Conservation des aliments

Résumé

La conservation des aliments est un ensemble de procédés de traitement permettant de conserver les propriétés gustatives (certains y ajoutent du goût, en particulier ceux qui nécessitent un additif) et nutritives, les caractéristiques de texture et de couleur des denrées alimentaires. Et aussi leur comestibilité, par la prévention des éventuelles intoxications alimentaires. La conservation des denrées alimentaires concerne donc tous les facteurs biotiques (micro-organismes, animaux, germination végétale, etc.) et abiotiques (lumière, oxygène, chaleur, irradiation, UV, etc.) qui peuvent détériorer la qualité de la denrée stockée. L'emballage et les conditions d'entreposage des aliments sont aussi essentiels. Histoire L'histoire de l'alimentation est étroitement liée à l'évolution des procédés de conservation. Dès ses origines, l'humanité a ressenti la nécessité de conserver les aliments pour assurer sa subsistance : stocker les aliments en période d'abondance pour faire fa

Source officielle

https://fr.wikipedia.org/wiki/Conservation_des_aliments

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Chargement

Root carbon and nutrient homeostasis determines downy oak sapling survival and recovery from drought

Leonie Corine Schönbeck

The role of carbon (C) and nutrient uptake, allocation, storage and especially their interactions in survival and recovery of trees under increased frequencies and intensities of drought events is not well understood. A full factorial experiment with four soil water content regimes ranging from extreme drought to well-watered conditions and two fertilization levels was carried out. We aimed to investigate whether nutrient addition mitigates drought effects on downy oak (Quercus pubescens Willd.) and whether storage pools of non-structural carbohydrates (NSC) are modified to enhance survival after 2.5 years of drought and recovery after drought relief. Physiological traits, such as photosynthesis, predawn leaf water potential as well as tissue biomass together with pools and dynamics of NSC and nutrients at the whole-tree level were investigated. Our results showed that fertilization played a minor role in saplings’ physiological processes to cope with drought and drought relief, but reduced sapling mortality during extreme drought. Irrespective of nutrient supply, Q. pubescens showed increased soluble sugar concentration in all tissues with increasing drought intensity, mostly because of starch degradation. After 28 days of drought relief, tissue sugar concentrations decreased, reaching comparable values to those of well-watered plants. Only during the recovery process from extreme drought, root NSC concentration strongly declined, leading to an almost complete NSC depletion after 28 days of rewetting, simultaneously with new leaves flushing. These findings suggest that extreme drought can lead to root carbon exhaustion. After drought relief, the repair and regrowth of organs can even exacerbate the root carbon depletion. We concluded that under future climate conditions with repeated drought events, the insufficient and lagged carbon replenishment in roots might eventually lead to carbon starvation and further mortality.

2021

Chargement

This work's objective was to develop a novel type of gliadin electrospun fiber with antibacterial properties by incorporating cuminaldehyde in the fibrous structure. Gliadin fibers containing various concentrations of cuminaldehyde were fabricated via an electrospinning process. The morphology and size of the fibers were affected by the concentration of incorporated cuminaldehyde. An optimum value was selected as the highest concentration of cuminaldehyde (20%, w/w). 1H NMR spectroscopy indicated the presence of incorporated cuminaldehyde in gliadin fibers. In addition, the FTIR spectroscopy suggested the occurrence of hydrogen interactions between C--O bonds of cuminaldehyde and N-H bonds of gliadin at 1651 and 3293 cm-1. Confocal Raman spectroscopy and X-ray diffraction revealed a homogenous distribution of cuminaldehyde in the amorphous cuminaldehyde-loaded gliadin fibers with almost no crystalline peaks of cuminaldehyde. Moreover, the gliadin fibers enhanced the thermostability of cuminaldehyde. The hydrophobic cuminaldehyde-loaded gliadin fiber showed a non-Fickian diffusion release, antibacterial activity against Staphylococcus aureus (PTTC 1112) Escherichia coli (PTCC 1399), and is non-toxic to the ASCs. These results confirm the capacity of cuminaldehydeloaded gliadin fibers for being used in food applications.

2021

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Purely Organic Optical Sensor for Broad-Range and Reversible Oxygen Sensing

Efe Armagan

Oxygen (O2) molecule is of paramount importance in nature, and it takes part in several biological and chemical activities such as energy generation, cellular respiration, and food deterioration, to name a few. Detection of O2 concentration is of extreme importance in many application fields to monitor the above-mentioned activities. In the last decade, optical oxygen sensors have become a popular research topic due to the need for continuous, reversible, and non-destructive O2 sensing. Rational design of O2 sensing materials, optimal integration of reporter luminophore chemistry with the other sensor components (encapsulation matrix, support material, additives), and simple fabrication procedures are the main bottlenecks and challenges in producing simple and affordable optical O2 sensors with stable and predictable sensing performance. The traditional approach, such as developing metal ion-based luminophores and integrating these sensing units into organic/inorganic matrix have shown their utility in many optical O2 sensor systems. However, a high degree of toxicity of metal ions hampers the effective use of such systems in many application areas. Therefore, it is crucial to develop purely organic optical O2 sensors to overcome the above-mentioned problem. Although a few studies investigate the O2 sensing performance of organic optical O2 sensors, their lack of O2 sensitivity range and poor reversibility are two main drawbacks of these sensors. In this thesis, I study improving the O2 sensitivity range of organic optical O2 sensors with good sensing reversibility by developing diamine-based organic O2 sensing material and embedding these indicators within a polymer matrix.

EPFL2021

Chargement

Root carbon and nutrient homeostasis determines downy oak sapling survival and recovery from drought

Leonie Corine Schönbeck

2021