{ "id": "cold-brew", "url": "https://coffearium.org/entries/cold-brew/", "license": "CC-BY-4.0", "title": "Cold brew", "summary": "Coffee extracted with water at room temperature or colder over hours instead of minutes – how immersion and slow-drip methods work, what low temperature changes in the cup, and how cold brew is kept safe.", "domain": "extraction", "kind": "Method", "stage": "brew", "topics": [ "science" ], "topicSections": {}, "lang": "en", "status": "verified", "reviewer": "Coffearium verification pass", "lastVerified": "2026-10-15T00:00:00.000Z", "updated": "2026-10-15T00:00:00.000Z", "added": "2026-10-15T00:00:00.000Z", "brief": [ "Cold brew is coffee extracted with water at room temperature or lower; it can be made by steeping (immersion) or by letting cold water drip through the grounds.1,9", "In one study, caffeine and 3-caffeoylquinic acid in cold brew reached equilibrium after 6–7 h at 21–25 °C; the hot brew it was compared with steeped for 6 min.2", "Brewed to equilibrium, full immersion extracted 19.55% of the coffee at 4 °C, 20.74% at 22 °C and 22.28% from 92 °C in one study.6", "Studies disagree on acidity. Several found higher pH and lower titratable acidity in cold brew; two found comparable pH, and one found titratable acidity set by roast, not temperature.2,3,4,5,6", "Cold brew is prepared without sterilising temperatures and has a pH above 4.6; two US county health authorities require cold holding and a short shelf life.9,12,13" ], "quickFacts": [ { "label": "Water temperature", "value": "Room temperature or lower (below body temperature in one review)" }, { "label": "Methods", "value": "Full immersion (steep, then filter); slow or cold drip (water drips through the bed); one review also lists cold press" }, { "label": "Brew ratio in studies", "value": "10 mL of water per gram of coffee (three studies); concentrates at 5 g of water per gram" }, { "label": "Time to equilibrium", "value": "6–7 h at 21–25 °C for caffeine and 3-CQA (one study); brews left 12–14 h at 22 °C and 24–36 h at 4 °C (another)" }, { "label": "Extraction at equilibrium", "value": "19.55% at 4 °C, 20.74% at 22 °C, 22.28% from 92 °C (one study)" }, { "label": "pH", "value": "4.81–5.75 in four studies that report values; above 4.6, the US threshold for low-acid foods" }, { "label": "Food-business holding (two US county rules)", "value": "5 °C (source: 41 °F) or below; date-marked for no more than 7 days; sealed kegs or bottles no more than 48 h without a HACCP plan" } ], "aka": [ "Cold-brew coffee", "Cold brewed coffee", "Cold drip", "Slow drip" ], "linkTerms": [ "cold brew", "cold brewing", "cold drip", "slow drip", "nitro cold brew", "cold brew concentrate", "iced coffee" ], "related": [ "brew-methods", "extraction-yield-and-tds", "acids-in-coffee", "caffeine", "caffeine-and-roast-degree", "water-for-coffee", "grinding", "particle-size-and-fines", "freshness-and-storage", "extraction-variables" ], "contested": [ "pH of cold and hot brew: in a 2018 study of six light roasts, pH was comparable, 4.85–5.13 for both3, and a 2017 study found comparable pH after 24 h of cold brewing.2 Four other studies found a higher pH in cold brew than in hot brew of the same coffee, in the 2024 study only slightly.4,5,6,7", "Titratable acidity of cold and hot brew: three studies found lower titratable acidity in every cold brew.3,4,5 A 2022 study that brewed to equilibrium and diluted every brew to the same strength found that titratable acidity varied only with roast degree, not with brew temperature6; a 2024 study by the same group found that it rose with brew temperature and time.7", "Caffeine in cold and hot brew: one study found more caffeine in cold brew than in a 6 min hot brew at the same ratio for coarse grinds2; another reports caffeine as comparable across brewing temperatures, although its table lists the darkest cold brew at 1,962 mg/L against 1,035–1,114 mg/L for the other brews5, and a 2020 review describes similar levels.9", "Steeping time: caffeine and 3-CQA reached equilibrium within 6–7 h at 21–25 °C2, and a sensory study saw few changes after 8 h7; yet a coarse grind steeped for 22 h gave more dissolved solids than 14 h.4 Single compounds, total solids and flavour may not level