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Cell Counting for Professional Brewers

Cell Counting for Professional Brewers

In this tutorial, you will learn:

  • The importance of yeast cell counting in brewing.
  • Step-by-step instructions for counting yeast cells.
  • How to calculate the ideal pitch rate for your brew.

Why Yeast Cell Count Matters

Accurate yeast cell counting is crucial for achieving consistent fermentation and high-quality beer. Understanding how to calculate your pitch rate can help you optimize your brewing process.

Cell Counting for Professional Brewers — Transcript & Step-by-Step Guide

Use this cleaned, edited transcript and the structured steps below to perform accurate yeast cell counts and calculate the correct pitch rate for consistent fermentations.

Required Equipment

  • Microscope with 40× objective
  • 0.1% methylene blue solution
  • Hemocytometer with a clean, dry coverslip
  • Vortex mixer
  • Handheld tally counter
  • Pipettes (and tips)
Step-by-step: From sample prep to pitch rate
  1. Prepare the sample. Vortex your diluted yeast sample so it is homogeneous. Track every dilution you make (e.g., 1 mL slurry into 99 mL water for 1:100).
  2. Stain the sample. Mix the yeast suspension 1:1 with 0.1% methylene blue. Mix until color is uniform. Let sit 1–2 minutes, then re-homogenize.
  3. Load the hemocytometer. Draw the stained suspension and fill one chamber until the field under the coverslip is just full (no overflow).
  4. Focus at 40× and evaluate viability. Blue cells are non-viable; clear cells are viable.
  5. Count cells. In the central grid (25 squares), count viable cells in five designated squares. Exclude cells on two adjoining borders (e.g., left and bottom); include those on the opposite borders. Budding cells count as one if the bud is < ½ the mother cell.
  6. Handle clumping. If cells clump, use a declumping agent (e.g., sulfuric acid with EDTA) or count 25 squares for better representation.
  7. Compute cell density (cells/mL). Multiply the five-square count by 50,000 (chamber factor) and by the dilution factor.
  8. Compute total cells available. Multiply slurry density (cells/mL) by total slurry volume (mL).
  9. Determine pitch rate. For ales < 16°P: 1 million cells/mL/°P. For lagers < 16°P: 1.5 million cells/mL/°P. For gravities > 16°P: consult BSI.
  10. Compute total cells required. Pitch rate × wort volume (mL).

Working examples (density, volume, total cells)

Example A — Density

Given: 120 viable cells counted across five squares; dilution factor = 100.

Calculation: 120 × 50,000 × 100 = 600,000,000 cells/mL (6.0 × 108 cells/mL).

Example B — Slurry volume

Given: 4 gallons slurry.

Assuming: 1 US gal ≈ 3,800 mL → 4 × 3,800 = 15,200 mL.

Example C — Total cells available

600,000,000 cells/mL × 15,200 mL ≈ 9.12 × 1012 cells (≈ 9.12 trillion).

Example D — Pitch rate and cells required

Given: 12°P ale wort, volume = 15 bbl.

  • Pitch rate: 12°P × 1,000,000 = 12,000,000 cells/mL.
  • Wort volume in mL: 15 bbl × 31 gal/bbl × 3,800 mL/gal ≈ 1,800,000 mL.
  • Total cells required: 12,000,000 × 1,800,000 = 2.16 × 1013 cells (21.6 trillion).

Note: The original narration says “2.16 trillion,” but 12,000,000 × 1,800,000 = 21,600,000,000,000 (21.6 trillion). If you intend 2.16 trillion, the pitch rate or volume needs adjusting (e.g., 1.2M cells/mL or ~1.8×105 mL).

Full transcript (edited for clarity)

[Music]

This tutorial explains how to perform a yeast cell count and calculate the correct pitch rate for your brew.

Equipment

  • Microscope with 40× objective
  • 0.1% methylene blue solution
  • Hemocytometer with a clean, dry coverslip
  • Vortex mixer
  • Handheld counter
  • Pipettes

Sample Preparation

Vortex the diluted yeast sample. Draw a portion of the homogenized yeast suspension and record any dilutions for later calculations. For example, dilute 1 mL slurry into 99 mL water. Mix the sample 1:1 with 0.1% methylene blue until color is uniform. Allow it to sit for 1–2 minutes, then re-homogenize before counting.

Loading & Viewing

Draw the stained suspension and fill the hemocytometer chamber from one well until the field under the coverslip is full. View at 40×. Blue cells are non-viable; clear cells are viable.

Counting Rules

Find the central square (25 smaller squares, each with a 4×4 grid). Count viable cells in five squares using a fixed pattern. Exclude buds and cells on two adjoining borders (e.g., left and bottom); include those on the opposite borders. Budding cells count as one if the bud is less than half the mother cell. If clumping occurs, use a declumping agent (e.g., sulfuric acid with EDTA) or count 25 squares for accuracy.

Dilutions

A 1:10 dilution is 1 mL yeast + 9 mL water (total 10 mL). A 1:100 can be made directly (1 mL + 99 mL) or via two sequential 1:10 dilutions. Three sequential 1:10 dilutions yield 1:1,000. The total dilution factor is the product of the denominators (e.g., 1:10 followed by 1:4 = 1:40).

Calculations

Cell density (cells/mL) = (cells counted in five squares) × 50,000 × (dilution factor). Multiply density by slurry volume (mL) for total cells available. Pitch rate guidelines: ales < 16°P → 1M cells/mL/°P; lagers < 16°P → 1.5M cells/mL/°P; consult BSI for worts > 16°P. Total cells required = pitch rate × wort volume (mL).

Quick FAQ

What does methylene blue indicate?
Blue = non-viable; clear = viable. It’s used to estimate viability alongside total counts.

What if cells are clumped?
Use a declumping agent (e.g., sulfuric acid with EDTA) or count more squares (e.g., 25) for a more representative average.

What pitch rate should I use?
Ales below 16°P: ~1M cells/mL/°P. Lagers below 16°P: ~1.5M cells/mL/°P. For gravities above 16°P, contact BSI for a tailored recommendation.