Meat slurry and mechanically deboned meat (MDM) products are often processed when warm or at room temperature. However, due to the nature of both product and co-product streams, this can limit the shelf life and holding potential of such products. Cooling meat slurry and similar materials can extend their shelf life and open up new markets and processing options.
A leading Australian supplier of poultry products has improved the quality of waste products produced at one of its facilities by implementing a new cooling solution from HRS Heat Exchangers.
The plant in question produces a range of butchered and prepared chicken products, and therefore also generates waste in the form of trimmings and material not required for human consumption, such as ground chicken necks, backs and feet. The new equipment supplied by HRS allows this material to be sold as a pet food ingredient.
Australian regulations mean that ingredients for both human and animal consumption must be kept at an appropriate temperature (typically below 39°F) during processing. Because of the highly viscous nature of the material, and the risk of freezing during cooling, it was determined that a scraped-surface heat exchanger would thoroughly mix the product during cooling and prevent freezing. The thick, viscous nature of the material means that a phenomenon known as "slugging" can occur. This means a channel of warmer product travels down the center while the product at the tube wall does not move. As the cooling medium (in this case glycol) is less than 23°F, this creates the risk that the product at the tube wall will freeze, while the material in the center is not cooled sufficiently.
Matt Hale, International Sales & Marketing Director at HRS Heat Exchangers, says: “In a traditional tubular heat exchanger this product would be likely to freeze on the tube walls due to the low fluid velocities. The HRS R Series has scrapers which turn at high velocity, mixing the product and increasing heat transfer. As a result, we can specify a heat exchanger with a smaller surface area, lower working pressures, a smaller footprint and lower capex compared with other designs. Due to the limited space available, creating a solution with a small footprint was a key priority for this product.”
The chilling system is based on three HRS R3 Series scraped-surface heat exchangers providing continuous cooling. Using three units in a parallel arrangement means that any two heat exchangers can continue to work (with a standard treatment capacity of 5,500 lbs./hr.) while the third is cleaned, serviced or just on stand-by. However, at times of peak production all three units can be run simultaneously, giving the system a maximum treatment capacity of 7,700 lbs./hr.
To ensure efficient and reliable operation with this difficult product, HRS adapted the internal scraper configuration to achieve the high performance necessary, while implementing a heavy-duty gearbox to withstand the higher torques required to keep the product moving. A glycol cooling system reduces the temperature of the product from 53°F to just 38°F in a continuous pass, with a total retention time around 4 minutes. An autonomous control system ensures that any outgoing product which has not reached the required temperature is diverted back to the start of the process for further cooling.
