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Flavor Development of Cocoa during Roasting
Abstract
The desired flavor of cocoa results from the compositional changes that occur in the beans principally during roasting. The roasting process of cocoa beans is necessary to develope the final chocolate flavor. The flavor of cocoa is highly complex in character, and unfortunately not yet fully understood, due to the very large number of different substances present. Maillard reaction or non-enzymatique browing is one of the most important and complex reaction involving flavor development during the roasting process. Sugars and amino acids are the components that undergo the most significant changes during roasting and are suited for use as monitors of compositional changes occuring during the process. There are around 500 volatile compounds which have been already identified in cocoa aroma. The roasting process, heating the cocoa beans to 120-140°C during 20-40 minutes in general depending on cocoa bean type, is needed to develope the final flavor desired.
... Given the elevated temperatures, a substantial impact could be expected from roasting and conching. Cocoa bean roasting is typically done at 120-140 °C for 20-30 min [2,5,6], whereas during conching, temperatures of ~ 50-80 °C are applied for up to 3 days [1,2,7]. ...
... Several studies have addressed the changes in odorant concentrations during cocoa processing [6,[8][9][10][11][12][13][14][15]. It was shown that the high temperatures during roasting converted thermolabile precursors formed during fermentation [16,17] into important odour-active compounds such as Strecker aldehydes, pyrazines, and furanones [8][9][10]18]. ...
... It was shown that the high temperatures during roasting converted thermolabile precursors formed during fermentation [16,17] into important odour-active compounds such as Strecker aldehydes, pyrazines, and furanones [8][9][10]18]. At the same time, the concentrations of some undesired odorants such as acetic acid were reduced [6,11]. Conching not only improved the rheological properties of the chocolate but also affected chocolate flavour [14,19]. ...
The compounds responsible for smoky and mouldy–musty off-flavours in fermented cocoa have recently been elucidated; however, their behaviour during further processing into chocolate was still unclear. The compounds 2-methoxyphenol, 3-methylphenol, 4-methylphenol, 3-ethylphenol, 4-ethylphenol, and 3-propylphenol known to contribute to smoky off-flavours showed a tendency towards a minor increase during roasting and processing into cocoa liquor. This increase amounted to 1.4-fold at the most, however, was clearly compensated by losses of 30–63% during further processing into chocolate mass and conching. Among the off-flavour compounds identified in mouldy–musty smelling cocoa, faecal, mothball-like 3-methyl-1H-indole showed a clear decrease during roasting and processing into cocoa liquor, at least at rather high roasting temperatures, and a further decrease during processing into chocolate mass and conching. In contrast, faecal, mothball-like 1H-indole substantially increased during roasting and processing into cocoa liquor, namely from concentrations below its odour threshold value to concentrations up to 8 times beyond its odour threshold value. During processing into chocolate mass and conching, 1H-indole remained virtually unchanged. The data suggested that the monitoring of off-flavour compounds at the incoming goods inspection in the chocolate industry should not be limited to the fermented beans as such but additionally include the analysis of a bean sample after test roasting to correctly assess the off-flavour potential of 3-methyl-1H-indole and 1H-indole.
... The roasting itself fulfils two objectives: removal of undesired aroma compounds, mainly acetic acid [6,7] and the formation of characteristic cocoa aroma compounds. As suggested in several studies, mainly free amino acids, peptides and reducing sugars are involved in cocoa flavour formation [1,2,7], and earlier sensory experiments revealed that, for example, without the application of oligopeptides, no characteristic cocoa aroma was obtained [4]. ...
... The roasting itself fulfils two objectives: removal of undesired aroma compounds, mainly acetic acid [6,7] and the formation of characteristic cocoa aroma compounds. As suggested in several studies, mainly free amino acids, peptides and reducing sugars are involved in cocoa flavour formation [1,2,7], and earlier sensory experiments revealed that, for example, without the application of oligopeptides, no characteristic cocoa aroma was obtained [4]. ...
The influence of the roasting procedure on the composition of key aroma compounds in fermented Forastero cocoa beans was investigated. For this purpose, the volatile fractions from the unroasted, fermented and the roasted cocoa were isolated by extraction/SAFE distillation, and the odour-active constituents were characterised by gas chromatography–olfactometry in combination with an aroma extract dilution analysis. A total of 41 aroma compounds in the flavour dilution (FD) factor range of 2–8192 were identified in the unroasted and 42 compounds with FD factors of 2–8192 in the roasted cocoa beans. Qualitatively, the set of aroma compounds was nearly identical in both samples; however, differences in the flavour dilution factors were observed. 2- and 3-Methyl butanoic acid (sweaty) and acetic acid (vinegar-like, sour) showed the highest FD factors in the unroasted beans, while 3-methylbutanal (malty), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like) and 2- and 3-methyl butanoic acid (sweaty) were detectable by GC/O in the highest dilutions in the roasted seeds. Quantitation of the most odour-active compounds by means of stable isotope dilution assays, followed by calculation of odour activity values (OAV, ratio of concentration to odour threshold), revealed concentrations above the threshold level for 20 compounds in the unroasted and 24 compounds in the roasted beans. The roasting procedure led to a strong increase, in particular, in the concentrations of the two Strecker aldehydes 3-methylbutanal (malty) and phenylacetaldehyde (honey-like) as well as 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like).
