Towards efficient peer-to-peer networks: A distributed cycle minimization approach

Master'sMASTER OF SCIENC

Inhibitory effect of α-cyclodextrin on α-amylase activity

Purpose: To explore the effect of α-cyclodextrin on the activity of α-amylase with a view to expanding its application range.Methods: The concentration of α-cyclodextrin, temperature, pH and interaction time were used as single factors to explore the influence of α-cyclodextrin on the activity of α-amylase and endogenous fluorescence in the enzyme system.Results: The results showed that the concentration, time, pH and temperature affect the interaction of them. The most obvious conditions for inhibition of α-amylase activity are as follows: 10 mmol/L concentration of α-cyclodextrin, pH 6.9, duration of 120 min and temperature at 55 oC. In addition, the fluorescence intensity of α-amylase changed as a result of the addition of α-cyclodextrin.Conclusion: The activity of α-amylase can be inhibited by α-cyclodextrin. At the same time, the addition of α-cyclodextrin will lead to the transfer of tryptophan group in α-amylase, which cause the change of microenvironment and changes the endogenous fluorescence intensity of α-amylase.Keywords: α-Cyclodextrin, α-Amylase, Fluorescence intensity, Inhibitio

Evaluation of gliadins-diglycosylated cyanidins interaction from litchi pericarp through ultraviolet and fluorescence measurements

The low stability of anthocyanins limits their use in industry, which can be surpassed by gliadins linkage. This work was aimed to study the anthocyanins-gliadins bonding properties. HPLC-DAD-ESI-M..

Recovery of oil with unsaturated fatty acids and polyphenols from chaenomelessinensis (Thouin) Koehne: Process optimization of pilot-scale subcritical fluid assisted extraction

The potential effects of three modern extraction technologies (cold-pressing, microwaves and subcritical fluids) on the recovery of oil from Chaenomelessinensis (Thouin) Koehne seeds have been evaluated and compared to those of conventional chemical extraction methods (Soxhlet extraction). This oil contains unsaturated fatty acids and polyphenols. Subcritical fluid extraction (SbFE) provided the highest yield—25.79 g oil/100 g dry seeds—of the three methods. Moreover, the fatty acid composition in the oil samples was analysed using gas chromatography–mass spectrometry. This analysis showed that the percentages of monounsaturated (46.61%), and polyunsaturated fatty acids (42.14%), after applying SbFE were higher than those obtained by Soxhlet, cold-pressing or microwave-assisted extraction. In addition, the oil obtained under optimized SbFE conditions (35 min extraction at 35 °C with four extraction cycles), showed significant polyphenol (527.36 mg GAE/kg oil), and flavonoid (15.32 mg RE/kg oil), content, had a good appearance and was of high quality

Comparing the LC-MS phenolic acids profiles of aeven different varieties of brown rice (Oryza sativa L.)

Brown rice, an important material of whole-grain food, is increasingly popular for its health benefits. Thus, seven varieties of brown rice from southern China were analyzed in this study, concerning the free and bound phenolic compounds in the extract. The phenolic profiles of different brown rice were obtained and compared by the combination of HPLC and LC-MS analysis, in which eleven phenolic acids were identified. It was indicated that the total phenolic contents of different brown rice varied from 92.32 to 196.54 mg of gallic acid equivalent (GAE)/100 g DW. Ferulic acid and p-coumaric acid, free and bound, dominated within the phenolic acids. To be mentioned, the total phenols of Luotiangongmi (a kind of red rice) were significantly higher than the other six varieties. The high phenolic content of brown rice can further guide us to explore the functional properties of the crops

Recovery of Oil with Unsaturated Fatty Acids and Polyphenols from Chaenomelessinensis (Thouin) Koehne: Process Optimization of Pilot-Scale Subcritical Fluid Assisted Extraction

