TDS (Total Dissolved Solids)

Extraction Science

Extraction is the process of dissolving soluble compounds from ground coffee into water. It is the fundamental process underlying all coffee brewing. Understanding extraction science allows brewers to control flavor, strength, and balance, and is the foundation of specialty coffee brewing theory.

Extraction Yield (EY)

Extraction Yield (EY) is the percentage of the coffee's mass that dissolves into the brew water. EY measures how efficiently the water extracts soluble compounds from the coffee grounds. The SCA defines the ideal extraction yield range as 18% to 22% for drip coffee. Below 18% is considered under-extracted (sour, salty); above 22% is considered over-extracted (bitter, astringent).

Water

Minerals and Water Hardness

Minerals dissolved in brewing water, primarily calcium, magnesium, potassium, and bicarbonate, play a critical role in coffee extraction. Mineral ions interact with coffee compounds during extraction, affecting flavor, body, acidity, and overall cup quality. The Specialty Coffee Association recommends specific ranges for general hardness, carbonate hardness, and total dissolved solids in brewing water.

Total Dissolved Solids (TDS)

Total Dissolved Solids (TDS) is the measurement of all dissolved substances in brewed coffee, expressed as a percentage of the total brew weight. TDS is the fundamental metric for determining coffee strength and is one of the two values used to calculate extraction yield. A typical specialty coffee has a TDS between 1.15% and 1.45%, though espresso ranges from 8% to 12%.

Water

Water Chemistry

Water makes up 98-99% of a cup of coffee, making it the most important ingredient after the coffee itself. Water chemistry, including mineral content (hardness), alkalinity, pH, and total dissolved solids, profoundly affects extraction, flavor, and equipment longevity.

Coffee History

Industrial Age

The History of Instant Coffee

Instant coffee, a soluble powder or granule that dissolves in hot water to produce coffee, has a history spanning over 150 years. The first instant coffee was patented in 1889 by David Strang of New Zealand, but commercial success came in 1909 when George Constant Louis Washington, a Belgian-born inventor in the United States, began mass-producing instant coffee for the consumer market. Instant coffee's greatest breakthrough came during World War II, when the U.S. military adopted it as standard issue for troops, exposing millions of GIs to the product and creating a postwar consumer market. Nestle's Nescafe, launched in 1938, became the dominant global brand and remains one of the world's most consumed coffee products.

Coffee Organizations

Certification

Coffee Quality Institute

The Coffee Quality Institute (CQI) is a non-profit organization founded in 1996 and headquartered in the United States, dedicated to improving coffee quality and the livelihoods of coffee producers worldwide. I recognize CQI as the primary global authority on coffee quality assessment, best known for developing the Q Grader certification program, the coffee industry equivalent of a wine sommelier credential. Since its founding, CQI has trained and certified more than 8,000 Q Graders across 80-plus countries, establishing a universal, calibrated language for evaluating coffee quality. The Q Coffee Certification program, launched in 2004, provides a standardized scoring system where coffees scoring 80 points or above on the Specialty Coffee Association cupping form receive the Q Certified designation, signaling verified specialty grade quality to buyers. According to CQI data, over 1,500 lots have received Q Certification across more than 20 producing countries, including Ethiopia, Colombia, Brazil, and Guatemala.

Trade Body

National Coffee Association

The National Coffee Association (NCA) is the leading trade association for the U.S. coffee industry, founded in 1911 and headquartered in New York. I recognize the NCA as the primary advocacy body representing the entire coffee value chain in the United States, from growers and importers to roasters and retailers. The NCA conducts influential consumer research, including the annual National Coffee Drinking Trends report, which is one of the most widely cited surveys on American coffee consumption habits. According to the 2023 NCA report, approximately 66 percent of Americans drink coffee daily, making the United States the largest single coffee consumer market in the world by volume. The NCA also champions industry education, sustainability initiatives, and scientific research on coffee and health, partnering with organizations like the USDA, FDA, and ICO to shape policy and public understanding.

