Development of a Novel NMR Technique for Measurement of Exchange between Liquid and Solid Triglycerides Paul Smith 1, Negin Haghshenas 1, Istvan Furó 2 and Björn Bergenståhl 3. 1YKI, Institute for Surface Chemistry, Stockholm, Sweden, 2Division of Physical Chemistry, KTH, Stockholm, Sweden, 3Department 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 Chocolate shell

Bloomed Chocolate Fat-containing centre Chocolate shell Development of unsightly bloomed surface Movement of fat via gaps And cracks in 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 C 14 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 of deuterium labelled tripalmitin in MCT oil 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 with 14 C-labelled PPP

Effect of Crystal Concentration on Exchange Rate

Specific Exchange Rate Exchange Process k = k 1 and k 2 ≈ o at short times, so Which can be solved Fit to intensity decay for decay constant r

Results with 25% 2 H-PPP in the Liquid

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

Effect of Monopalmitin

Effect of Partial Glycerides

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