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Application of PCR-DGGE to the study of dynamics and biodiversity of microbial contaminants during the processing of Hibiscus sabdariffa drinks and concentrates

Ndiaye N.A., Hamdouche Y., Kane A., Cisse M., Berthiot L., Touré-Kané N.C., Montet D.. 2016. Fruits, 71 (3) : p. 141-149.

DOI: 10.1051/fruits/2016001

Introduction. Bissap (Hibiscus sabdariffa L.) is a common plant in the tropics. In Senegal, the calyces are used to make a popular juice. In the food industry, small and medium-sized enterprises (SMEs) are responsible for the transformation of bissap calyces into drinks, concentrates, jam, etc. In spite of the very low pH of the juice (pH < 3), problems of contamination and fermentation are often observed in the final products post-pasteurization. They are mainly due to Pseudomonas spp., E. coli, Klebsiella spp. and Pichia opuntiae. To solve this issue, monitoring of the microbial ecology was performed during the full process of bissap products. Methods and results. Fresh calyces and dried mixed calyces of the two varieties of Hibiscus sabdariffa ('Koor' and 'Vimto'), as well as juice samples, were collected at every stage of the processing of a bissap drink and syrup in a Senegalese SME. The monitoring of microbial flora was performed by using molecular fingerprinting. The molecular technique PCR-DGGE was employed to evaluate the microbial dynamics using bacterial 16S rDNA, yeast 26S rDNA and 28S rDNA mold profiles at each critical stage of the process. Results and discussion. The genetic profiles generated contributed to identifying the critical points in the manufacturing processes. A multivariate analysis based on the presence or absence of spots in the denaturing gradient electrophoresis gels (DGGE) showed that the microbial flora (bacteria, yeasts, molds) of bissap evolved during the following phases: harvest (fresh flower), drying (dried calyces) and processing (before filtration, after pasteurization and before packaging). Conclusion. Our work contributed to determining the microorganisms responsible for the microbial contamination of the final products, and highlighted the origin of these contaminants. The most important critical point was identified as the pasteurization step.

Mots-clés : hibiscus sabdariffa; contamination biologique; biosécurité; flore microbienne; jus de fruits; calice; sirop de fruits; récolte; séchage; technologie alimentaire; analyse microbiologique; Écologie microbienne; technique analytique; pcr; Électrophorèse sur gel; sénégal; france; qtl; sécurité des aliments

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