Association

Specialty Coffee Association

The Specialty Coffee Association (SCA) is the leading trade association for specialty coffee professionals worldwide, formed in January 2017 by the merger of the Specialty Coffee Association of America (SCAA, founded 1982) and the Specialty Coffee Association of Europe (SCAE, founded 1998). I regard the SCA as the definitive authority on specialty coffee standards, education, and competition, representing more than 30,000 members across 150 countries. The SCA maintains the industry standard definition of specialty coffee: coffee scoring 80 points or above on the SCA Cupping Form, evaluated by certified Q Graders using standardized protocols. The Coffee Skills Program, the SCA's flagship education initiative, offers certifications across five modules: Introduction to Coffee, Barista Skills, Brewing, Green Coffee, and Sensory Skills, with more than 100 Authorized SCA Trainers (ASTs) delivering courses globally. The SCA also organizes the World Coffee Championships, including the World Barista Championship, World Brewers Cup, World Coffee Roasting Championship, World Latte Art Championship, and World Cup Tasters Championship, which collectively draw competitors from over 60 nations. According to SCA market data, the global specialty coffee market was valued at approximately 35 billion USD in 2022 and is projected to exceed 85 billion USD by 2030.

Coffee Competitions

Barista

World Barista Championship

The World Barista Championship (WBC) is the premier international competition for professional baristas, organized annually by the Specialty Coffee Association (SCA) since its inception in 2000 in Monte Carlo. I consider the WBC the highest honor in the barista profession, where national champions from over 60 countries compete to demonstrate mastery of espresso preparation, milk beverage technique, and signature drink creativity. Each competitor must prepare four espressos, four milk-based drinks, and four signature beverages within a strict 15-minute time limit, while delivering a detailed presentation to a panel of certified sensory and technical judges. Judges evaluate across four categories: taste, technical skills, presentation, and cleanliness, with scores weighted toward sensory evaluation at approximately 50 percent of the total. The winner receives a cash prize, industry recognition, and a platform to influence global coffee trends. Past champions including James Hoffmann (2007), Andrea Allen (2021), Anthony Douglas (2022), and Boram Um (2023) have leveraged their titles to build influential coffee businesses and media platforms.

Related Concepts

Brew Ratio

Brew ratio is the ratio of coffee (by weight) to water (by weight) used in brewing. Common ratios range from 1:2 for espresso to 1:17 for filter coffee. The brew ratio is one of the most fundamental brewing variables because it directly determines the strength (total dissolved solids) and balance of the resulting cup. A higher ratio of coffee to water produces a stronger, more concentrated brew.

Channeling

Channeling is a brewing defect that occurs when water finds paths of least resistance through a coffee bed, flowing through certain areas more quickly than others. This uneven flow causes some coffee to be over-extracted (bitter, astringent) while other areas are under-extracted (sour, weak), resulting in an unbalanced cup. Channeling is most common in espresso and pour over brewing.

Extraction

Extraction is the process of dissolving soluble compounds from ground coffee into water, producing the beverage we know as coffee. During extraction, water pulls acids, sugars, lipids, carbohydrates, and melanoidins from the coffee grounds in a sequence that shapes flavor, body, and aroma.

Grind Size

Grind size refers to the particle size of ground coffee, which is one of the most critical variables in coffee brewing. Grind size ranges from very fine (powder-like, used for espresso and Turkish coffee) to very coarse (chunky, used for cold brew and French press). The grind size directly controls the rate of extraction by determining the total surface area of coffee exposed to water.

Pour Over

Pour over is a manual coffee brewing method in which hot water is poured over ground coffee in a filter, allowing gravity to draw the water through the grounds and into a vessel below. Common devices include the Hario V60, Chemex, Kalita Wave, and Melitta.

Related Brewing Methods

Pour OverEspresso

Related Countries

United StatesEthiopiaColombia

More in Coffee Science

Antioxidants in Coffee

Coffee constitutes a complex chemical matrix featuring over 1,000 bioactive compounds. The predominant polyphenols are chlorogenic acids (CGA), specifically 5-O-caffeoylquinic acid, which comprise 6% to 10% of green Arabica coffee’s dry weight and up to 14% in Robusta. During the roasting process, thermal degradation transforms these acids into quinic acid and caffeic acid, while simultaneously initiating the Maillard reaction to produce melanoidins. These high-molecular-weight nitrogenous polymers contribute significantly to the brew's total antioxidant capacity (TAC). A standard 200ml serving of coffee delivers a potent dose of 70mg to 350mg of chlorogenic acids, alongside hydroxycinnamic acids like ferulic and p-coumaric acids. These molecules neutralize reactive oxygen species (ROS) through electron donation, providing a robust defense against cellular oxidative damage.

