Robert Roberts Limited

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Operation of Brewing Equipment

Contact Time

Time of Contact Between the Coffee Grounds and Water

• START: when brew water contacts coffee bed
• STOP: when brew goes from stream to drip

Temperature of the water

• 92°C to 96°C (195°F to 205°F) as water is emerging out of spray head
• Cold or warm water doesn’t extract properly
• Throughout 90 to 100% of brew cycle
• Measure temperature 30 seconds into brew cycle, half way through brew cycle, & 30 seconds before the end of brew cycle

• Lower than the ideal range results in under-extraction (less acidity and flavour)
• Higher than the ideal range results in over-extraction (astringency and/or bitterness).
• Optimal acidity, aroma, flavour complexity, and body is achieved when coffee is filter brewed at ideal temperature.

Turbulence

Turbulence is the mixing action caused by the water passing through and over the coffee grounds.

Turbulence causes the coffee particles to separate allowing a uniform flow of water through and around them for proper extraction.

Wettability

• Each gram of coffee will absorb two ml. of water.
• Some coffee particles accept water more readily than others. Due to:
  
  1. Origin of coffee
  2. Age of green beans
  3. Non-uniform roasting of coffee bean
  4. Excess of oil surrounding the cellular structure
  5. Surges of carbon dioxide from freshly roasted coffee
  6. High concentrations of calcium and sodium bicarbonate in brew water
  7. Grind Particle Size Distribution

Uniform Dispersion of the Brewing Water Over the Coffee Bed

• Exit hole allows a smaller amount to flow out than is dispensed by the spray head.
• Entire bed must have equal wetting.
• Spray head design is critical
• Examine spent grounds after brewing.
• Look for light tan foam or dry patches.