The new Gold System (Type SIITM) uses advanced technology to hold products for a fraction of a second at high temperatures before flash cooling. Invensys claims that this effective sterilisation strategy preserves vitamin content, nutritional content and product quality, and is therefore the ideal solution for the ultra heat treatment (UHT) of heat-sensitive products.
At the heart of SII is an infusion chamber. Using plate, tubular or scraped heat exchangers, a product is preheated to between 55ºC and 75ºC before entering the top of the infusion chamber. Less than 0.2 seconds later, the product reaches the required UHT temperature of 140ºC.
A number of new techniques have been developed by Invensys to ensure that the product does not suffer from chemical damage, or burn onto the infusion chamber.
For example, the lamination nozzle arrangement ensures that product is dispersed in a circular pattern to avoid atomisation. The chamber itself is thoroughly deaerated using a vacuum to ensure maximum heat transfer.
Steam enters the chamber from its side, moving towards the centre via laminar flow, and condenses into the product without cavitation. This, in turn, prevents uncontrolled homogenisation.
Eventually the product comes into contact with the wall at the lower part of the infusion chamber, which is equipped with a cooling jacket. The thin film of condensate this generates on the inside of the chamber eliminates product fouling.
Temperature control in the chamber is crucial and is carried out via pressure control. A temperature sensor mounted in the product discharge pump housing is used to monitor actual sterilisation temperature and will ramp the steam pressure controller if necessary. This fine control of sterilisation temperature prevents the partial overheating of product constituents that can be an issue with injection and SSHE technologies.
Next comes the rotary holding cell where an APV-patented design ensures product is held for under 0.5 seconds. This extremely short period is achieved by having a thin piece of gold wrapped around the temperature transmitter in the pump house. As gold is 20 times more heat conductive than stainless steel, the temperature can be maintained much more quickly and accurately.
The last step in SII is the vacuum chamber, from which steam is removed to a condenser. The product is pumped directly from here to a spray dryer or plate/tubular/scraped surface heat exchanger section for final cooling.
The result, says Invensys, is a process that brings a huge number of benefits over other technologies currently in the marketplace, including uniform bacterial kill rate for low and high viscosity products, consistent product quality, less fouling and proven long operating times. SII technology can handle product capacities from 100-8000 l/h, a maximum viscosity at sterilisation temperature of 500 cp and maximum total solids of 60 per cent.