{ "id": "development-time", "url": "https://coffearium.org/entries/development-time/", "license": "CC-BY-4.0", "title": "Development time", "summary": "The time from first crack to the end of the roast – how it is measured, what the development time ratio is, and what studies found when only this phase was changed at the same roast colour.", "domain": "roasting", "kind": "Process", "stage": "roast", "topics": [ "science" ], "topicSections": {}, "lang": "en", "status": "verified", "reviewer": "Coffearium verification pass", "lastVerified": "2026-10-17T00:00:00.000Z", "updated": "2026-10-17T00:00:00.000Z", "added": "2026-10-17T00:00:00.000Z", "brief": [ "Development time is the time from first crack, when beans start to crack audibly, to the end of the roast.1,2", "In one study at a fixed colour, lengthening development from 90 to 390 s lowered sweetness, acidity and fruitiness and raised bitterness and roasted notes; body did not change.1", "In a pooled analysis of seven sensory studies, development time affected flavour more than time to first crack.2", "To keep the same colour, longer development needed a lower end temperature (191.1 °C after 390 s, 204.1 °C after 90 s, one study).1", "The development time ratio, development as a share of total roast time, is a practitioner convention (20–25% in a 2014 trade-press article); no peer-reviewed test of it was found.10,1,2" ], "quickFacts": [ { "label": "Definition", "value": "First crack to the end of the roast" }, { "label": "Development time ratio", "value": "Development time ÷ total roast time (practitioner convention)" }, { "label": "Range studied at one colour", "value": "90–390 s after first crack at about 570 s (one study, Agtron 76)" }, { "label": "Longer development, same colour", "value": "Less sweet, acidic and fruity; more bitter and roasted; body unchanged" }, { "label": "End temperature at the same colour", "value": "Lower the longer the development (204.1 → 191.1 °C, one study)" }, { "label": "Not tested in peer-reviewed work", "value": "The development time ratio as such" } ], "aka": [ "Development phase", "Roast development time" ], "linkTerms": [ "development time", "development time ratio", "DTR", "time after first crack" ], "related": [ "preheating-and-charge", "drying-phase", "browning-phase", "first-crack", "second-crack", "roast-profile", "roasting", "roast-degree-and-colour", "roast-defects", "acids-in-coffee", "maillard-reaction", "body-and-mouthfeel", "drum-roaster", "cupping" ], "contested": [ "Where development ends: most sensory studies define development time as first crack to the end of the roast1,2,3,5; a 2024 titratable-acidity study calls the span from first crack to second crack the development phase.6", "Development time ratio as a target: a practitioner observed that roasts he judged successful spent 20–25% of the roast after first crack and says it “seems to be a prerequisite for a successful roast”10, later “a handy rule of thumb”11; the author of roast-logging software argues that nothing in coffee changes in relation to a percentage of total roast time.12 The peer-reviewed studies found varied development in seconds and did not test the ratio.1,2", "Development and body: a practitioner writes that a roast that is not well developed will likely lack body, and that roast degree and development determine body11; in a sensory study at one colour, body did not differ between development times1, and an eight-study analysis concluded that roasting had no effect on body.2", "Colour or development as the quality check: in two studies that varied both, colour predicted flavour better than timing2; at one fixed colour, development time alone still shifted chemistry and flavour, and the authors conclude that colour alone is not a sufficient indicator.1" ], "corrections": [], "sources": [ { "id": "s1", "title": "The Effect of Roast Development Time Modulations on the Sensory Profile and Chemical Composition of the Coffee Brew as Measured by NMR and DHS-GC–MS", "authors": "Alstrup, J.; Petersen, M. A.; Larsen, F. H.; Münchow, M.", "year": 2020, "publisher": "Beverages 6(4), 70", "url": "https://www.mdpi.com/2306-5710/6/4/70", "doi": "10.3390/beverages6040070", "tier": "A", "quote": "The findings suggest that a short development time increases the fruity, sweet and acidic characteristics of the coffee, whereas a longer development time shifts the balance towards a more roasty, nutty, and bitter profile.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s2", "title": "Roasting Conditions and Coffee Flavor: A Multi-Study Empirical Investigation", "authors": "Münchow, M.; Alstrup, J.; Steen, I.; Giacalone, D.", "year": 2020, "publisher": "Beverages 6(2), 29", "url": "https://www.mdpi.com/2306-5710/6/2/29", "doi": "10.3390/beverages6020029", "tier": "A", "quote": "With respect to our last aim, therefore, the results clearly showed that out of the two roasting phases, development time had a larger influence on coffee flavour than time to first crack.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s3", "title": "Common roasting defects in coffee: Aroma composition, sensory characterization and consumer perception", "authors": "Giacalone, D.; Degn, T. K.; Yang, N.; Liu, C.; Fisk, I.; Münchow, M.", "year": 2019, "publisher": "Food Quality and Preference 71, 463–474", "url": "https://doi.org/10.1016/j.foodqual.2018.03.009", "doi": "10.1016/j.foodqual.2018.03.009", "tier": "A", "quote": "Time from ‘first crack’ to the end of the roast.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s4", "title": "Coffee-roasting variables associated with volatile organic profiles and sensory evaluation using multivariate analysis", "authors": "Catão, A. A.; Mateus, N. de S.; Garcia, C. da C.; da Silva, M. C.; Novaes, F. J. M.; Alves, S.; Marriott, P. J.; da Silva, A. I.", "year": 2022, "publisher": "Applied Food Research 2(2), 100223", "url": "https://doi.org/10.1016/j.afres.2022.100223", "doi": "10.1016/j.afres.2022.100223", "tier": "A", "quote": "30 seconds are enough to diminish a couple of points in coffee quality", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s5", "title": "Multi-sensory evaluation of Gayo Arabica coffee with various roasting times during the development phase", "authors": "Fadhil, R.; Adam, F.; Subekti, P.; Agustina, R.", "year": 2025, "publisher": "The Annals of the University Dunarea de Jos of Galati, Fascicle VI – Food Technology 49(1), 159–176", "url": "https://gup.ugal.ro/ugaljournals/index.php/food/article/view/9287", "doi": "10.35219/foodtechnology.2025.1.10", "tier": "A", "quote": "The Development Phase was calculated from the beginning of the first crack to the end of roasting.