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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