In recent years, the industry has witnessed a significant shift from the traditional use of chemicals to thermal sterilization using steam injection. This change is driven by the drawbacks associated with chemical methods, including residues that can affect the product’s aroma and potentially alter its structure. Thermal treatment has emerged as an efficient way to sterilize without these drawbacks.
How sterilization by thermal treatments works
Often thermal treatment systems are integrated in the mixer. The thermal processing happens in two phases: 1) heating by steam injection and 2) drying by cooling.
In the heating process, the injected steam effectively breaks down concentrations of microbes. Moist heat, provided by steam, is renowned for its ability to eliminate both microbes and pathogens efficiently. The steam is added during mixing, because heat transfer between steam and product is optimal when both the product and steam are in motion. This results in a highly efficient heating process, where the entire batch is heated uniformly to a specified temperature, for a specified time.
This sterilization process achieves a 99.999% (5 log) reduction in the population of microbes, significantly reducing the risk of product recall, spoilage, contamination, and diseases.
Drying with conditioned air to eliminate moisture
During the heating process the product absorbs the heat of the steam. In the cooling section, the heat and moist are dried out by air and the product is cooled down to its original temperature. To prevent recontamination, it’s critical to use clean and conditioned air. A HEPA (high-efficiency particulate air) filtration system is necessary. This filtration system guarantees that only clean air enters the mixer, and that it remains clean throughout the entire process. Additionally, this sequence of heating followed by cooling allows producers to add heat-sensitive additives and liquids, to further improve their feed.
Mixing during thermal treatment for homogeneous output
A key element of this thermal treatment system is that the product is gently mixed continuously during both heating and cooling. This results in a consistent, homogeneous output with no segregation or decomposition of the product.
Author: Peter Raeven – Technical consultant feed at Dinnissen Process Technology (p.raeven@dinnissen.com)
