Noël Durand

Ochratoxin A contamination of coffee batches from Kenya in relation to cultivation methods and post-harvest processing treatments

This study set out to assess the relative importance of sound and unsound beans in a batch of coffee with regard to ochratoxin A (OTA) contamination. Initially, unsound beans were found to account for 95% of contamination in a batch of coffee, whatever the methods used for post–harvest processing. It was also found that beans displaying traces of attacks by Colletotrichum kahawae were the greatest contributors to OTA contamination. In a second stage, the study compared the contamination of sound beans with that of beans attacked by Colletotrichum kahawae. On average, beans attacked by Colletotrichum kahawae had a statistically higher OTA content than sound beans (18.0 µg kg−1 as opposed to 1.2 µg kg−1). In addition, the average OTA content in unsound beans varied depending on growing conditions.

Effect of operating conditions on ochratoxin A extraction from roasted coffee.

Operating conditions affect ochratoxin A (OTA) extraction from roasted coffee. The OTA content found in the beverage can thus be greater than that found in the roasted coffee used to prepare it. Three extraction parameters were studied for roasted coffee: type of extraction solvent (alkaline, neutral, acid), temperature (ambient temperature/23°C, 60°C and 85°C), and extraction time (5, 20, 30, 40, 50, 60 and 80 min). The alkaline solvent used in the method recommended by the European Union extracted OTA better, but a maximum content was obtained at 60°C after 50 min. At least a 100% improvement in extraction was obtained when compared with the European Union usual quantification method that is carried out at ambient temperature. It turned out that the OTA extraction parameters for roasted coffee, as defined by that method, were not optimum and needed to be modified. These results were verified in double-extraction experiments showing that OTA is not completely extracted by this method. Confirmation was obtained by comparison of extraction methods on several commercial samples of roasted coffee.

Study on the Coffea arabica/Colletotrichum kahawae pathosystem: Impact of a biological plant protection product

Coffee berry disease (Colletotrichum kahawae) causes fruits rots on Arabica coffee leading to harvest losses of around 40%. Using biological molecules may be one way of reducing chemical pesticide use by stimulating natural defence reactions in plants. FEN 560 is a natural product extracted from fenugreek (Trigonella foenum-greacum) and its stimulating effect is now recognized on the Vitis vinifera L./Uncinula necator pathosystem. In order to study its effect on the Coffea arabica/C. kahawae pathosystem, the enzymatic activity of phenylalanine ammonia lyase (PAL), along with caffeine and chlorogenic acid (CGA) concentrations were monitored in the seedling hypocotyls of two varieties of C. arabica with different degrees of susceptibility, contaminated by C. kahawae and treated with FEN 560. After observing symptoms on seedlings, a real FEN 560 effect was seen on the pathosystem. However, it did not seem to stimulate the alkaloid (caffeine) or polyphenol (CGA) biosynthesis pathways. However, the pathogen did trigger synthesis of caffeine and CGA, which therefore seem to be useful markers for studying resistance to coffee berry disease in C. arabica.ZusammenfassungDie Kaffeebeerenkrankheit (Colletotrichum kahawae) verursacht Fruchtfäulen an Arabica-Kaffee mit Ernteverlusten bis zu 40%. Die Verwendung natürlicher Wirkstoffe kann durch die Stimulierung pflanzlicher Abwehrreaktionen den Einsatz chemisch-synthetischer Wirkstoffe reduzieren. FEN 560 ist ein Naturprodukt aus dem Bockshornklee (Trigonella foenumgreacum), dessen abwehrstimulierende Wirkung im Wirt-Pathogen-System Vitis vinifera L./Uncinula necator bekannt ist. Die Wirkung von FEN 560 im Wirt-Pathogen-System Coffea arabica/C. kahawae sollte anhand der enzymatischen Aktivität der Phenylalaninammoniumlyase (PAL) sowie der Konzentrationen von Koffein und Chlorogensäure (CGA) in den Hypokotylen zweier befallener und mit FEN 560 behandelter Sorten von C. arabica mit unterschiedlicher Anfälligkeit untersucht werden. Eine abwehrstimulierende Wirkung von FEN 560 konnte nach dem Auftreten von Krankheitssymptomen an den Hypokotylen beobachtet werden, obwohl weder die Synthesewege der Alkaloide (Koffein) noch der Polyphenole (CGA) hochgefahren wurden. Allerdings stimulierte das Pathogen die Synthese von Koffein und CGA, die daher als brauchbare Marker zur Untersuchung von Resistenzen gegenüber der Kaffeebeerenkrankheit in C. arabica dienen könnten.