off at the same time." ], "corrections": [], "sources": [ { "id": "s1", "title": "The Brew – Extracting for Excellence", "authors": "Mestdagh, F.; Glabasnia, A.; Giuliano, P.", "year": 2017, "publisher": "In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 15, pp. 355–380", "url": "https://doi.org/10.1016/B978-0-12-803520-7.00015-3", "doi": "10.1016/B978-0-12-803520-7.00015-3", "tier": "B", "quote": "Iced coffee on the other hand is prepared using hot water, generally using the drip-brewing method.", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s2", "title": "The Effect of Time, Roasting Temperature, and Grind Size on Caffeine and Chlorogenic Acid Concentrations in Cold Brew Coffee", "authors": "Fuller, M.; Rao, N. Z.", "year": 2017, "publisher": "Scientific Reports 7, 17979", "url": "https://www.nature.com/articles/s41598-017-18247-4", "doi": "10.1038/s41598-017-18247-4", "tier": "A", "quote": "Any water/grind interaction longer than 400 minutes (6.7 hours) did not result in additional significant extraction of 3-CGA.", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s3", "title": "Acidity and Antioxidant Activity of Cold Brew Coffee", "authors": "Rao, N. Z.; Fuller, M.", "year": 2018, "publisher": "Scientific Reports 8, 16030", "url": "https://www.nature.com/articles/s41598-018-34392-w", "doi": "10.1038/s41598-018-34392-w", "tier": "A", "quote": "This work found the pH measurements for all coffee samples tested to be comparable, ranging between 4.85 to 5.13.", "accessed": "2026-10-21T00:00:00.000Z" }, { "id": "s4", "title": "Effect of grinding, extraction time and type of coffee on the physicochemical and flavour characteristics of cold brew coffee", "authors": "Cordoba, N.; Pataquiva, L.; Osorio, C.; Moreno, F. L. M.; Ruiz, R. Y.", "year": 2019, "publisher": "Scientific Reports 9, 8440", "url": "https://www.nature.com/articles/s41598-019-44886-w", "doi": "10.1038/s41598-019-44886-w", "tier": "A", "quote": "All cold brew coffee samples had lower TA values than their hot counterparts.", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s5", "title": "Physiochemical Characteristics of Hot and Cold Brew Coffee Chemistry: The Effects of Roast Level and Brewing Temperature on Compound Extraction", "authors": "Rao, N. Z.; Fuller, M.; Grim, M. D.", "year": 2020, "publisher": "Foods 9(7), 902", "url": "https://jdc.jefferson.edu/cgi/viewcontent.cgi?article=1005&context=jclsfp", "doi": "10.3390/foods9070902", "tier": "A", "quote": "As was found in previous studies [8,26], TDS was higher for hot brew coffees than cold brew coffees at all roast levels.", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s6", "title": "Sensory Analysis of Full Immersion Coffee: Cold Brew Is More Floral, and Less Bitter, Sour, and Rubbery Than Hot Brew", "authors": "Batali, M. E.; Lim, L. X.; Liang, J.; Yeager, S. E.; Thompson, A. N.; Han, J.; Ristenpart, W. D.; Guinard, J.-X.", "year": 2022, "publisher": "Foods 11(16), 2440", "url": "https://escholarship.org/content/qt4ws465qm/qt4ws465qm.pdf", "doi": "10.3390/foods11162440", "tier": "A", "quote": "cold brew is less sour, per our descriptive analysis, but not necessarily less acidic chemically", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s7", "title": "Sensory analysis of the flavor profile of full immersion hot, room temperature, and cold brewed coffee over time", "authors": "Liang, J.; Batali, M. E.; Routt, C.; Ristenpart, W. D.; Guinard, J.-X.", "year": 2024, "publisher": "Scientific Reports 14, 19298", "url": "https://www.nature.com/articles/s41598-024-69867-6", "doi": "10.1038/s41598-024-69867-6", "tier": "A", "quote": "roast level was the largest driver of differences among the samples, followed by brewing temperature, then brew time", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s8", "title": "An equilibrium desorption model for the strength and extraction yield of full immersion brewed coffee", "authors": "Liang, J.; Chan, K. C.; Ristenpart, W. D.", "year": 2021, "publisher": "Scientific Reports 11, 6904", "url": "https://www.nature.com/articles/s41598-021-85787-1", "doi": "10.1038/s41598-021-85787-1", "tier": "A", "quote": "full immersion brewing offers precise control over the TDS at equilibrium but little