1. Mass transfer and aroma compounds Flavour release from food products Violaine ATHES, Cristian TRELEA october 2012 Erasmus Mundus Master Course FIPDes Food Innovation & Product Design

2. Small volatile molecules (MM<300g/mol), which partial pressure at atmospheric pressure is sufficient to induce a stimulus on olfactive sensors. Aroma compounds Aroma compounds « Key» compounds of organoleptic quality of foods

3. Aroma compounds properties Volatile molecules: odorous Low MM Low concentrations in food products Complex medium = Interactions between aroma compounds and other constituents of the food matrix How to formulate food products (aromatisation) for a perception meeting consumers expectations?

4. Product developpement Formulation/Process Storage in packaging Consumption Unit operations - mixing - cooking - Drying - separation - … Food Matrix Headspace Packaging Food Matrix Oral cavity, Pharynx, Nasal cavity Aroma compounds transfer in processes and products From process engineering to product engineering…

5. Sensorial analysis Consumers studies Food & Aroma Formulation / Process Reverse engineering Physico-chemical properties of aroma compounds

6. Sensorial analysis “Flavour Release” in air “unit operation” Mass transfer coupled to heat and momentum transfer Food & Aroma Formulation / Process

7. “Flavour Release” in mouth “unit operation in mouth” Mass transfer coupled to heat and momentum transfer

8. Flavour release during food consumption Nasal cavity Oral cavity Pharynx Œsophagus Tracheus => Difference in behaviours of flavour release 8 Flavour release Velo-pharynx opening Olfactive receptors Step 1: in mouth

9. Nasal cavity Oral cavity Pharynx Œsophagus Tracheus 9 Step 1: in mouth Step 2: Pharynx Flavour release Olfactive receptors Flavour release during food consumption => Difference in behaviours of flavour release => Layer on pharynx mucosa

10. Atmospheric Pressure Chemical Ionisation Mass Spectrometry Air sampling Heating (100°C) Ionisation Detection (mass spectrometry) Quantification (Real time evolution of known volatile compounds concentration) IN VITRO ANALYSIS

11. IN VIVO ANALYSIS

12. EXPERIMENTAL in vitro DEVICE GAZ Food sample Flow air Flow air + aroma API- MS Atmospheric pressure ionisation - mass spectrometer Calibration C gas time (min) Each volatile compound Constant temperature t = 0 “Headspace” IN VITRO

13. GAS LIQUID Interface Concentration Dg=0 C(t=0) C ’(t=0) x Partition EQUILIBRIUM : initial condition in the case of a closed packaging

14. Homogeneous LIQUID Convection (kl) Convection (kg) C(t) C’(x,t) Concentration Partition+Transfer Interface GAS Dg Dg+C(t)Dg DYNAMIC DILUTION of GAS PHASE Opening of packaging « convective» model : liquid product

15. I. Thermodynamic properties Equilibrium PARTITION COEFFICIENT

16. GAS LIQUID Interface Concentration Dg=0 C(t=0) C ’(t=0) x Partition EQUILIBRIUM at interface

17. THERMODYNAMIC PROPERTIES Vapour – Liquid equilibrium Binary mixture : solvent (j: water ) + aroma (i) 1. Vapour phase «Ideal» : Dalton law à T : 2. Liquid phase 2.1 «Ideal» solution : Raoult law 2.2 «non ideal» solution : activity coefficient a) diluted solution : Henry law ( ) b) concentration dependance ( ) Vapour Liquid P

18. Equilibrium Partition coefficient between gas and liquid Henry Constant Vapour+Gas Liquid P T à T : THERMODYNAMIC PROPERTIES LIQUID – GAS (AIR) EQUILIBRIUM

19. THERMODYNAMIC PROPERTIES PARTITION COEFFICIENT Activity coefficient (non ideality in solution) volatility = partition coefficient Vapour Pressure (pure compounds) T xixi 01 1

20. Partition coefficients of some aroma compounds in water  Volatility variation (K) from 10 -2 to 10 -5 depending on aroma (*) Theoretical K 

21. II. Kinetic properties Mass transfer DIFFUSION CONVECTION

22. LIQUID homogeneous Convection (kl) Convection (kg) C(t) C’(x,t) Concentration Partition+Transfer Interface GAS Dg Dg+C(t)Dg Convective model

23. TRANSFER GAS-LIQUID INTERFACE CLCL CGCG GASLIQUID (A) kLkL kGkG

24. (Resistances in serie) 2.2. Mass transfer at interface liquid/air: Cg(t))( KglCl(t) ko J(t) -= Kgl1 klkg += ko 1 2.3. Mass balance in liquid J(t).A dt (t)dCl Vl. -= 2.1. Mass balance in air Dg.Cg(t)J(t).A dt dCg(t) Vg. -= Interface liquid / air : Condition initiale : Cg(t=0) = Kgl. Cl(t=0) = 0 Kgl = Cg*/Cl* Numerical solution (Matlab) Cg(t) & Cl(t) Convective model for a flavour release from a liquid in mouth ( in vitro )

25. Quantification of interactions between aroma compounds and non- volatile compounds (water, fat) ReferencesComplex food matrix Partition coefficient air / water Partition coefficient fat* / water Partition coefficient in emulsions * Data often available for organic solvent (octanol) rather than fat (LogP)

26. diacetyl  - décalactone water oil + air Guyot et al., 1996 Buttery et al., 1973 Fat content % m/m Example of result Partition coefficient prediction of aroma compounds in an emulsion : k air/emulsion

27. ANALYSE IN VIVO