Milk Protein Powder
Dairy industrials have expended a great amount of efforts during the last 20 years to build up commercial-scale processes for manufacturing dairy powders with good functional, nutrional and flavor properties suitable for use as food and animal feed ingredients. These products can be easily spray dried and the resulting proteins powders powders is that proteins can now be obtained in their native form. A schematic diagram describes the steps involved in fabrication of different dairy milk powders at an industrial level (Figure 1). A brief description of some of frequently used High Milk Protein Powders (HMPP) in dairy industry and fundamental research is given below.
Milk Protein Concentrate powders
Milk protein concentrates (MPC) are manufactured by means of membrane separation from skim milk. A well known manufactured MPC powder contains a ratio of casein to whey proteins of about 82% casein and 18% whey proteins. Caseins are present in their natural, native structure known as a micelle while whey proteins are in undamaged/undenatured form (Schuck et al., 1998). Developments in current years have resulted in MPCs of diverse compositions being produced and incorporated into a broad range of dairy products. For example, MPCs powders are often used in recombined cheese industry, and to standardise the protein content in normal milk without loss of product properties. MPC forms a white opaque dispersion of low viscosity when dispersed in water, looking very similar to milk. It is sold as a fine white powder with no odor, bland flavor and a smooth creamy mouth feel. The drying of these high proteins concentrates led to loss of functionality.
This is generally illustrated by a loss in solubility, a poor reconstitutability and hydration properties (Mulvihill and Ennis, 2003) Infact, solubility is a prerequisite for many other functional properties of proteins (viscosity, gel, foaming, emulsions…) because it enables the functionality of the protein ingredients to be fully realized (Schuck et al., 1999). The solubility of MPC powders deteriorates during storage and it could be improved by addition of monovalent salts to the ultrafiltered retentate or by removal of calcium ions earlier to drying (Augustin and Udabage, 2007). Recently, the effects of storage time and temperature on the solubility of MPC were investigated indicating that, the solubility of MPC decreased exponentially with time (Anema et al., 2006).
Native Micellar Casein powders
Native Micellar Casein (NMC) is basically a whey-protein-free milk protein concentrate powder which may be obtained by tangential membrane microfiltration of milk followed by spray drying diafiltrated retentate (Schuck et al., 1994). Due to its high protein contents this powder can be used as a relevant model of milk micelles (Famelart et al., 1999a). NMCs reveal high water holding and cheese making capacities but mediocre reconstitution properties. Moreover, the reconstitutability of these powders can be significantly improved by lowering both inlet and outlet air drying temperatures. Another solution is to enrich the concentrate with suitable soluble proteins or carbohydrates before spray drying (Schuck et al., 1994; Schuck et al., 1998).
In recent years, several studies are made to improve the rehydration properties of NMC powders with or without salt addition (Gaiani et al., 2005; Hussain et al., 2011b; Schuck et al., 2002). Indeed, by improving its rehydration properties, this powder would be able to serve as an attractive material for dairy and food industry.
Sweet Whey Powders
Sweet Whey Powders (SWP) are significant byproducts of the cheese industry. Due to their abundant functional properties, such as browning, bulking, foaming, solubility and water binding; SWPs are utilized as ingredients in different food industries. For several reasons, the food industry has yet to fully identify the potential of SWP as a food ingredient, such as whey protein concentrate (WPC) or whey protein isolate (WPI). The leading structural component of a SWP particle is lactose (amorphous or crystalline) whereas fat exists in either globular or non globular (free fat) forms. (Mulvihill and Grufferty, 1997).
Nevertheless, on the basis of processing conditions and the resulting physical state of lactose, sweet whey powder can be either hygroscopic or non not. Being a food ingredient, the qualities of final manufactured food items are numerously affected by distinctive physicochemical properties of SWP, particularly during storage and distribution (Saltmarch and Labuza, 1980). Indeed, a substantial quantity of SWP is used as a constituent of animal feeds (Banavara et al., 2003).
Whey Protein Concentrates
The manufacture of Whey Proteins Concentrates (WPC), with a protein content ranging from 35-80%, involves different phases of whey treatment: ultrafiltration/ diafiltration, concentration by evaporation under reduced pressure, and spray drying. Novel modifications and advancements have been made in recent years to obtain a better feed of WPC with less lactose and more proteins (Barba et al., 2001; Yee et al., 2007). WPC powders that contain between 35 and 55% of proteins are mainly used in animal feed manufacture (Onwulata et al., 2003; Yun et al., 2005). Commercial WPC develops off flavor during storage and this problem is one of the major factor limiting its applications in delicate formula (Javidipour and Qian, 2008; Liaw et al., 2010). Two mechanisms (lipids oxidation and Maillard browning) are supposed to be the main causes of off flavor (Whitfield, 1992).
Whey Protein Isolate powders
Whey Proteins Isolate (WPI) powders are manufactured by a stirred-bed ion exchange chromatography or microfiltration process. The ion exchange method is based on several steps: (1) the pH of whey is adjusted to have proper charge on protein molecules; (2) these molecules are adsorbed by a ion exchanger when passed through it and deproteinzed whey is eluted from the reactor; (3) the pH is readjusted to desorb the proteins and after their subsequent elution from ion exchanger, desorbed proteins are concentrated by ultrafiltration and spray-dried. Hence, resulting product contain more than 90% of proteins. In the microfiltration method (MF), lipids, protein aggregates and microbial debris are removed from whey by a microfiltration process using a suitable membrane (pores diameters 1µ m).
