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UHT (Ultra High Temperature) Liquid Dairy


SPX FLOW has an extensive range of processes for UHT or aseptic processing of liquid dairy products. The choice of process will depend on a number of factors including product physical properties, required capacity and required end-product quality.

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


In order to arrive at the most cost-effective solution and obtain a product with the required qualities, it is essential to choose the right aseptic processing system for the task. In many cases, the choice is straightforward, but in other cases there may be more than one possibility.

More Capabilities

In order to arrive at the most cost-effective solution and obtain a product with the required qualities, it is essential to choose the right aseptic processing system for the task. In many cases, the choice is straightforward, but in other cases there may be more than one possibility.

The main factors to consider when choosing an aseptic processing system are:

  • Product to be processed
  • Quality required in the final product
  • Range of viscosity
  • Presence of particulates or fibres
  • Product acidity
  • Sensitivity to high temperatures
  • Requirement for flexibility in product and capacity
  • Preference for direct or indirect system

Indirect plate heat exchanger systems

A UHT system based on APV plate heat exchangers is used where the primary requirement is a dependable system for heating liquid products at minimum costs. With plate heat exchangers, the operating costs are low because of the high regenerative capability.

Careful design of the heating and regenerative systems optimises the performance of the APV unit and minimises product damage.

The APV unit has a high degree of flexibility and can be supplied with variable capacity and with two-speed or variable-speed homogenisers. The system can be built with a capacity of up to 25-30,000 l/hour.


  • Excellent for low-viscosity products
  • High regenerative effect and low energy consumption
  • High heat transfer area in minimal space
  • Easy inspection
  • Low hold-up volume
  • High degree of flexibility
  • Variable capacity
  • Large capacity plants possible
  • Relatively low investment
  • Low CIP costs


  • Limited capability for particulates or fibres
  • Exchange of gaskets required
  • Unsuitable for higher pressure drops
  • Some product degradation


The system based on plate heat exchangers is used for milk, flavoured milk, fermented milk products such as drinking yogurt, as well as cream and coffee whiteners. The system is also used for aseptic processing of juice and, in many cases, combined plants for milk and juice treatment are installed.

Indirect tubular heat exchanger system

Various APV tubular systems are available, but the most commonly used system is the multiple-tube-in-tube (MTNT) system. The heat transfer modules are multiple, small-diameter, sanitary tubes aligned within a large diameter shell. The diameter of the inner tubes can vary, but is usually in the range of 10-12 mm. The APV tubular system is designed with a "loose" jacket around the tube bundles giving a floating head design. This allows thermal expansion without any risk of tube cracking, prevents stress corrosion, and allows easy inspection of all heat exchange surfaces.

APV Tubular heat exchangers are increasingly used for a wide range of duties, both in the low-viscosity range as an alternative to plate heat exchangers, and in the high-viscosity range for products containing suspended solids and particulates as an alternative to scraped-surface heat exchangers. A special feature is a corrugated tube design. The corrugation generates turbulence in the product flow and thereby improves the heat transfer efficiency. Corrugated tubes can be supplied as double, triple and quadruple tubes.

The system can be built with high thermal efficiency and this, together with the very robust design, means that operating costs are quite low.


  • Less vulnerable to fouling providing long production time
  • Accepts high operating pressures
  • Processes products with particulates
  • Processes high-viscosity products
  • Low shear characteristics for cream
  • Low requirement for gasket material and easy gasket exchange
  • Very robust design
  • Low maintenance costs
  • Can be built as a multi-purpose plant


  • Lower regenerative effect than for plate heat exchanger
  • Higher degree of product degradation


The tubular-based system is used for milk, flavoured milk, cream, ice cream mix, evaporated milk, desserts and puddings. The system is also used for juices, and especially for juices with pulp.

Direct steam infusion systems

In the direct steam infusion system, the product is pre-heated to a temperature of approximately 75°C, after which it is introduced into an atmosphere of steam through multiple nozzles in a pressurised stainless steel chamber. The product falls through the steam atmosphere and hits the bottom of the chamber which is formed as a cone. The product leaves the chamber through a holding cell to a flash chamber where it is flash cooled before aseptic homogenisation and final cooling to packaging temperature.

