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| Author(s): |
Aline Aparecida Possignolo
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB) |
| Defense date: | 2010-06-11 |
| Examining board members: |
Antonio Vargas de Oliveira Figueira;
Irene da Silva Coelho;
Priscila Efraim
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| Advisor: | Antonio Vargas de Oliveira Figueira |
| Abstract | |
Typical chocolate flavor is unique, only obtained from fermented, dried and roasted cocoa seeds, and can not be synthesized artificially. The flavor development is influenced by the genetic constitution, post-harvest processing and manufactures. Cotyledons proteins are believed to be the precursors of the chocolate flavor. The aim of the present work was to analyze qualitative and quantitative protein differences in seeds of three cocoa genotypes after harvesting and during the fermentation and to correlate these results with differences in quality (flavor and aroma) obtained by sensorial evaluation. One of the challenges was the isolation of proteins from cocoa seeds, avoiding the high content of polyphenols and polysaccharides which disturb protein separation and proteome analysis. The methodology of extraction by filtration in Miracloth, solubilization and precipitation in trichloroacetic acid showed the highest gel resolution and reprodutivity, and, thus, was chosen to be used in the analyses of the proteome of cocoa seeds during the fermentation. It was also necessary to use commercial kit for protein purification and a silver-based staining method with nitrate to guarantee gels with spots resolution and satisfactory reproducibility. Proteins were excised from de gels and after tryptic digestion, MS analysis was conducted by on line chromatografhy using a Cap-LC coupled to a mass spectrometer. The spectra were processed using MASCOT MS/MS Ion Search, and the sequences searched against NCBI databases. The 2-DE maps analysis of cocoa seeds showed significant variation of the spots number among the genotypes. At the end of fermentation, proteins still present in the Sial 70 and Catongo genotypes were acid and the degradation process was characterized by the disappearance of almost all the neutral or basic proteins and also some acid proteins. The genotype CCN 51 did not show the same degradation profile. Of the spots submitted to the mass spectrometer, 89 were identified. The 21kDa protein and vicilin were the most abundant proteins in the cocoa cotyledons. Correlating sensorial analysis and the proteomic results we could observe the existence of quantitative as qualitative correlation of proteins from cocoa cotyledons and possibly with the precursors proteins of chocolate flavor (AU) | |
| FAPESP's process: | 07/05979-4 - Qualitative and quantitative evaluation of proteins of seeds of varieties of Theobroma cacao during the process of fermentation and its effect in the development of the chocolate flavor |
| Grantee: | Aline Aparecida Possignolo |
| Support Opportunities: | Scholarships in Brazil - Master |