Application Reports

Production of Flavored Milk Drinks

Flavored milk drinks are available in many varieties. Viscosities range from that of whole milk, to “thick milkshake” products which achieve their viscosity through use of thickening additives, sometimes in combination with freezing. Yogurt drinks are similar in composition, but are processed differently and are not covered in this report. Milk ingredients are also used in smoothies to add texture and interest. Find out more about the Manufacture of Smoothies.

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The Process

A typical mix would be prepared in the following manner: 

  • Liquid ingredients are weighed/metered into the process vessel. Heating follows to aid dissolving/hydration of subsequent ingredients.
  • Powdered ingredients - skim milk powder, sugars, etc. are added to the liquid and mixed until dispersed. 
  • Stabilizers and emulsifiers are added. These may be dry premixed with other ingredients, e.g. sugar, to reduce agglomeration and “weight” the powder to aid incorporation into the liquid.
  • Flavor and coloring may be added at this stage.
  • The mix is homogenized, usually by passing through a high pressure homogenizer.

 

Subsequent processing varies according to the type of product:

  • Some “thick milkshakes” are frozen at point of sale.
  • Short shelf life products are pasteurized, typically in a continuous plate heat exchanger before cooling, bottling and then storage at 35 - 40°F (2 - 4°C).
  • Long life products are sterilized at around 285°F (140°C), then packed under aseptic conditions, usually in Tetrapak® type cartons, or plastic bottles.
  • Sterilized milk products are heated to around 275°F (135°C), then cooled to 140°F (60°C) before being filled into bottles. These are sterilized after being hermetically sealed. 

 

In most countries, legislation covers the composition and labelling of these products. These regulations restrict the use of certain ingredients and specify minimum content of fat and total solids.

The Problem

The process is subject to a number of problems when using agitators and conventional powder/liquid blending systems:

  • The powders are very cohesive and must be added at a controlled rate to reduce agglomeration of particles.
  • Premixing of powders increases labor costs and process time.
  • Stabilizing and emulsifying agents have a strong tendency to agglomerate and require special handling.
  • Poor dispersion can lead to clusters of partially hydrated material building up on the walls of the heat exchanger, impairing heat transfer.
  • Incomplete hydration also reduces yield of raw materials.
  • Long processing times are required to complete dispersion and achieve a satisfactory consistency.
  • Potential full yield of stabilizers is difficult to obtain using traditional methods.
  • Many formulations contain unnecessarily high levels of these raw materials to compensate for poor yield and wastage. 

The Solution

The above problems can be overcome by using a Silverson High Shear mixer. Operation is as follows: 

Stage 1

The high speed rotation of the rotor blades creates a powerful suction which draws the liquid and solid/powdered ingredients into the workhead.

Stage 2

The materials are subjected to intense shear in the confined area of the workhead. Agglomerates are broken down in the gap between the rotor blades and stator wall. A lump-free mixture is rapidly obtained.

Stage 3

The product is forced out of the stator as fresh material is drawn into the workhead. A circulatory mixing cycle develops in which all the material passes through the Silverson workhead.

The Advantages

  • Premixing of powdered ingredients is not necessary.
  • Agglomerate-free mix.
  • Stable emulsion.
  • Rapid mixing times.
  • Maximized yield of raw materials as thickening agents are fully hydrated and other ingredients are properly dispersed.

 

The batch size, formulation, type of ingredients and the viscosity of the mix dictates which machine from the Silverson product line is suited to individual processing requirements:

Silverson Flashmix

  • Ideal for larger batches
  • Capable of rapidly incorporating large volumes of powders
  • Minimized aeration
  • Powders can be added without the need to premixing
  • Can be fitted with additional small hopper for dosing small volume liquid ingredients
  • Suitable for higher viscosity mixes
  • Suitable for operation at higher temperatures
  • Minimized cleaning requirements
  • Controlled powder addition rate
  • Minimum operator input required

High Shear In-Line Mixers

  • Ideal for larger batches
  • Easily retrofitted to existing plant
  • Must be used in conjunction with an efficient in-tank agitator to wet out powder
  • Aeration free
  • Self-pumping
  • Can be used to discharge vessel
  • Ultra Sanitary models available

High Shear Batch Mixers

  • Suitable for batches of up to 400 US gallons
  • Can be used on mobile floor stands
  • Can easily be moved from vessel to vessel

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