Low-field NMR instrumentation offers a user-friendly and cost-effective means for assessment of water and oil droplet size measurements in food emulsions. Examples are given of major food application areas, and these are supported with validation data in terms of precision and equivalence to other methods. The NMR method gives the same results as other techniques, such as microscopy, laser diffraction and electric sensing, but with similar or better precision. NMR distinguishes itself by a simple and non-perturbing sample preparation procedure (in addition to the aforementioned advantages). For reliable results, the NMR parameters should be properly chosen and adjusted. A survey is given of experimental NMR parameters than can have an impact on the performance of water and oil droplet size determination. Copyright  2002 John Wiley & Sons, Ltd. KEYWORDS: NMR;1 H NMR; droplets; emulsion; foods; laser diffraction; microscopy INTRODUCTIONIn food research, the pressure to bring products faster to the market has become stronger, and the systems under investigation are becoming ever more complex both in structure and in chemical composition. 1 NMR spectroscopy has become an indispensable technique that can relate meso-and microstructural parameters to consumer-related features, such as shelf-life and mouthfeel.2 However, NMR is still considered an expert technique, whereas the rapid pace of product development requires understanding and/or control of food structures at the laboratory bench/kitchen table or manufacturing plant. In recent decades, low-cost and easy-to-handle benchtop NMR systems 3 have been developed which can determine phase-compositional 4 and microstructural 5 parameters of food materials. These systems operate at low field, typically 0.47 T (20 MHz for 1 H), and this poses intrinsic limitations on sensitivity and resolution. Nevertheless, these systems have gained a considerable position in food industry laboratories, with applications ranging from research and development to process and product control.The classical NMR application in the microstructural domain is the assessment of water droplet size distributions in food emulsions.6 -8 These methods are being used to explain and predict physical and microbiological stability of water-in-oil food emulsions, 9 such as margarines and low-calorie spreads. A more recent development is the assessment of oil droplet size distributions in oil-in-water systems.10 These systems also are fairly abundant as Ł Correspondence to: J. P. M. van Duynhoven, Unilever R&D Vlaardingen, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands. E-mail: john-van.duynhoven@unilever.com mayonnaises, cheese, dressings, spreads, etc. 11 Both the water and oil droplet size distribution measurements are based on the restricted diffusion of the liquid inside a droplet, a phenomenon that can be described analytically. The droplet size determination by low-field NMR has several significant advantages over other, and perhaps more obvious, methods. A summary of the typical ch...

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Synchrotron X-ray tomography reveals the evolving internal morphology of a multi-phase soft solid, ice cream, enabling time dependent quantitation.

SummaryKnowledge of the water droplet size distribution of fat spreads is necessary for the development and production of high quality microbiological safe products. Fat spreads are water-inoil emulsions. The water droplet size distribution can be determined by confocal scanning laser microscopy (CSLM) after staining the fat with Nile Red. The profiles of the nonfluorescent water droplets in the 2D images are identified and measured using image analysis. The 'true' water droplet size distribution is calculated from the distribution of the measured profile diameters using a Wicksell transformation of lognormal distributions. The influence of the fluorescent staining and CSLM parameters on the information were studied. The CSLM method was tested on fat spreads with a fat content ranging from 40% to 80%. The results were compared with those obtained by nuclear magnetic resonance spectroscopy (NMR). The distribution parameters [volume weighed geometric mean diameter ( D 3,3 ) and the standard deviation ( σ ) of the logarithm of the droplet diameter] calculated for 80% fat spreads are in good agreement with those obtained by NMR (within ± 7% relative). Small differences were found for 65% fat spreads and large differences were identified for 40% fat spreads. The precision for the determination of the D 3,3 value by CSLM is worse than that of NMR, even when three images were used to calculate this parameter [3-11% and 1-6% relative standard deviation (RSD), respectively]. The precision for the determination of exp( σ ) by CSLM is comparable or better than that of NMR (1-5% and 3-6% RSD, respectively). CSLM proved to be a reliable method for the determination of the water droplet size distribution of margarines (80% fat). The advantage of CSLM compared to NMR is that visual information is given about the water droplet size distribution in the sample.

Efficient design of multi-component food products containing dry and wet components such as biscuits with a moist fruit filling, is of growing interests for food industry. Technology is needed to prevent or reduce water migration from the moist filling to the dry porous cereal material. This can be done by using moisture barrier systems. Knowledge of the microstructure and its relation to water mobility is necessary to develop stable products. This paper describes a study that uses X-ray microtomography (μCT) for the characterisation and visualisation of the 3-D structure of crackers with different porosity, coated biscuit shells and soup inclusions. μCT was used for imaging the inner cellular structure of the cereal matrix or to analyse the integrity of moisture barriers applied on the cereal product. 3-D image analysis methods were developed to obtain quantitative information about the cellular matrix which can be used as input for simulation models for moisture migration. The developed 3-D image analysis method maps the open cellular structure onto a network (graph) representation in which the nodes correspond to the pores and the vertices to the pore-topore interconnection. The pores (nodes) have properties such as volume, surface area and location whereas the vertices have properties such as direct (open connection) and indirect (separated by a single lamella) area. To check the segmentation and network description a model for pore to pore resistance was used. The obtained results demonstrate the potential of μCT and 3-D image analysis for extracting structural information which can be used in models for the moisture penetration in a cellular bakery product

We prepared dispersions from bacterial cellulose microfibrils (CMF) of a commercial Nata de Coco source. We used an ultra-high-energy mechanical deagglomeration process that is able to disperse the CMFs from the pellicle in which they are organized in an irregular network. Because of the strong attractions between the CMFs, the dispersion remained highly heterogeneous, consisting of fiber bundles, flocs, and voids spanning tens to hundreds of micrometers depending on concentration. The size of these flocs increased with CMF concentration, the size of the bundles stayed constant, and the size of the voids decreased. The observed percolation threshold in MFC dispersions is lower than the theoretical prediction, which is accounted for by the attractive interactions in the system. Because bacterial cellulose is chemically very pure, it can be used to study the interaction of attractive and highly shape-anisotropic, semiflexible fiberlike colloidal particles.

Revealing the microstructural stability of a three-phase soft solid (ice cream) by 4D synchrotron X-ray tomography