Creating Fermentation Profiles
A fermentation profile displays the specific gravity (SG) over time during the fermentation process. It enables us to assess how well the yeast is performing. Fermentation processes are inherently unique, and the fermentation curve represents a distinct fingerprint. Access to this data provides a deep understanding of the fermentation process and serves as an essential tool for consistently producing high-quality beer.
Measuring the Lag-phase
The lag-phase refers to the period between pitching the yeast and the start of fermentation. By closely examining the above curves, we can clearly observe the initial horizontal phase where the SG remains constant. The length of these lag-phases depends on various factors, such as pitching temperature, yeast characteristics (e.g., strain, cell count, vitality, and health), levels of complex sugars, original gravity, and other parameters.
Optimizing Pitching Temperature
Pitching temperature is one of the most critical parameters that influence cell growth, the initial rate of fermentation, and the duration of the lag-phase. Understanding the ideal pitching temperature for different yeast strains can significantly enhance throughput while maintaining high-quality standards.
Accurately Determining the End of Fermentation
Precisely determining the end of fermentation is crucial for consistency and quality. Allowing the beer to sit in the fermenter for a specific duration is a common method to ensure fermentation completion. However, this approach is not ideal for commercial brewers who aim to optimize fermenter utilization and maintain consistent quality. Monitoring the specific gravity throughout the fermentation process provides valuable insights into the different stages of fermentation, including its conclusion.
Comparing Batches and Gaining Insights
When brewers have multiple data sets of the same recipe, they can compare them to understand variations between each fermentation and their impact on brew quality.
Utilizing Fermentation Profiles for Yeast Cropping
Optimizing Yeast Harvesting
Yeast harvesting can significantly reduce costs for breweries. Most brewers reuse yeast for a certain number of batches, often five times or more, before replacing it with a new culture. By comparing fermentation profiles between batches and examining the lag-phase duration and fermentation rate, brewers can quantitatively assess the yeast’s performance.
Top Cropping at the Peak of Fermentation
Top cropping is a method of harvesting yeast from the surface of the fermenter, typically used with ale strains. Compared to bottom cropping, this technique yields yeast with higher vitality and viability. However, it is more challenging due to the closed nature of most conical fermenters used today. Top cropping should be performed when the fermentation rate reaches its peak.
Precise Timing for Bottom Cropping
Collecting yeast must commence as soon as possible after fermentation completion because yeast cells begin to break down and deteriorate at that point. Utilize fermentation profiles to determine the exact end of fermentation and identify the optimal time for yeast collection. Large conical fermenters pose challenges for yeast handling, as the yeast packs tightly in the cone. Harvesting typically occurs 24-48 hours after a cold crash, and delays beyond this timeframe significantly reduce yeast viability.