1,721,536 research outputs found
Abir Mokni, Assad Sila, Ines Makhlouf, Blecker Christophe, Sabine Danthine, Hamadi Attia, Ali Bougatef, Souhail Besbes.
No full textpublication date: 2017-12-07; filing date: 201
Study of surface and techno-functional properties of proteose peptone fractions
No full textThe total proteose-peptone fractions are complex heterogeneous mixture of thermoresistant proteins of whey. The general objective of this work was to contribute to a better knowledge and understanding of surface properties and techno-functional properties (foaming and emulsifying properties) and well as setting a relationship between the different properties. In this work, PPT fractions were extracted according to a classical approach and other industrially transposable by considering respectively the skimmed UHT milk and whey protein concentrate (WPC) as raw materials. The using of such both sources allowed to highlight the fundamental differences in the composition of the extracts of PPT. This has begotten a direct impact on the surfactant properties of the PPT. It has been therefore established that these differences at interfaces can have major consequences on their techno-functional behavior. This study also made it possible to determine the contribution of components especially non-hydrophobic and hydrophobic fractions in the interfacial behavior of PPT and the influence of pH, protein concentration, source and method of extraction. The setting in relationship of properties showed the existence of some statistically significant correlations between the interfacial parameters and, foaming and emulsifying properties. It will be therefore possible to predict the behavior of techno-functional PPT from some physico-chemical parameters. Finally, this study also showed that PPT fractions can be used as techno-functional agents in various food formulations based foams or emulsions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Contribution à l’étude de la conservation des graines de grenade (Punica granatum L.) par déshydratation osmotique
No full textThe aim of this work was to create a complete conservation process of pomegranate seeds (Punica granatum L.). This process is essentially based on osmotic dehydration (OD), which was associated to freezing and air-drying process. Several parameters were studied to optimize the process such as osmotic solution (sucrose, glucose, and sucrose/glucose and date juice with sucrose added), temperature (30, 40, and 50°C) and state of the fruit (fresh and frozen). All these conditions were linked to seed proprieties (texture, structure, and colour).
The study of osmotic dehydration parameters (water loss (WL), solids gain (SG) and weight reduction (WR)) showed that most significant changes of mass transfer took place during the first 20 min of dewatering using frozen seeds, independently of temperature and sugar type. During this period, seeds water loss was estimated at 46% in sucrose, 41% in sucrose/glucose mix, 39% in date juice, and 37% in glucose. Mass transfer was slower starting from fresh fruit but led to a higher rate of WL at the end of the process. This fact can be explained by scanning electron microscopy, which showed damage of seed cell structure after freezing. This has practical consequences in terms of the modification of seeds texture. The same process also revealed a modification of seed texture and cell structure after osmotic dehydration. Using a sucrose solution and a temperature of 50°C favoured the best mass transfer.
The determination of different water fractions of seed by differential scanning calorimetry (DSC) showed that the % of frozen water decreased 3.5 times contrary the % of unfreezable water that increased 2.5 times. This favours a better seeds conservation. During osmotic dehydration, there was a non negligible leaching of natural solutes from seeds into the solution, which might have an important impact on the sensorial and nutritional value of seeds.
Using only osmotic dehydration could not maintain the stability of seeds during conservation. In fact, after the osmotic process, water activity of seeds was found to be higher than 0.9, allowing to the development of microorganisms and some undesirable reactions. As a consequence, a drying of the pomegranate seeds (during four hours) was investigated at three different temperatures (40, 50, and 60 °C) with air flow rate of 2 ms-1. Prior to the drying process, seeds were osmodehydrated in a sucrose solution (55°Brix) during 20 min at 50°C. The drying kinetics and the effects of OD and air-drying temperature on antioxidant capacity, total phenolic, colour, and texture were determined.
This work is a contribution to the study of physico-chemical properties of pomegranate seeds (Punica granatum L.) during freezing, osmotic dehydration and drying. After the global process, the pomegranate seed characteristics lead to new industrial developments
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Study of the physicochemical and technofunctional properties of vegetal creams in relation to the reconstitution conditions
No full textIn this work, an integrated approach was adopted to study vegetal creams in order to have a global understanding of their properties. This approach included: (i) the influence of fat and other ingredients of the formulation, particularly a low molecular weight surfactant, Tween 60 (ii) and the manufacturing process implemented for their preparation.
