La « faillite » du ciblage monétaire en Tunisie ?

Les monétaristes ont montré que l’accélération de la masse monétaire ne ferait qu’attiser l’inflation. Leur idée a gagné en influence auprès des banques centrales, les incitant dans les années soixante-dix à s’efforcer de mieux maîtriser l’inflation en utilisant les agrégats monétaires comme les variables de leurs objectifs intermédiaires. Cependant, même si l’utilisation des cibles monétaires est répandue dans le monde entier, il n’existe pas de consensus sur la causalité entre la monnaie et les prix. Ce problème a fait l’objet d’un débat très animé entre les économistes surtout durant les trois dernières décennies caractérisées par l’innovation financière. La stratégie de ciblage de l’agrégat monétaire n’est efficace que si ce dernier, considéré comme une cible intermédiaire, possède des propriétés satisfaisantes en termes de stabilité, de contrôlabilité et du contenu en information. Dans ce papier, nous allons étudier l’efficacité de la politique d’ancrage monétaire en Tunisie en analysant les propriétés de l’agrégat M3. Les résultats montrent que le choix de cet agrégat comme un objectif intermédiaire ne semble pas être justifié

Chemistry of Camel Milk Proteins in Food Processing

Camel milk and its extracted protein fractions were found to provide various potential techno-functional properties which can be used in the food industry. This chapter summarizes existing knowledge on camel milk protein’s chemistry to explain the different reactions and their control for the major processes utilized by the modern milk processing industry. The composition and chemical properties of camel milk proteins including caseins and whey proteins are investigated. The effect of processing upon denaturation, aggregation, and destabilization of milk proteins is updated. Technological consequences of thermal processing as well as techno-functional properties of camel milk proteins are also described in different techno-functional properties including foaming, emulsifying, and gelling properties. This chapter aims to improve camel milk production and consumption worldwide not only in the arid countries and the hot regions

Characteristics of Cow Milk Proteins and the Effect of Processing on Their Allergenicity

Milk proteins are well known for their nutritional and functional properties. However, they are also members of the Big-8 food allergens including egg, fish, shellfish, soy, peanuts, wheat and tree nuts, in terms of prevalence. The most common milk allergens are casein fractions and β-lactoglobulin naturally not present in human breast milk. Thus, the examination of cow’s milk proteins as potential allergens that may cause food allergies and the identification of methods of reducing their immunogenicity are of great interest. The main objective of this chapter is to review the physico-chemical characteristics cow milk proteins as well as their studied allergenicity and immunogenicity as a function of some denatured dairy processes such as heating, high pressure, enzymatic hydrolysis and lactic acid fermentation