The special design of the infusion system makes it possible to operate with high accuracy within a very narrow range of operating parameters. Consequently, the product is only exposed to the very high temperature for a very short time - from a few seconds to a mere fraction of a second. These conditions provide the desired kill rate of microorganisms, but the heat treatment is so brief that no significant chemical changes take place, and consequently an outstandingproduct quality is obtained. The process also strips off air as well as unwanted gasses and odours, which is a further contribution to quality.

The system is very flexible and can be used for many types of products with a wide range of viscosities. Capacities range from 1,000 l/hour to 35,000 l/hour.


  • Superior product quality
  • Gentle heating due to direct steam contact
  • Handles highly heat-sensitive products
  • Wide viscosity range
  • Long production runs possible
  • High degree of flexibility


  • Relatively higher capital costs than for indirect system
  • Relatively higher operating costs because of a lower percentage of heat regeneration
  • Requires a source of culinary steam

Products treated by this system include milk & milk concentrate, cream, whipping cream, flavoured cream, yogurt, soya milk products, baby food, ice cream mix, processed cheese, puddings, desserts and other very heat-sensitive products.

Direct steam injection systems

The direct steam injection system operates by direct injection of steam into the product through a specially designed nozzle. This is followed by cooling in a flash chamber. Pre-heating and final cooling take place in a plate heat exchanger or sometimes in a tubular heat exchanger.

This system provides very fast heating and cooling, but somewhat slower than in the infusion system. In both instances, the product is in direct contact with steam. These conditions give a very good product quality because of the more gentle treatment of the product compared with indirectly heated systems.

Long operating times are possible because only a very small area in the nozzle is subjected to burn on. The injection system handles low to medium viscosity products, and the capacity range is from 2,000 to 35,000 l/hour.


  • Good product quality
  • Long production runs
  • Easy up-scale to large capacities


  • Relatively higher capital costs than for indirect systems
  • Relatively higher operating costs because of a lower percentage of heat regeneration
  • Used mostly for low-viscosity products
  • Requires a source of culinary steam


Examples of products treated in injection systems include milk, cream, flavoured milk, soya milk and ice cream mix.

Indirect scraped-surface heat exchanger systems

APV's scraped-surface heat exchangers are specially designed to heat or cool viscous or sticky products or products containing particulates.

The scraped-surface heat exchanger consists of a smooth cylinder through which the product is pumped. Rotating scraper blades keep the heating surface free from scale and deposits. Both vertical and horizontal models are available.

In a typical aseptic plant, the product is pumped by a rotary lobe pump or similar pump type to feed one or more cooling cylinders. Capacities up to approximately 10,000 l/hour are available.

The products handled in a scraped-surface heat exchanger system vary considerably in their properties, but they are all characterised by the fact that they cannot be treated in any of the conventional continuous heat treatment systems.

Even though systems based on scraped-surface heat exchangers are more expensive, both in terms of investment and energy consumption, they are still very competitive compared with batch sterilising systems.


  • Handles high-viscosity and sticky products
  • Handles particulates
  • Handles heavy-fouling products


  • Relatively high capital costs
  • Relatively high energy requirements
  • Higher maintenance costs owing to scraper blades, bearings and seals
  • Limitation in respect of size of particulates
  • High spare parts requirement


A wide range of products can be processed in scraped-surface heat exchangers, including milk concentrate, yogurt, processed cheese, whey protein concentrate and quarg products.

Process Diagram and Benefits


SPX FLOW's global experience as a supplier of processing technology and equipment for dairy products is a key factor in our ability to deliver cost-effective solutions tailored to individual customer requirements.

  • The wide range of process systems offered by SPX FLOW means that the optimum design can be selected to produce product of the highest possible quality.
  • Designs based on standard principles with components tailor-made to customers' specific needs. All systems are equipped with user-friendly, automatic control systems, including plant pre-sterilisation and CIP cleaning.
  • Fail-safe systems with built-in safeguards and alarm systems preventing non-sterile products from being discharged into the filling lines.
  • Easy and simple maintenance
  • SPX FLOW offers an enormous range of resources to the dairy industry in process engineering, equipment manufacturing, project management - for both large and small projects - and world-class development facilities.