control over E.", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s9", "title": "Current Challenges of Cold Brew Coffee – Roasting, Extraction, Flavor Profile, Contamination, and Food Safety", "authors": "Kwok, R.; Lee Wee Ting, K.; Schwarz, S.; Claassen, L.; Lachenmeier, D. W.", "year": 2020, "publisher": "Challenges 11(2), 26", "url": "https://www.mdpi.com/2078-1547/11/2/26", "doi": "10.3390/challe11020026", "tier": "A", "tierNote": "Peer-reviewed viewpoint article; recommendations the authors base on their own consulting experience are reported as such, never as established.", "quote": "The long brewing time of cold brew can facilitate microbiological activity.", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s10", "title": "Characterization and comparison of cold brew and cold drip coffee extraction methods", "authors": "Angeloni, G.; Guerrini, L.; Masella, P.; Innocenti, M.; Bellumori, M.; Parenti, A.", "year": 2019, "publisher": "Journal of the Science of Food and Agriculture 99, 391–399", "url": "https://www.research.unipd.it/handle/11577/3407672", "doi": "10.1002/jsfa.9200", "tier": "A", "quote": "few studies have investigated slow, cold extraction methods, despite their popularity among baristas", "abstractOnly": true, "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s11", "title": "21 CFR § 113.3 – Definitions (Thermally processed low-acid foods packaged in hermetically sealed containers)", "authors": "United States Food and Drug Administration (Code of Federal Regulations)", "publisher": "Legal Information Institute, Cornell Law School (text of the US Code of Federal Regulations)", "url": "https://www.law.cornell.edu/cfr/text/21/113.3", "tier": "A", "quote": "any foods, other than alcoholic beverages, with a finished equilibrium pH greater than 4.6", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s12", "title": "Cold Brew Coffee Safety – HACCP", "authors": "Peoria City/County Health Department (Illinois, USA)", "year": 2022, "publisher": "Peoria City/County Health Department", "url": "https://www.pcchd.org/DocumentCenter/View/2439/Cold-Brew-Coffee-Safety-HACCP-2022", "tier": "A", "quote": "Cold brew is date marked for no more than 7 days from the date of production", "accessed": "2026-10-15T00:00:00.000Z" }, { "id": "s13", "title": "Cold-Brew Coffee (safety concerns, things to know and application requirements), 3/2024; archived file", "authors": "Maricopa County (Arizona, USA); the issuing department is not named in the document", "year": 2024, "publisher": "Maricopa County", "url": "https://www.swm.maricopa.gov/DocumentCenter/View/44843/Cold-Brew-Coffee-Guidance-PDF-Archived", "tier": "A", "quote": "Brew, hold, and dispense at 41°F or below", "accessed": "2026-10-15T00:00:00.000Z" } ], "markdown": "## What cold brew is\n\nCold brew is coffee made with cold water: water at room temperature or lower.1 A 2020 review defines it as an extraction style with water below body temperature, not as a drink of its own.9 No definition or regulatory standard for cold brew existed when that review was written.9\n\nWithout heat, extraction is slow. Cold brew generally needs a long time, up to 24 hours, to reach a sufficient extraction yield.1,4 Typical steeping times run from 8 to 24 hours.4 According to a textbook chapter, less aroma is lost by evaporation than in hot brewing, so more volatile compounds stay in the drink.1\n\nThe result can be drunk cold, or hot after dilution with water.1 It is a different drink from iced coffee, which is brewed hot and then cooled.1\n\n## Immersion and slow drip\n\nA 2020 review lists three methods: immersion, cold drip and cold press.9 This entry describes the first two.\n\n**Full immersion.** The ground coffee sits in the water, with or without stirring, and the brew is filtered afterwards.9 Studies often put the grounds in a filter bag inside the vessel.2,4 As the liquid grows stronger, extraction slows and approaches an equilibrium, as in hot immersion brewing.2,8\n\n**Slow drip, or cold drip.** Cold water, typically iced water, drips through the coffee bed and a filter.9 A 2019 study found significant chemical and physical differences between cold drip and immersion cold brew, and differences in flavour.10\n\n
\n
\n