The MF permeate is ultrafiltrated/diafiltered, concentrated and spray dried to give final WPI powder form. WPI prepared by former method has less casein glycomacropeptide content than prepared by the latter one (Abd El-Salam et al., 2009; Morr and Ha, 1993). For the purpose of this review, only NMC and WPI powders are briefly discussed, no peculiarity will be made between WPI and WPC and both will be considered as WPI which differs only with WPC that former has higher protein and proportionality lower concentration of lactose and minerals.
Role of salts in dairy industry
The evolution of new food products that may add to attenuate issues related to public health in a positive way is a big challenge for the dairy industry. Salt played a significant role throughout human olden times. History reveals that Egyptian called it ’natron’ and the Latin term ‘salarium’ originates from salt and refers to the amount of salt that was given to the worker as his salary. In the present circumstances, salt content in food is the core focus of consideration of the world food industry especially in the dairy one. Salt is one of the most commonly and extensively used additives in dairy industry for the reason of its low cost and varied properties. It brings out particular functions for example improves taste, texture, and enhances shelf life of dairy products (Albarracin et al., 2011). Moreover, its consumption is directly related to life style, cultural, social, sensory, economical, psychological and technological factors (Purdy and Armstrong, 2007).
Sodium Chloride (NaCl) is an alimentary salt widely used in dairy industry as it is a major determinant of water activity. In addition, it acts as preservative, contributes directly to the flavor as a consequence of its effect on different biochemical mechanisms and is a source of dietary sodium (Guinee, 2004). The most important dairy product that involves the major utilization of salt is cheese. Cheeses differ in their composition of their nutrients such as proteins, lipids, carbohydrates, minerals, calcium, phosphorus, and vitamins A and B. It is one of the most nutrious food products with large variety of shapes, packaging and tastes containing 48% fat and 23-25% proteins that play an important role in the nutrition of people of all ages (Perry, 2004; Walther et al., 2008). During production process of cheese, salt is added at the end of process, after shaping and/or molding and pressing except in the case of Domiati cheese (Cruz et al., 2011).
Table of contents :
CHAPITRE 1. INTRODUCTION GENERALE ET OBJECTIFS DE L’ETUDE
Publications dans des journaux internationaux:
Conférences avec comité de lecture:
CHAPITRE II. ÉTUDE BIBLIOGRAPHIQUE
2. Milk Protein Powders
2.1. Milk Protein Concentrate powders
2.2. Native Micellar Casein powders
2.2. Sweet Whey Powders
2.3. Whey Protein Concentrates
2.4. Whey Protein Isolate powders
3. Role of salts in dairy industry
4. Milk protein powders rehydration in salt media
4.1. Effect of salt on casein powders rehydration properties
4.2. Effect of salt on whey powders rehydration properties
5. Multiscale characterization of milk proteins under salt conditions
5.1. Effect of salt on casein micelles secondary structure
5.2. Effect of salt on casein micelles size and morphology
5.3. Effect of salt on whey proteins secondary structure
5.4. Effect of salt and other microenvironments on whey proteins size and morphology
6. Use of salt in milk proteins functional properties
6.1. Effect of salts on hydration related functional properties of milk proteins
6.2. Effect of salts on interfacial related functional properties of milk proteins.
6.2.1. Emulsifying Properties
6.2.2. Foaming Properties
6.3. Effect of salts protein–protein interactions properties of milk proteins
6.3.1. Aggregation Properties
6.3.2. Gelling Properties
Synthèse et positionnement de l’étude
CHAPITRE III :MATERIEL ET METHODES
Caractérisation des poudres
1.1. COMPOSITION CHIMIQUE
1.1.1. Dosage de l’eau
1.1.2. Dosage des cendres
1.1.3. Dosage des protéines
1.1.4. Dosage du lactose
1.1.5. Dosage des lipides
1.2. CARACTERISATION PHYSIQUE
2. OBTENTION DES CINETIQUES DE REHYDRATATION AVEC LE REACTEUR INSTRUMENTE
2.1. Montage expérimental
2.3. Les sondes
2.3.1. Sonde de turbidité
2.3.2. Sonde de pH
2.4. ETALONNAGE ET VALIDATION DES SONDES
3. CARACTERISATION DES DISPERSIONS PROTEINES
3.1. Préparation des dispersions protéiques
3.2. Observations macroscopique et microscopique des dispersions protéiques
3.2.2. Microscopie électronique à transmission
3.2.4. Détermination de taille à l’échelle micrométrique: diffusion statique de la lumière
3.3. DETERMINATION DE L’HYDROPHOBICITE DE SURFACE
4. CARACTERISATION DES DISPERSIONS LORS DES RAMPES DE TEMPERATURE
4.1. Spectroscopie FTIR
4.1.1. Principe de FTIR
4.1.3. Acquisition des spectres et premiers traitements
4.1.4. Curve fitting et procédure de déconvolution
4.2. Propriétés rhéologiques
4.2.1. Principe de mesure
4.2.2. Mode opératoire
4.3. Mesures des propriétés thermiques par DSC
5. Analyse statistique des données
CHAPITRE IV : RESULTATS ET DISCUSSION
Chapitre IV. I Réhydratation de poudres de protéines laitières dans des milieux complexes
Relations entre les proprietes morphologiques et la rehydratation des poudres de lait
CHAPITRE IV. II Caractérisation multi-niveau des solutions protéiques réhydratées
Caractérisation multi-échelle de dispersions protéines contenant des caséines micellaires dans
des milieux salins
Caractérisation multi-échelle des isolats de protéines solubles dans des environnements elevés NaCl
CARACTERISATION MORPHOLOGIQUE DES AGREGATS DES PROTEINES SERIQUES INDUITS PAR
CHAPITRE IV. III PROPRIETES FONCTIONNELLES DES SOLUTIONS PROTEIQUES REHYDRATEES
Chapitré V : Conclusion générale et Perspectives
CHAPITRE VI : REFERENCES