The potential effects of three modern extraction technologies (cold-pressing, microwaves and subcritical fluids) on the recovery of oil from Chaenomelessinensis (Thouin) Koehne seeds have been evaluated and compared to those of conventional chemical extraction methods (Soxhlet extraction). This oil contains unsaturated fatty acids and polyphenols. Subcritical fluid extraction (SbFE) provided the highest yield—25.79 g oil/100 g dry seeds—of the three methods. Moreover, the fatty acid composition in the oil samples was analysed using gas chromatography–mass spectrometry. This analysis showed that the percentages of monounsaturated (46.61%), and polyunsaturated fatty acids (42.14%), after applying SbFE were higher than those obtained by Soxhlet, cold-pressing or microwave-assisted extraction. In addition, the oil obtained under optimized SbFE conditions (35 min extraction at 35 °C with four extraction cycles), showed significant polyphenol (527.36 mg GAE/kg oil), and flavonoid (15.32 mg RE/kg oil), content, had a good appearance and was of high quality

L'extraction de l'inuline assistée par champs électriques pulsés : purification des jus de chicorées par filtration

Le procédé industriel d’extraction d'inuline consiste en une diffusion de longue durée et à température élevée. Ce procédé induit l’extraction des sucres mais également des impuretés. Les étapes de purification de jus deviennent alors plus complexes. Pour pallier à ces problèmes, il est essentiel de réduire la température de diffusion pour limiter l’extraction des impuretés. Récemment, la technique de champs électriques pulsés (CEP) a démonté ses avantages dans le domaine sucrier et également dans d’autres applications agro-alimentaires. L’objectif de ce travail de thèse est de d’optimiser et valider la faisabilité de cette techniques dans le cas de la chicorée. Une purification par filtration dynamique est envisagée et proposée pour remplacer la purification classique. Les résultats de l’extraction montrent qu’il est possible d’intensifier l’extraction de l’inuline par application de CEP. Le prétraitement des cossettes de chicorées à 600 V/cm et 50 ms, réduit de 20°C la température de diffusion (60°C au lieu de 80°C actuellement). Une économie d’énergie importante est réalisée (gain 90 kJ/kg chicory juice). La combinaison innovante d’un prétraitement électrique et un traitement thermique (chauffage ohmique) provoque une perméabilisation importante des cellules et permet de réaliser des diffusions « à froid ». Les analyses qualitatives de jus de diffusion classique et jus CEP montrent que la pureté des extraits CEP est plus élevée (87.2% vs 86.7%). Les essais de filtration sur membrane montrent que les performances de la filtration (pureté, flux, colmatage,…) dépendent énormément de l’origine de l’extrait. Le jus CEP contient moins d’impureté que le jus thermique, est donc plus facile à filtré. Cependant, col matage de membrane restent dans les deux cas important. Un module de filtration dynamique avec disque rotatif a été utilisé pour améliorer les performances de la filtration. Ce module a permit de réduire le colmatage des membranes, améliorer la pureté des extraits et atteindre des facteurs de réduction volumique important (10).Industrial inulin extraction requires high temperature and long duration to ensure inulin productivity. In addition complex steps are necessary to purify extracted chicory juice and to obtain inulin with desirable purity. In order to avoid the extracting of inulin at high temperature, to obtain chicory juice with better quality and to purify chicory juice with more simple operation, pulsed electric fields (PEF) and membrane filtration were applied to this study : PEF was used to intensify inulin extraction from chicory roots. By pre-treatment of chicory slices at 600 V/cm, diffusion temperature at pilot scale can be decreased to 60oC from about 80oC (industrial extraction condition) to obtain comparable juice inulin concentration. Moreover, this moderate temperature diffusion brought out interesting energy savings compared to that of conventional diffusion. For the goal of extracting inulin at “cold” condition (for example 30oC) PEF induced combined electroporation/ohmic heating pretreatment was applied for chicory tissue denaturation. Better solute extraction was observed after effective damage of chicory tissue diffusivity.Juice extracted from PEF assisted diffusion (PEF juice) was confirmed had higher inulin purity and less impurity in comparison to juice from conventional thermal diffusion process. The juice was purified by membrane filtration in order to investigate a simple chicory juice purification method. Since it contains less impurity, dead-end filtration performance of PEF juice was significantly improved, with less membrane fouling and higher inulin purity in filtrate. However, permeate flux of membrane filtration was seriously restricted by the membrane fouling. In order to improve filtration flux, rotating disk module was introduced in this study for clarification and purification of chicory juice. Elevated shear rate of rotating disk (1500–2000 rpm) could effectively control or even eliminate membrane fouling and lead to satisfying carbohydrate transmission (98%) and desirable permeate flux even at high volume reduction ratio (10). In view of energy saving, optimization of RDM assisted chicory juice filtration was carried out and yielded optimal operation conditions to maximize average flux and minimize specific energy consumption

