Measuring Droplet Size in Food Emulsions with TD-NMR
Measuring Droplet Size Distribution in Food Emulsions with TD-NMR
Water-in-oil (W/O) and oil-in-water (O/W) emulsions are common in the food industry, in margarine, low fat spreads, butter, mayonnaise, salad dressing and soft cheese. Droplet size distribution (DSD) affects the taste, smell and visual appearance, as well as shelf life and spread behaviour.
TD-NMR (Time Domain NMR) is a fast, accurate and non-invasive method for measuring droplet size distribution. The Bruker minispec Droplet Size Analyser is designed specifically for this purpose, with specifications optimised for droplet size analysis. TD-NMR can be used to analyse both free and flocculated droplets, and measures individual droplet size, not just cluster size.
Blue Scientific is the official UK distributor for Bruker TD-NMR. If you have any questions or if you would like a quote, please get in touch.
Water Droplet Size in W/O Emulsions:
- Low fat spread
- Other W/O emulsions
Oil Droplet Size in O/W Emulsions:
- Salad dressing
- Soft cheese
- Other O/W emulsions
Applications in Other Industries
The minispec can also be used to analyse emulsions in other industries, such as cosmetics. A wide range of droplet sizes can be quantified, and analysis is possible even when the same molecules are present both within and outside the droplets. If you have any questions about whether it would be suitable for your application, please get in touch.
Benefits of TD-NMR
- Lowest cost per measurement compared to alternative methods
- Very fast analysis in just a few minutes
- Similar or better accuracy compared to other analytical techniques such as microscopy, laser diffraction and electric sensing
- Minimal sample preparation with no pre-treatment or dilution. The sample remains unaltered.
- Measure both W/O and O/W droplets
- Measure droplet size rather than cluster size
TD-NMR is the standard method used by Unilever for quality control of their spreads and dressings.
TD-NMR Compared to Alternative Methods
There are several techniques in common use for measuring droplet size. Unlike methods such as light microscopy, laser light scattering and electric sensing, TD-NMR requires minimal sample preparation and no dilution. The sample remains unaltered. Results are taken from the whole sample volume, and are not affected by colour or opacity.
TD-NMR is much faster than light microscopy and is not restricted to O/W emulsions as with laser light scattering. Results are much more precise than electrical sensing. TD-NMR also has the lowest cost per measurement compared to alternative methods.
How it Works
Time Domain NMR is based on the physical laws of restricted diffusion of oil or water molecules in droplet particles. Using special gradient sequences, signals from oil and water can be distinguished. This means that the droplets phase can be investigated selectively. A series of gradient experiments is performed with various pulse sequence parameters. The resulting data sets include information about droplet size distribution. Parameters of distribution functions are automatically determined by the software; in this case using log-Gaussian distribution parameters.
Data Analysis and Fitting
Results are calculated by the software. Assuming spherical droplets and a uni-modal log-Gaussian distribution, Marquardt or Simplex algorithms are used to fit the diffusion decay curve. The resulting volume weighted mean droplet diameter D50.3 and the corresponding standard deviation σ of the Gaussian distribution are automatically calculated. Full information about droplet size distribution in the emulsion is presented in a report.
Blue Scientific is the official UK distributor for Bruker TD-NMR. For quotes, demonstrations, or if you have any questions, please get in touch: