Solid Fat Content Analysis: TD-NMR for Fats & Oils

Solid Fat Content Analysis

A History of Collaboration between Bruker and Unilever

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Solid Fat Content Analysis with TD-NMR

As early as the 1960s, Unilever was investigating ways of analysing various fat compositions, and in the early 70s their focus shifted to liquid and solid content analysis in particular.

Methods available at the time were not suited to the small scale lab environment or the quick and precise nature of the analysis required. Dilatometry was too inaccurate. DSC (Digital Scanning Calorimetry) could only seriously be considered within a full R&D environment.

High resolution NMR, though clearly a viable method, was beyond the scale of such a single application with its relatively high cost, especially as the method needed to be applied across all Unilever fat refineries/factories around the world. Continuous wave (CW-)NMR was also tested, but was found to be too time consuming and inaccurate.

Solid Fat Content Analysis with TD-NMR

Bruker was already supplying the first NMR systems to Unilever, but for the analysis in mind Unilever and Bruker were envisioning an instrument that was compact, easy to handle and that could be operated in a standard food laboratory for determining the melting curve of fat compositions.

Such a solution would provide the ideal tool with which to create the optimum fat composition to meet customer demand, as well as offer effective control of oil and fat production.

A pioneering development led by Mr. W. Burk and Dr. B. Knüttel (Bruker BioSpin GmbH) and Dr. K. van Putte / Dr. J. van den Enden (Unilever Research Labs) was successful in fulfilling the initial need and only two years later, in 1972, the first Bruker minispec Time-Domain NMR system, the p20, was launched at an analytics exhibition in Paris.

Only a year later the system’s operation was simplified and the minispec p20i appeared in 1973. In the following years Bruker supplied many of these Solid Fat Content (SFC) Analysers to Unilever factories around the world.

Bruker minispec p20i TD-NMR

Bruker minispec p20i, introduced in 1973

The partnership developed not only the technology but also the SFC (solid fat content) calibration standards, standards still used by manufacturers today,  that form the intrinsic protocols within every Bruker SFC Analyser, helping deliver reliable results to the food industry worldwide.

Bruker minispec pc20 TD-NMR

The second half of the seventies brought microprocessor technology to the fore, and it wasn’t long before Bruker was able to revise the software, improve ergonomics and add new applications (such as the measurement of oil content in oil seeds) with its pc20 (1980) and pc120 (1983) models.

The pc20 was as an award winning system – receiving the I-R 100 Award (now the R&D 100) soon after its market introduction.

Droplet Size Distribution of Water in Oil Emulsions

The successful partnership was revitalised in the mid-eighties, when Dr’s J. van den Enden and J. Siebesma (Unilever Research) and Mr. W. Burk (Bruker BioSpin GmbH) worked on a new approach for analysing droplet size distribution in water in oil emulsions (such as margarines and diet spreads).

NMR is able to measure the emulsion as is – with no changes to the sample matrix, unlike other approaches such as laser light scattering, or microscopic analysis, in which the operator must press the emulsion between two glass layers for an optical inspection.

First running on pc120 systems the method involved a series of pulsed field gradient experiments followed by a mathematical calculation of the log-normal droplet size distribution. This varying of the gradient pulse lengths over a series of TD-NMR experiments is called σ-var method. The results deliver clear indication of the product’s shelf life, consumption (how it feels in the mouth), as well as the current state of the product.

Today Unilever uses this approach in all their spread-producing facilities as it normally takes just 5 to 10 minutes for a full droplet size evaluation using the σ-var method. Typically a uni-modal log-normal distribution of the droplet sizes is assumed, which is a very good approximation for typical consumer food products.

Next Generation TD-NMR for Combined Applications

Over time Bruker recognised the need to encapsulate water droplet size and solid fat content / SFC analysis within a single system, and the minispec generation was launched in 1993. This system replaced oscilloscopes forever with its large LCD display for viewing the NMR signal directly.

The first fully-PC-controlled TD-NMR system, the celebrated minispec mq-series, offered new levels of variability at its launch in 1999. Just a few years later, in 2001, oil in water emulsion analysis joined the growing list of TD-NMR applications.

Bruker minispec TD-NMR

minispec mq20 for SFC and droplet size analysis

Samples such as mayonnaise, salad dressings and soft cheese can be measured by TD-NMR, including the (sometimes) low concentrations of the droplets phase in oil in water emulsions, thanks to Bruker’s special high sensitivity probe which was capable of executing all droplet applications, including those samples with just a few percent of droplets phase.

Dr. John van Duynhoven, together with Dr. Gert-Jan Goudappel of Unilever Research Vlaardingen continued researching the method to further improve on speed, minimum level of droplets phase, number of data points for curve fitting (and thus even include bi-modal droplet size distribution fitting).

Unilever introduced a new droplet size approach in 2000 after they proved that varying the G (gradient strength) rather than varying σ (the length of the gradient pulses) was more advantageous.

Today more than 40 minispecs are in use in Unilever factories all over the world. At Unilever’s 6 global R&D centers their rapid results play a critical role in product innovation projects.

Original article published by Bruker on

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