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s6", "title": "The effect of roast profiles on the dynamics of titratable acidity during coffee roasting", "authors": "Anokye-Bempah, L.; Styczynski, T.; de Andrade Teixeira Fernandes, N.; Gervay-Hague, J.; Ristenpart, W. D.; Donis-González, I. R.", "year": 2024, "publisher": "Scientific Reports 14, 8237", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC11002029/", "doi": "10.1038/s41598-024-57256-y", "tier": "A", "quote": "This phase is commonly referred to as the “development” phase.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s7", "title": "A heat and mass transfer study of coffee bean roasting", "authors": "Fadai, N. T.; Melrose, J.; Please, C. P.; Schulman, A.; Van Gorder, R. A.", "year": 2017, "publisher": "International Journal of Heat and Mass Transfer 104, 787–799", "url": "https://ora.ox.ac.uk/objects/uuid:c2433f0b-fc40-4d7c-a207-5453349f6f91/files/m2e0c0e8fb121aa744f0a35396a18ff60", "doi": "10.1016/j.ijheatmasstransfer.2016.08.083", "tier": "A", "quote": "After the first minute, the bean's temperature and moisture content become nearly spatially uniform.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s8", "title": "Use of colour parameters for roasted coffee assessment", "authors": "Bicho, N. C.; Leitão, A. E.; Ramalho, J. C.; Lidon, F. C.", "year": 2012, "publisher": "Ciência e Tecnologia de Alimentos 32(3), 436–442", "url": "https://www.redalyc.org/pdf/3959/395940113004.pdf", "doi": "10.1590/S0101-20612012005000068", "tier": "A", "quote": "after milling, only L* and H° decreased progressively", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s9", "title": "The Roast – Creating the Beans' Signature", "authors": "Schenker, S.; Rothgeb, T.", "year": 2017, "publisher": "In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 11, pp. 245–271", "url": "https://doi.org/10.1016/B978-0-12-803520-7.00011-6", "doi": "10.1016/B978-0-12-803520-7.00011-6", "tier": "B", "quote": "A few seconds can make the difference between a correctly roasted product with the desired degree of roast and an over-roasted product.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s10", "title": "Roast Development Time and the Prerequisite for Any Successful Roast", "authors": "Rao, S.", "year": 2014, "publisher": "Daily Coffee News", "url": "https://dailycoffeenews.com/2014/08/12/roast-development-time-and-the-prerequisite-for-any-successful-roast", "tier": "C", "quote": "Put another way, \"development time\" was between 20%–25% of total roast time.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s11", "title": "Development Time Ratio", "authors": "Rao, S.", "year": 2016, "publisher": "scottrao.com (author's blog; roasting consultant)", "url": "https://www.scottrao.com/blog/2016/8/25/development-time-ratio", "tier": "C", "quote": "DTR is not a guarantee of development; it's simply one of many indicators of how a roast progressed.", "accessed": "2026-10-17T00:00:00.000Z" }, { "id": "s12", "title": "Development Time Ratio Considered Harmful", "authors": "Wilson, N.", "year": 2016, "publisher": "Typica (blog of the Typica roast-logging software)", "url": "https://typica.us/typica/2016/08/13/development-time-ratio-considered-harmful.html", "tier": "C", "quote": "The problem is that there is nothing that changes in coffee in relation to a percent of total roasting time.", "accessed": "2026-10-17T00:00:00.000Z" } ], "markdown": "## What development time is\n\nDevelopment time is the time from first crack to the end of the roast.1,2,3 First crack is the moment a popping sound is first heard, as built-up steam pressure cracks the beans.2 The end of the roast is the drop, when the beans leave the roaster and are cooled.9 It is step 5 of 6 in Coffearium's roast steps, after first crack and before second crack.\n\nA roast can therefore be split into two timed parts. The first is the time to first crack. The second is the development time; together they make the total roast time.2 Studies report development in minutes and seconds, for example 2:40 min in an 11:25 min roast.3\n\nResearchers expect this last phase to be when aroma forms fastest.2 Early in the roast, much of the energy goes into heating and evaporating water. Towards the end, the process becomes progressively more exothermic and needs much less heat input.2 The authors of a 2020 study describe the beans as particularly sensitive to heat at this stage.1\n\nRoasters decide during this phase when to drop the batch.9 According to a roasting textbook chapter, sight and smell matter most after first crack.9 A few seconds can separate the intended roast degree from an over-roasted one.9\n\n## The development time ratio\n\nSome roasters express development as a share of the total roast time. In the trade press, this share is called the development time ratio (DTR):10\n\nDTR = development time ÷ total roast time × 100%\n\nFor example, 2:40 min of development in an 11:25 min roast gives about 23% (our calculation).3\n\n**What practitioners say.** A 2014 trade-press article by a roasting consultant reported that roasts he liked spent 20–25% of the roast after first crack.10 The same author later called this a rule of thumb that can be broken, and not a guarantee of a good roast.11 Its use is disputed: the author of roast-logging software argues that nothing in the coffee changes in relation to a percentage of the total time.12\n\n**What studies tested.** The peer-reviewed studies found for this entry changed development in seconds, not as a ratio.1,2 No peer-reviewed test of the ratio itself was found. The figure shows how the two measures relate on a curve.\n\n
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A · Development time and the ratio

