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

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. (Résumé d'auteur

Coffee Bourbon Pointu of Reunion Island: The post-harvest process is one of the keys to achieve the best sensorial quality

International audienceProducing coffee in a European country is a challenge according to the cost of labour. Faced to the need to substitute non profitable crops like perfume plants (Geranium rosa), farmers of the Reunion Island, the French island in the Indian Ocean (Figure 1), decided to grow coffee helped by a development project ("Café Bourbon pointu de la Réunion"). This project has been set up to study the feasibility of producing a high value coffee, a "gourmet coffee". The coffee Bourbon pointu, caffeine low, is well known for its fruity taste since the 19th century. It received 39 gold medals at the 1869 Colonial Fair and the gold medal at the 1897 Anvers World Fair. The coffee Bourbon pointu cultivation is abandoned in 1940 because of the production costs that makes this cultivation non profitable. It is now boosted for a high value niche market. Four years of agronomic trials (screening of the lines, development of good cultural methods) and experiments on the post-harvest process give a lot of results. Crossing these results with sensorial evaluations led to produce a high value coffee. Studies about the behaviour of the coffee trees in various environmental conditions permitted to define the favourable "terroir" to produce a high value coffee. This paper focuses on the post-harvest processes and the method used to define the process giving the best sensorial results. (Résumé d'auteur

Coffee Bourbon Pointu of Reunion Island: How to define a terroir to obtain a «Gourmet» coffee

International audienceNew ways of coffee consumption have emerged with the development of specialty coffees and terroir coffees. Producing coffee in a European country is a challenge according to the cost of labour. Nevertheless, farmers of the Reunion Island, the French island in the Indian Ocean, decided to grow coffee helped by a development project ("Café Bourbon pointu de la Réunion") with the aim of producing a high value coffee for a niche market. Producing coffee on the Reunion Island is not new: the first coffee plants were introduced in the 18th century from Yemen. Coffee cultivation has contributed to develop the island. "Bourbon pointu" is the result of a natural mutation of a Yemen Arabica coffee plant, discovered in 1771 in a plantation near the village of Sainte Marie. The coffee Bourbon pointu, caffeine low, is well known for its special citrus fruity taste. (Résumé d'auteur