A · Full immersion

\n
    \n
  1. Vessel with water. All the water is added at the start, at room temperature or in the fridge.1,9
    2. \n
  2. Grounds in a filter bag. The coffee steeps in the water and is filtered out at the end.4,9
    3. \n
  3. Lid. According to a textbook chapter, long brewing can give oxidised flavours unless exposure to air is controlled.1
    4. \n
\n

B · Slow drip

\n
    \n
  1. Reservoir. Holds the water, typically iced.9
    2. \n
  2. Drops. Water drips onto the coffee bed.4,9
    3. \n
  3. Coffee bed and filter. Water passes through the grounds and is filtered on the way out.9
    4. \n
  4. Carafe. Collects the brew below.9
    5. \n
\n
Two ways of making cold brew. Schematic, not to scale.
\n
\n\n## Time, temperature and grind\n\nCold water extracts the same coffee more slowly than hot water.1,2 In one study, a hot brew steeped for 6 minutes; the cold brew of the same coffee and ratio reached equilibrium after about 400 minutes.2\n\nTemperature also changes how much is extracted in the end. In a 2022 study, full immersion brews were left until their strength stopped rising.6 Fridge brews at 4 °C needed 24–36 h, room-temperature brews at 22 °C 12–14 h, and brews started at 92 °C 1–2 h.6 The colder the water, the less was extracted.6\n\n
\n
\n
Extraction yield at equilibrium in full immersion brews at three water temperatures, with the brew time each set needed. Values are averages over three coffees and three roast degrees.6 The 92 °C brews started hot and then stood at room temperature.6
\n
\n\nGrind is usually coarse. Studies used coarse grinds of 701–900 µm, a median of 972 µm, or particles sieved to 500–2,000 µm.4,5,7 In one study, a medium grind of 501–700 µm caked in the filter bags; the coarse grind steeped for 22 h gave the most dissolved solids.4 In another, grind size did not change caffeine or 3-caffeoylquinic acid significantly.2\n\n## Acidity compared with hot brew\n\nCold brew is often called less acidic. The measurements disagree, partly because pH and titratable acidity are different measures. In one study, cold and hot brews had comparable pH but different amounts of titratable acid.3\n\n- **pH.** Two studies found comparable pH in cold and hot brews.2,3 Four others found a higher pH, meaning less acidic, in cold brew.4,5,6,7\n- **Titratable acidity.** Three studies found less titratable acid in every cold brew.3,4,5 One study compared brews at the same strength; there, titratable acidity depended on roast, not brew temperature.6\n- **Flavour.** In the same study, a trained panel found cold brew less sour and less bitter, and more floral, than hot brew served cold.6 Its authors conclude that cold brew is less sour, but not necessarily less acidic chemically.6\n\nRoast degree mattered more than temperature. In a 2024 sensory study, roast caused the largest differences, then brew temperature, then brew time.7 The acids entry explains pH and titratable acidity in more detail.\n\n## Caffeine\n\nCaffeine dissolves well in water, and a 2020 review describes similar levels in cold and hot brew.9 Measurements vary. One study found more caffeine in coarse-ground cold brew than in a hot brew made at the same ratio.2 Another reports caffeine as comparable across roast degrees and brew temperatures.5 Its own table, however, lists the darkest cold brew at 1,962 mg/L, against 1,035–1,114 mg/L for the other brews.5\n\nThe caffeine in a cup also depends on how strong the brew is and how much it is diluted. In one study, cold brew made with 10 mL of water per gram of coffee held 930–1,230 mg of caffeine per litre.2 Caffeine by serving size is covered in the caffeine entry.\n\n## Concentrate and dilution\n\nCold brew is often made strong and diluted before serving. Studies of concentrate used 100 g of coffee to 500 g of water, a brew ratio of 5.6,7 A 2020 review gives 1:5 as the usual ratio.9 At equilibrium these concentrates held about 3.5–4.3% total dissolved solids (TDS).6,7 For tasting, one study diluted every brew to exactly 2% TDS.6\n\nStudies of ready-to-drink cold brew used about 10 mL of water per gram of coffee.2,3,5 Their brews held about 1.9–2.1% TDS.5\n\n**An example recipe.** The steps below combine values from the studies above. They are an example, not a tested standard.