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cocoa roasting

process / process-cocoa-roasting

カカオ焙炒

Heat treatment of cacao beans or nibs defined by time and temperature.

On this page (6 sections)
  1. Overview
  2. Sources for this overview (2)
  3. Topic hubs
  4. Follow the connections
  5. Related entries (9)
  6. How processing and cooking change it (3)
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Reading the bitterness

Cacao roasting is a heat treatment of beans or nibs defined by time and temperature. A study using 100% chocolate made from unroasted cacao from 3 origins—Madagascar, Ghana, and Peru—conducted a planned roasting experiment with 27 treatments, including a raw control at 24°C for 0 minutes. A total of 145 consumers aged 18–65 (38 men) rated liking on a 9-point hedonic scale and attribute intensity with gLMS.

Roasting temperature had the largest effect in this study. The authors report that a 1-standard-deviation increase in temperature, equivalent to 42°C, lowered the mean square root of bitterness intensity by 0.153 units, corresponding to a 1.56-unit decline from a mean bitterness value of 26.9 on gLMS. This runs counter to an expectation that higher roasting temperature strengthens bitterness. Decreases in bitterness and astringency were reported to correlate with improved consumer acceptance. However, no p value is given for this effect size and no r value for the correlation.

The authors report that the total decline in bitterness across the full range of roasting conditions differed by origin: about 8 points for Ghana, 2.4 for Madagascar, and 3 for Peru. These are not values for each 42°C increment. The study used unsweetened chocolate, so extrapolation to sweetened milk chocolate cannot be established from it. Another study found 5 diketopiperazines with dose-over-threshold (DoT) ratios above 1.0 in roasted cacao nibs, but it did not compare roast levels or report a relationship between roasting conditions and perceived bitterness.

Sources for this overview

  1. Optimizing consumer acceptability of 100% chocolate through roasting treatments and effects on bitterness and other important sensory characteristics

    McClure AP; Hopfer H; Grun IU / 2022 / journal article / full text checked

    Checked for this overview: The roast experiment's origins, treatment conditions, and consumer-panel design. / The numerical decrease in bitterness with increasing roasting temperature. / Origin-specific decreases in bitterness and the limitation to unsweetened chocolate.

  2. Structures, sensory activity, and dose/response functions of 2,5-diketopiperazines in roasted cocoa nibs (Theobroma cacao)

    Stark T; Hofmann T / 2005 / journal article / abstract checked

    Checked for this overview: That the presence of bitterness-related compounds does not predict the direction of perceived bitterness.

Follow the connections

cocoa roasting →reduces→ bitterness →can be measured separately …→ astringency

cocoa bean drying →differs from→ cocoa roasting

Structured claims — open a section to read each claim's confidence, evidence and limits

How processing and cooking change it (3)

cocoa roasting reduces bitternesssupported

Scope: 27 roasting treatments across 3 origins, 145 chocolate consumers, gLMS

Note: The direction is the reverse of the intuition that 「焙煎温度が高いほど苦くなる」 (in translation: "the higher the roasting temperature, the more bitter it becomes"). No p-value is given for this effect size.

The source states that the effect of roasting temperature was the largest, and that a 1-standard-deviation increase in roasting temperature (i.e., 42 degC) lowered the mean square-root bitterness intensity by 0.153 units, corresponding to a 1.56-unit decrease in the mean bitterness on the gLMS scale (26.9), and that the decreases in bitterness and astringency correlated with increased consumer acceptability.
Limitations: The sentence stating the effect size does not give a p-value, and the bitterness-liking correlation does not give an r-value. The authors note as a limitation that chocolate consumers evaluated unsweetened chocolate containing no other ingredients.
Source: Optimizing consumer acceptability of 100% chocolate through roasting treatments and effects on bitterness and other important sensory characteristics (McClure AP; Hopfer H; Grun IU, 2022) · full text checked
Context: Found that roasted cacao nibs contain 5 diketopiperazines with a DoT (dose-over-threshold) factor above 1.0; the source does not compare roast levels and does not report a relationship between roasting conditions and perceived bitterness.
Limitations: This is placed here only to record that the mere existence, at the compound level, of roasting-related bitter compounds does not predict the direction of perceived intensity found by McClure 2022. The source does not state that these compounds are generated by roasting.
Source: Structures, sensory activity, and dose/response functions of 2,5-diketopiperazines in roasted cocoa nibs (Theobroma cacao) (Stark T; Hofmann T, 2005) · abstract checked
Show dataprocess-cocoa-roasting —reduces→ sensation-bitter
claim: clm-cocoa-roast-temperature-bitterness / type: processing / updated: 2026-08-30
cocoa roasting reduces bitternesssupported

Scope: Unsweetened (100%) chocolate, 3 cacao origins (Ghana, Madagascar, Peru), gLMS sensory evaluation by a consumer panel of 145

Note: The source reports that bitterness on the gLMS scale fell by an average of about 1.56 units for every 42°C rise in roasting temperature. The size of the decline varied by origin: a drop of about 8 points for Ghana, about 2.4 points for Madagascar, and about 3 points for Peru is reported. The subject is unsweetened chocolate, and extrapolation to sweetened milk chocolate cannot be confirmed from this study.

For every 1 standard deviation (42°C) rise in roasting temperature, the bitterness score on the gLMS scale fell by an average of about 1.56 units. The total decline across the full temperature range tested varied by origin: about 8 points for Ghana, about 2.4 points for Madagascar, and about 3 points for Peru (the latter is not expressed as a 「42℃ごと」 (in translation: "per 42°C") value).
Limitations: The subject is unsweetened chocolate, and extrapolation to sweetened milk chocolate cannot be confirmed from this paper.
Source: Optimizing consumer acceptability of 100% chocolate through roasting treatments and effects on bitterness and other important sensory characteristics (McClure AP; Hopfer H; Grun IU, 2022) · full text checked
Show dataprocess-cocoa-roasting —reduces→ sensation-bitter
claim: clm-w51-roasting-reduces-bitterness / type: processing / updated: 2026-09-03
cocoa bean drying differs from cocoa roastingsupported

Scope: ICCO's process chart lists drying and roasting as separate steps.

Drying and Roasting are organized under separate headings.
Limitations: This does not claim that their thermal effects cannot overlap in particular equipment.
Source: Processing Cocoa (International Cocoa Organization) · full text checked
Show dataprocess-cocoa-bean-drying —differs_from→ process-cocoa-roasting
claim: cl-terms-drying-roasting-boundary / type: processing / updated: 2026-09-10

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