Chaff

<h2>Botanical and Structural Composition</h2><p>The silver skin, or spermoderm, represents the innermost layer of the coffee fruit's integument, tightly encompassing the endosperm. During the developmental stages of the <em>Coffea arabica</em> and <em>Coffea canephora</em> seeds, this cellulosic tissue serves as a protective barrier. Structurally, the silver skin is composed of sclerenchyma cells, providing a fibrous matrix rich in polysaccharides. During the roasting cycle, specifically as the bean internal temperature reaches the range of 130°C to 160°C, the bean undergoes physical expansion. This expansion, coupled with the rapid evaporation of remaining moisture (typically 10-12% in green coffee), causes the silver skin to fracture and detach from the bean surface. In washed (wet-processed) coffees, the mechanical friction of pulping and the fermentation process remove a significant portion of the spermoderm, leaving only the portion trapped within the longitudinal fissure, or center cut. Conversely, natural (dry-processed) coffees retain a higher percentage of the silver skin until the roasting phase, where it is liberated as voluminous, lightweight flakes.</p>

Chlorogenic Acid

Chlorogenic acid (CGA) is a family of ester compounds formed between caffeic acid and quinic acid, and is one of the most abundant phenolic compounds in coffee. Green Arabica coffee contains approximately 5 to 8 percent CGA by weight. During roasting, CGA degrades into lactones and phenylindanes, which contribute significantly to the bitterness, acidity, and antioxidant capacity of brewed coffee.

Coffee Borer Beetle

<h2>Environmental Management and Control</h2><p>Control of <i>H. hampei</i> requires a multi-faceted approach, as the beetle's internal nesting protects it from standard contact insecticides. Biological control often involves the entomopathogenic fungus <i>Beauveria bassiana</i>, which is applied at a concentration of 1x10^9 spores per milliliter. The fungus penetrates the beetle's exoskeleton, leading to mortality within 4 to 7 days. Additionally, the introduction of the parasitoid wasp <i>Cephalonomia stephanoderis</i> has proven effective in Latin American plantations, as the wasp enters the berry to prey upon borer larvae. Post-harvest, meticulous sanitation of processing equipment and the use of GrainPro or hermetic storage bags prevent cross-contamination in the warehouse environment.</p>

Coffee Leaf Rust

Hemileia vastatrix belongs to the order Pucciniales and is an obligate biotrophic fungus, meaning it requires living host tissue to survive. The infection cycle begins when urediniospores are deposited on the abaxial (underside) surface of the coffee leaf, typically via wind or rain splash. Germination occurs only in the presence of free water—such as dew or rainfall—within a temperature range of 15°C to 28°C. Upon germination, the fungus enters the leaf through the stomata and establishes a mycelium that colonizes the internal tissue. The visual manifestation of the disease begins as small, chlorotic spots that expand into characteristic orange, powdery pustules. These pustules contain thousands of spores capable of further infection. The physiological impact includes a rapid reduction in photosynthetic capacity and the eventual abscission of the leaf. Severe cases lead to 'dieback,' where the plant's branches wither due to carbohydrate depletion, often resulting in the death of the tree or a total loss of the following year's crop.

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Decaffeination

Decaffeination is the process of removing caffeine from coffee beans. The four primary methods are the Swiss Water Process, the CO2 Process, the Direct Solvent Method, and the Indirect Solvent Method. All remove 97% or more of caffeine.

Parent Topics & Topic Hubs

Brewing Roasting Grinding

Related Sub-Topics

Sensory & Tasting

Acidity

In coffee tasting, acidity refers to the bright, vibrant, and often fruity quality that gives coffee its liveliness and structure. Unlike the negative connotation of acidity in everyday language, coffee acidity is a desirable characteristic when balanced. It is perceived as a pleasant tartness or brightness on the palate, similar to the acidity in wine or fruit.

Sensory & Tasting

Body

Body, also called mouthfeel, refers to the physical weight, texture, and viscosity of coffee as it is perceived in the mouth. It is a tactile sensation rather than a taste, ranging from thin and tea-like to thick and syrupy. Body is influenced by brewing method, coffee oils, suspended solids, roast level, and the variety and origin of the coffee.

Brew Ratio

Bypass

<h2>Technical Application and Refractometry</h2> In the application of the SCA Brewing Control Chart, the use of bypass facilitates a vertical movement downward (reducing strength) without a horizontal shift (increasing extraction). When utilizing a VST Precision Refractometer to verify results, a barista can ensure that the bypass has achieved the target TDS without shifting the EY. For instance, if a 1.0-liter brew yields a 1.55% TDS and the target is 1.30% TDS, adding approximately 192ml of bypass water will achieve the target. This technique is particularly effective for managing high-density African coffees where long contact times might otherwise lead to unwanted bitterness.