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  1. Charge. Green coffee enters the roaster; the clock starts.9
    2. \n
  2. Time to first crack. From charge to first crack.2
    3. \n
  3. First crack. Timed when a popping sound is first heard.2
    4. \n
  4. Development time. From first crack to the end of the roast.1,2
    5. \n
  5. Drop. The beans leave the roaster and are cooled.9
    6. \n
  6. Total roast time. Time to first crack plus development time.2 The development time ratio is 4 divided by 6, a practitioner measure.10
    7. \n
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B · Same colour, different development

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  1. Shared first crack. In one study, four roasts of one coffee ran alike up to first crack at about 570 s.1
    2. \n
  2. Short development. 90 s, ended at 204.1 °C; the fastest, most acidic and fruity roast.1
    3. \n
  3. Long, flat development. 390 s with little temperature rise, ended at 191.1 °C – the “baked” roast.1 The two open dots are 143 s and 266 s.1
    4. \n
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Development time and the development time ratio on a roast curve (A); four developments ended at the same colour, Agtron 76 (B). Durations in B are proportional to the published times; heights are not. Schematic, not to scale.1
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\n\n## What longer development does to the cup\n\nA 2020 study isolated development time.1 It roasted one washed Colombian arabica coffee four times in a 1 kg drum roaster.1 The roasts ran alike to first crack and all ended at the same colour, Agtron 76 ± 1.1 Only the development time differed: 90, 143, 266 and 390 s.1 The beans looked identical.1\n\nForty-six experienced tasters scored the brews. Longer development lowered sweetness, acidity, fruitiness and clean cup, and raised bitterness, astringency, roasted and nutty–chocolate notes.1 Body did not change.1 The authors call the differences substantial, given the identical colour.1\n\n
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Mean intensity of six attributes after four development times at one colour (Agtron 76), 46 experienced tasters; lines only join the measured points. Body did not differ significantly; all other attributes did.1
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\n\nIn this study, short development did not behave as a defect: the 90 s roast scored highest for acidity, fruitiness and clean cup.1 At the extremes, development becomes a roast defect. A roast stopped 10 s after first crack was the least liked of six in a consumer test.3 A drawn-out development with little temperature rise is the definition of a baked roast.1 Both are described under roast defects.\n\n## Development, end temperature and colour\n\nRoast colour depends on where the roast ends, not only on how long it lasts. To give the same colour, the four roasts above had to be ended at different temperatures.1 The shortest development ended at 204.1 °C, the longest at 191.1 °C.1 The authors do not state where in the roaster that temperature was measured.1\n\nWhen the end point is not adjusted, longer development also means a darker roast. In a 2025 study of a washed Indonesian arabica coffee, development of 2:50, 3:50 and 4:50 min gave colours of Agtron 55, 45 and 35.5 In that design, colour and development changed together, so their effects cannot be separated.\n\nColour and development are therefore two separate checks. Colour predicted flavour better than timing in the two studies that varied both.2 At one fixed colour, development time still shifted chemistry and flavour, and the authors recommend logging both.1 Roast degree and its measurement are covered under roast degree and colour.\n\n**Previous step:** first crack. **Next step:** second crack.\n\n\n\n## Reference values\n\nValues reported in the sources. They describe particular coffees, roasters and probes; they are not targets.\n\n| Parameter | Value reported | Source |\n|---|---|---|\n| Definition | First crack to the end of the roast | Alstrup et al.; Münchow et al.; Giacalone et al.; Fadhil et al.1,2,3,5 |\n| Alternative definition (titratable-acidity study) | First crack to second crack | Anokye-Bempah et al.6 |\n| Development-time study: green coffee | Washed Colombian arabica, 1,200–1,800 m, moisture 10% (basis not stated), density 880 g/L, screen 17 | Alstrup et al.1 |\n| Development-time study: roast | 1 kg drum; first crack at about 570 s; development 90, 143, 266, 390 s | Alstrup et al.1 |\n| End temperature for those roasts | 204.1, 201.2, 198.4, 191.1 °C | Alstrup et al.1 |\n| Mean sensory intensity, 90 → 390 s (15-point scale) | Sweetness 8.7, 8.3, 7.2, 6.3; acidity 8.5, 7.6, 5.8, 5.4; fruit+berry 7.3, 6.4, 4.6, 4.4; bitter 5.7, 6.5, 8.0, 8.6; roasted 5.4, 6.3, 8.3, 8.8; body 6.9, 7.4, 7.2, 7.1 (not significant, p = 0.37) | Alstrup et al.1 |\n| Common colour | Agtron 76 ± 1 (Javalytics meter, finely ground, three replicates) | Alstrup et al.1 |\n| Development as share of total time, those roasts | About 14%, 20%, 32%, 41% (our calculation) | from Alstrup et al.1 |\n| Eight sensory studies, development range in the regression (studies 2–8) | 1:20–6:45 min; time to first