Larval cases of caddisfly (Insecta: Trichoptera) affinity in Early Permian marine environments of Gondwana

Caddisflies (Trichoptera) are small, cosmopolitan insects closely related to the Lepidoptera (moths and butterflies). Most caddisflies construct protective cases during their larval development. Although the earliest recognisable caddisflies date back to the early Mesozoic (Early and Middle Triassic), being particularly numerous and diverse during the Late Jurassic and Early Cretaceous, the first records of their larval case constructions are known exclusively from much younger, Early to Middle Jurassic non-marine deposits in the northern hemisphere. Here we present fossils from the Early Permian (Asselian-Sakmarian) marine deposits of Brazil which have strong morphological and compositional similarity to larval cases of caddisflies. If they are, which is very probable, these finds not only push back the fossil record of true caddisflies, but also indicate that their larvae constructed cases at the very beginning of their evolution in marine environments. Since modern caddisflies that construct larval cases in marine environments are only known from eastern Australia and New Zealand, we suggest that this marine ecology may have first evolved in western Gondwana during the Early Permian and later spread across southern Pangea

Changements de structure associées aux variations de température et d'hydratation des produits céréaliers suivis par RMN à bas champ

International audienceBased on spin-spin T2 relaxation time measurements, the time-domain NMR (TD-NMR) spectroscopy has been used to provide relevant information on the water and biopolymer motion and transfer in bread. This technique permits to characterize molecular interaction and transformations in a non-invasive and non-destructive way, in real time during a process (heating, freezing, hydration ...). In bread, proteins of gluten when hydrated form a viscous mass that confers to the dough, structure, viscosity, mixing tolerance and gas holding ability. On the other hand, starch, in presence of water and increasing temperature, undergoes a series of changes known as swelling, gelatinization and retrogradation that induce variations in water distribution, in starch structure and interactions between them. Our studies aims at understanding and ranking the contribution of these biochemical transformations that contribute to the crumb structure and the textural properties of bread made with cereal flour or a gluten free mix. The water transfers and the extent of starch gelatinization in dough and crumb were studied by TD-NMR during and after the heating/cooling process of dough at various water levels. Preliminary fast field cycling NMR experiments make it possible to envisage further works in order to understand the role of water in the formation of bread crumbs

Gluten-free bread baked under reduced pressure characterized by TD-NMR

International audienceBased on spin-spin T2 relaxation time measurements, the time-domain NMR (TD-NMR) spectroscopy has been used to provide relevant information on the water and biopolymer motion and transfer in bread [1]. This technique permits to characterize molecular interaction and transformations in a non-invasive and non-destructive way, in real time during a process (heating, freezing, hydration ...). In bread, proteins of gluten when hydrated form a viscous mass that confers to the dough, structure, viscosity, mixing tolerance and gas holding ability [2]. On the other hand, starch, in presence of water and increasing temperature, undergoes a series of changes known as swelling, gelatinization and retrogradation that induce variations in water distribution, in starch structure and interactions between them [3]. This study aimed at understanding and ranking the contribution of these biochemical transformations that contribute to the crumb structure and the textural properties of bread prepared with a gluten free mix (Schär). The water transfers and the extent of starch gelatinization in crumb were studied by TD-NMR after the heating/cooling process of dough hydrated at 55% and 48% (wet basis). Two baking processes were compared, one at the atmospheric pressure while the other was carried out at reduced pressure (-20 kPa). Bread baking using partial vacuum results in greater oven-rise and greater gas fraction in the crumb, giving an increased softness of the crumb for a more pleasant mouthfeel. Under reduced pressure, the boiling point of water decreases but, until now, no study was conducted to check if this baking condition modifies or not the starch gelatinization and protein denaturation. By comparing rheological measurements (modulus of elasticity using a compression stress relaxation experiment) with TD-NMR data, it was shown that the crumb softness was mostly driven by the gas fraction while the biochemical changes (starch gelatinization, protein denaturation), monitored by TD-NMR, were little modified when dough was baked under partial vacuum

The Sedimentary Geochemistry and Paleoenvironments Project.

Authors thank the donors of The American Chemical Society Petroleum Research Fund for partial support of SGP website development (61017-ND2). EAS is funded by National Science Foundation grant (NSF) EAR-1922966. BGS authors (JE, PW) publish with permission of the Executive Director of the British Geological Survey, UKRI.Publisher PDFPeer reviewe