Lactose – milk sugar - is made of several types and grades: pharmacopoeial, refined, nutritional, raw sugar (technical lactose).

Milk raw sugar is made of several grades depending on the content of lactose, water and nitrogen compounds: improved, prime and first grade.

Milk sugar is produced in several ways: condensation of whey with the following crystallization of lactose from supersaturated solution or drying of milk whey that was preliminary purified by membrane methods.

 

The average composition of raw sugar,%

  • Water content -2,0-3,0
  • Ash - 1.5-3.0
  • Nitrogen compounds - 1.0-3.0
  • Lactose - 95.5 (improved grade); 93.1 (prime grade); 90.0 (first grade).

 

The technological process of the milk raw sugar:

  • Acceptance, evaluation of quality of raw product
  • Purifying of milk from fat and casein dust
  • Thermal coagulation of whey proteins 90-95 °С
    • Cheese whey is acidified to 30-35 °Т
    • Curd and casein whey is deoxidized with alkali - 10-15 °Т
  • Centrifugation for clarification of whey
  • Condensation of purified clarified whey - 60-65 % of solids
  • The crystallization of lactose
    • Continuous operation - 35 hours, from 90 to 10 °С
    • Accelerated mode - 15 hours, from 70 to 10 °С
  • Separation of the crystals from the molasses by centrifugation
    • Humidity of crystallized milk sugar - 8-12 %
  • Drying of milk sugar
    • The temperature of the heating air at the inlet of the drying plant - 130-140 °С, at the outlet - 65-75 °С
  • Cooling in pneumotransport
  • Packing, packaging

 

The result is raw sugar. The further processing of raw sugar results in refined or pharmacopoeial milk sugar with lactose content of 99,0-99,5 %:

 

Nutritional milk sugar.

The composition of milk sugar,%: lactose - 95.7, moisture - 1.8, ash - 1.5, nitrogen compounds - 0.16.

Additional operation of the technology of nutritional milk sugar is refining. It is carried out at 70-80 °С during 30 minutes with constant stirring.

Impurities are removed by clarifying activated carbon, diatomites.

 

Refined milk sugar.

Composition,%: Lactose - 98.6, Moisture - 1.0, ash - 0.3.

Milk raw sugar of prime grade is used as raw product.

Additional operations of the process are dissolution of raw sugar in hot water at the temperature of 900С; purification and filtration for isolation of the activated carbon and coloring agents, grinding of lactose powder.

 

The technological process of lactose production with use of membrane plants

  • collection, cooling of whey;
  • removal of the protein dust and fat;
  • heat treatment;
  • ultrafiltration of whey (removal of whey proteins);
  • nanofiltration of whey (condensation and partial demineralization);
  • demineralization of lactose concentrates via electrodialysis;
  • if required, decalcification;
  • separation and molasses, bleaching by decanters;
  • drying.

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