There are no shortcuts to enjoy fine chocolate: chocolate makers have to start their process with high-quality cacao seeds endowed with a natural bouquet of ancillary flavour precursors, ranging from nutty to floral and fruity notes. But how and where do the flavour precursors in fine cacao and chocolate develop and express their best potential?
Basically, before turning cacao beans into cocoa liquor, flavours develop during fermentation and roasting. After optional ingredients (sugar, milk, vanilla, etc.) are added to the chocolate mass and mixed, conching is the last process where flavours will shine through like sparkling facets from a rough diamond.
FLAVOUR DEVELOPMENT IN FRESH CACAO SEEDS DURING FERMENTATION
Development of the cocoa flavour precursors during fermentation occurs from the sweet white pulp surrounding the cacao seeds to the cotyledons of the seeds.
The fruit pulp covering the cacao beans has a distinct combination of flavours for each variety of cacao. During the fermentation process (seeds and pulp together) the acidity of the pulp formed during acetic fermentation helps break down the structure of the outer surface of the beans. This allows liquids from the pulp to penetrate and infuse the beans.Within the cotyledons of the cacao beans, there are two important types of cells: storage cells containing fat and proteins (the substances feeding the seed after its germination), and the pigment cells containing polyphenolic compounds and methylxanthines (theobromine and caffeine), which impart bitterness. During fermentation, their levels fall by around 30%, probably due to diffusion from the cotyledons. Polyphenolic compounds in cacao (flavonoids) are those responsible for the colour inside the seed, for imparting astringency in the mouth and for antioxidant health benefits. Proteins and peptides complex with the polyphenolic compounds to give the brown or brown/purple colouration that is typical in fermented, dried cocoa beans. As seen for methylxanthines, the levels of polyphenols in cacao drop significantly during fermentation and drying, as well.
Image 1. Guasare cacao seeds during fermentation - (Credit to Cacao Marquez)
Another important group of aromatic compounds is the Maillard reaction precursors. These are formed from the storage proteins and sucrose (sugar). The storage proteins are hydrolysed by peptidase enzymes into oligopeptides and amino acids, while sucrose is converted by invertase into reducing sugars, which are unstable and reactive. The resulting components are involved in Maillard reactions during roasting of the cocoa beans to form cocoa flavour compounds.Flavour development in fermented and dried cacao seeds during roastingRoasting develops the flavour in the beans from the precursors formed during fermentation and drying.Whole bean roasting is the original method to produce cocoa masses with delicate flavours, due to the preservation of the subtle cocoa flavour notes within the shell during roasting.Generally, the final roasting temperature is between 110°C and 140°C (230°F and 284°F).
Image 2. Cocoa roasting
However, the combination of temperature/time to which the cacao seeds are roasted has an effect on the flavour balance of the final chocolate. As recent studies proved, roasting temperatures ranging from 90°C to 110°C for at least 20 minutes were found optimum for higher consumer’s acceptability scores (appearance, aroma, flavour, texture and overall quality attributes). Flavour development in chocolate during conching. Although the fermentation, drying, and roasting can develop the precursors of chocolate flavours, unpleasant acidic and astringent notes are still entrapped in the chocolate matrix. Conching chocolate is the process able to remove the undesirable flavours, while retaining the pleasant ones. In addition, the conching process has the objective to develop the flow properties of chocolate by distributing the cocoa particles, the sugar particles, and the desired flavours homogeneously throughout the mass.
Chocolate conching is carried out by agitating the chocolate over an extended period in a large tank, known as a conche.The mixing continuously changes the chocolate surface, exposing it to aeration, while the constant friction of the mass against the walls of the tank provides heating that enables the unwanted acetic components—obtained during fermentation and partly present during roasting—to escape. Conversely, the delicate flavours—the distinct notes of the cacao—remain and get better dispersed in the final chocolate bar before the final steps of tempering and moulding.
• “Industrial Chocolate Manufacture and Use: Fourth Edition”. Stephen T. Beckett (2009)
• "Effect of the roasting temperature and time of cocoa beans on the sensory characteristics and acceptability of chocolate". Rocha et al. (2017)
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