UHPLC–MS/MS analysis of cocoa bean proteomes from four different genotypes

Metabolomic insights into flavour precursor dynamics during fermentation of cacao beans cultivated in diverse climatic production zones in Colombia

The market for flavour superior quality cacao provides significant economic and non-economic benefits to farmers. Flavor precursor metabolites, formed during various post-harvest stages, are crucial for developing superior sensory attributes. However, identifying these metabolites and understanding how climate variations and post-harvest practices influence them remains a challenge. This study investigates how the fermentation methodology applied and climate conditions in different zones of the cacao beans producing region of Arauca - Colombia, influence the metabolomic profile of cacao beans and their flavour precursor metabolites. Untargeted metabolomic analysis was performed by UHPLC-ESI-Orbitrap-MS on cacao beans fermented for 0, 24, 48, 72, 96, and 120 h from 9 production zones. The PLS-DA model highlighted that the metabolomics fingerprint changes through fermentation time. Among the most discriminant metabolites, 18 oligopeptides, sucrose, glucose, fructose, flavanols, and acids were tentatively identified. The chemometric analysis showed that fermentation time has a significant impact on the metabolomic profile of cacao beans, while agroclimatic conditions had a minor influence. Metabolomic analyses defined 96 h as the optimal fermentation time to maximize the amount of aroma precursors. Metabolomic analyses identified 96 h as the optimal fermentation time to maximize the amount of aroma precursors across all 9 cacao production zones evaluated. This study underscores the central role of fermentation in shaping flavor precursors, and contributes to the development of new approaches for cacao processing based on the tracking of biochemical and functional compounds (quality biomarkers).

Key Aromatic Volatile Compounds from Roasted Cocoa Beans, Cocoa Liquor, and Chocolate

The characteristic aromas at each stage of chocolate processing change in quantity and quality depending on the cocoa variety, the chemical composition of the beans, the specific protein storage content, and the polysaccharides and polyphenols determining the type and quantity of the precursors formed during the fermentation and drying process, leading to the formation of specific chocolate aromas in the subsequent roasting and conching processes. Bean aroma is frequently profiled, identified, and semiquantified by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPMEGC-MS) and by gas chromatography olfactometry (GC-O). In general, the flavors generated in chocolate processing include fruity, floral, chocolate, woody, caramel, earthy, and undesirable notes. Each processing stage contributes to or depletes the aroma compounds that may be desirable or undesirable, as discussed in this report.

Antioxidant activity, total polyphenol content and methylxantine ratio in four materials of Theobroma cacao L. from Tolima, Colombia

The International Cocoa Organization recognized Colombian cocoa as "fine aroma," but in recent years, clone CCN 51 has grown in popularity, widely due to its high yield. The Tolima department is the fourth producer of cacao in Colombia, but there is a lack of knowledge of the chemical properties of regional cocoa genotypes. The aim of this study was to evaluate the morphological, antioxidant activity, total polyphenol content and the methylxanthines ratio of four regional genotypes (UTLP02, UTVE01, UTGC01 and UTLM02) of Theobroma cacao L. from Tolima, Colombia. The universal clone of CCN51 was used as control. The highest values for the qualitative descriptors were obtained by the variants UTVE01 and CCN51 with FRAP and TPC ranging from 44.51 ± 0.90 to 106.77 ± 5.21 mg GAE/g and 27.13 ± 0.14 to 52.12 ± 4.71 mmol TE/g respectively. The genotypes with the highest values for FRAP and TPC were UTGC01 and CCN51. According to the methylxanthine ratio, UTVE01 was classified as Criollo, while UTLM02, UTGC01 and UTLP02, CCN51 are Trinitario and Forastero, respectively. Although CCN51 is considered a remarkable material in terms of productivity, the genotypes evaluated present good yields and interesting values of TPC and antioxidant activity, making them promising trees in local breeding programs.

Chemical and biological properties of cocoa beans affected by processing: a review

Cocoa (Theobroma cacao L.) is widely cultivated in tropical countries. The cocoa beans are a popular ingredient of confectionery. Cocoa beans contain various chemicals that contribute to their bioactivity and nutritional properties. There has been increasing interest in developing cocoa beans for "healthy" food products. Cocoa beans have special combination of nutrients such as lipids, carbohydrates, proteins and other compounds of biological activities. The bioactive phytochemicals include methylxanthines, polyphenols, biogenic amines, melanoidins, isoprostanoids and oxalates. These phytochemicals of cocoa are related to various in vivo and in vitro biological activities such as antioxidation, anti-cancer, anti-microbial, anti-inflammation, anti-diabetes, cardiovascular protection, physical improvement, anti-photoaging, anti-depression and blood glucose regulation. The potential of bioactive compounds in cocoa remains to be maximized for food and nutritional applications. The current processing technology promotes the degradation of beneficial bioactive compounds, while maximizing the flavors and its precursors. It is not optimized for the utilization of cocoa beans for "healthy" product formulations. Modifications of the current processing line and non-conventional processing are needed to better preserve and utilize the beneficial bioactive compounds in cocoa beans.

