The Barista’s Path: From Bean to Cup — Chapter 6

Fix Your Coffee: Solving Bitterness, Sourness & Flat Flavors

You've invested in premium Kenyan beans from Cafe Nairobi, but something's off - your coffee tastes bitter, sour, or lifeless. Don't blame the beans yet! According to Specialty Coffee Association (SCAA) research, 90% of flavor issues stem from brewing technique. This guide helps you diagnose and fix common problems using science-backed methods.

Why Troubleshooting Matters

• • $4 Billion Wasted annually on under-extracted coffee (National Coffee Association)
  • Proper brewing unlocks 28% more flavor compounds (SCAA Water Chemistry Report)
  • Cafe Nairobi's Kenyan beans are optimized for 92-96% extraction yield - your technique determines if you hit that sweet spot

The Extraction Science Behind Your Cup

Coffee brewing is chemical extraction - dissolving 30% soluble solids from beans into water. The SCAA's Golden Cup standard targets 18-22% extraction for balanced flavor:

Key Control Points (per SCAA Brewing Control Chart):

1. 1. Grind size (most impactful)
   2. Water temperature (195-205°F)
   3. Contact time
   4. Turbulence (agitation)

Problem 1: Sour Coffee (Under-Extraction)

Why it happens:

• • Grind too coarse (common with blade grinders)
  • Water below 195°F
  • Brew time too short
  • Insufficient agitation

SCAA-Approved Fixes:

1. 1. Grind finer - particles should resemble coarse sand
   2. Increase water temp to 200±5°F (93±3°C)
   3. Extend brew time:
      1. Pour-over: 2:45-3:30 minutes
      2. French press: 4-5 minutes
   4. Swirl brewer during bloom for even saturation

Problem 2: Bitter Coffee (Over-Extraction)

Why it happens:

• • Grind too fine (mud-like texture)
  • Water above 205°F
  • Extended steep time
  • Old beans (oils turn rancid)

SCAA-Approved Fixes:

1. 1. Grind coarser - aim for sea salt texture
   2. Lower water temp to 195°F (90°C) for dark roasts
   3. Shorten contact time:
      1. Espresso: 25-30 second shot
      2. Pour-over: don't exceed 4 minutes
   4. Use fresh beans - within 3 weeks of roast date

Problem 3: Flat/Lifeless Coffee

Why it happens:

• • Stale beans (>4 weeks post-roast)
  • Poor water quality (low mineral content)
  • Incorrect coffee:water ratio
  • Inconsistent grind (burr grinder essential)

SCAA-Approved Fixes:

1. 1. Verify freshness: Roast date should be visible (Cafe Nairobi uses roast-stamped bags)
   2. Optimize water: 150 ppm TDS with 50-100 ppm hardness (Third Wave Water recommended)
   3. Use precise ratios:

1. Upgrade to burr grinder - Kruve Brewler sieve confirms particle uniformity

Advanced Fixes (Pro Barista Techniques)

Water Chemistry:

• • Ideal profile: 150 ppm TDS, 50-100 ppm hardness, pH 7.0
  • Avoid distilled/softened water - magnesium enhances extraction

Equipment Maintenance:

• • Descale machines monthly (citric acid solution)
  • Clean grinders weekly (Grindz tablets)
  • Replace paper filters with metal mesh for fuller body

Cupping Diagnosis:

1. 1. Brew using SCAA cupping protocol (8.25g/150ml @ 200°F)
   2. Compare to control cup from Cafe Nairobi
   3. Isolate whether issue is in beans or the technique

Your Action Plan (SCAA-Certified)

1. Identify your issue using extraction chart above
2. Adjust one variable at a time (start with grind size)
3. Measure inputs:
   1. Digital scale (0.1g precision)
   2. Thermometer
   3. Timer
4. Validate with cupping - download SCAA form SCAA cupping protocols
5. Share results @CafeNairobi #BrewScience

Next Up:  The Science of Extraction and Flavor Balancing