:

Calcium together with the rennet causes the coagulation of milk. When a part precipitates

of calcium, this does not curdle well. To counteract this defect, chloride is added

calcium to pasteurized milk before curdling.

Milk curd

Coagulation is a phenomenon that consists in the precipitation in lumps of

casein micelles, which bind and form a gel (similar to gelatin),

compact that is imprisoned in the serum.

Principles of Coagulation

The coagulation of the milk can be carried out by acids by rennet or by mixing the

two previous ones.

A. Acid coagulation (lactic acid):

This type of coagulation is what is observed when you leave your luck

milk collected in an appropriate way.

Lactic acid bacteria degrade lactose to form lactic acid, which increases

acidity (low pH) of the milk causing the alteration of casein micelles. The

acidification is always accompanied by a demineralization of micelles.

(Loss of calcium).

The milk starts to coagulate at a pH of 5.2 or less

Rennet or enzymatic coagulation:

This coagulation is observed when enough milk is added to the warm milk

of rennet. This mechanism causes a breakdown of casein, with which it loses

its stabilizing properties, in the presence of calcium. Casein micelles form

a network which retains in its interior the lacto serum and the fat globules. At

development of milk coagulation by rennet action involved several

factors:

• The dose (amount of rennet).
• The temperature.
• The acidity of the milk.
• Content of calcium phosphate in milk.
• Size of casein micelles.
• Content of calcium phosphate in milk.
• Amount of soluble proteins in milk.

Cuajada con melao.