Pangenome analyses of LuxS-coding genes and enzymatic repertoires in cocoa-related lactic acid bacteria

Lactobacillaceae presents potential for interspecific Quorum Sensing (QS) in spontaneous cocoa fermentation, correlated with high abundance of luxS. Three Brazilian isolates from cocoa fermentation were characterized by Whole Genome Sequencing and luxS gene was surveyed in their genomes, in comparison with public databases. They were classified as Lactiplantibacillus plantarum, Limosilactobacillus fermentum and Pediococcus acidilactici. LuxS genes were conserved in core genomes of the novel isolates, but in some non-cocoa related Lactic Acid Bacteria (LAB) it was accessory and plasmid-borne. The conservation and horizontal acquisition of luxS reinforces that QS is determinant for bacterial adaptation in several environments, especially taking into account the luxS has been correlated with modulation of bacteriocin production, stress tolerance and biofilm formation. Therefore, in this paper, new clade and species-specific primers were designed for future application for screening of luxS gene in LAB to evaluate the adaptive potential to diverse food fermentations.

Comparison of the contents of phenolic compounds including flavonoids and antioxidant activity of rice (Oryza sativa) and Chinese wild rice (Zizania latifolia)

The contents of phenolic compounds, especially flavonoids, and antioxidant activity of rice (Oryza sativa, Os) and Chinese wild rice (Zizania latifolia, Zl) harvested in China were compared. Zl possessed significantly higher contents of total phenolics, flavonoids, and proanthocyanidins and exhibited higher antioxidant activity than in the Os Xian group, the Os Geng group, and red rice. The flavonoid contents of Os and Zl were compared using a UHPLC-QqQ-MS-based metabolomics approach. A total of 159 flavonoids were identified, among which 78 showed differential expression (72 up-regulated and six down-regulated in the Zl group). The Kyoto Encyclopaedia of Genes and Genomes annotation and classification indicated that the differentially expressed flavonoids were mainly related to anthocyanin biosynthesis. Moreover, candidate genes for flavonoid biosynthesis in Os and Zl were identified in this study. Compared with non-pigmented and red rice, Zl may be more nutritious and is thus considered a better source of natural antioxidants.

Dynamics of antioxidant activities, metabolites, phenolic acids, flavonoids, and phenolic biosynthetic genes in germinating Chinese wild rice (Zizania latifolia)

In this study, the antioxidant activity of germinating Chinese wild rice was found to decline initially, after which it increased. The largest difference in antioxidant activity was observed between the 36-h (G36) and the 120-h germination (G120) stage. We further assessed the dynamic changes in metabolites, phenolic acids, flavonoids, and phenolic biosynthetic genes in germinating Chinese wild rice. Ultra-high performance liquid chromatography-triple quadrupole mass spectrometry revealed that 315 metabolites were up-regulated and 28 were down-regulated between G36 and G120. Levels of p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillin, p-coumaric acid, ferulic acid, and epigallocatechin increased significantly during germination. Gene expression of four phenylalanine ammonia-lyases, one 4-coumarate-CoA ligase, one cinnamoyl-CoA reductase, two cinnamyl alcohol dehydrogenases, one chalcone synthase, and one chalcone isomerase was significantly higher at G120 than at G36 and promoted phenolics accumulation. This study elucidated the biochemical mechanisms involved in antioxidant activity and phenolic profile changes during Chinese wild rice germination.

The pathogen Moniliophthora perniciosa promotes differential proteomic modulation of cacao genotypes with contrasting resistance to witches´ broom disease

BACKGROUND

Witches' broom disease (WBD) of cacao (Theobroma cacao L.), caused by Moniliophthora perniciosa, is the most important limiting factor for the cacao production in Brazil. Hence, the development of cacao genotypes with durable resistance is the key challenge for control the disease. Proteomic methods are often used to study the interactions between hosts and pathogens, therefore helping classical plant breeding projects on the development of resistant genotypes. The present study compared the proteomic alterations between two cacao genotypes standard for WBD resistance and susceptibility, in response to M. perniciosa infection at 72 h and 45 days post-inoculation; respectively the very early stages of the biotrophic and necrotrophic stages of the cacao x M. perniciosa interaction.

RESULTS

A total of 554 proteins were identified, being 246 in the susceptible Catongo and 308 in the resistant TSH1188 genotypes. The identified proteins were involved mainly in metabolism, energy, defense and oxidative stress. The resistant genotype showed more expressed proteins with more variability associated with stress and defense, while the susceptible genotype exhibited more repressed proteins. Among these proteins, stand out pathogenesis related proteins (PRs), oxidative stress regulation related proteins, and trypsin inhibitors. Interaction networks were predicted, and a complex protein-protein interaction was observed. Some proteins showed a high number of interactions, suggesting that those proteins may function as cross-talkers between these biological functions.

CONCLUSIONS

We present the first study reporting the proteomic alterations of resistant and susceptible genotypes in the T. cacao x M. perniciosa pathosystem. The important altered proteins identified in the present study are related to key biologic functions in resistance, such as oxidative stress, especially in the resistant genotype TSH1188, that showed a strong mechanism of detoxification. Also, the positive regulation of defense and stress proteins were more evident in this genotype. Proteins with significant roles against fungal plant pathogens, such as chitinases, trypsin inhibitors and PR 5 were also identified, and they may be good resistance markers. Finally, important biological functions, such as stress and defense, photosynthesis, oxidative stress and carbohydrate metabolism were differentially impacted with M. perniciosa infection in each genotype.