Formulation of Redispersible Freeze-dried Emulsions. Gladness M. Manecka

Transcription

1 Formulation of Redispersible Freeze-dried Emulsions Gladness M. Manecka 1

2 Introduction Stabilisation Destabilisation Oil Water Coalescence Flocculation Emulsifier + Homogenisation 2 Oil-in-water emulsion Water-in-oil emulsion Creaming Sedimentation

3 Lecithins Fat globules in aqueous phase Oil-in-water Alcohols Caseinates Fatty Acids 3 Air and milk fat in water Water-in-oil

4 Dry Emulsions What products? - Creamers - Instant soups - Gravies Why? - Increase shelf life - Protect the ingredients - Decrease storage and transport costs 4

5 Dry Emulsions How? Oil Water Homogenisation Primary Emulsion Secondary Emulsion A protein is generally used to get to the primary emulsion To form the second layer a polysaccharide is added The electrostatic deposition occurs at a ph where protein and polysaccharide are oppositely charged Reference: Spray drying behaviour and functionality of emulsions with β-lactoglobulin/pectin interfacial complexes, Y. Serfert, J. Schröder, A. Mescher, J. Laackmann, K. Rätzke, M.Q. Shaikh, V. Gaukel, H.-U. Moritz, H.P. Schuchmann, P. Walzel, S. Drusch, K. Schwarz, Food Hydrocolloids 31 (2013) 438e445 5

6 Dry Emulsions How? - Spray-Drying ready powder - Rotary Evaporation - Freeze-Drying/Lyophilisation Spray-drying process [ Rotary Evaporator [ 6

7 Freeze Drying Freezing Pressure (atm) Process Solid Liquid Freezing 1 atm Sublimation Gas Sublimation Desorption Water Phase Diagram Temperature ( C) 7

8 Freeze Drying How freezing affects emulsions? (1) The growing ice around the droplets forces them together leading to the formation of bigger droplets before the oil crystallises. (1) (2) Cryoprotectant: molecule capable of inhibiting or slowing down the ice crystal growth Ice Crystals (2) When growing, the ice crystals invade the oil droplets and weaken the interface which will lead to instability after rehydration. Oil droplet Reference: Factors Influencing the Freeze-Thaw Stability of Emulsions-Based Foods, B.M. Degner, C.Chung, V. Schlegel, R. Hutkins and D.J. McClements, Comprehensive Reviews in Food Science and Food Safety, Vol. 13,

9 My Work Redispersible freeze dried emulsions Maillard conjugate as emulsifier Maillard Conjugate? Protein = hydrophobicity + Sugar High temperature Controlled humidity Polysaccharide = hydrophilicity Protein Hypothesis: thickness layer comparable to the one given by a bilayered interface and a decreased sensitivity to environmental changes. 9

10 Maillard Conjugates Sodium caseinate from milk Maltodextrin or dextrin from starch Reaction 60 C 96 hours Before 79% humidity 10 After

11 Emulsions Freeze-Thaw Stability Two different observations depending on the conjugate used: - Sodium caseinate-maltodextrin phase separation and increase of the viscosity of the oil/conjugate phase - Sodium caseinate-dextrin visual stability but increase of the mean droplet size Two formulations: Oil Water Caseinate-maltodextrin conjugate Cryoprotectant Oil Water Caseinate-dextrin conjugate 11

12 Emulsions Freeze-Drying and Rehydration Droplet size distribution of emulsion (15% wt. sodium caseinate-dextrin conjugate, 20% sunflower oil, 80% water) before freeze drying and after rehydration Evolution of the viscosity with an increasing shear rate on the native emulsion and after rehydration 12

13 Emulsions Freeze-Thaw Stability with a Cryoprotectant 30% wt. sucrose Emulsion unstable after freeze-thawing Four cycles of freezing and thawing 13 Evolution of the droplet size distribution of emulsion (7.5% wt sodium caseinate-maltodextrin conjugate, 20% sunflower oil, 80% water, 30% sucrose) during freeze-thawing cycles

14 Emulsions Freeze-Drying and Rehydration Droplet size distribution of emulsion (7.5% wt. sodium caseinate-maltodextrin conjugate, 20% sunflower oil, 80% water) with or without cryoprotectant Without cryoprotectant The droplet size (D [4,3]) increased from 3μm to 114μm With cryoprotectant The droplet size (D [4,3]) increased from 23μm to 27μm 14

15 Emulsions Freeze-Drying and Rehydration Without cryoprotectant With cryoprotectant 15

16 Summary Maillard conjugates are potential emulsifiers for the stabilisation of redispersible freeze-dried emulsions Freezing is the crucial step influencing the stability of the emulsion after rehydration The reconstitution of the emulsion can be significatively improved by adding a cryoprotectant 16

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