Roasting is an important unit operation for the development of characteristic chocolate aroma during manufacturing. However, there is an increase in interest in minimally processed chocolate products due to their potential positive health benefits. The odor-important compounds and sensory characteristics of minimally processed (unroasted) and conventionally roasted dark chocolates were determined by gas chromatography-olfactometry, aroma extract dilution analysis (AEDA), and stable isotope dilution analysis (SIDA). Except for acetic acid, all odorants had higher odor-activity values (OAVs) in roasted chocolate. Acetic acid, developed during fermentation and drying, had the highest OAV in both chocolates but was better preserved in unroasted chocolate. Compounds making a greater aroma impact on roasted chocolate compared with unroasted chocolate included dimethyl trisulfide, 2-ethyl-3,5-dimethylpyrazine, and 3-methylbutanal. Nine significant sensory attributes in unroasted and roasted chocolates were identified. Vinegar (aroma) and roasted (aroma and aroma by mouth), sweet (taste), and hardness (texture) attributes differed between unroasted and roasted chocolates. The results of this study enforce the embracement of low thermal processes to showcase the inherent flavor potential of cacao beans but also to support the concept of chocolate "terroir" by potentially preserving important aroma compounds developed during fermentation.
The unique aroma of cocoa develops during fermentation and roasting. In particular, amino acids are well known to thermally generate the so-called Strecker aldehydes. In addition, 1-amino-1-desoxyketoses, known as Amadori rearrangement products (ARPs), are also suggested as key intermediates in the formation of these odorants. To study their role as precursors of cocoa aroma compounds, selected ARPs as well as the respective amino acids were monitored during different processing steps in order to correlate their amounts with the formation of the corresponding Strecker aldehydes. The amounts of ARPs formed during cocoa fermentation and a comparison with the amounts of Strecker aldehydes generated after roasting showed a good correlation between ARP formation/degradation and Strecker aldehydes formation. Interestingly, the ARPs were already available in unfermented cocoa beans. To unequivocally elucidate the role of ARPs as precursors of the Strecker aldehydes in "competition" with the free amino acids, an isotope enrichment experiment was performed. The obtained data clearly suggested the ARPs as effective precursors of Strecker aldehydes.
Introduction Food Processing and Major Benefits Conclusions and Future Research Needs References
The volatile fraction of commercial cocoa powders was isolated using thin-layer high-vacuum distillation (TLHVD) of Soxhlet extracts. Calculated and experimental recovery of the internal standard n-undecanoic acid methylester did agree, and a good reproducibility was found for the procedure. Around 70 volatile compounds were identified and semi-quantified using internal standard-based gas chromatography (GC), coupled GC–mass spectrometry (GC–MS) and GC-olfactometry (GC-O). Dehydromevalonic acid lactone, (R)-(−)-pantolactone and two diastereomer solerols were identified for the first time after purification by micropreparative GC and re-analysis using GC–MS and chiral GC. Strong sensory contributions also came from acetic acid, 2/3-methyl butanoic acid, phenylacetaldehyde, furaneol, dihydroxymaltol, vanillin and phenylacetic acid.
The most notable attribute of chocolate which accounts for its universal appeal is its unique flavour. The mix and balance ofthe numerous compounds which contribute to the final flavour depend on genetics, environmental conditions, harvesting and processing. With chocolate the chemical complexity of flavour development is evident when one realizes the numerous parameters which may influence its development. Its complexity is equally obvious when considering that, even today, this desirable flavour has not been duplicated by the flavour chemist.
Aromavorstufen aus Ghana-Rohkakao wurden in Stoffklassen aufgetrennt und deren Bedeutung für die Aromabildung untersucht. Für den spezifischen Reaktionsablauf, einen Seitenweg der Maillard-Reaktion, 1st insbesondere ein Mitwirken der erstmals isolierten und charakterisierten Peptide notwendig. Fenner wurde der Verlauf der Aromabildung anhand von Vorstufen aus anderen Kakaoprovenienzen studiert. Die bisher bekannten 310 Aromastoffe wurden nach chemischen Gesichtspunkten gegliedert und mit anderen Lebensmittelaromen verglichen, um Aussagen über spezifische Komponenten zu erhalten.Specificity of Cocoa AromaAroma precursors in crude cocoa from Ghana were separated into substance classes and their significance in aroma formation was examined. Coaction of a peptide, which was isolated and characterized for the first time, is especially necessary for the specific reaction which occurs via a side path of Maillard-reaction. Furthermore, aroma formation in other varieties of cocoa was studied on the basis of precursors. From chemical viewpoint the 310 aroma components known so far were classified and compared with other food aromas in order to obtain information on the specific components.
The role of individual organic acids in relation to the excessive acidity exhibited by Asian cocoa liquors has been investigated.
Volatile fatty acids (other than acetic) did not affect significantly either acidity scores or liquor pH. Variations in levels of specific water soluble, acids, viz. lactic, citric and acetic, were found to be particularly important in accounting for differences in both acidity scores and pH values between Asian liquors and a West African liquor. However, only when adjustments were made for differences in levels of total water‐soluble acids between the liquors did sensory scores for acidity and pH values achieve parity.
Volatile flavour analysis using headspace sampling techniques indicated that 2‐phenylethyl acetate and, to a lesser extent, linalool were important contributors to the fruity flavour attribute exhibited by Asian cocoa liquors.
More than 300 volatile compounds have been identified in roasted cocoa beans and its products, making chocolate one of the
most complicated natural flavors. Most beans, after harvesting, are subjected to a fermentation that is an important step
in the formation of flavor precursors. Roasting is essential to the development of chocolate flavor both with respect to the
loss of undesirable volatiles and the generating of key aroma compounds. Flavor is modified to meet demand using blends of
beans and through variation in roasting conditions and the mechanical treatments employed to process beans into chocolate
liquor and coating. The effect of fermentation and roasting on certain chemical properties related to flavor in chocolate
is reviewed. Particular attention is given to monocarbonyls, headspace volatiles, pyrrole aldehydes and alkylpyrazines.