Mass transfer and aroma compounds

Flavour release from food products

Violaine ATHES, Cristian TRELEA

october 2012

Erasmus Mundus Master Course FIPDesFood Innovation & Product Design

• 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

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?

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…

Sensorial analysisConsumers studies

Food & AromaFormulation / Process

Reverse engineering

Physico-chemical properties of aroma

compounds

Sensorial analysis

“Flavour Release” in air

“unit operation”Mass transfer

coupled to heat and momentum transfer

Food & AromaFormulation / Process

“Flavour Release” in mouth

“unit operation in mouth”Mass transfer

coupled to heat and momentum transfer

Flavour release during food consumptionFlavour release during food consumption

Nasal cavity

Oral cavityPharynx

ŒsophagusTracheus

=> Difference in behaviours of flavour release8

Flavour release

Velo-pharynx opening

Olfactive receptorsOlfactive receptors

Step 1: in mouth

Nasal cavity

Oral cavityPharynx

ŒsophagusTracheus

9

Step 1: in mouth

Step 2: Pharynx

Flavour release

Olfactive receptorsOlfactive receptors

Flavour release during food consumptionFlavour release during food consumption

=> Difference in behaviours of flavour release

=> Layer on pharynx mucosa

Atmospheric Pressure Chemical Ionisation Mass Spectrometry

Airsampling

Heating (100°C)

Ionisation

Detection (mass spectrometry)

Quantification (Real time evolution of known volatile compounds concentration)

IN VITRO ANALYSIS

IN VIVO ANALYSIS

EXPERIMENTAL in vitro

DEVICE

GAZ

Foodsample

Flow air

Flow air + aroma

API- MS

Atmospheric pressure ionisation - mass spectrometer

Calibration

Cgas

time (min) Each volatile compound

Constant temperature

t = 0

“Headspace”

IN VITRO

GAS

LIQUID

Interface

Concentration

Dg=0

C(t=0)

C ’(t=0)x

Partition

EQUILIBRIUM : initial condition in the case of a closed packaging

HomogeneousLIQUID

Convection (kl)

Convection (kg)

C(t)

C’( x,t)

ConcentrationPartition+Transfer

Interface

GAS

DgDg+C(t)Dg

DYNAMIC DILUTION of GAS PHASE Opening of packaging

« convective» model : liquid product

I. Thermodynamic properties

Equilibrium

PARTITION COEFFICIENT

GAS

LIQUID

Interface

Concentration

Dg=0

C(t=0)

C ’(t=0)x

Partition

EQUILIBRIUM at interface

THERMODYNAMIC PROPERTIESVapour – Liquid equilibrium

Binary mixture: solvent (j: water) + aroma (i)

1. Vapour phase

«Ideal» : Dalton law à T :

2. Liquid phase2.1 «Ideal» solution : Raoult law2.2 «non ideal» solution : activity coefficient

a) diluted solution : Henry law ( )b) concentration dependance ( )

i

i

Pi yi P .

Pi i xi Pi T ai Pi T . . ( ) . ( )0 0

Vapour

Liquid

P

• Equilibrium

• Partition coefficient between gas and liquid

Ky

x

P T

Pglig

i

i i

T

. ( )0

P x P T y Pi i i i ig

T . . ( ) .0

gazigazvapeurT PPPPP

Ky

x

P T

Pglig

i

i i

T

. ( )0

xi 0

Henry Constant

( )i

Vapour+Gas

Liquid

PT

à T :

THERMODYNAMIC PROPERTIESLIQUID – GAS (AIR) EQUILIBRIUM

THERMODYNAMIC PROPERTIESPARTITION COEFFICIENT

Activity coefficient(non ideality in solution)

Pi T0( )

i Pi T. ( )0

volatility = partition coefficient

Vapour Pressure(pure compounds)

T

i

xi0 1

1

j

Partition coefficients of some aroma compounds in water

Molecule MW (g/mol) C’

(kg/m3)

Activity coeff.

Infinite dilution in water

Vapor pressure

at 25°C (Pa)

K exp.

Water

K calc.

Water (*)

2,5-Dimethyl-pyrazine

108.14 8.37E-3 23 448 5.7E-5 6.3E-5

Diacetyl 86.09 9.61E-4 11 8 283 3.9E-4 5.7E-4

E-(2)-hexenal 98.1 5 ppm 687 390 1.6E-3 -

Acetaldehyde 44.05 1.1E-3 4 120 000 2.7E-3 2.9E-3

Menthone 154.25 8.93E-5 24 870 44.5 7.1E-3 6.9E-3

Anethole 148.2 5 ppm 63 405 4 8.2E-3 -

Ethyl acetate 88 5 E-4 12 112 66 7 E-3 5 E-3

Ethyl butyrate 116.6 5 ppm 1 116 2 300 4 E-2 -

Ethyl hexanoate 144.2 5 ppm 17 260 150 4 E-2 -

Ethyl octanoate 172.3 5 ppm 313 328 16 2 E-2 -

Dimethylsulfide 62.13 8.46E-4 208 62 980 2.5E-2 8.1E-2

Volatility variation (K) from 10-2 to 10-5 depending on aroma

(*) Theoretical

K

II. Kinetic properties

Mass transfer

• DIFFUSION

• CONVECTION

LIQUIDhomogeneous

Convection (kl)

Convection (kg)

C(t)

C’( x,t)

ConcentrationPartition+Transfer

Interface

GAS

DgDg+C(t)Dg

Convective model

TRANSFERGAS-LIQUID INTERFACE

)CC(kJ *LLLi

CL

CG

)CC(kJ G*GGi

GAS LIQUID(A)

kL

kG

*L

*G

glC

CK

Ji kO KglCL CG ( )

1 1

kO kG

KglkL

(Resistancesin 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).Adt

(t)dClVl. -=

2.1. Mass balance in air Dg.Cg(t)J(t).Adt

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)

Quantification of interactions between aroma compounds and non-volatile compounds (water, fat)

References Complex food matrix

wateri

airiwaterair

i C

Ck /

wateri

fatieaufat

i C

Ck /

Partition coefficientair / water

Partition coefficientfat* / water

producti

airiproductair

i C

Ck /

Partition coefficient in emulsions

* Data often available for organic solvent (octanol)rather than fat (LogP)

diacetyl - décalactone

water water oil+

airairair

wateri

airiwaterair

i C

Ck /

Guyot et al., 1996

wateri

fatiwaterfat

i C

Ck /

)( /

//

/

waterfatfatwater

waterairemulsionair

i

emulsioni

airiemulsionair

i

kFF

kk

C

Ck

Buttery et al., 1973

Fat content % m/mFat content % m/m

emulsionairik

/ emulsionairik

/

emulsionairik

/Example of result

Partition coefficient prediction of aroma compounds in an emulsion : k air/emulsion

ANALYSE IN VIVO