\n\n1. Grind coffee coarse. Studies used 701–900 µm or similar.4\n2. Weigh 1 part coffee to 10 parts water for a drink, or 1 to 5 for a concentrate.2,7\n3. Put the grounds in a filter bag or jar, add the water and close the lid.1,2\n4. Steep. At 21–25 °C caffeine and 3-caffeoylquinic acid stopped rising after 6–7 h; brews in a fridge at 4 °C were left 24–36 h.2,6\n5. Filter through paper, as two of the studies did.3,6\n6. Dilute a concentrate to taste, and keep the brew in the fridge (see Food safety).1,12\n\n## Iced coffee and nitro cold brew\n\n**Iced coffee.** A textbook chapter describes iced coffee as brewed with hot water, usually by drip.1 It is then cooled, for example with ice, and served over more ice.1 A 2020 review does not count hot-brewed coffee that is simply cooled as cold brew.9 In a 2022 study, brews started at 92 °C and served cold were more bitter, sour and rubbery than cold brews of the same coffees.6 No study opened for this entry tested coffee brewed hot directly onto ice (flash-chilled or Japanese-style iced coffee).\n\n**Nitro cold brew.** Nitro cold brew is cold brew kept under nitrogen, for example in kegs.9 According to a 2020 review, which calls the evidence anecdotal, storage under nitrogen pressure avoids oxidation and extends shelf life.9 But kegs and bottles also create low-oxygen conditions, which carry a food-safety risk (see below).9,13 No peer-reviewed study of how nitrogen changes flavour or foam was opened for this entry.\n\n## Food safety and storage\n\nCold brew is prepared without sterilising temperatures.9 Its long brewing time can also allow microbes to grow.9 Cold brew has a pH above 4.6, typically 4.9–6.0, a low acidity that does not effectively suppress microbial growth.9\n\nA pH of 4.6 is a legal threshold. US federal rules define low-acid foods as foods with a pH above 4.6 and a water activity above 0.85.11 The definition belongs to the rules for thermally processed foods in hermetically sealed containers.11 A 2020 review links ready-to-drink cold brew, especially under anaerobic conditions, to a risk of botulism, to be controlled by pH control or thermal processing.9 A nitro cold brew sold in reduced oxygen packaging was recalled in the USA in September 2017.9 Its production process could have allowed botulinum toxin to form.9\n\nTwo US county health authorities set rules for cafés and other food businesses.12,13\n\n- Cold brew is brewed, held and served at 5 °C (source: 41 °F) or below.12,13\n- It is date-marked for no more than 7 days from production.12,13\n- Kegged or bottled cold brew stays sealed for no more than 48 h; after that it is discarded, unpacked or opened.12,13\n- Otherwise a hazard analysis and critical control point (HACCP) plan, a variance, or both are needed. The exception is a product shown not to be a time/temperature control for safety (TCS) food.12,13\n\nThese are local US rules, quoted as published. Rules differ between countries, and no European authority guidance on cold brew was found for this entry.\n\n\n\n## Extraction kinetics at low temperature\n\n**First-order approach to equilibrium.** In a 2017 study, 35.0 g of a Kona Typica coffee steeped in 350 mL of water at 21–25 °C, sampled from 15 min to 24 h.2 Caffeine and 3-caffeoylquinic acid (3-CQA, called 3-CGA in the paper) followed first-order kinetics and reached equilibrium at about 400 min (6.7 h) for all roasts and grinds.2 Steeping beyond 400 min gave no further significant extraction of 3-CQA.2 The same coffee brewed with 98 °C water in a French press for 6 min was the hot reference.2\n\n
\n
\n
Caffeine in cold brew of a medium roast after 400 min and 24 h at 21–25 °C, and in a 6 min hot brew at the same ratio (35.0 g in 350 mL), for medium and coarse grinds; means, confidence intervals not drawn.2 Lines join the two published time points only; the paper reports equilibrium at about 400 min, and the time course in between appears only as a graph.2
\n
