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Sweetened Condensed Milk

Sweetened condensed (SCM) milk is primarily used in the household for the preparation of various foods and as an additive to coffee. The long shelf-life of SCM at ambient temperature makes this product very convenient in places without a refrigerated distribution chain.The composition of SCM also makes it suitable for children. Some producers fortify their SCM with vitamins and others produce flavoured varieties such as coffee or chocolate SCM. Industrial applications include the confectionery industry. Different types of SCM are commonly produced, such as:


  • Sweetened condensed milk
  • Sweetened condensed skimmed milk
  • Sweetened condensed part skimmed milk
  • Sweetened condensed high-fat milk

All types can be processed from milk directly, or by re-combination of milk powder with water.

SPX FLOW's in-depth knowledge and active involvement in the development of the world's sweetened condensed milk industry, combined with proven experience in project management of major capital projects makes SPX FLOW the ideal partner for the design and installation of state-of-the-art processing equipment.

Capabilities

The raw materials in the production of sweetened condensed milk are standardised milk, sucrose and lactose. In the production of combined sweetened condensed milk, almost all preserved milk products can be used as raw materials. The fat can be either anhydrous milk fat (AMF) or a locally produced vegetable oil.

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Production of sweetened condensed milk

The raw materials in the production of sweetened condensed milk are standardised milk, sucrose and lactose. In the production of combined sweetened condensed milk, almost all preserved milk products can be used as raw materials. The fat can be either anhydrous milk fat (AMF) or a locally produced vegetable oil.

Standardization of milk

The milk is standardized to the desired fat content. This step can be carried out with the APV Compomaster integrated into the pasteurisation line. Alternatively, standardisation can be performed in batches.

Sucrose addition

The stage at which sucrose is added determines some of the final product qualities. By combining the newest heat treatment and evaporation techniques, SPX FLOW has optimised the process in which sucrose is added to the milk prior to heat treatment and evaporation, and today, this is the most common process.

If the sucrose is added to the milk concentrate, the concentrate and sucrose are weighed out, mixed in a mixing tank and then heated by circulating through a plate heat exchanger.

Heat treatment

Prior to evaporation, the liquid is heat-treated in a plate heat exchanger or at a higher temperature in an infusion plant. The heat treatment has two primary purposes:

  • To destroy the bacteria, yeasts, moulds and enzymes
  • To control the viscosity of the final product.

In modern SCM plants, state-of-the-art processing involves heat treatment prior to evaporation in an infusion plant integrated into the evaporator. This provides superior product quality especially withthe colour and age thickening.

Evaporation

Falling film evaporators are used for concentration. These continuously concentrate mix to the required total solids level.

The heat treatment is usually carried out as an integrated part of the evaporation process in order to secure high product quality.

The evaporators are usually of the multi-stage design with thermal vapour recompression (TVR). The reason for this choice is the relatively high boiling point elevation which occurs in the product after addition of sucrose and concentration to a high solids content. The multi-stage TVR design also minimises the overall energy consumption of the evaporation process.

SPX FLOW has gained considerable experience in the special heat treatment systems and evaporation plants required for the high solids contents in SCM. This is important for both consistently high product quality and long production runs.

When sucrose is added prior to heat treatment, evaporators are typically supplied with and integrated two-stage or three-stage vacuum cooling system with lactose seeding. If sucrose is added to the milk concentrate, a separate vacuum cooling system is used.

Vacuum cooling

Lactose is present in sweetened condensed milk in a supersaturated state. The crystallisation of lactose is important in order to secure a pleasant mouth-feel. One of the most significant aspects in ensuring the formation of small crystals is the vacuum cooling process (flash cooling). In the APV system, this is achieved by cooling the mix in a two-stage or three-stage flash cooler. In the final stage, the mix is cooled to 20-25°C, but before the final cooling, the mix is seeded with lactose crystals.

From the flash cooling plant the sweetened condensed milk is pumped to the crystallisation tanks where it is left for crystallisation. Because of the high viscosity of the product, crystallisation tanks for sweetened condensed milk are designed with a special agitator and are equipped with air filters to avoid post-contamination of the finished product.

The combination of vacuum cooling and in-line addition of lactose producers are sweetened condensed milk with a large number of small lactose crystals, resulting in a very smooth product.

Can filling

The SCM is pumped from the crystallisation or storage tank to a filling machine. The cans and lids are sterilised by steam, flame or UV-radiation before filling.

Production of Recombined Sweetened Condensed Milk

Recombination

Water is filled into the mixing tank and circulated through a plate heat exchanger where it is heated to 60°C. Milk powder and water are mixed in a turbo-mixer. The turbo-mixer ensures complete dissolution of the raw materials. After recombination of the milk powder, the sucrose is added in the same way. Oil or fat is dosed into the turbo-mixer by means of a positive pump.

Ingredients for SCM may also be mixed in a tank. The tank is equipped with a special agitator which makes it possible to dissolve skimmed milk powder, sugar and oil.

Heat treatment and homogenization

After recombination, the mix is pre-heated and filtered through a vibrating sieve where any undissolved particles are removed. The mix is then homogenised at 50-150 bar, then heated in a plate heat exchanger with a duplex pasteurisation section.

Vacuum cooling and can filling

Recombined sweetened condensed milk is vacuum cooled, seeded by lactose, crystallised and filled in same way as ordinary sweetened condensed milk.

Process Diagram and Benefits

APV_sweetcondensedprocessdiagram

  • SPX FLOW's state of the art processing involves heat treatment prior to evaporation, in an infusion plant integrated into the evaporator. This gives superior product quality in terms of colour and age thickening.
  • Use of APV multi-stage evaporators with thermal vapour recompression, minimises overall energy consumption of the evaporation process.
  • SPX FLOW's experience in systems design and processing technology ensures that product is produced to a consistently high quality for long production runs.
  • The combination of vacuum cooling and in-line addition of lactose produces a sweetened condensed milk with a large number of small lactose crystals, resulting in a very smooth product.