L'extraction de l'inuline assistée par champs électriques pulsés (purification des jus de chicorées par filtration)

Le procédé industriel d extraction d'inuline consiste en une diffusion de longue durée et à température élevée. Ce procédé induit l extraction des sucres mais également des impuretés. Les étapes de purification de jus deviennent alors plus complexes. Pour pallier à ces problèmes, il est essentiel de réduire la température de diffusion pour limiter l extraction des impuretés. Récemment, la technique de champs électriques pulsés (CEP) a démonté ses avantages dans le domaine sucrier et également dans d autres applications agro-alimentaires. L objectif de ce travail de thèse est de d optimiser et valider la faisabilité de cette techniques dans le cas de la chicorée. Une purification par filtration dynamique est envisagée et proposée pour remplacer la purification classique. Les résultats de l extraction montrent qu il est possible d intensifier l extraction de l inuline par application de CEP. Le prétraitement des cossettes de chicorées à 600 V/cm et 50 ms, réduit de 20C la température de diffusion (60C au lieu de 80C actuellement). Une économie d énergie importante est réalisée (gain 90 kJ/kg chicory juice). La combinaison innovante d un prétraitement électrique et un traitement thermique (chauffage ohmique) provoque une perméabilisation importante des cellules et permet de réaliser des diffusions à froid . Les analyses qualitatives de jus de diffusion classique et jus CEP montrent que la pureté des extraits CEP est plus élevée (87.2% vs 86.7%). Les essais de filtration sur membrane montrent que les performances de la filtration (pureté, flux, colmatage, ) dépendent énormément de l origine de l extrait. Le jus CEP contient moins d impureté que le jus thermique, est donc plus facile à filtré. Cependant, col matage de membrane restent dans les deux cas important. Un module de filtration dynamique avec disque rotatif a été utilisé pour améliorer les performances de la filtration. Ce module a permit de réduire le colmatage des membranes, améliorer la pureté des extraits et atteindre des facteurs de réduction volumique important (10).Industrial inulin extraction requires high temperature and long duration to ensure inulin productivity. In addition complex steps are necessary to purify extracted chicory juice and to obtain inulin with desirable purity. In order to avoid the extracting of inulin at high temperature, to obtain chicory juice with better quality and to purify chicory juice with more simple operation, pulsed electric fields (PEF) and membrane filtration were applied to this study : PEF was used to intensify inulin extraction from chicory roots. By pre-treatment of chicory slices at 600 V/cm, diffusion temperature at pilot scale can be decreased to 60oC from about 80oC (industrial extraction condition) to obtain comparable juice inulin concentration. Moreover, this moderate temperature diffusion brought out interesting energy savings compared to that of conventional diffusion. For the goal of extracting inulin at cold condition (for example 30oC) PEF induced combined electroporation/ohmic heating pretreatment was applied for chicory tissue denaturation. Better solute extraction was observed after effective damage of chicory tissue diffusivity.Juice extracted from PEF assisted diffusion (PEF juice) was confirmed had higher inulin purity and less impurity in comparison to juice from conventional thermal diffusion process. The juice was purified by membrane filtration in order to investigate a simple chicory juice purification method. Since it contains less impurity, dead-end filtration performance of PEF juice was significantly improved, with less membrane fouling and higher inulin purity in filtrate. However, permeate flux of membrane filtration was seriously restricted by the membrane fouling. In order to improve filtration flux, rotating disk module was introduced in this study for clarification and purification of chicory juice. Elevated shear rate of rotating disk (1500 2000 rpm) could effectively control or even eliminate membrane fouling and lead to satisfying carbohydrate transmission (98%) and desirable permeate flux even at high volume reduction ratio (10). In view of energy saving, optimization of RDM assisted chicory juice filtration was carried out and yielded optimal operation conditions to maximize average flux and minimize specific energy consumption.COMPIEGNE-BU (601592101) / SudocSudocFranceF