IDENTIFICATION OF FERMENTATION STAGES OF COCOA BEANS USING A LOW COST ELECTRONIC NOSE

The cocoa bean is one of the most demanded agricultural commodities worldwide, and its fermentation is a key step that determines the sensory and chemical quality of chocolate. Traditionally, cocoa fermentation is evaluated through the cutting test, which involves cutting at least 200 beans per batch to assess their degree of fermentation and possible defects such as mold or insect damage. However, this method is destructive, time-consuming, and dependent on trained personnel. In addition, there is the influence of aroma on the fermentation of beans, which makes the need for trained specialists more important. Therefore, there is a growing need for fast, non-destructive, and reliable analytical methods to monitor fermentation. Recent advances in sensor technologies and data analysis have enabled the development of systems such as electronic noses (e-noses), which allow rapid assessment of food quality. In this study, a low-cost e-nose was used to monitor the fermentation degree of cocoa beans. Hybrid cocoa bean samples were collected from Bahia, Brazil, and fermented for 1 to 7 days under controlled humidity and temperature conditions. After fermentation, samples were sun-dried for two days and stored at 4 °C until analysis. The e-nose system consisted of a sampling chamber equipped with eight metal oxide semiconductor (MOS) gas sensors: MQ2, MQ3, MQ4, MQ6, MQ8, MQ9, MQ135, and MQ138, each with distinct sensitivities to volatile compounds such as alcohols, methane, carbon monoxide, ammonia, and aromatic compounds. For each analysis, three beans were placed in the chamber for two minutes, followed by two minutes of flushing with fresh air. All measurements were performed in triplicate