Crumbing the past: micro-CT as a tool for characterising the structure of archaeological cereal-food remains

Charred cereal-based food remains are frequently classified as amorphous charred objects (ACOs) because their internal structure is difficult to characterise using conventional two-dimensional approaches. Here, we evaluate the potential of micro-CT as a non-destructive tool for analysing the internal structure of archaeological cereal-food remains from the Early Neolithic level of El Portalón de Cueva Mayor (Burgos, Spain). Five ACO fragments and a range of modern fresh and charred bread samples were examined using stereomicroscopy, FE-SEM and micro-CT, and their pore architecture was quantified using 3D image analysis. The analysed archaeological specimens show high porosity (61.24 - 74.84%), very high connectivity index values (0.995 - 0.996), connectivity density values between 42.25 and 106.25 mm −3 , fractal dimensions between 2.689 and 2.786, and average wall thickness values of 0.105 - 0.111 mm. Together, these parameters reveal a highly developed and interconnected pore network that is compatible with a bread-like matrix and may be consistent with fermentation. However, the 2D pore-size distributions, calculated from image analysis following previously proposed methodologies, are dominated by small to medium pores and, on their own, do not allow an unambiguous classification as fermented dough. We therefore interpret the specimens as plausible remains of fermented, bread-like products. Our results show that micro-CT provides useful quantitative data for the structural characterisation of archaeological cereal preparations, especially when combined with SEM observations and ingredient identification.