\n\n**What heat changes.** A textbook chapter explains the difference through solubility; no study opened for this entry measured coffee oil in cold brew. Without heat, low-polarity compounds such as coffee oil are extracted poorly, while highly polar compounds are still extracted rather well.1 The solubility of flavour compounds depends strongly on temperature and differs between compounds.1 A 2020 study suggests that changes in the bean during roasting potentially altered mass transfer rates, solubility and extraction yield as a function of water temperature.5 A 2018 study suggests that the extra compounds in hot brew may be larger molecules with temperature-dependent solubilities, many of them acidic.3\n\n**Rate and end point.** Hot immersion is fast: at a brew ratio of 5, a 99 °C brew exceeded 4% TDS within 20 min.8 The 2022 study shows that cold water also lowers the end point: equilibrium extraction fell from 22.28% for brews started at 92 °C to 20.74% at 22 °C and 19.55% at 4 °C, with TDS of 4.27%, 3.98% and 3.76%.6 In a 2024 follow-up at the same ratio, final TDS was 3.97 ± 0.63% at 92 °C, 3.93 ± 0.10% at 22 °C and 3.52 ± 0.59% at 4 °C.7 Equilibrium yield in hot full immersion is discussed in the brew methods and extraction yield entries.\n\n**How long is long enough.** The 2024 study sampled cold brews at 0, 4, 8, 12 and 24 h and hot brews at 0, 4, 10, 30 and 60 min.7 At 4 °C and 22 °C, the rapid rise in TDS was near its end by 8 h, and few sensory attributes changed significantly after that.7 The authors note that common practice runs from 12 to 24 h and see room for shorter brew times.7 A 2020 review proposes 2 h at 15 °C with 80 g/L for medium roasts, but states that its target extraction figure stems from experience and has no scientific basis yet.9\n\n**Immersion versus drip.** A 2019 comparison of cold brew and cold drip found significant differences between and within the two methods in pH, total solids, refractive index, density, viscosity, caffeine and cinnamic acids, depending on extraction temperature and contact time.10 Its panel found differences in bitterness, sweetness, sourness and overall intensity.10 According to a 2020 review, cold drips were perceived as more bitter.9 Only the abstract of the 2019 study could be read for this entry, so its values are not given.\n\n## Acidity: what the measurements show\n\nFive studies compared cold and hot brews of the same coffees. Their set-ups differ, which explains part of the disagreement.\n\n| Study | Set-up | pH | Titratable acidity | TDS |\n|---|---|---|---|---|\n| Fuller & Rao, 20172 | 35.0 g in 350 mL; cold 24 h at 21–25 °C; hot 98 °C, 6 min | Cold 5.40–5.54, hot 5.35–5.61; “comparable” | Not measured | Not measured |\n| Rao & Fuller, 20183 | Six light roasts, 35.0 g in 350 mL; cold 7 h at 21–25 °C; hot boiling water, 6 min | Comparable, 4.85–5.13 | Lower in every cold brew | Not reported |\n| Cordoba et al., 20194 | Two Colombian coffees, 60 g per 700 g water; cold 14 or 22 h at 20 °C | Higher in cold brew | Lower in every cold brew | Highest at coarse grind, 22 h |\n| Rao, Fuller & Grim, 20205 | One Colombian coffee, three roasts; 20 g in 200 mL; cold 7 h at room temperature; hot 100 °C, 6 min | Higher in cold brew at every roast | Lower in cold brew at every roast | Higher in hot brew at every roast |\n| Batali et al., 20226 | Three coffees, three roasts; ratio 5, to equilibrium at 4, 22 and 92 °C; diluted to 2% TDS | Lower at 92 °C than at 22 and 4 °C | Varied with roast only | Higher at 92 °C |\n\nIn the 2020 study, the gaps in pH and titratable acidity between hot and cold brew grew with roast degree; the TDS gap did not grow steadily.5 Its values, means of the published table:5\n\n| Roast (final bean temperature) | pH cold / hot | Titratable acidity cold / hot (mL 0.1 N NaOH) | TDS cold / hot (%) |\n|---|---|---|---|\n| 194 °C | 5.00 / 4.80 | 4.66 / 4.82 | 1.88 / 1.96 |\n| 203 °C | 5.30 / 5.04 | 3.15 / 3.55 | 2.06 / 2.12 |\n| 209 °C | 5.75 / 5.39 | 1.53 / 2.06 | 2.05 / 2.23 |\n\n**Strength as a confounder.** Cold brews often hold fewer dissolved solids than hot brews of the same ratio.5 Titratable acidity is measured per volume of brew, so part of a lower value may reflect a weaker brew rather than a different acid profile; this is our reading, not a finding of the studies. The 2022 study removed this effect by brewing to equilibrium and diluting every brew to the same TDS; it then found titratable acidity set by roast, not temperature.6 The 2024 study diluted every concentrate by the same factor, 2 by mass, not to the same TDS; it found titratable acidity rising with temperature and brew time.7 The 2018 study did not report TDS, so it cannot separate the two effects.