The effect of fat was investigated by adopting an original approach that consisted in studying both the thermal and structural behavior of the non-emulsified fat (NEF) and the emulsified fat (EF). This clearly demonstrated the impact of the physicochemical characteristics of fat on the physicochemical and technofunctional properties of creams. It well established that small differences in the composition of fats may have great effects on the technofunctional behavior of creams. The influence of fat on the final properties of creams was mainly marked through the crystallization and melting behaviors of fat, and through the crystalline varieties formed during maturation. The effect of temperature on the stability of creams based on the physical evolution of the fat was also highlighted.
The addition of tween 60 to the formulation significantly improved the properties of particle size, rheology, stability and whipping of creams. This improvement was the result of not only synergistic effect of surfactant molecules of buttermilk and tween 60 during emulsification but also desorption of proteins from the drop surfaces and modification of crystallization of the EF.
The study of the influence of the process showed that the choice of the emulsification method and operating parameters are important considerations in the reconstitution of creams. It was shown that it was possible to modulate the properties of creams by only modifying the process.Au cours de ce travail, une approche intégrée a été adoptée pour étudier les crèmes végétales dans le but d’avoir une compréhension globale de leurs propriétés. Cette approche a inclus aussi bien l’influence de la MG et des autres ingrédients de la formulation, particulièrement celle d’un tensioactif de faible poids moléculaire, le tween 60, que celle du procédé de fabrication mis en œuvre pour leur préparation.
L’effet de la MG a été traité en adoptant une approche originale qui à consisté à étudier à la fois le comportement thermique et structural de la MG non émulsionnée (MGNE) et de la MG émulsionnée (MGE), ce qui a permis de mettre clairement en évidence l’impact des caractéristiques physico-chimiques de la MG sur les propriétés physico-chimiques et technofonctionnelles des crèmes. Il est bien établi que de petites différences dans la composition des MG peuvent avoir de grandes répercussions dans le comportement technofonctionnel des crèmes. L’influence de la MG sur les propriétés finales des crèmes a été marquée principalement à travers le comportement de la MG en cristallisation et en fusion, et à travers les variétés cristallines formées lors de la maturation. L’effet de la température sur la stabilité des crèmes en fonction de l’évolution physique de la MG a été également mis en évidence.
L’ajout du tween 60 à la formulation améliore de façon significative les propriétés de granulométrie, de rhéologie, de stabilité et de foisonnement des crèmes. Cette amélioration des propriétés des crèmes résulte non seulement de l’effet synergique des molécules tensioactives du babeurre et celles du T60 pendant l’émulsification mais aussi du déplacement des protéines des surfaces des globules et de la modification du comportement à la cristallisation de la MGE.
L’influence du procédé a montré que le choix de l’outil d’émulsification ainsi que les paramètres opératoires sont effectivement des éléments importants à considérer dans la reconstitution des crèmes. Nous avons montré qu’il est possible de moduler les propriétés des crèmes en jouant uniquement sur le procédé
Propriétés physico-chimiques des fractions solubles de protéines de spiruline (Spirulina platensis)
Full text linkpeer reviewedThe aim of this study was to evaluate the physicochemical properties of Spirulina colored soluble protein fractions extracted from spray-dried Spirulina powder. Three fractions, including the blue soluble Spirulina protein, the green soluble Spirulina protein, and the total soluble Spirulina protein fractions were obtained. Investigations on their behavior at air/water interface were carried out using dynamic methods of drop volume and bubble pressure surface tension measurements. Evaluation of their monolayer films’ mechanical behavior was done via compression isotherms using Langmuir film balance. The protein contents of the fractions were 82.76, 82.29, and 74.53% for the blue, the green, and the total fractions, respectively. Surface tension decay increased with increasing concentration for all the fractions. No significant difference in surface tension decay was observed between the samples at 0.3% (w/w). Surface tension decay was less important at pH 3 for all the fractions. The total fraction and the blue fraction appeared to form more elastic films than the green fraction. The blue soluble fraction also presented the highest collapse pressure and initial expansion area
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