The raw product for the production of whey powder is whey obtained from the cheese production (cheese whey), cottage cheese (curd whey) and casein (casein whey).

Contents of lactose, lactic acid and salt in whey are the main factors that determine the modes and methods of its processing and, finally, - the duration and quality of drying.

Preparation of raw product before drying should aim at reducing the content of lactic acid and conversion of lactose contained in whey from the amorphous to the crystalline state.

This allows:

  • improving and greatly simplifying the process of whey drying;
  • improving the performance of the drying plant;
  • obtaining a product of high quality with good flowability, low hygroscopicity, non-caking during storage;
  • increasing output of the finished product.

 

The principal operation steps of whey powder production:

  • collection of whey;
  • removal of casein dust;
  • cooling (t = 8-10 °С);
  • accumulation (at t = 8-10 °С);
  • separation for the purpose of fat extraction (t = 40-45 °С);
  • pasteurization (t = 72-74 °С; τ = 15-20 s- for sweet whey; 58-62 °С, 15-20 s- for acid whey);
  • cooling (t = 8-10 °С);
  • condensing on the membrane plant (to the content of solids = 18-24%);
  • cooling (t = 8-10 °С);
  • concentration in evaporator (up to solids = 55%);
  • crystallization (crystallization degree of 60-70%);
  • cooling to the crystallization temperature (t = 30-32 °С);
  • drying;
  • packaging, storage.

 

- Operations are optional.

To keep the original quality of whey before processing it is immediately cooled after receiving to 8-10 °С; at the temperature above 10 °С - time of ageing is not more than 1 hour.

An effective way of removing casein dust and mechanical impurities is centrifugation by using self-discharging separators, vibratory or rotary filters.

The whey contains 0.1-0.6% of casein dust and approximately 0.45% of fat that should be separated as casein micelles burn up on the evaporator pipe resulting in the occurrence of discolored particles in finished product and the residue of fat - in formation of powder deposits in the drying chamber.

During the whey processing using membrane technology (nanofiltration, reverse osmosis) the fat content of the processed whey should not exceed 0.06%.

Pasteurization is required for inhibition of lactic acid processes, inactivation of enzymes and rennet residues.

Before start of the concentration process in evaporator it is advisable to concentrate whey on plants of nanofiltration or reverse osmosis. These plants allow concentrating the product to the solids content of 18-24% saving energy and reducing the load on the vacuum evaporator and removing up to 70% moisture from whey without significant energy consumptions.

EXAMPLE of energy consumptions for processing 300 000 kg / day of cheese whey by using membrane filtration and by using just vacuum evaporator.

Parameter Just vacuum evaporator Just membrane plant
1

Data accepted for calculations:

      Raw product quantity, kg

      Solids in raw whey, %

      Solids after NF, %

      Solids after evaporator, %

      Solids in the finished product, %

 

300 000

5,6

---

55

97

 

300 000

5,6

20

55

97

2

Quantity of removed water, kg:

      Membrane plant

      Evaporator

---

269 455

216 000

53 455

3

Number of evaporators «Wiegand-8», pcs.

Runtime, h

3

17,96

1

11,9

4

Consumptions for processing per day:

      Steam, kg

      Gas, m3

      Power, kW

 

118 560

9 485

1885,8

 

23 520

1 882

1616,5

5

Savings per day:

      Steam, kg

      Gas, m3

      Power, kW

 

---

---

---

 

95 040

7 603

269,3

 

To preserve the native properties and thermal stability of the whey components the temperature of condensation in evaporator is 50-62 °С.

Removal of water in evaporator is 6 times more economical than by spray drying - it is important to concentrate solution at the most that is also important for carrying out further crystallization of amorphous lactose.

Condensed whey that leaves the vacuum evaporator is subjected to an instantaneous initial cooling in the flow to the temperature of enhanced crystallization of lactose (30-320) and is fed into crystallizers.

Both processes are combined and implemented in a cooling and crystallizing unit (OKU-KMZ) developed and manufactured by our company.

While drying whey with previously crystallized lactose in the drying chamber less powder deposits are formed, the finished product has good flowability, low hygroscopicity and non-caking during storage. Increase of the output is at expense of binding more moisture.

 

Quality of the concentrate intended for spray-drying shall meet the following requirements:

  • the degree of crystallization - 60-70% of present lactose;
  • average crystal size - 20 microns;
  • maximum crystal size - 30 microns;
  • PH = 6.2-6.3
  • temperature 15-18 °С.

 

After finishing the crystallization process the whey concentrate is sent for drying in the spray drying plant of type A1 OR2CH equipped for processing of whey. The plant has a special design of fluid bed, system of blowing walls, the necessary power of fans and atomizing device and is equipped with fabric filters for green operation.

 

Parameters of drying are determined by the following factors:

  • requirements to moisture in the finished product;
  • the solids content in the concentrate before drying;
  • the degree of crystallization of lactose in the concentrate;
  • the amount of lactic acid in whey (titratable acidity, active);
  • the viscosity of the concentrate.

 

When drying a concentrate with low solids content there are increased losses of powder with outgoing air since the powder particles are smaller in weight and size, the solubility of the finished product deteriorates (fine particles have less wetting ability and sinkability).

Performance of the drying plant at drying whey with non-crystallized lactose is reduced by 20-30% with simultaneous deterioration of the quality of the finished product (increased hygroscopicity, caking, decreased flowability and solubility).

At spray drying of whey with increased acidity the finished product adheres to the walls of the cyclone and the drying tower. Accumulation of powder deposits in the cyclone and discharging devices leads to stop the drying plant for additional cleaning; the drying process is not stable, the hygroscopicity and caking whey powder increase, the solubility decreases.

 

The solubility index is influenced by the following factors:

  • a low-quality raw product with a high content of lactic acid (due to the high activity of bacteria) that requires intensive heat treatment which results in irreversible denaturation of proteins;
  • high temperature of the concentrate during evaporation that causes apparent thickening that leads to an increase in viscosity and poor atomization increasing the drying temperature;
  • the higher temperature and viscosity during processing, the greater the expected rate of solubility.

 

The temperature at the outlet may serve as performance indicator of the drying plant. The high temperature at the outlet means that the drying air is not used in an optimum way that may be caused by poor atomiztion, poor air distribution, high viscosity of concentrates, acidity, etc.

 

Applications of whey powder:

  • confectionery;
  • bakery industry;
  • milk production;
  • ice cream;
  • cream cheese;
  • cottage cheese;
  • condensed milk;
  • chocolate glazed curd bar;
  • fat and oil industry and production of spreads;
  • meat production;
  • brewing industry;
  • flavors, stabilizers, thickeners and other nutritional supplements;
  • sports nutrition;
  • beverages;
  • cosmetic industry;
  • food for farm animals.

 

In the dairy industry:

It improves the overall quality of products related to dairy foods - flavor, texture, foam stability and moisture retention. It promotes the dispersion of milk fat helping to reduce significantly the fat content in certain mixtures and to prevent defects such as foaming, blending and separation of the oil. It has nutritional value and high content of calcium. It returns some dairy components lost during the cheese-making process for the treatment of cheeses.

In the confectionery industry:

It ensures emulsification and whipping / foaming in confectionery products such as mousse, meringue and nougat. It helps to stabilize the cream and foams and improves whipping and foaming characteristics that are important for many confectionery products.

In the bakery industry:

It improves the organoleptic characteristics, nutritional value by biologically suitable amino acids and brings a high content of calcium.

In the meat industry, the production of ice cream, chocolate and gassy products, animal feeds:

Used as a substitute for milk or skimmed milk powder.

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