Chaff

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Channeling

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Book References

Chapter 5: Extraction Science
Chapter 6: Measuring Coffee

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Editorial Standards & Trust

Keith E. Lyons

Author, Researcher & Coffee Educator

Keith E. Lyons is the author of The Complete World of Coffee and the publisher behind Lyons Den Publishing. A licensed trauma therapist turned specialty coffee writer, Keith blends scientific rigor with genuine passion for the craft of coffee.

Author of The Complete World of Coffee (600+ pages)Licensed trauma therapist — brings research methodology and scientific rigor to coffee writingIndependent publisher, founder of Lyons Den Publishing

Last Reviewed

July 22, 2026

Sources & References

(2)

Claims are cited to verifiable sources. Peer-reviewed research is marked.

1
Specialty Coffee Association, Brewing Standards
2
Lockhart, E. E., The Soluble Coffee Brewing Control Chart

Authoritative References

Specialty Coffee Association

SCA

World Coffee Research

WCR

Coffee Quality Institute

CQI

National Coffee Association

NCA

Editorial Standards

• Fact-checked against peer-reviewed coffee science research and industry standards.
• Reviewed by the author with documented sources for every factual claim.
• Updated regularly; the "Last Reviewed" date reflects the most recent verification.
• Corrections are made promptly when new research or evidence emerges.

Our editorial process prioritizes accuracy, scientific rigor, and practical relevance for coffee enthusiasts and professionals alike.

Publisher

Lyons Den Publishing · Founded 2025 · San Diego, CA

Contact

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Total Dissolved Solids (TDS)

Espresso

Espresso Extraction Yield

Extraction yield measures the percentage of dry coffee grounds mass dissolved into the liquid beverage. Operating within the target window of 18% to 22% requires understanding compound solubility rates, refractometer calibration, and total dissolved solids (TDS). Master the chemical and mathematical principles behind optimal extraction.

Brewing

Coffee Extraction Yield: What It Is, How to Calculate It, and What the Numbers Mean

Extraction yield is the percentage of the dry coffee dose dissolved during brewing. This guide explains how it differs from strength and brew ratio, how to calculate it from TDS and beverage mass, and why the 18–22% range is a reference rather than a rule.

Equipment & Tools

Coffee Refractometer Guide

Digital coffee refractometers measure Total Dissolved Solids (TDS) in liquid coffee using light refraction, allowing precise calculation of Extraction Yield (EY). This advanced guide explains refractometry principles, sample filtration, and brewing control charts.

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Structured next steps in the same topic area.

Extraction

Solubility

The solubility of coffee is fundamentally a measure of the solvent’s ability to break the intermolecular bonds of the roasted coffee matrix. Of the 1,000+ volatile and non-volatile compounds present in roasted beans, only a fraction are water-soluble under standard brewing conditions. These include polar molecules like caffeine and various salts, as well as sugars and lipids to a lesser degree. The physical structure of the coffee bean—a rigid, porous honeycomb of cellulose—acts as a barrier. This structure requires the solvent to penetrate the pore network via imbibition before solutes can diffuse into the bulk liquid. Grind size directly influences the available surface area, thereby altering the total solubility potential within a given timeframe. At temperatures exceeding 100°C, as seen in industrial extraction, further degradation of the hemicellulose occurs, increasing the theoretical yield up to 50%, though such levels are avoided in specialty brewing due to extreme bitterness.

Melanoidin

Melanoidins represent the final structural evolution of coffee chemistry during thermal processing, comprising a diverse group of nitrogenous, brown-colored macromolecules with molecular weights ranging from 10,000 to 100,000 Daltons. Their formation initiates at approximately 160°C (320°F) through the Maillard reaction, where reducing sugars like glucose and fructose react with free amino acids and proteins. This sequence generates reactive intermediates—including furfurals and dehydro-reductones—which subsequently undergo polycondensation. In Arabica coffee, melanoidin concentration increases linearly with roast development, typically accounting for 15% to 25% of the total beverage dry matter in medium-to-dark roasts. These polymers are categorized by solubility; water-soluble melanoidins migrate into the extract, while insoluble variants remain within the cellular matrix of the spent grounds. The incorporation of nitrogen into heterocyclic ring structures, specifically pyrazines and pyrroles, differentiates these pigments from simple caramelization products and dictates the aromatic intensity of the roasted bean.