Electromagnetic fields effects on microbial growth in cocoa fermentation: A controlled experimental approach using established growth models.

Understanding the effects of electromagnetic fields is crucial in the fermentation of cocoa beans, since through precise control of fermentation conditions the sensory and nutritional properties of cocoa beans could be improved. This study aimed to evaluate the effect of oscillating magnetic fields (OMF) on the kinetic growth of the core microbial communities of the Collections Castro Naranjal (CCN 51) cocoa bean. The data was obtained by three different models: Gompertz, Baranyi, and Logistic. The cocoa beans were subjected to different OMF strengths ranging from 0 mT to 80 mT for 1 h using the Helmholtz coil electromagnetic device. The viable microbial populations of lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeast (Y) were quantified using the colony-forming unit (CFU) counting method. The logistic model appropriately described the growth of LAB and Y under magnetic field exposure. Whereas the Baranyi model was suitable for describing AAB growth. The microbial populations in cocoa beans exposed to magnetic fields showed lower (maximum specific growth rate (µmax), values than untreated controls, with AAB exhibiting the highest average growth rate value at 5 mT and Y having the lowest average maximum growth rate value at 80 mT. The lower maximum specific growth rates and longer lag phases when exposed to magnetic fields compared to controls demonstrate the influence of magnetic fields on microbial growth kinetics.

Raman Spectroscopic and Sensory Evaluation of Cocoa Liquor Prepared with Ecuadorian Cocoa Beans Treated with Gamma Irradiation or Induced Electromagnetic Field Fermentation.

Cocoa liquor is the primary precursor of the worldwide highly appreciated commodity chocolate. Its quality depends on several factors, such as the type of cocoa, the fermentation process, and the control of the contaminants in the fermented beans. This study aims to evaluate whether the induced magnetic field treatment during the fermentation process or the pathogen reduction with gamma irradiation after the fermentation affect the characteristics of the cocoa liquor obtained from Ecuadorian cocoa beans. For this purpose, liquor samples from controls (standard process), from beans treated with an induced magnetic field up to 80 mT, and from beans irradiated with nominal doses up to 3 kGy were characterized through Raman spectroscopic analysis and sensorial evaluation. The most relevant bands of the cocoa liquor were assigned according to reports from the literature, spectroscopic data, and chemometrics. The spectra corresponding to different treatments and doses were visually very similar, but they could be discriminated using OPLS-DA models, where the most intense Raman signals were attributed to the lipid components. The sensorial evaluation rated the presence of floral, fruity, almondy, acid, and bitter flavors, along with astringency and intense aroma, and these attributes exhibited variable behavior depending on the dose of the irradiation or magnetic treatment. Therefore, both treatments may exert an influence on cocoa beans and, therefore, on the cocoa liquor quality.

Corrigendum to "Optimization of cacao beans fermentation by native species and electromagnetic fields" [Heliyon 9(4) April 2023 e15065].

[This corrects the article DOI: 10.1016/j.heliyon.2023.e15065.].

Experimental Prototype of Electromagnetic Emissions for Biotechnological Research: Monitoring Cocoa Bean Fermentation Parameters.

A Helmholtz-type electromagnetic emission device, which uses an oscillating magnetic field (OMF), with potential applications in biotechnological research, was built and validated. The coils were connected to an alternating current (AC) generator to generate a 0.5 to 110 mT field at their center. OMF measurements were performed with a Hall effect sensor with a digital signal connection (Arduino nano) and data output to a PC using LabVIEW v2017SP1 software. The fermentation process of the cocoa bean variety CCN 51, exposed to four levels of OMF density for 60 min (0, 5, 40, and 80 mT/60 min), was analyzed. Different variables of the grain fermentation process were evaluated over six days. The ANOVA test probed the device's linearity, accuracy, precision, repeatability, reliability, and robustness. Moreover, CCN 51 cocoa beans' EMF-exposure effect was evaluated under different OMF densities for 60 min. The results show the validity of the equipment under working conditions and the impact of EMF (electromagnetic fields) on the yield, deformation, and pH of cocoa beans. Thus, we concluded that the operation of the prototype is valid for use in biotechnological studies.

Optimization of cacao beans fermentation by native species and electromagnetic fields.

Acid and bitter notes of the cocoa clone Cacao Castro Naranjal 51 (CCN 51) negatively affect the final quality of the chocolate. Thence, the fermentative process of cocoa beans using native species and electromagnetic fields (EMF) was carried out to evaluate the effect on the yield and quality of CCN 51 cocoa beans. The variables magnetic field density (D), exposure time (T), and inoculum concentration (IC) were optimized through response surface methodology to obtain two statistically validated second-order models, explaining 88.39% and 92.51% of the variability in the yield and quality of the beans, respectively. In the coordinate: 5 mT(D), 22.5 min (T), and 1.6% (CI), yield and bean quality improved to 110% and 120% above the control (without magnetic field). The metagenomic analysis showed that the changes in the microbial communities favored the aroma profile at low and intermediate field densities (5-42 mT) with high yields and floral, fruity, and nutty notes. Conversely, field densities (80 mT) were evaluated with low yields and undesirable notes of acidity and bitterness. The findings revealed that EMF effectively improves the yield and quality of CCN 51 cocoa beans with future applications in the development and quality of chocolate products.