(12e) How Temperature during Fermentation Affects Quality and Flavor in Cocoa Liquor

The cocoa tree belongs to the genus Theobroma cacao L., it has four categories Criollo, Forastero, Trinitario and Clones (these are generated by human selection, to increase desired features. This tree produces a well-known product, cocoa beans, which are used by different industries such as food, cosmetic and pharmaceuticals because of its physical and chemical properties. To use cocoa beans by the industries, they need to pass across different transformation processes, the first one is the harvest from the tree, followed by the cut of the pods, fermentation of the beans and the final step is drying the beans.

Fermentation is a spontaneous process that occurs in wooden boxes, it usually takes between five to seven days; during this period the temperature varies between 25°C to 50 °C, this range allows the growth of different microorganisms (e.g. yeast, lactic acid bacteria and acetic acid bacteria), they metabolize the sugars and other compounds in the beans to produce volatile compounds which are linked to the aroma and flavor in the cocoa liquor. The importance of several strains of yeast and their presence during the first 48 hours of cocoa fermentation to develop a quality fermentation had been reported in the literature. The drying process of the beans takes place slowly and progressive under sunlight, the humidity of the bean needs to be lower than 7%, to avoid the presence of fungi or insects.

Colombian Cocoa has been recognized by the International Cocoa Organization (ICCO) as fine or flavor (95%), this means that cocoa has aroma and flavor of fruits, flowers, nuts, and malt. However, due to the dissimilar ecological, genetic, microclimatic conditions and fermentation process (e.g. time, mass, temperature) in the country; the cocoa produced has a high variability of the chemical compounds that determine aroma and flavor. On the other hand, one of the most cultivated varieties in Colombia is the clone CCN51, because of its high productivity and resistance disease. However, this clone lacks pronounced specific flavors that make it common cocoa. Though, this clone is interesting for this project because the changes in its flavor could be more noticeable.

The main goal of this research is to identify the influence of different temperature profiles during fermentation of cocoa clone CCN51 in the quality of dry beans, sensory profile, volatile compound profile of cocoa liquor and the presense of yeast in the first 48 hours of fermentation.

Fermentation quality is reported by the fermentation index, after a cut test to the dry bean to check the physical changes, this is an indirect tool to predict the potential flavor of the beans. In the cut test, the beans can exhibit a fine, medium and deficient fermentation, that is represented by a color range from dark brown, light brown and violet, respectively. Also, fungi or insect bites are checked in the open bean. Index values around 70 to 100 percent indicate a good fermentation process.

The sensory profile consists of an evaluation of the cocoa liquor (obtained from the fermented and dry beans) by professional cocoa tasters. There is a scale from 0 to 10 for basic, specific and acquired attributes; basic attributes are acid, bitter, sweet and astringent, specific correspond to cocoa, flower, fruit, and nuts, and acquired to mold, chemical, green, smoked and wood. A sensory profile is used to determine the acceptance in the market. The sensory profile of clone CCN51 has been determined as common due to the high presence of acidity, astringent and low notes of specific flavors.

Volatile compounds contribute and are responsible for the aroma and sensorial profile of the cocoa liquor, this analysis is carried out using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME GC-MS). This technique is used to identify and quantify the accumulation of volatile compounds in cocoa liquor.

The cocoa plantation used for the fermentation, lab scale, was hybrid CCN51, it was harvested from San Vicente de Chucurí, Santander, Colombia. They were in storage from 4 to 5 days since the harvest time and manually open, then the pulp was placed in contact with the pods for 3 to 4 hours allowing the inoculation with native microorganism and transferred into acrylic boxes permitting the drainage, the fermenting mass was turned into a different acrylic box at 48, 72, 96, 120 hours until it completed 6 days of fermentation. The boxes were incubated at three different temperature profiles. The first temperature profile was the same reached on fermentation boxes at San Vicente de Chucurí; the other two temperature profiles were found in literature about controlled laboratory cocoa fermentation. After the fermentation process, the beans were dried at sun exposure until they reached less than 7% humidity. The fermented and dried beans were sent to the Federación Nacional de Cacaoteros (FEDECACAO), to evaluate the fermentation index by the cut test of beans and the sensorial analysis by an expert panel. Finally, the volatile compound in the cocoa liquor was extracted and quantified by solid-phase micro extraction-gas chromatography-mass spectrometry (SPME-GC-MS).

The three temperature profiles showed different fermentation indexes and flavor in the sensory analysis, for both basic and specific flavors. Comparing these results with previous fermentations reported in the literature for cocoa CCN51 from the same region, it is notable the influence of temperature to improve the flavor of cocoa.The presence and maximum amount of yeast were different in all the temperature profiles, it is important to remember that the yeasts are responsible for metabolized volatile compounds associated with flavor in the cocoa liquor. On the other hand, the cocoa liquor for each temperature profile exhibits similar volatile compounds but in different amounts for each one.

These results let us know the importance of fermentation temperature to obtain quality dry beans that can be transformed into cocoa liquor that has a sensory profile with characteristic organoleptic desired in the food industry and can be compared with the presence and quality of volatile compounds developed through the fermentation process.