Development of a Novel NMR Technique for Measurement of

Exchange between Liquid and Solid Triglycerides

Paul Smith1, Negin Haghshenas1, Istvan Furó2 and Björn Bergenståhl3.

1 YKI, Institute for Surface Chemistry, Stockholm, Sweden,

2 Division of Physical Chemistry, KTH, Stockholm, Sweden,

3 Department of Food Technology, Lund University, Sweden.

Acknowledgements

• Future Technologies for Food Production (LiFT)

• Karlshamns AB

• Hans Ringblom, YKI

• Jari Alander, Karlshamns AB

• Charlotta Damberg, NMR Center, Göteborg

Exchange between Solid and Liquid Triglycerides

• Introduction– Reasons for Research– Scientific Background

• Method Development

• Results

• Conclusions

Fresh Chocolate

Fat-containing centre

Chocolateshell

Bloomed Chocolate

Fat-containing centre

Chocolateshell

Development ofunsightly bloomedsurface

Movementof fat via gapsAnd cracksin chocolate

Chocolate Bloom

• Uncontrolled recrystallisation of metastable form V () cocoa butter to stable form VI (also ).

• Facilitated by the presence of liquid oil in the system.

• Leads to a rough, grey surface comprising many small crystals

Scientific Background

• Migration of liquid molecules through the cocoa butter matrix.

• Exchange with molecules in fat crystals.• Problems in measurement arise because of

difficulties with similar fats and also equilibrium or near-equilibrium systems.

Project Objectives

• To measure the exchange between liquid and solid tripalmitin molecules at equilibrium.

• To measure the effects of temperature and additives on the process

• To determine the underpinning mechanisms

Initial Work

• Use of Radiolabelling Technique.

• Allowed measurement of exchange.

• Reproducible results.

• Complex experimental handling.

• Expensive C14 labelled chemicals required.

NMR technique

• Deuterium labelled triglycerides in liquid

• Measure difference between liquid and solid deuterium signals

• Determine proportion of change of liquid signal with time

Experimental 1

Saturated solution ofdeuterium labelledtripalmitin in MCToil

Tripalmitin crystals

Experimental 2

Initially deuterium-labelled molecules in solution, Surrounding non-labelled crystals

Experimental 3

Gradual exchange of labelled and non-labelled molecules.Labelled concentration in solution decreases

Molecular Interactions

Representation of the exchange mechanism between unlabelled and labelled PPP, on the addition of PPP crystals to oil saturated with14C-labelled PPP

Effect of Crystal Concentration on Exchange Rate

0.88

0.92

0.96

1

0 0.2 0.4 0.6 0.8 1

Time (hour)

Intensity (a. u.)

Specific Exchange Rate

PPP[ ]liquid

k1

⏐ → ⏐

k2

← ⏐ ⏐

PPP[ ]solid

Exchange Process

k = k1 and k2≈ o at short times, so

€

d 2H -PPPliquid[ ]=r ⋅ 2H -PPPliquid[ ]⋅dt

€

ln2H −PPPliquid[ ]

t2H −PPPliquid[ ]

0

⎧ ⎨ ⎩

⎫ ⎬ ⎭

=−r ⋅t

€

k=r ⋅PPP[ ]liquid

A

Which can be solved

Fit to intensity decay for decay constant r

Results with 25% 2H-PPP in the Liquid

Mass of added

1H-PPP crystals,

M (mg/ml)

r

(102/h)

τ

( )h

A

(102/ )m

Specific exchange

ratek

( /( mg h m2))

27.4 8.2 ± 0.4 8.4 ± 0.4 570 11.2 ± 0.6

26.6 7.9 ± 0.4 8.8 ± 0.5 553 11.1 ± 0.6

28.1 8.6 ± 0.7 8.1 ± 0.7 584 11.4 ± 0.9

27.9 7.8 ± 0.4 8.9 ± 0.5 580 10.4 ± 0.6

Standard deviation 0.36

Results with Different Fractions of 2H-PPP and Different Amounts of Added Crystal

Fraction of

2H-PPP in

MCT

Mass of added

1H-PPP

crystals, Ma

(mg/ml)

r

(102/h)

τ

( )h

Aa

(102/m)

Specific

exchange rate

k

(m /g (h m2))

25% 15.5 3.5 ± 0.5 19.8 ± 2.8 323 8.4 ± 1.2

25% 20.6 6.2 ± 0.3 11.2 ± 0.5 427 11.3 ± 0.6

25% 27.5 11.0 ± 0.5b

25% 33.1 8.8 ± 0.5 7.9 ± 0.6 689 9.9 ± 0.6

25% 37.0 8.6 ± 0.6 8.1 ± 0.6 768 8.7 ± 0.6

25% 41.1 9.4 ± 0.8 7.4 ± 0.6 853 8.6 ± 0.7

10% 24.6 5.9 ± 0.4 11.8 ± 0.8 511 9.0 ± 0.6

10% 29.8 7.5 ± 0.4 9.2 ± 0.5 619 9.4 ± 0.5

50% 28.5 6.9 ± 1.0 10.0 ± 1.5 591 9.1 ± 1.3

Effect of Monopalmitin

0.88

0.9

0.92

0.94

0.96

0.98

1

0 10 20 30 40 50 60

Time (minutes)

Sig

nal In

ten

sit

y 0%

1%

2%

3%

5%

Effect of Partial Glycerides

0.88

0.9

0.92

0.94

0.96

0.98

1

1.02

0 10 20 30 40 50 60

Time (minutes)

Sig

nal In

ten

sit

y

Monoolein

Diolein

Monopalmitin

Dipalmitin

Conclusions

• A new method for measurement of exchange has been developed

• Exchange is approximately 3-4 monolayers per hour.

• Partial glycerides slow the reaction with dipalmitin having a particularly large effect

Planned Further Work

• Detailed Analysis of Results

• Investigation of Different Emulsifiers