Evaluación del efecto del tiempo de fermentación y condiciones de secado de cinco subvariedades de cacao (Theobroma cacao L.) cultivadas en Upala, Costa Rica, sobre el perfil de ácidos orgánicos, compuestos volátiles y péptidos precursores de aromas claves para su calidad final
Fecha
2024
Tipo
tesis de maestría
Autores
Alvarado Marenco, Priscilla
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En el presente estudio se evaluó el efecto de tres tiempos de fermentación (3, 5 y 6 días) y tres tipos de secado con aire caliente a 40 °C (circulación continua, flujo transversal a 1 m/s y flujo transversal a 2 m/s) sobre el perfil de ácidos orgánicos, compuestos volátiles y péptidos precursores de aromas clave, de cinco subvariedades de cacao orgánico cultivadas en Upala, Costa Rica. Tres de ellas son originarias del territorio upaleño (Umm, Ucs, Uea), una trasladada desde Talamanca (TU) y una corresponde a una mezcla de clones de alta productividad (CL). La fermentación a nivel piloto se realizó en cajones de madera con 25 kg de cacao en baba cada uno, en un equipo con condiciones de temperatura (40 – 55 °C) y humedad relativa (80 - 85 %) controladas a lo largo del proceso. Posteriormente se secaron hasta alcanzar una humedad de 7,0 – 7,5 %. Los resultados obtenidos evidenciaron que los ácidos cítrico, succínico, láctico, tartárico, glucónico y málico tienen diferencias significativas (p≤0,05) entre subvariedades, y que la talamanqueña producida en Upala tiene una mayor diversidad de ácidos orgánicos. Con respecto al tiempo de fermentación, coincidiendo con las distintas etapas de la fermentación, se observaron diferencias significativas en la concentración (mg/100 g) de los ácidos cítrico, láctico y acético del día 3 con respecto al día 5 y 6; por otra parte, para un mismo día de fermentación, no existe diferencia significativa en el contenido de ácidos orgánicos de las muestras de los tres tipos de secador. Se identificaron 96 compuestos volátiles diferentes, por medio de HS-SPME-GC-MS, siendo la subvariedad upaleña Ucs la que tuvo mayor cantidad de compuestos previamente asociados con aromas (n=37) y la subvariedad Uea la que tuvo menos (n=28). Los compuestos se clasificaron en diez familias químicas, la mayoría pertenecientes a alcoholes, ácidos carboxílicos y ésteres. En todas las muestras para los tres tiempos de fermentación se identificaron compuestos asociados con notas características de chocolate, entre ellos la trimetil y la tetrametil pirazina. Se encontraron 31 compuestos que no muestran diferencia significativa (p>0,05) para la interacción entre la subvariedad y el día de fermentación. Compuestos volátiles de las subvariedades fermentadas Ucs y TU, producidas en la misma finca, se separaron del resto, y parecen no mostrar diferencia entre el día 5 y el día 6 de fermentación. Por otra parte, el tipo de secado no afecta significativamente el perfil de compuestos volátiles. La separación electroforética por SDS-PAGE de los péptidos presentes mostró que no hay diferencia significativa en la cantidad de estos péptidos en función del tiempo de fermentación ni del tipo de secado. Con respecto a la subvariedad, la única que presenta una diferencia significativa es la subvariedad upaleña Umm, que tiene péptidos de mayor peso molecular. El análisis multifactorial confirmó que las subvariedades se agrupan en función del día de fermentación, a la vez, evidenció relación entre la cantidad de péptidos precursores de aromas, la presencia de ácidos orgánicos, principalmente ácido cítrico, y los compuestos volátiles, con las distintas fases de la fermentación. Para una misma subvariedad y un mismo día de fermentación, el tipo de secado no tuvo efecto en ninguna de las variables respuesta estudiadas; sin embargo, sí se identificaron diferencias entre el cacao del día 3 y el cacao con 5 y 6 días de fermentación. Los resultados obtenidos aportan una base científica importante para continuar estudiando los compuestos clave que definen el perfil aromático del cacao upaleño, de manera que se pueda establecer la viabilidad de disminuir los tiempos asociados a los procesos de fermentación y secado sin afectar las características distintivas que le otorgan a este cacao la denominación de fino y de aroma.
