Yeast Assimilation System

This system is primarily designed for craft breweries with big production output ranging from 20000HL to 100000HL per year or even bigger capacities.

It wors as a separate unit between the wort heat exchanger and the fermentation tank, and offering the following advantages:

Basic requirements for yeast activation and proliferation:

1. Concentration: The concentration of wort used for yeast proliferation should be standardized (increase with each activation), which facilitates control of mashing process parameters during transfer;

2. α-Amino nitrogen: Content not less than 180-220 mg/L;

3. Yeast nutrients such as zinc can be appropriately added to the wort used for yeast cultivation, depending on the yeast condition;

Key Technical Parameters for Yeast Propagation:

1. Final Cell Count at Activation: The number of yeast cells in the expansion tank at the end of the activation culture. The final cell count should be controlled according to the culture temperature. As the culture temperature decreases, the peak concentration achievable will gradually decrease; therefore, a higher cell concentration should be achieved at a higher culture temperature (this also ensures a reasonable transfer sugar content).

2. Yeast Culture Temperature: The appropriate culture temperature should be determined based on the propagation ratio to achieve a reasonable yeast concentration. It is important to maintain the expansion range at 3 degrees Celsius higher than the main fermentation temperature of the fermenter to avoid negative effects such as slow fermentation and easy settling of yeast caused by rapid cooling.

3. Ventilation Control: A slightly higher ventilation temperature is recommended during high-temperature propagation (when yeast proliferates rapidly), gradually decreasing thereafter. The ventilation pressure should be adjusted based on the circulation effect. The ventilation frequency serves to replenish dissolved oxygen and agitate settling yeast; therefore, the ventilation interval should not be too large. Simultaneous circulation and aeration are necessary.

4. Cultivation Time: Under the premise of achieving the required cell concentration, the propagation time should be shortened as much as possible to prevent yeast from aging in a low-nutrient, high-oxygen environment.

5. Yeast proliferation process pressure control: Maintain positive pressure or 0 < pressure control ≤ 0.05 MPa to prevent outside air from entering and causing contamination.

6. Hygiene requirements: The tubing throughout the entire propagation process should maintain normal CIP washing and related aseptic techniques.