crack 6:36–10:07 min in Table 2 (the text gives 7:21–10:07 min) | Münchow et al.2 |\n| Same, development as share of total time (36 roasts, studies 2–8) | About 13–41% (our calculation) | from Münchow et al.2 |\n| Defect study: normal roast (designed to Specialty Coffee Association of Europe guidelines for development and total time) | 2:40 min of 11:25 min, about 23% (our calculation) | Giacalone et al.3 |\n| Defect study: light and baked roasts | 0:10 of 8:40 min; 6:20 of 18:00 min; about 2% and 35% (our calculation) | Giacalone et al.3 |\n| Gayo study | Drying and Maillard phases 4:00 min each; development 2:50, 3:50, 4:50 min of 10:50, 11:50, 12:50 min (about 26%, 32%, 38%, our calculation); Agtron 55, 45, 35 (figure caption); cupping 85.00, 82.00, 81.00 (two Q graders) | Fadhil et al.5 |\n| Time after first crack, multivariate study | 1.0 and 2.0 min compared; 30 s enough to lower quality by a couple of points | Catão et al.4 |\n| Practitioner target | 20–25% of total roast time | Rao (Tier C)10 |\n\n## What happens after first crack\n\n**The heat balance turns.** The early roast is mainly endothermic, because water must be heated and evaporated. Towards the end the process becomes progressively more exothermic and needs much less heat.2 A 2020 study describes the typical practice of roasters: starting near maximum burner output and stepping it down to slow the browning reactions as the roast goes on.1 The eight-study programme roasted on the same principle: high energy input first, then only reductions.2\n\n**Why this phase weighs heavily.** The authors of the development-time study explain the stage's sensitivity by steam release: the bean dries out, browning reactions speed up and move from the surface towards the centre.1 The eight-study analysis expected development to be the main aroma-forming phase, and its results agreed.2 The reactions themselves are described under the Maillard reaction.\n\n**What changed in the brew.** In the development-time study, longer development at the same colour:1\n- generally lowered the acids measured by NMR, all to about the same extent, so their ratio did not change (details under acids in coffee);1\n- degraded the chlorogenic acids 5-CQA and 3-CQA, which the authors link to more bitterness;1\n- raised pyridine, some alcohols with fusel or roasty character, and slightly raised Maillard-derived pyrazines;1\n- lowered 2,3-butanedione and 2,3-pentanedione, buttery, caramel-like compounds the authors propose as a possible partial explanation of perceived sweetness.1\n\nNo simple sugars were detected in any brew; the method would have found 1 mM, and taste thresholds of sugars are generally above 20 mM.1 The authors therefore doubt that sugars explain the sweetness scores.1 Of 146 headspace peaks, 49 differed between roasts; the fastest and the baked roast differed most, the two middle roasts least.1 Faster roasts, ending at higher temperatures, had more volatiles in the headspace.1\n\n## Inside and outside the bean\n\nThis section collects what peer-reviewed sources say about differences between the surface and the centre of the bean. The evidence is indirect.\n\n- **A gradient exists.** In one study of arabica and robusta coffees, whole beans read darker than the same beans ground, which the authors suggest may result from the temperature gradient across the bean. The gap shrank as the roast got darker.8 Roast degree and colour explains why the meter sees mostly the surface of whole beans.\n- **But temperature evens out early, in one model.** A single-bean model adapted from earlier work predicts that, after the first minute, the bean's temperature and moisture become nearly uniform; the same study's new model shows a much slower drying front.7 The model treats the bean as a sphere.7\n- **Fast roasts did not taste unfinished.** The development-time study notes that extremely fast roasts are traditionally seen as defects because of a theoretically more pronounced surface-to-centre gradient.1 Yet its shortest development scored highest for acidity, fruitiness and clean cup.1\n\nNo study opened for this entry measured colour or chemistry at the surface and centre of beans roasted with different development times. Claims about a separate “internal development” are therefore not made here.\n\n## Time after first crack: the wider evidence\n\n**Development weighs more than time to first crack.** A 2020 analysis pooled eight descriptive sensory studies of washed arabica on a 1 kg drum and a 15 kg convection roaster.2 In a regression across seven of the studies, which the authors present as the effect of timing at constant colour, development time affected all nine attributes; time to first crack affected five.2 Development reached p < 0.001 for seven attributes, time to first crack for three.2 In the first study, total roast time correlated with no flavour attribute.2\n\n**Size of the effect.** The regression slope for acidity was −0.011 cm per second of development. The authors translate this into a decrease of about 2 cm on the line scale for a 3 min development (their methods describe a 15 cm scale, the discussion a 10 cm scale).2 Slopes for sweetness and body were close to zero despite reaching significance, and the authors treat them as likely spurious.2 They conclude that roasting had no effect on body.2\n\n**Colour still comes first.