In the present study, the effect of three fermentation times (3, 5, and 6 days) and three types of air drying at 40 °C (continuous circulation, cross flow at 1 m/s, and cross flow at 2 m/s) on the profile of organic acids, volatile compounds and key aroma precursor peptides of five organic cocoa subvarieties grown in Upala, Costa Rica, was evaluated. Three of them are native to Upala (upaleñas: Umm, Ucs, Uea), one transferred from Talamanca (TU-talamanqueña), and one corresponds to a mixture of high-productivity clones (CL). The fermentation process was carried out with average batches of 25 kg cocoa pulp-beans in a wooden box, in equipment with controlled temperature and relative humidity conditions similar to those of the producing area. They were then dried in the three different dryers to a moisture content of 7,0–7,5%. The results obtained showed that the concentration (mg/ 100 g) of citric, succinic, lactic, tartaric, gluconic, and malic acids have significant differences (p ≤ 0,05) concerning the subvariety and that the talamanqueña produced in Upala has a greater diversity of organic acids. For fermentation time, coinciding with the different phases of fermentation, significant differences were observed in the concentration of citric, lactic, and acetic acid on day 3 for days 5 and 6; on the other hand, for the same fermentation day, there is no significant difference in the organic acid content of the samples from the three types of dryers. Ninety-six different volatile compounds were identified by HS-SPME-GC-MS; the upaleña subvariety Ucs had the highest number of compounds previously associated with aromas (n=37) and the Uea the lowest (n=28). The compounds were classified into 10 chemical families, most of them belonging to alcohols, carboxylic acids, and esters. Compounds associated with characteristic chocolate notes, were identified and were present in all samples for all three fermentation times, including trimethyl and tetramethyl pyrazine that play a predominant role in the cocoa aroma. Thirty-one compounds there is no significant difference (p > 0,05) for the interaction between subvariety and fermentation day. Principal component analysis (PCA) evidenced that the fermented cocoa subvarieties Ucs and TU, produced on the same farm for about 50 years, cluster separately from the rest and appear to show no difference between days 5 and 6. As for the type of dryer, it was found that it does not affect the profile of volatile compounds. Electrophoretic separation by SDS-PAGE of the peptides showed that there is no significant difference in the number of peptides present as a function of fermentation time or type of drying; for the subvariety, the only one that presents a significant difference is the upaleño Umm, which has peptides of higher molecular weight. The multifactorial analysis confirmed that the subvarieties are grouped according to the day of fermentation and, at the same time, showed a relationship between the amount of aroma precursor peptides, the presence of organic acids, mainly citric acid, and volatile compounds, with the different phases of fermentation. For the same subvariety and the same fermentation day, the type of dryer did not affect the profile of organic acids, volatile compounds and key aroma precursor peptides; however, differences were identified between partially fermented cocoa (day 3) and fermented cocoa (days 5 and 6). The results obtained provide an important scientific basis for further study on the aromatic profile of Upala cocoa subvarieties to establish the feasibility of adjusting the parameters associated with the fermentation and drying processes without harming the perception of the quality characteristics associated with the denomination of fine-flavor cocoa.
In the present study, the effect of three fermentation times (3, 5, and 6 days) and three types of air drying at 40 °C (continuous circulation, cross flow at 1 m/s, and cross flow at 2 m/s) on the profile of organic acids, volatile compounds and key aroma precursor peptides of five organic cocoa subvarieties grown in Upala, Costa Rica, was evaluated. Three of them are native to Upala (upaleñas: Umm, Ucs, Uea), one transferred from Talamanca (TU-talamanqueña), and one corresponds to a mixture of high-productivity clones (CL). The fermentation process was carried out with average batches of 25 kg cocoa pulp-beans in a wooden box, in equipment with controlled temperature and relative humidity conditions similar to those of the producing area. They were then dried in the three different dryers to a moisture content of 7,0–7,5%. The results obtained showed that the concentration (mg/ 100 g) of citric, succinic, lactic, tartaric, gluconic, and malic acids have significant differences (p ≤ 0,05) concerning the subvariety and that the talamanqueña produced in Upala has a greater diversity of organic acids. For fermentation time, coinciding with the different phases of fermentation, significant differences were observed in the concentration of citric, lactic, and acetic acid on day 3 for days 5 and 6; on the other hand, for the same fermentation day, there is no significant difference in the organic acid content of the samples from the three types of dryers. Ninety-six different volatile compounds were identified by HS-SPME-GC-MS; the upaleña subvariety Ucs had the highest number of compounds previously associated with aromas (n=37) and the Uea the lowest (n=28). The compounds were classified into 10 chemical families, most of them belonging to alcohols, carboxylic acids, and esters. Compounds associated with characteristic chocolate notes, were identified and were present in all samples for all three fermentation times, including trimethyl and tetramethyl pyrazine that play a predominant role in the cocoa aroma. Thirty-one compounds there is no significant difference (p > 0,05) for the interaction between subvariety and fermentation day. Principal component analysis (PCA) evidenced that the fermented cocoa subvarieties Ucs and TU, produced on the same farm for about 50 years, cluster separately from the rest and appear to show no difference between days 5 and 6. As for the type of dryer, it was found that it does not affect the profile of volatile compounds. Electrophoretic separation by SDS-PAGE of the peptides showed that there is no significant difference in the number of peptides present as a function of fermentation time or type of drying; for the subvariety, the only one that presents a significant difference is the upaleño Umm, which has peptides of higher molecular weight. The multifactorial analysis confirmed that the subvarieties are grouped according to the day of fermentation and, at the same time, showed a relationship between the amount of aroma precursor peptides, the presence of organic acids, mainly citric acid, and volatile compounds, with the different phases of fermentation. For the same subvariety and the same fermentation day, the type of dryer did not affect the profile of organic acids, volatile compounds and key aroma precursor peptides; however, differences were identified between partially fermented cocoa (day 3) and fermented cocoa (days 5 and 6). The results obtained provide an important scientific basis for further study on the aromatic profile of Upala cocoa subvarieties to establish the feasibility of adjusting the parameters associated with the fermentation and drying processes without harming the perception of the quality characteristics associated with the denomination of fine-flavor cocoa.
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COMPUESTO VOLÁTIL, FERMENTACIÓN, TIEMPO, ÁCIDO ORGÁNICO, CULTIVOS, SECADO, COSTA RICA, COSTA RICA