The Secret behind Yeast Production

What is yeast, and where does it come from
Did you know that yeast is a by-product of the (beer) brewing process? However, it is far from being a waste. It contains precious elements such as amino acids, proteins, and minerals, and above all, it is an indispensable ingredient for many food preparations, both industrially and at home: bread, pizza, desserts, and many others.
But how do we go from a waste product to such a precious ingredient? The process consists of dehydrating and drying brewer's yeast. In this article, we are going to delve into all the details.

Yeast Indirect Drying
The secret behind the efficient production of dry yeast is indirect drying, that is, a yeast drying process obtained with a drum dryer.
This technique offers a distinct advantage over the traditional direct drying processes, and these are the reasons why:

• Reduced Hot Air Requirement: Indirect drying requires less hot air since the necessary heat for evaporation is generated by steam and transferred through the drum's metal wall.
• Efficient Heat Utilization: All the heat is efficiently used within the machine, minimizing waste and preventing heat from escaping unused. This optimizes resources and reduces costs.
• Energy Efficiency: The process is more energy-efficient due to the above-described optimized use of heat.
• Elimination of Large Dust Recovery Systems: There is no need for extensive dust recovery systems, such as huge filters, because the process does not involve substantial amounts of drying gas.
• Low Emission Levels: To ensure low emission values, exhaust vapors can be cleaned with a small biofilter before being released into the atmosphere, enhancing the environmental benefits.

The heart of the yeast drying process: the drum dryer
As mentioned, the indirect yeast drying process is possible only thanks to a specific machine, that is the drum dryer, and particularly a double drum dryer.
The double drum dryer is a machine that features two cast iron cylinders that are internally heated through saturated steam. This is the core of the system, but let’s discover how the entire process works.
 
Decanter
The yeast drying process begins with the decanter, where the thickened yeast concentrate is prepared. This initial step involves separating the yeast from excess liquid, resulting in a concentrated yeast slurry.

Holding Tank
The concentrated yeast slurry is then transferred to a holding tank. Here, it is temporarily stored and continuously fed into the next phase of the process, ensuring a consistent supply to the twin drum dryers.

Drum Dryer
This is the core step of yeast drying. To enhance comprehension, let’s break it into further sub-steps:

• Feeding the Dryer: The yeast concentrate from the holding tank is fed between the rotating cylinders of the double drum dryer, forming a hot sump.
• Spreading the Yeast: The yeast is evenly distributed over the rollers in a thin layer as it emerges from the sump.
• Heating and Evaporation: Inside the drum dryer, the cylinders are heated with saturated steam, which condenses on the drum walls. The continuous removal of condensate maximizes the surface area for steam condensation. The steam system is closed-loop, ensuring no contact between the product and the steam or condensate. The heat from the cylinders causes the water in the thin yeast layer to evaporate.
• Scraping the Yeast: After the cylinders rotate through two-thirds of a revolution, a knife scrapes off the dried yeast. The knife holder ensures even pressure across the drum’s length and prevents vibrations, ensuring uniform product removal. Knife pressure can be adjusted from outside the process area.
• Transporting the Product: Finally, two discharge screws and a pneumatic conveying system transport the dried yeast to downstream processing steps.

Mill Sifte
The next stage is the sifting stage that ensures uniformity in particle size and bulk density, vital for product consistency and packaging efficiency.
At this step, dried yeast flakes are subjected to size reduction by fast-rotating beater-bars passing through a sieve screen. This action results in the desired particle size distribution, essential for achieving uniform bulk density.
Simultaneously, impurities and oversized hard particles are sifted and separated from the main product stream. These contaminants are discharged through a grit outlet, ensuring the purity of the final yeast product.

Storage Silo
Once the yeast has undergone milling and sifting, it is ready for storage in a dedicated silo. The storage silo provides a controlled environment to preserve the quality of the dried yeast before it is further processed or packaged. In particular, it ensures that the product remains dry, free from contaminants, and maintains its desired properties until it is needed for the next stage of production.

Packaging Machine
From the storage silo, the dried yeast is transferred to the packaging area, where it undergoes the packaging process. The packaging machine carefully measures and dispenses the appropriate amount of dried yeast into packaging containers, such as bags, pouches, or jars, depending on the specific requirements of the end product and market demand. The packaging machine ensures accurate filling, seals the packages securely to maintain product freshness, and labels them with relevant information, including batch numbers and expiration dates.

Storage
Once packaged, the dried yeast products are stored in designated storage areas, ready for distribution.
Proper storage conditions are crucial to maintaining the quality and shelf life of the product. The storage area should be clean, dry, and well-ventilated, with controlled temperature and humidity levels to prevent moisture absorption and spoilage. Organized storage facilitates efficient inventory management and ensures the timely delivery of products to customers. Whether stored in warehouses or distribution centers, the goal is to preserve the quality of the dried yeast until it reaches its final destination for consumption or use in various applications.

Conclusion
In the yeast drying process, the drum dryer stands as a critical element in yeast processing. Through indirect drying, the double drum dryer machine efficiently removes moisture from yeast concentrate, minimizing energy consumption and environmental impact. As a symbol of innovation and efficiency, it facilitates the transformation of by-products into valuable resources. In summary, the drum dryer is the secret behind yeast production.