Résumé
Cereal storage in underground silos was used from the Neolithic period until now in many populations across the world. For thousands of years, soil-dug silos were an essential commodity for life and survival of human populations. It also represented an important economic feature in some communities, as found in France during the Middle Age. The SilArchaeoBio project is based on an experimental archaeology approach, trying to recreate pre-industrial pits in two sites, in the Perpignan area. The project is looking at the preservation of three different cereals (ancient wheat, barley and einkorn) in underground silos, dug with similar means than pre-industrial populations (when possible). After a variable duration of storage, the grain properties were analysed: germinative capacity, grain quality and food-safety assessment. Furthermore, a thorough monitoring of the storage conditions is applied. Several probes were used to record the temperature, humidity and CO2 concentration in several locations inside the silos, across a several-months experiment.A two-phase sampling (spring and summer) provided enough material to analyse more parameters in the lab. A mycotoxins dosage (Aflatoxins and ochratoxins) was processed and the results were correlated with a quantification of microbial communities by quantitative PCR: ITS marker to estimate the fungi population and 16S marker to evaluate the bacteria. A precise composition of the grain microbiome will be assessed by metabarcoding, to hopefully establish a link between storage conditions (variations in temperature and humidity) and the prevalence of some microbial populations like mycotoxins producers.In parallel, further experiments are processed in controlled environments, to simplify a complex system influenced by numerous parameters (forecast, soil properties, insects invasion). Microcosms are used to study the kinetics of the initial development of the grain microbiome. A simple experimental design allows to test microbial growth on three types of cereal, in a controlled temperature and humidity set-up. Mycotoxins titration and qPCR analysis will allow a better understanding of the early phase of grain colonisation by microbes.Thanks to all the findings obtained both in the lab and in the underground silos, a stronger knowledge on fungal and bacterial populations equilibrium will allow a better grasp on grain storage and how we could use/revisit ancient preservation techniques to improve cereal storage, save energy and lower the impact of agriculture on climate change.