\n\n**Antioxidant capacity.** The 2018 study found lower antioxidant activity in every cold brew.3 In the 2020 study, it changed with roast only in cold brew.5 This entry makes no health claims; health effects belong to a future health entry.\n\n## Reference values\n\nParameters reported in the studies opened for this entry. They describe research set-ups, not a standard.\n\n| Parameter | Reported values | Source |\n|---|---|---|\n| Water temperature | Room temperature or lower; 20 °C, 21–25 °C, 22 °C, 4 °C | Mestdagh et al.1; Cordoba et al.4; Fuller & Rao2; Batali et al.6 |\n| Brew ratio, drink | 35.0 g in 350 mL; 20 g in 200 mL; 60 g per 700 g water | Fuller & Rao2; Rao et al.5; Cordoba et al.4 |\n| Brew ratio, concentrate | 100 g coffee to 500 g water (ratio 5) | Batali et al.6; Liang et al.7 |\n| Grind | 701–900 µm (coarse); median 972 µm; sieved 500–2,000 µm | Cordoba et al.4; Liang et al.7; Rao et al.5 |\n| Time to equilibrium | ≈400 min (6.7 h) at 21–25 °C for caffeine and 3-CQA | Fuller & Rao2 |\n| Brew time used to reach equilibrium | 24–36 h at 4 °C; 12–14 h at 22 °C; 1–2 h from 92 °C | Batali et al.6 |\n| Typical steeping times | 8–24 h | Cordoba et al.4 |\n| Extraction at equilibrium (ratio 5) | 19.55% (4 °C), 20.74% (22 °C), 22.28% (92 °C) | Batali et al.6 |\n| TDS, drink-strength cold brew | 1.88–2.06% | Rao et al.5 |\n| TDS, concentrate at equilibrium | 3.52–3.98% (4 and 22 °C) | Batali et al.6; Liang et al.7 |\n| pH | 4.81 lowest (two Colombian coffees); 4.85–5.13 (light roasts); 5.00–5.75 (three roasts); 5.40–5.63 (medium and dark) | Cordoba et al.4; Rao & Fuller3; Rao et al.5; Fuller & Rao2 |\n| Caffeine, drink strength | 930–1,230 mg/L (one Kona coffee, two roasts, two grinds) | Fuller & Rao2 |\n| US low-acid food threshold | pH > 4.6 and water activity > 0.85 | 21 CFR 113.311 |\n| Holding in food businesses (two US counties) | ≤5 °C (source: 41 °F); date mark ≤7 days; sealed packs ≤48 h without HACCP plan | County rules12,13 |\n\n## Food-safety rules in detail\n\n**Why cold brew is a concern.** A 2020 review lists the reasons: no sterilising temperatures during preparation, long brewing times that can favour microbial activity, and a pH above 4.6.9 It reports that microorganisms may stay viable in cold brew for 7–28 days, citing earlier challenge studies.9 It recommends that cold brew be considered specifically in HACCP systems, and that dispensing equipment be cleaned with special care.9\n\n**The low-acid threshold.** The US definition of a low-acid food – a finished equilibrium pH above 4.6 and a water activity above 0.85, alcoholic beverages excluded – belongs to the federal rules for thermally processed foods in hermetically sealed containers.11 Every cold brew pH reported in the studies above lies above 4.6.2,3,4,5\n\n**Time and temperature control.** Both counties regard cold brew as a TCS food; one accepts evidence about its pH and water activity to show otherwise, the other laboratory testing.12,13 The other states that cold brewing results in a pH and water activity range in which pathogens could grow and form toxins.12 Both describe kegging and bottling as reduced oxygen packaging, and both cite sections of the US Food Code on HACCP plans and variances.12,13\n\n**Shelf life in the literature.** The 2020 review suggests a maximum storage time of two days for artisanal producers, and sale on the day of preparation as the optimum.9 This is a recommendation, not an authority limit.\n\n## Open questions\n\n- **Cold drip in numbers.** Few studies have looked at slow, cold extraction, despite its popularity among baristas.10 No open full text comparing drip towers and immersion was available for this entry.\n- **Fridge-temperature kinetics.** The equilibrium model for immersion brewing was tested only at 80–99 °C, not on cold brew.8\n- **Acidity at equal strength.** Most hot–cold comparisons used the same ratio, not the same strength; only one compared brews diluted to equal TDS.6\n- **Nitrogen and flavour.** No peer-reviewed measurement of how nitrogen infusion changes flavour, body or foam was opened for this entry.\n- **European guidance.** No European or Swiss authority guidance specific to cold brew was found; no definition or regulatory standard existed as of 2020.9\n\n## Key studies\n\n
\n