Techno-functional properties of dromadery milk

Le lait de dromadaire, connu pour ses propriétés nutritionnelles et ses vertus médicinales, possède aussi une bonne aptitude moussante. Sa composition protéique différente de celle du lait de vache (absence de β-lactoglobuline et taux plus élevé de caséine β) suggère l’implication de mécanismes différents pour justifier de telles propriétés moussantes. Afin d’approfondir ces mécanismes, les propriétés interfaciales et moussantes des protéines du lait de dromadaire ont été étudiées seules, en mélange ou dans leur environnement naturel en fonction de certaines conditions physico-chimiques, notamment l’impact du pH et celui de traitements thermiques. Deux barèmes différents, 70°C et 90°C pendant 30 min, ont été étudiés à pH neutre et acide afin de comprendre le rôle de chacune des dénaturations appliquées et leur impact sur les propriétés moussantes. Cette étude a été réalisée en parallèle sur le lait de vache afin de pouvoir corréler et approfondir leurs propriétés respectives.Dans la première partie de ce travail, l’α-lactalbumine et la caséine β, protéines majeures des phases solubles et colloïdales du lait de dromadaire, ont été purifiées à partir de lait frais écrémé afin de caractériser leurs propriétés moussantes respectives. L’impact du traitement thermique (70°C ou 90°C pendant 30 min) et du pH a été étudié sur leurs propriétés interfaciales et moussantes. A pH neutre, le traitement thermique améliore les propriétés moussantes de l’α-lactalbumine du lait du dromadaire contrairement aux pH acides (4,3), où ces propriétés diminuent à cause de l’agrégation des protéines, facilitée par la diminution des répulsions et par la mise en place de ponts disulfures. Par ailleurs, la baisse de pH de 7 à 5 diminue aussi les propriétés moussantes de la caséine β suite à sa moins bonne solubilité proche de son pH isoélectrique. La caséine β bovine, moins hydrophobe que la caséine β du lait de dromadaire, donne dans ces conditions une mousse plus stable dans le temps.Le deuxième volet de ce travail s’est tourné vers l’étude des systèmes protéiques du lait de dromadaire dans les fractions solubles (lactosérums doux et acides) et sous forme de caséinates de sodium, ainsi que dans différents mélanges binaires de protéines purifiées α-lactalbumine/β-caséine à différents ratios massiques. Les lactosérums acides issus du lait de dromadaire ont montré de très bonnes propriétés moussantes ainsi qu’une meilleure stabilité au cours du temps par rapport à ceux du lait de vache. Cette tensioactivité des protéines du lactosérum acide à l’interface air/eau a été conservée, même après un traitement thermique à 90°C, ce qui explique l’aptitude importante au moussage de ces lactosérums.Concernant les caséinates de sodium, ces protéines produisent le maximum de mousse à pH neutre avec une efficacité plus importante pour les caséinates de sodium du lait de dromadaire, probablement grâce aux teneurs plus importantes en caséine β, associées à la forte amphipolarité de cette caséine. La stabilité des mousses ainsi créées a été augmentée après le traitement thermique des solutions de caséinates, notamment à pH 5 pour les caséinates de sodium bovines. Ainsi, les agrégats induits par l’acidification et le chauffage s’adsorbent lentement, mais contribuent fortement au maintien du film protéique créé.L’étude du mélange binaire contenant l’α-La et la caséine β issues du lait de dromadaire a été effectuée et comparée aux protéines bovines : α-La/β-caséine et β-Lg/β-caséine. Les résultats obtenus dans ce travail indiquent que les mélanges protéiques contenant des taux plus élevés en caséine β présentent les meilleures propriétés moussantes, stabilisantes et interfaciales. Ainsi, la caséine β joue un rôle important dans la création et la stabilisation des mousses du lait de dromadaire.Camel milk proteins isolates, prior to foaming properties, were studied as a function of pH and temperature of heat treatment. The purity of the extracted camel α-lactalbumin (α-La) and β-casein was estimated by combining different analytical methods such as high pressure liquid chromatography (HPLC) and SDS-PAGE electrophoresis.The increased temperature treatment changed the foaming properties of camel α-La solution and its ability to unfold at the air/water interface. At neutral pH, heat treatment was found to improve foamability, whereas at acid pH (4.3) this property decreased. Heat treatment caused changes in α-La surface charge and free thiol group concentration, which confirmed the pronounced aggregation of heated camel α-La solution. Otherwise, the foaming and interfacial properties of extracted bovine and camel β-casein showed that at neutral pH, maximum of foam volume was achieved by both camel and bovine β-caseins. This property decreased at acid pH because of the casein precipitation and the lower surface protein coverage. Findings indicated also that varying pH affected the physicochemical properties of the bovine and camel β-casein solutions by decreasing the surface negative charge and intrinsic fluorescence. These results were more pronounced on the bovine β-casein suggesting a higher acid-sensitivity of this protein when compared to its camel counterpart.The second part of this work investigated the foaming and adsorption behavior of camel proteins mixed systems compared to bovine systems including whey fraction, sodium caseinates (Na-cas) and α-La/β-casein mixed systems at different ratios. The results showed that, acid wheys gave better foams when compared to sweet whey for both milks, with higher values for the camel whey. This behavior was explained by the proximity of the isoelectric point (pI) of whey proteins (4.9–5.2), where proteins were found to carry the lowest negative charge as confirmed by the zeta potential measurements. Unlike whey fraction, camel and bovine Na-cas exhibited lowest foaming and interfacial properties near its pI because of the casein precipitation. Whereas, created foams were more stable at pH 5 than at pH 7 especially after a heat treatment. The heat treatment of 70 °C and 90 °C during 30 min affected also the physicochemical properties of the bovine and camel Na-cas by decreasing intrinsic fluorescence confirming also the pronounced caseins precipitation at pH 5 where caseins were found to carry the lowest negative charge as found by the zeta potential measurementsMixed solutions of the two isolated camel proteins (α-La and β-casein) at different ratios (100:0; 75:25; 50:50; 25:75; 0:100) give more foam with a higher β-casein amount in all camel and bovine mixtures. Good correlation was observed with the adsorption and the interfacial rheological properties of camel and bovine protein mixtures. Thus, the proteins adsorbed layers are mainly affected by the presence of β-casein molecules, which are suggested to be probably the most abundant protein at interface and the most efficient in reducing the interfacial properties. Whereas, globular proteins such as α-La and β-Lg are involved in the protein layer composition but could not compact well at the interface to ensure foams creation and stabilization because of their rigid molecular structure.This work therefore suggests new alternatives for the production of foam from proteins derived from dromedary milk, a dairy product characterized both by a high biological value but also by interesting functional properties of its proteins, in particular their surfactant power

