Why Espresso Tastes Sour and How to Fix Sour Espresso
The 6 most common causes of sour espresso — and the exact adjustment to fix each one
Quick Answer: Fix Sour Espresso
Sour espresso is caused by under-extraction. The most common fix for sour espresso is making the grind finer by 1-2 steps. If sour espresso persists, increase brew temperature by 2-3°F, extend extraction time, or increase the espresso yield ratio.
6 Causes of Sour Espresso (and How to Fix Each One)
1. Espresso Grind Is Too Coarse (Most Common Cause of Sour Espresso)
A coarse espresso grind allows water to pass through the coffee puck too quickly, dissolving only the bright acidic compounds without reaching the sweet and balanced flavors deeper in the coffee cell structure. Under-extracted sour espresso tastes sharp, astringent, and lacking body.
Fix: Fine the espresso grind by 1-2 settings. Target 25-30 seconds total extraction for a 1:2 ratio double espresso (18g in, 36g out). Slower espresso extraction allows water to dissolve sweet sugars and caramels that balance sour acidity.
2. Espresso Extraction Time Is Too Short
Espresso extraction shorter than 20 seconds produces under-developed flavors dominated by citric and malic acids. Short espresso shots taste sour because water has insufficient contact time to extract balancing sugars and chocolate compounds from the coffee grounds.
Fix: Extend the espresso extraction to 25-30 seconds by grinding finer. Avoid simply running more water through the same coarse grind — increasing espresso extraction time through finer grind produces better flavor than extending water volume at coarse grind.
3. Espresso Brew Temperature Is Too Low
Water temperature below 190°F (88°C) cannot dissolve espresso flavor compounds efficiently. Low-temperature espresso extraction produces sour, tea-like shots lacking body and sweetness. Some espresso machines lose temperature between the boiler and the group head.
Fix: Increase espresso brew temperature by 2-3°F. Target 200-205°F (93-96°C) for light-medium roast espresso. Allow the espresso machine to warm up for 20-30 minutes before the first shot. Flush the espresso group head before pulling a shot to stabilize temperature.
4. Espresso Coffee Beans Are Too Fresh (Under-Degassed)
Espresso beans within 1-3 days of roasting contain excessive CO2 gas. Fresh-roasted espresso beans produce aggressive bubbling during extraction, creating channels that cause under-extraction and sour espresso. The CO2 in under-degassed espresso beans also contributes directly to perceived acidity.
Fix: Rest espresso beans for 7-14 days after roasting before brewing. Light roast espresso beans benefit from 10-21 days of degassing. Store espresso beans in a sealed container with a one-way valve during the degassing period.
5. Espresso Yield Ratio Is Too Low (Ristretto Over-Concentration)
A very short espresso yield (less than 1:1.5 ratio) concentrates the early-dissolving sour acids without balancing sweet compounds that extract later. Under-yielded espresso tastes intensely sour because the espresso shot stops before sweetness develops.
Fix: Increase the espresso yield to a 1:2 ratio (18g in, 36g out) or longer. A 1:2.5 ratio espresso often tastes sweeter and more balanced than a short 1:1.5 ristretto. Longer espresso ratios extract balancing sweetness without adding bitterness when grind is correct.
6. Espresso Channeling Causes Sour Under-Extraction Zones
Espresso channeling creates fast-flowing paths through the coffee puck that under-extract surrounding grounds. While channeled espresso can taste both bitter (in the channel) and sour (around the channel), overall sourness dominates when most of the coffee puck remains under-extracted.
Fix: Use a WDT tool to distribute espresso grounds evenly before tamping. Level the espresso dose in the portafilter basket. Tamp with consistent straight-down pressure. A bottomless portafilter reveals channeling — look for spurting or uneven espresso flow during extraction.
Sour Espresso vs Bright Acidity: Understanding the Difference
Not all espresso acidity is a defect. Specialty espresso from light-roast single-origin beans features pleasant bright acidity as a desirable flavor characteristic. Understanding the difference between sour espresso (defect) and bright espresso acidity (feature) prevents unnecessary adjustments.
Sour Espresso (Defect)
- - Sharp, vinegar-like acidity in espresso
- - Thin body, watery espresso texture
- - Astringent, mouth-puckering aftertaste
- - Pale, fast-flowing espresso crema
- - Unpleasant sourness that lingers
Bright Acidity (Desirable in Specialty Espresso)
- - Fruity, citrus, or berry-like espresso notes
- - Medium-full body espresso with sweetness
- - Clean, pleasant espresso aftertaste
- - Tiger-striped espresso crema
- - Refreshing acidity balanced by sweetness
Related Espresso Troubleshooting Guides
Why Espresso Tastes Bitter (and How to Fix Bitter Espresso)
The companion guide to fixing bitter over-extracted espresso
Dialing In Espresso Guide
Master the complete espresso dialing-in process step by step
Espresso Troubleshooting Guide
Diagnose and fix common espresso problems beyond sour taste
Water Temperature for Coffee and Espresso
Understand how brew temperature affects espresso extraction and sourness
Best Coffee Beans for Home Baristas
Choose espresso beans with appropriate roast profiles for balanced extraction
Beginner Grinder Guide
Grinder selection and setup to prevent grind-related sour espresso