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Cocoa quality depends on several parameters, such as cocoa variety, environmental growth conditions, cultivation technique, and post-harvest treatments applied to coca beans. In this work, we studied the impact of cocoa post-harvest processing on both microbial communities structure and volatile composition. Cocoa beans samples were fermented in wooden boxes in Ivory Coast at different time intervals with turning and without turning, and derived from pods stored for two different duration times. Cocoa beans were analyzed using a molecular fingerprinting method (PCR-DGGE) in order to detect variations in microbial communities' structure; this global analysis was coupled to SPME-GC-MS for assessing cocoa volatile profiles. The results showed that the main parameter that influenced microbial communities structure was fermentation time, followed by turning, whereas, pods storage duration had a minor impact. Similar results were obtained for aromatic profile, except for pods storage duration that significantly affected volatile compound production. Global statistical analysis using Canonical Correspondence Analysis (CCA), showed the relationship between microbial communities and volatile composition. Furthermore, this study allowed the identification of discriminating microbial and chemical markers of cocoa post-harvest processing.

International audience; Pollen from wind-pollinated plants is the predominant cause of pollinosis which corresponds mainly to allergic rhinitis and conjunctivitis. Bacterial communities associated to leaves and roots surface were analysed for many years with both culture-dependent and independent methods. However, microbiota of pollen grains was rarely investigated and never with a molecular fingerprint technique. The aim of this study was to perform a preliminary analysis of the pollen microbiota by applying PCR-TTGE method. Pollen samples were collected from various anemophilous trees genera (Cephalotaxus, Cupressus, Pinus, Platanus and Quercus) in Montpellier (France) in 2013. Thorough pollen preparation was essential to a successful recovery of DNA from pollen. Regarding the results, pollen microbiota was tree genus-dependent. In addition, intra-tree genus variations were also observed. The Gammaproteobacteria class was the most represented in pollen samples whatever the tree genus. Among this class, some bacteria were recognized as phytopathogens (Pseudomonas, Erwinia) but also opportunistic human pathogens (Pseudomonas, some enterobacteria). PCR-TTGE is a suitable tool to analyse the microbiota associated with pollen responsible for phytopathogenicity or affecting the human respiratory tract.

Two main types of processing are applied to coffee: the dry and wet processes. The aim of this study was to measure the impact of post-harvest processing on coffee microbial ecology and search for microbial markers of process discrimination. Coffee samples were collected in three farms in two locations of West Cameroon (Bafoussam and Dschang). Samples of Coffea arabica were collected along wet and dry methods and Coffea canephora samples were collected only during treatment using the dry method. Bacterial and fungal communities present on coffee beans were determined by using a molecular method PCR-DGGE (Denaturing Gradient Gel Electrophoresis) generating 16S rDNA and 26S rDNA profiles for bacteria and fungi. Results showed that microbial ecology structures were different depending on three main parameters: i) the method applied, ii) the coffee species and iii) their geographical origin. Statistical analysis applied allowed to measure the impact of all parameters and showed that the method was the major parameter influencing microbial communities' structure. Microbial DNA markers that appear specific of coffee origin, species or treatment were identified, such as lactic acid bacteria (LAB) which were detected only during wet process. They are specific of the fermentation step. DNA from Wallemia sp. was only detected in Robusta coffee beans (Coffea canephora). The study of microbial communities at the molecular level appears as a promising approach to discriminate between coffee processing types.

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. (Resume d'auteur)

This study aimed to evaluate molecular microbial markers associated with cocoa fermentation and drying steps. The dynamics of microbial populations were analyzed during postharvest processing (fermentation and sun drying) of cocoa from Ivory Coast. The variations in bacterial and yeast communities structure were monitored by a molecular technique (PCR-DGGE) using 16S rRNA and 26S rRNA profiles. Dominant microbial species were determined by sequencing. Our results showed that treatments of cocoa generated great variations in the microbial ecology in terms of number of species detected. The bacterial ecology quickly underwent dramatical changes during the fermentation step after two days. The dominance of Enterobacteria was first observed and then accompanied by Lactic acid bacteria and at the latest stages by acetic acid bacteria. Furthermore, Hanseniaspora opuntiae yeast species predominated during cocoa bean fermentation and drying processes. In addition, two bacterial species were only identified during the drying step of fermented cocoa beans and are potential candidates for biological markers of this process. (Resume d'auteur)

Biopreservation has recently been endorsed as an alternative to reduce microbial risks and conserve fresh products. This study focused on the importance of lactic acid bacteria (LAB) and its efficiency as a bioprotective agent. One hundred and fifty LAB strains were isolated from iceberg lettuce, characterized and identified using 16S rDNA sequencing and API 50CH. All strains displayed a considerable antibacterial activity against pathogenic bacteria namely Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella typhimurium and Staphylococcus aureus. All the isolates were found to correspond to Lactobacillus plantarum strain. The results deduced that the production of organic acids was the most frequent mechanism of inhibition used among the tested isolates. Furthermore, it was proven that LAB strain harmed the growth of two foodborne pathogen bacteria, S. typhimurium and L. monocytogenes, in shredded iceberg lettuce.