** In the two studies that varied both, roast colour correlated more strongly with flavour than development time.2 Assessors also found it harder to describe differences when colour was held constant.2\n\n**Roasted bread and the baked defect.** Longer development, not a longer time to first crack, went with more \"roasted bread\".2 The authors tie this to the baked defect, which they report the Specialty Coffee Association (SCA) roaster certification characterises by intense roasted-bread notes.2\n\n**Other roasters, other designs.** On a professional roaster, time after first crack (1.0 and 2.0 min) had the largest influence of five variables on both sensory and chemical data.4 The authors report that 30 s was enough to cost a couple of points of cup quality.4 In a 2025 study of an Indonesian washed arabica, the shortest of three developments scored highest with two Q graders (85.00 against 82.00 and 81.00).5 There colour darkened with development, so the result mixes both effects.5\n\n## The ratio: practice and evidence\n\nThe development time ratio comes from practice. A roasting consultant reported in 2014 that, in roasts he judged successful, development was 20–25% of the total time.10 He limited the claim to roasts dropped between the end of first crack and the onset of second crack, and noted that results depend on how first crack is timed.10 In 2016 he called the ratio one of many indicators, and suggested a lower target where burner capacity is high relative to batch size.11 The author of roast-logging software argues against the ratio as a quality check, because coffee does not respond to a percentage of total time.12\n\n
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Development as a share of total roast time: a practitioner target (Tier C) and the roasts of four studies, recalculated by us from their published timings.10,3,1,2,5
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\n\nWhat the studies allow:\n- **Seconds, not shares.** The sensory studies changed development in seconds.1,2 In the development-time study, all roasts reached first crack at about the same time, so a longer development and a higher ratio were the same change.1\n- **The two parts act differently.** The ratio rises when development lengthens and also when time to first crack shortens. The eight-study analysis found that the two phases affected flavour differently, development more strongly.2 A single ratio can therefore describe roasts that these studies would not treat as equivalent (our reading).\n- **Recalculated, the studied roasts span the target.** At one colour, development of about 14% to 41% of the roast gave clearly different cups.1 The normal roast of the defect study, designed to Specialty Coffee Association of Europe guidelines, sat at about 23%.3 These shares are our calculation, not values the authors report.\n\n## Risks and defects\n\n- **Too short.** A roast ended 10 s after first crack was much lighter (Agtron 116.6 against 74.4) and was the least liked of six roasts.3 Roast defects discusses the two meanings of \"underdeveloped\".\n- **Too long and flat.** A baked roast stretches the time after first crack with little or no rise in temperature.1 It cannot be seen on the bean: in the development-time study it had the same colour as the others.1 The roast log shows it.\n- **Too far.** According to a roasting textbook chapter, the late, exothermic roast speeds up, and a few seconds can turn the intended degree into an over-roasted product; the roast must be stopped abruptly and cooled efficiently.9\n- **Colour alone misses it.** Roasts at the same colour differed clearly in flavour and chemistry.1\n\n## Measuring development time\n\n- **The start is timed by ear.** Studies take first crack as the moment a popping sound is first heard.2,3 A practitioner notes that timing the start of first crack differently changes the results.10\n- **Logged with the profile.** The development-time study logged its roasts with commercial roasting software.1 Roast profile describes probes, logs and the rate of rise.\n- **Read with colour.** The authors recommend that quality control combine colour readings with development-time data.1\n- **Temperatures are machine-specific.** End temperatures, such as the 191.1–204.1 °C of the development-time study, describe one roaster and probe.1 Roast profile explains why probe readings do not transfer between machines.\n\n## Open questions\n\n- **Other roast degrees.** The development-time study used one coffee at Agtron 76 ± 1; whether the effects hold at other degrees is open.1\n- **Other coffees and roasters.** The eight-study analysis used washed coffees on a drum and a convection roaster, and warns against generalising to naturals, pulped naturals and other roasters.2\n- **Consumers.** Whether consumers notice development-time differences, and which they prefer, was not tested in the development-time study.1\n- **The ratio.** No peer-reviewed study found for this entry tested the development time ratio as such.1,2\n- **Inside the bean.** No measurement of surface-versus-centre roast degree at different development times was found.\n\n## Key studies\n\n
\n

