Milk powder agglomerate growth and properties in fluidized bed agglomeration

[EN] Fluidized bed agglomeration is used to produce large and porous dry agglomerates with improved instant properties. Water (or binder solution) is sprayed in the fluidized bed of particles to render their surface sticky. The agglomerate growth results from the repetition of different steps (wetting of the particle surface, particles collision and bridging, and drying) and depends on the processing conditions and product properties. In this work, skim and whole milk powders were fluidized in hot air and agglomerated by spraying water in a bench-scale batch fluidized bed. The aim was to study the impact of the sprayed water flow rate (0 5.5 g.min−1), particle load (300 400 g), initial particle size (200 350 ìm), and composition (skim whole milk) on the growth mechanisms and on the properties of the agglomerates obtained. Powder samples were regularly taken in the fluidized bed during agglomeration and characterized for the size, size distribution, and water content. Whatever the conditions tested, the size increase and the evolution of the particle size distribution during agglomeration were found to mainly depend on the relative amount of water sprayed in the particle bed. Agglomeration occurred in two stages, with first the rapid association of initial particles into intermediate structures, and second, the progressive growth of porous agglomerates. In any case, agglomeration allowed improving instant properties of the milk powder.Barkouti, A.; Turchiuli, C.; Carcel Carrión, JA.; Dumoulin, E. (2013). Milk powder agglomerate growth and properties in fluidized bed agglomeration. Dairy Science and Technology. 93(4-5):523-535. doi:10.1007/s13594-013-0132-7S523535934-5Banjac M, Stakic M, Voronjec D (1998) Kinetics of agglomeration of milk powder in a vibro-fluidized bed. Proc. 11th International Drying Symposium (IDS'98), B: 998–1005.Banjac M, Stamenić M, Lečić M, Stakić M (2009) Size distribution of agglomerates of milk powder in wet granulation process in a vibro-fluidized bed. Brazilian J Chem Eng 26:515–525Dewettinck K, Deroo L, Messens W, Huyghebaert A (1998) Agglomeration tendency during top-spray fluidized bed coating with gums. Lebensm Wiss Technol 31:576–584Forny L, Marabi A, Palzer S (2011) Wetting, disintegration and dissolution of agglomerated water soluble powders. Powder Technol 206:72–78Fries L, Dosta M, Antonyuk S, Heinrich S, Palzer S (2010) Moisture distribution in fluidized beds with liquid injection. Proc. 17th International Drying Symposium (IDS 2010), Magdeburg, Germany.Heinrich S, Blumschein J, Henneberg M, Ihlow M, Mörl L (2003) Study of dynamic multidimensional temperature and concentration distributions in liquid-sprayed fluidized beds. Chem Eng Sci 58:5135–5160Jimenez T (2007) Agglomération de particules par voie humide en lit fluidisé [Wet fluidized bed agglomeration of particles]. PhD, ENSIA, Massy, France.Jimenez T, Turchiuli C, Dumoulin E (2006) Particles agglomeration in a conical fluidized bed in relation with air temperature profiles. Chem Eng Sci 61:5954–5961Kim EH-J, Dong Chen X, Pearce D (2009) Surface composition of industrial spray-dried milk powder. J Food Eng 94:169–181Koga S, Kobayashi T, Inoue I (1989) Drying and agglomeration of skim milk powder by a vibro-fluidized bed, heat transfer. Japan Res 18:1–8Maronga SJ, Wnukowski P (1997) Establishing temperature and humidity profiles in fluidized bed particulate coating. Powder Technol 94:181–185Maronga SJ, Wnukowski P (1998) The use of humidity and temperature profiles in optimizing the size of fluidized bed in a coating process. Chem Eng Sci 37:423–432Murrieta-Pazos I, Gaiani C, Galet L, Cuq B, Desobry S, Scher J (2011) Comparative study of particle structure evolution during water sorption: skim and whole milk powders. Coll and Surf B Biointerfaces 87:1–10Neff E, Morris HAL (1968) Agglomeration of milk powder and its influence on reconstitution properties. J Dairy Sci 51:330–338Niskanen T, Yliruusi J, Niskanen M, Kontro O (1990) Granulation of potassium chloride in instrumented fluidized bed granulator—part I: effect of flow rate. Acta Pharm Fenn 99:13–22Palzer S (2011) Agglomeration of pharmaceutical, detergent, chemical and food powders—similarities and differences of materials and processes. Powder Technol 206:2–17Saad MM, Barkouti A, Rondet E, Ruiz T, Cuq B (2011) Study of agglomeration mechanisms of food powders: application to durum wheat semolina. Powder Technol 208:399–408Turchiuli C, Smail R, Dumoulin E (2012) Fluidized bed agglomeration of skim milk powder: analysis of sampling for the follow-up of agglomerate growth. Powder Technol 238:161–168Vuataz G (2002) The phase diagram of milk: a new tool for optimizing the drying process. Lait 82:485–500Waldie B, Wilkinson D, Zachra L (1987) Kinetics and mechanisms of growth in batch and continuous fluidized bed granulation. Chem Eng Sci 42:653–66

European Drying Conference -EuroDrying

Abstract: Fluidized bed agglomeration of skim milk powder by spraying water was used to produce dry agglomerates with improved instant properties. The growth of agglomerates was studied following the evolution of the particle size distribution during agglomeration under different conditions of processing. During the first minutes, initial particles (180µm) associated to form two size populations (250 and 400 µm). The smallest one disappeared quickly while the largest one increased in size until 650-700 µm at the end of experiment (30-40 min). The tested conditions corresponding to a lower final particle moisture content (6.8-7.0 % d.b.) generated the smaller agglomerates (650-640 µm)

Study of agglomeration mechanisms of food powders: application to durum wheat semolina

Contacts: fax: +33 4 9961 3076. E-mail address: [email protected] wet agglomeration of durum wheat semolina is an important stage in couscous production which contributes to the final quality of the end products (couscous grains). There is still a lack of studies in investigating the agglomeration mechanisms of durum wheat semolina. The present study aims to investigate the agglomeration mechanisms occurring during the wetting/mixing process of durum wheat semolina. This process implies the mixing of semolina with different quantities of water in low shear mixers at fixed operating speed. The wet agglomeration mechanisms promote significant changes in size and textural parameters that have been investigated. The evolution in the diameter of the agglomerated structures (nuclei, agglomerates and dough pieces) composing the bed bulk, shows a continuous growth process associated to the expansion of their internal structure. Descriptions of the internal and the external structures of these elements are investigated by scanning electron microscopy. The evolution of solid volume fraction is depicted with respect to the water content at both bed bulk scale and agglomerate scale. At the bed bulk scale, a three-stage texturing phenomenon is identified. At the agglomerate scale, the evolution of solid volume fraction can be related to the evolution of the agglomerate size. The relation between the diameter and the solid volume fraction of the agglomerates can be modeled by a power law equation and could thus indicate that the agglomeration mechanism of durum wheat semolina is a fractal formation proces