Fuller & Rao, 2017 – Cold brew kinetics. Followed caffeine and 3-caffeoylquinic acid in cold brew of a medium and a dark roast at two grind sizes over 24 h. Both compounds followed first-order kinetics and levelled off after about 400 minutes; grind size had no significant effect, and coarse cold brews held more caffeine than 6 min hot brews.

\n

Scientific Reports 7, 17979 · doi:10.1038/s41598-017-18247-4

\n
\n\n
\n

Rao, Fuller & Grim, 2020 – Roast degree and brew temperature. Brewed one Colombian coffee at three roast degrees hot and cold at the same ratio. Cold brews had higher pH, lower titratable acidity and lower TDS at every roast, and the pH and acidity gaps grew with roast degree; the authors describe caffeine as comparable.

\n

Foods 9(7), 902 · doi:10.3390/foods9070902

\n
\n\n
\n

Batali et al., 2022 – Cold brew against chilled hot brew. Brewed 27 combinations of origin, roast and temperature (4, 22 and 92 °C) to equilibrium, diluted all to 2% TDS and served them cold. Colder water extracted less; a trained panel found cold brews more floral and less bitter, sour and rubbery, while titratable acidity depended on roast, not temperature.

\n

Foods 11(16), 2440 · doi:10.3390/foods11162440

\n
\n\n
\n

Liang et al., 2024 – Brew time. Followed TDS, acidity and flavour of full immersion brews at 4, 22 and 92 °C over time. TDS rose quickly and then levelled off, sensory profiles changed little after about 8 h at 4 and 22 °C, and roast degree outweighed temperature and time.

\n

Scientific Reports 14, 19298 · doi:10.1038/s41598-024-69867-6

\n
\n\n
\n

Kwok et al., 2020 – Challenges of cold brew. Reviews roasting, extraction, flavour, contamination and food safety of cold brew. It stresses the missing heat step and a pH above 4.6, links low-oxygen packaging to botulism risk, and calls for short shelf lives and HACCP controls.

\n

Challenges 11(2), 26 · doi:10.3390/challe11020026

\n
" }