Alstrup et al., 2020 – Development time at one colour. One washed Colombian arabica coffee roasted four times on a 1 kg drum to Agtron 76, with 90–390 s of development after first crack at about 570 s. Sensory panel, NMR and GC–MS all separated the roasts: short development was fruitier, sweeter and more acidic, long development more roasted, nutty and bitter, with body unchanged.

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Beverages 6(4), 70 · doi:10.3390/beverages6040070

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Münchow et al., 2020 – Colour versus timing. Pools eight descriptive sensory studies of washed arabica. Colour predicted flavour best; at constant colour, development time mattered more than time to first crack, and roasting had no effect on body.

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Beverages 6(2), 29 · doi:10.3390/beverages6020029

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Giacalone et al., 2019 – Common roasting defects. One Kenyan coffee roasted to a normal and five defect profiles, with development from 0:10 to 6:20 min. The 10 s development gave the lightest, least liked roast; the baked roast, with the longest development, was close to normal in colour and liking.

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Food Quality and Preference 71, 463–474 · doi:10.1016/j.foodqual.2018.03.009

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Catão et al., 2022 – Roasting variables and quality. Five operating variables tested on a professional roaster, with sensory and volatile analysis. Time after first crack had the largest influence on both, and 30 s was enough to lower cup quality by a couple of points.

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Applied Food Research 2(2), 100223 · doi:10.1016/j.afres.2022.100223

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" }