Effect of post-harvest treatments on the occurrence of ochratoxin A in raw cocoa beans

Abstract Cocoa beans are the principal raw material for chocolate manufacture. Moulds have an important place in the change in the quality of cocoa beans due to their role in the production of free fatty acids and mycotoxins, namely ochratoxin A (OTA). This study investigated the impact of the key post-harvest treatments, namely the fermentation and drying methods on OTA contamination of raw cocoa beans. Analytical methods for OTA detection were based on solid–liquid extraction, clean-up using an immunoaffinity column, and identification by reversed-phase HPLC with fluorescence detection. Of a total of 104 randomly selected cocoa samples analysed, 32% had OTA contents above 2 µg kg–1. Cocoa sourced from pods in a bad state of health had a maximum OTA content of 39.2 µg kg–1, while that obtained from healthy pods recorded 11.2 µg kg–1. The production of OTA in cocoa beans increased according to the pod-opening delay and reached 39.2 µg kg–1 after an opening delay of 7 days after harvest, while 6.1 and 11.2 µg kg–1 were observed when pods were opened after 0 and 4 days. OTA production also seemed to depend considerably to the cocoa fermentation materials. When using plastic boxes for bean fermentation, the OTA production was enhanced and reached an average OTA content of about 4.9 µg kg–1, while the raw cocoa treated in banana leaves and wooden boxes recorded 1.6 and 2.2 µg kg–1 on average respectively. In parallel, the OTA production was not really influenced by either the mixing or the duration of the fermentation or the drying materials.

Multi-response modeling of reaction-diffusion to explain alpha-galactoside behavior during the soaking-cooking process in cowpea

A modelling approach was developed to better understand the behavior of the flatulence-causing oligosaccharides in cowpea seeds during isothermal water soaking-cooking process. Concentrations of verbascose, stachyose and raffinose were measured both in the seed and in the soaking water during the process (T=30, 60 and 95°C). A reaction-diffusion model was built for the three considered alpha-galactosides both in the seed and in the soaking water, together with a model of water transport in the seed. The model reproduced coupled reaction-diffusion of alpha-galactosides during the soaking-cooking process with a good fit. Produced, diffused and degraded alpha-galactoside fractions were identified by performing a mass balance. During soaking at 30°C, degradation predominated (maximum found for raffinose degradation rate constant of 3.22×10-4s-1) whereas diffusion predominated at higher temperatures (95°C).

Microbiological safety of flours used in follow up for infant formulas produced in Ouagadougou, Burkina Faso

The prevalence of diarrheal diseases in children aged from 6 to 24 months in Burkina Faso is 38%. These diarrheas may be due to the consumption of contaminated weaning food. Therefore, the microbiological quality of follow up infant flours used as supplement foods is a key-point to reduce children diseases. In this study, the microbiological safety of locally-produced infant flours was investigated. One hundred and ninety-nine (199) samples were collected mainly in retails outlets and in Recovery and Nutrition Education Centers. According to the Burkina Faso regulations, microbiological analyses were carried out for Total Aerobic Mesophilic Flora (TAMF), thermotolerant coliforms, Salmonella spp. and yeasts/molds. The bacterial and fungal isolates were identified using phenotypic and genotypic methods and the study of the production of mycotoxins was carried out from the fungal isolates. In collected samples, the TAMF count ranged from 0 to 1.8 × 106 CFU/g with a total average of 6.3 × 104 CFU/g. About 2% of the samples had a microbial load exceeding the standards (105 CFU/g). No Salmonella spp. was isolated in the final infant flours. However, the presence of Enterobacteriaceae (Klebsiella spp. Enterobacter spp. and Cronobacter spp.) was detected and molecular characterization revealed also the presence of fungal species of the genus Aspergillus spp., Penicillium spp. and Fusarium spp. Some of these species were found to produce aflatoxins, ochratoxin A and fumonisins, which are potential carcinogenic toxins. These results demonstrated the need for a preventive approach based on the application of Hazard Analysis Critical Control Point in the food industry to ensure food safety of infant flours in Burkina Faso.

Kinetic study of enzymatic α-galactoside hydrolysis in cowpea seeds

The endogenous alpha-galactosidase activity of cowpea seeds was characterized and modelled assuming Michaelian behavior. The aim is to use the resulting knowledge to optimize alpha-galactoside degradation during the soaking-cooking process. In this study, the alpha-galactosidase enzyme from Wankoun cowpea was extracted and its enzymatic activity was analyzed as a function of temperature, pH and the presence of some inhibitors. Enzymatic activity was optimal around 35 °C and a pH of 5.8. Activation and inactivation energy was evaluated at 50 ± 3 and 103 ± 9 kJ.mol-1, respectively. The strongest inhibitor was galactose with an inhibition constant KI of 0.28 ± 0.03 mM. Incubation of the enzyme extract with alpha-galactosides revealed a 10-h lag phase in the early stages that could be due to low pH, the action of inhibitors including galactose and the biosynthesis of alpha-galactosides. After the lag phase, the degradation of each alpha-galactoside occurred without the appearance of any intermediary product. The degradation of alpha-galactosides was observed with a Km of 1.7 ± 0.3 mM for raffinose; 3.6 ± 0.6 mM for stachyose and 15.9 ± 0.1 mM for verbascose. A long soaking step around 35 °C is suggested to maximize the alpha-galactosides enzymatic degradation.