Inflation targeting and volatility: Panel evidence

This article studies the effect of the transition to the regime of inflation targeting on the economic performance of the country and its ability to ensure better price stability. In order to verify the performance of this passage, we examine four factors: fiscal position, trade openness, financial openness and financial depth. The results show that the state of monetary, fiscal and financial system in emerging and developed countries plays a major role in controlling the dynamics. These results also show that the adoption of inflation targeting reduces the volatility of inflation in many countries

Promising Food Ingredients: Milk Proteins

Milk, well known for its nutritional properties, has also good functional properties as foaming, emulsifying and biological activities due to proteins. Milk proteins are then considered as promising food ingredients due to their particular structural characteristics leading to various interesting properties in the industrial field. Thus, the examination of the biological activities and techno-functional properties (foaming and emulsifying properties) of some milk protein fractions revealed interesting ingredients for food industry due to their nutritional value, which is of a great scientific and industrial relevance. This chapter presented an overview of the studied functional properties of some milk proteins

Antioxidant and antibacterial activities, interfacial and emulsifying properties of the apo and holo forms of purified camel and bovine α-lactalbumin

International audienceThe antioxidant and antibacterial activities of camel and bovine α-lactalbumin (α-La) in both calcium-loaded (holo) and calcium-depleted (apo) forms were investigated and compared. Antioxidant assay showed that camel and bovine α-La exhibited significant Ferric-reducing antioxidant power (FRAP), ferrous iron-chelating activity (FCA) and antiradical activities especially in their apo form. Camel apo α-La also exhibited attractive antibacterial activities against Gram-negative bacteria (Pseudomonas aeruginosa) and against fungal pathogens species (Penicillium bilaiae, Aspergillus tamari and Aspergillus sclerotiorum). Likewise, emulsifying properties (emulsification ability (EAI) and stability (ESI) indexes) and the surface characteristics (surface hydrophobicity, ζ-potential and interfacial tension) of the α-La were assessed. Maximum EAI were found at pH 7.0, with higher EAI values for the camel apo α-La (EAI ~19.5 m2/g). This behavior was explained by its relative high surface hydrophobicity and its greater efficiency to reduce the surface tension at the oil-water interface. Furthermore, emulsions were found to be more stable at pH 7.0 compared to pH 5.0 (ESI ~50%) due to the higher electrostatic repulsive forces between oil droplets at pH 7.0 in consistence with the ζ-potential results. This study concluded that the camel apo α-La has antibacterial, antioxidant, and emulsifying properties in agricultural and food industries

Effect of different heating temperatures on foaming properties of camel milk proteins: A comparison with bovine milk proteins

International audienceThe effect of different heat-treatment temperatures (70, 80, 90 and 100 °C) on the foaming properties (foam capacity and stability) and the physicochemical characteristics (surface hydrophobicity, ζ-potential, and interfacial tension values) of camel milk proteins was investigated. Overall, the results showed that while increasing the temperature, greater foamability was measured for camel milk proteins (up to 165%). This behaviour was linked to the heat denaturation and aggregation of camel milk proteins, which led to an increase in the surface hydrophobicity and a decrease in the electronegative charge and interfacial tension. Likewise, our results indicated that the highest β-casein amount in camel milk (∼44% of total proteins) as well as its secondary structure (β-sheet conformation) and its high hydrophobicity, regulated the foaming mechanism of camel milk proteins

Foaming and adsorption behaviour of camel β-casein and α-lactalbumin mixed layers at the air/water interface.

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