The largest volume in the total production of milk powder products is for whole milk powder of spray drying and its variants.

The main types of dairy powder products include cow whole milk powder with 20 and 25% fat content, domestic milk powder, cow skim milk powder, cream powder, high-fat cream powder, fermented powder products.

Dairy powder products are made from normalized pasteurized condensed whole or skim milk, cream, buttermilk dried on the spray drying plants. Moisture content in powder products varies from 2 to 7%.

Solubility is one of the main indicators of quality of dairy powder products. Solubility index should be not more than - 0.2-0.5 ml of primary sludge.

Canned powder milk differs from the other canned milk by higher solids content that gives them the highest transportability. Solids content depending on the type of product is 95-98%.

Qualitative characteristics of powder milk may be represented as a set of physical, chemical and microbiological parameters the most important of which are: protein, fat, lactose, minerals, moisture, titratable acidity, solubility index, an index of whey proteins, temperature resistance and microbiological contamination.

Whole milk powder (WMP)

It is fresh whole pasteurized milk dried to a fine powder.

Physical and chemical parameters of whole milk powder

Parameter Norm for whole milk powder
20% fatcontentin transport package 25% fat content for production of baby foods
spray drying film drying in transport package
consumption package transport package
Moisture content, %, not more than 4,0 4,0 4,0 5,0 3,0
Fat content, %, not more than 20,0 25,0 25,0 25,0 25,0
Protein content, %, not more than - - - - 23,0
Solubility index, cm3 of primary sludge, not more than:

-prime grade

-first grade

-baby foods

 

0,3

0,4

-

 

0,1

-

-

 

0,3

0,4

-

 

0,3

1,5

-

 

-

-

0,1

Acidity, 0Т, not more than 21 17 21 21 17
Cleanliness, group, not lower 2 1 2 2 1

 

Graded estimation of whole milk powder by organoleptic characteristics.

Parameter WMP characteristic
Prime grade First grade
Taste and smell Peculiar to fresh pasteurized milk at the spray drying and boiled milk at the film drying without foreign tastes and smells The same as for the prime grade. It is permissible to have a slight feedy taste and for milk of spray - the taste of overpasteurization
Consistency Fine dry powder or powder consisting of particles of agglomerated milk powder
Insignificant amount of lumps that easy fall to pieces under mechanical effect is permissible For film drying – dry powder from  fragmented films
Color White with a light cream color for spray milk; cream color for film milk
  Separate burnt particles are permissible

 

Technology of production of WMP consists of the following successively performed operations:

  • Acceptance and estimation of the quality of milk
  • Cleaning and cooling
  • Short-term milk stand-by
  • Normalization of milk
  • Pasteurization of milk formula
  • Temporary redundancy mixture
  • Thickening of infant formula
  • Homogenization of milk formula
  • Drying of condensed milk formula
  • Cooling of the milk powder in the flow
  • Packing and packaging of the finished product

 

Acceptance of milk at the plant is carried out after evaluation of its quality and suitability. To measure the mass and volume there are used mass measuring devices – non-stop counter devices, flow meters, etc.

Cleaning of milk from mechanical impurities and micro-organisms is carried out by using filters and centrifuge treatment in separator-cleaners. To intensify the allocation process of microorganisms from milk the bactofugation is used at which 99.97% of all bacteria are removed, E. coli is completely released and about 90% of all spore microorganisms are also removed.

Cooling. If the stand-by is less than 12 hours the cooling is made up to 4-8 °C. Cooling is performed by using a plate cooler.

The stand-by is carried out in bulk-capacity tanks, jacketed, with agitator.

Normalization of milk is the necessary operation to obtain the product with the standard content of fat and skim solids. For this purpose the skim milk or buttermilk are usually used (in an amount up to 20% of the total volume of component of the normalization).

Pasteurization. The essence of the operation is the destruction of microorganisms and inactivation of enzymes at possibly complete retaining the original properties and biological value of raw milk. Modes of heat treatment of normalized formula prior to concentration: 90-95 °C without holding; 105-109 °C without holding; in two stages - 85-87 °C and 120-130 °C without holding. The most effective heat treatment is at the temperature exceeding 100 °C.

Condensing of infant formula is in the flow. The processes of condensation and drying should be strictly synchronized. In the case of long-term stand-by of the condensed milk formula prior to drying formation of a new structure occurs in it as well as a significant increase in viscosity, destabilization of the fat phase that complicates the drying process and reduces the quality of the finished product. For concentration of milk formula there are used multiple effect microfilm vacuum evaporators (with falling film) or multiple effect circulation one. Milk formula is concentrated up to 42-50% of dry milk solids that corresponds to the density of 1,11-1,16 g/cm3 at 50 °С. Normalized formula that leaves the calorizator of the last effect of the evaporator is directed to homogenisation.

Homogenisation is essential to prevent the formation of free (unprotected protein coat) fat in milk powder (allows reducing the rate in 2-3 times) and is conducted at the temperature of 55-600С under pressure P1 = 10.0-15.0 MPa in a single-stage homogenizer; P1 = 11.5-12.5 MPa and P2 = 2.5-3.0 MPa in a two-stage one. Drying is the final step of obtaining the finished product. Homogenized concentrate is sent directly to the receiving tanks of the drying plant. The temperature of the condensed milk before drying should be not lower than 40 °С. In order to intensify the drying it is possible to heat it up to 55-60 °C. The moisture content in the finished powder should be about 4%.

The main parameter by which the drying mode is controlled is the drying air temperature:

  • Inlet air temperature - 160-180 °C
  • The temperature of the exhaust air - 65-95 °C

 

The powder from the storage hopper is fed to the packaging machines for packaging.

Disadvantages of dairy powder products:

  • racidification (tallowy flavor and smell) is a result from the oxidation of fat. Factors contributing to their occurrence are different: the composition and properties of fat, thermal effect in various manufacturing operations, storage conditions, method of packaging. The lowest resistance to oxidation has whole milk powder produced in spring; the highest resistance - produced in summer. This is due to the increased mass fraction of natural antioxidants in summer fat.
  • lumpiness is formed in the finished product due to absorption of moisture at low integrity of the packaging;
  • unpleasant smell and taste are caused because of storing products at high humidity and poor ventilation of the warehouse.

 

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