Organic Acids¶
Organic Acids in Coffee Naturally occurring acids contributing to coffee's flavor, brightness, and complexity. Present in green coffee, developed during roasting. Primary acids: chlorogenic, citric, malic, acetic, phosphoric, quinic. Essential for quality coffee's vibrancy. Total Acid Content Green coffee: 6-8% of dry weight (chlorogenic acids dominate). Roasted coffee: 4-6% (decreases with roasting, composition changes). Arabica higher than Robusta. Acidity perceived as brightness, tanginess, or liveliness. Chlorogenic Acids (CGAs) Definition & Content Family of phenolic compounds, most abundant acids in green coffee. 6-10% of green Arabica, 7-14% of green Robusta. Break down during roasting into other acids and compounds. Roasting Transformation CGAs decrease significantly during roasting (50-95% loss). Break down into quinic acid and caffeic acid. Contribute to bitterness and astringency. Dark roasts have lowest CGA content. Health Properties Antioxidant activity. Potential blood sugar regulation. Linked to coffee's health benefits. More present in light roasts. Lost in dark roasts. Flavor Contribution Green coffee: Contribute astringency. Roasted coffee: Indirect - breakdown products create bitterness. Not primary source of desirable acidity. More about mouthfeel than taste. Citric Acid Characteristics Bright, clean, citrus-like acidity. Think: lemon, lime, orange, grapefruit. Sharp, refreshing quality. Highly desirable in specialty coffee. Most recognizable acid to consumers. Origin Distribution High in Kenyan coffee (signature characteristic). Present in Ethiopian coffee. Central American coffees (moderate). Colombian coffee (moderate). Processing and altitude affect levels. Processing Impact Washed processing preserves citric acid well. Natural processing may develop citric notes through fermentation. High-altitude coffees generally higher citric acid. Roasting Stability Relatively stable through light to medium roasts. Diminishes significantly in dark roasts. Peak expression at City to City+ roast levels. Flavor Notes Lemon: Sharp, bright, clean. Lime: Zesty, tangy. Orange: Sweeter citrus, rounded. Grapefruit: Bitter-sweet citrus. Bergamot: Floral citrus (rare, Ethiopian). Malic Acid Characteristics Apple-like, stone fruit acidity. Crisp, refreshing character. Named from apples (Latin: malum). Creates clean, bright profile. Highly desirable in specialty coffee. Flavor Notes Green apple: Bright, tart, crisp. Red apple: Sweeter, mellower. Pear: Subtle, delicate fruitiness. Stone fruit: Peach, apricot nuances. Combined with sugars: Creates fruit-forward profile. Origin Presence East African coffees (Kenya, Rwanda, Burundi). Some Central American (Guatemala, Costa Rica). Colombian coffee (moderate levels). High-altitude coffees generally higher. Processing & Roasting Washed processing showcases malic acid well. Preserved in light roasts. Degrades in medium-dark roasts. Sweet spot: City roast level. Acetic Acid Characteristics Vinegar-like acid. Complex role: Low levels add brightness, high levels create defects. Most volatile acid. Develops during fermentation. Balance critical. Positive Levels 0.1-0.3%: Adds complexity, brightness. Enhances fruit notes. Wine-like characteristics (natural process). Contributes to overall acidity structure. Part of balanced profile. Negative Levels
0.5%: Vinegary, sour, unpleasant. Processing defect indicator. Over-fermentation product. Ruins cup quality. Must avoid. Processing Connection Develops during fermentation (washed, natural). Extended fermentation increases acetic acid. Over-fermentation creates excess. Anaerobic processing can increase (controlled). Quality control critical. Roasting Impact Present in green coffee, increases slightly in early roasting. Peaks in medium roasts. Decreases in dark roasts. Balance shifts with roast level. Phosphoric Acid Characteristics Soft, sweet, syrupy acidity. Wine-like, grape-like character. Creates roundness, not sharpness. Highly prized, relatively rare. Signature of exceptional coffees. Flavor Quality Sweetness integrated with acidity. Cola-like (Coke flavor connection). Syrupy body accompaniment. Non-aggressive brightness. Sophisticated complexity. Origin Specificity Kenyan coffee (signature acid, especially SL-28/34). Some Burundian coffee. Rwandan coffee (emerging). Not common in other origins. Terroir and varietal linked. Processing & Altitude High-altitude coffees. Washed processing. Extended soaking (Kenya double-wash). Specific varietals (SL-28, SL-34). Combination of factors. Market Value Highly sought by specialty roasters. Commands premium prices. Kenyan coffee value driver. Defines "Kenyan profile." Exceptional when present. Lactic Acid Characteristics Smooth, creamy, milky acidity. Yogurt-like character. Mellow, rounded mouthfeel. Not sharp or aggressive. Adds body perception. Flavor Notes Yogurt, buttermilk, cream, butter. Smooth texture contribution. Integrates rather than stands out. Background complexity. Complements other acids. Development Fermentation byproduct (lactic acid bacteria). Some processing methods encourage (extended fermentation). Natural process can develop. Certain anaerobic processes enhance. Processing Innovation Experimental fermentation focuses on lactic acid. Specific bacteria inoculation. Temperature control to favor LAB. Creates unique profiles. Growing trend in specialty. Tartaric Acid Characteristics Sharp, tangy, wine-like acidity. Grape, wine character. Less common in coffee than other acids. Adds complexity when present. Presence Some natural process coffees. Fermentation-heavy processing. Not dominant acid in coffee. Supporting player in acid structure. Quinic Acid Characteristics Bitter, astringent compound. NOT a desirable acid. Created from chlorogenic acid breakdown. Increases with roasting and stale coffee. Formation Roasting: CGAs break down into quinic acid. Over-roasting: Excessive quinic acid. Stale coffee: CGAs continue breaking down. Heat (holding coffee hot): Accelerates formation. Flavor Impact Bitterness, astringency, mouth-drying. Metallic taste notes. Unpleasant sourness. Day-old drip coffee flavor (sitting on hot plate). Avoid through proper roasting and freshness. Acid Balance & Interaction pH Levels Coffee pH: 4.85-5.10 typically. Acidic beverage (below 7.0). Lower pH = more acidic. Affected by: roast level (dark = higher pH), brewing method, water alkalinity. Perceived vs Measured Acidity Perception doesn't match pH exactly. Organic acid composition matters more. Balance and integration critical. Sweetness affects acidity perception. Synergy Multiple acids working together. Citric + malic: Bright fruit profile. Phosphoric + sugars: Sweet-tart complexity. Acetic (low) + others: Adds dimension. Balance creates complexity. Altitude & Acidity Higher altitude = higher acidity generally. Cooler temperatures preserve acids. Slower maturation develops acid structure. Premium coffee connection. Processing & Acidity Washed: Preserves and enhances clean acidity. Natural: Develops fermentation acids, fruit character. Honey: Balance between washed and natural. Experimental: Targeted acid development. Roasting & Acidity Light roast: Maximum acid preservation. Medium: Balanced acid expression. Dark: Significant acid loss, quinic acid increase. Acid degradation accelerates with heat. Brewing & Acid Extraction Temperature: Higher extracts more acid. Time: Longer contact extracts more. Water chemistry: Alkalinity buffers acids. Under-extraction: Sour, imbalanced acids. Over-extraction: Bitter quinic notes.
Related Notes: - Coffee Terminology MoC