New Tools for Aroma Barrier Testing Mika Vh-Nissi T. Hjelt, M. - - PowerPoint PPT Presentation

08.03.2007 1

New Tools for Aroma Barrier Testing

Mika Vähä-Nissi

• T. Hjelt, M. Jokio, R. Kokkonen,
• J. Kukkonen, A. Mikkelson

08.03.2007 2

What is KCL?

• Located in Espoo, Finland
• Founded in 1916
• Staff 300
• Research areas:

– Fibers – Papermaking solutions – Printing surfaces – End-use environment – Composite/ packaging materials

• Owners:

08.03.2007 3

Contents of presentation

Motivation

• Motivation for barrier studies?
• Why are aromas challenging?
• How to measure aroma barrier?

Test methods used for aroma barrier studies Case: Effect of base paper and paperboard Concluding remarks

08.03.2007 4

Motivation for barrier studies?

• Need to optimize existing materials:

– Cost and environmental issues – Global business and new retailing channels – Current packaging solutions for new products

• Need to develop new materials:

– New materials emerging – true performance? – Transformation from “passive” to “active” – Packaging concepts and processes changing

08.03.2007 5

What makes aromas challenging?

• Important characteristic of flavor and foods

– Even small inbalance detrimental to food quality

• Aromas consist of volatile organic compounds

– From tens to over thousand different compounds

• No widely accepted test methods or specifications

for aroma transfer into/ through materials

• Correlation with other barrier properties at best

indicative

08.03.2007 6

Permeation methods utilizing various detectors

• For nonporous materials

(continuous flushing)

• Reaching steady-state

permeation

• Commercial systems based
• n this have existed
• Also porous substrates
• No steady-state -

concentration gradient changes

08.03.2007 7

Sorption methods

• Solubility and diffusion of single materials
• Only qualitative comparison of multilayer materials

08.03.2007 8

Test methods used for aroma barrier

1) Gravimetric method

2) Desiccator method 3) Permeation cell AromaBar

Permeation

Solubility/ diffusion Diffusion (solubility)

08.03.2007 9

Desiccator method - sorption/ desorption

Procedure:

• Samples exposed to aroma
• Allowed to desorb for specific time
• Analyzed with HS-GC or extraction

Pros:

• For aroma blends & single aromas
• Diluted concentrations

Cons:

• Porous materials more difficult
• Not suitable for coated materials

08.03.2007 10

Permeation cell – manual quasi-isostatic method

Procedure:

• Two subcells, sample between
• Samples removed manually with

gas-tight syringe and injected into CG

Pros:

• For aroma blends & single aromas
• Diluted concentrations
• For uncoated and coated

paper/ board, and polymer films

Cons:

• Manual sampling and leakages
• No temperature/ humidity control

08.03.2007 11

Sample transfer

• ven

Test cell Cell

• ven

Aromas

• Transfer from vapor contact
• Automatic gas sampling
• For uncoated and coated paper

and board, and polymer films

• Controlled temperature

and humidity

• No interfering continuous

carrier gas flows

GC Control unit GC/ FID

2 1 3

1

Sample

2 3

Tem p. m ax. 1 5 0 °C Tem p. m ax. 6 0 °C

AromaBar – improved method for barrier tests

08.03.2007 12

AromaBar vs. Permeation cell methods

Improved data quality: Concept same

• Follow concentration in

receiving cell

• Mathematical analysis to obtain

diffusion coefficients (D)

Improved repeatability

• Standard deviation for 5 tests

with LDPE coated paper ∼ 10 %

• Better control of test procedure

Improved usability Temperature/ humidity control

( ) ( )

∑

∞ = +

⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + − + − + =

2 2 2 ) 1 (

4 1 2 exp 1 2 ) 1 ( 2 2 1 ) (

n n Max

L Dt n n L L M t M π π

08.03.2007 13

One aroma compound not enough…

Aroma compounds: different structures/ polarities, representative, safe and suitable for GC analysis Stability of single compounds need special attention!

08.03.2007 14

Diluted model solutions as aroma sources

w-% %

Diluted to lower vapor concentrations in order to avoid swelling of polymer (aim relative vapor pressures ≤ 10 % ) Lower concentrations for tests at elevated temperatures

08.03.2007 15

Case

Role of base sheet in aroma barrier

• ”Base sheet has no effect on barrier!”
• PE and dispersion coated papers excellent barriers

against inert gases – w hat about arom as?

• Possible to make some barrier already on paper

and paperboard machine? If base sheet has an effect on aroma barrier:

• Diffusion coefficient calculated based on coating

thickness decreases

• Is surface or total porosity more important?

08.03.2007 16

Case

Set 1 Set 1 for Permeation cell and Desiccator tests Set 2 Set 2 for AromaBar

08.03.2007 17

Case

Analysis of coated sheets from cross-cuts

Porosity profile of base sheet and total porosity, coating thickness and thickness distribution

08.03.2007 18

Case

Base sheet decreases diffusion

Example from AromaBar tests with aroma blend

08.03.2007 19

Case

Coating thickness variation not important…

08.03.2007 20

Case

Surface rather than total porosity

• f base sheet affects diffusion

Relative D of limonene vs. base sheet porosities

Relative D (limonene) of PE coating vs. base sheet porosities

AromaBar, 100 g/ m 2 sheets

♦ Permeation cell, 80 g/ m 2 sheets

08.03.2007 21

Case

Aroma loss via solubility determined by polymer

• Determined by polymer in

contact with aroma

• Aroma compounds

compete over sorption sites

• Solubility of compounds

(carvone and d-limonene) to fibers low

08.03.2007 22

Concluding remarks

• Aromas: numerous compounds at low concentrations

with different affinities to foods and packaging materials

• New sorption and quasi-isostatic permeation test

methods for aroma vapor barrier developed

• Base sheet decreases diffusion of aroma compounds

through PE coated sheets:

– Surface rather than total porosity of base sheet important – Potential to improve barrier further (e.g. HD paper)

• Solubility of typical compounds (carvone, limonene)

into fibers low

08.03.2007 23

Thank You for Co-Authors…

E-mail: name.name@kcl.fi

08.03.2007 24

… laboratorians/ technicians who made it possible, … SUSTAINPACK EU-project for supporting part of this study, … and Borealis Polymers for providing us with polyethylenes