AFM for Food Science Research
AFM can provide unique data in food science. Researchers are looking at the structure of molecules in conditions close to native conditions (e.g. gelatin, casein, xanthin polysaccharides, pectins, amylose, and 7S soya proteins). Larger structures are also being studied, such as polysaccharide gels, starch, gum, chocolate, and milk micelles.
AFM can provide high resolution images of small molecules and bigger structures. In food science, understanding the structure of foods such as chocolate can help improve the quality in terms of taste as a function of composition, additives, and processing variables. The unique ability of AFM to measure nanomechanical properties at the nanoscale can help distinguish different materials in blends. Samples can be investigated in air, at controlled humidity, or in a liquid environment. Finally, the effect of temperature can be investigated by heating or cooling the entire sample or local thermal analysis can be used to probe phase transitions at the nanoscale.
Food structure and functionality
Physico-chemical properties of food biopolymer (protein, carbohydrate polymer...)
Atomic Force Microscopy in Food Research
The application of atomic force microscopy (AFM) to food science may not seem an obvious one at first thought – after all what can a nano-technique such as AFM, more commonly associated with surface science labs, do for such an overtly macro and everyday material as food? The answer lies in the relationship between the structure of food and its function. Many of the desirable properties of the food that we enjoy rely upon nano- or microscale phenomena. In addition, the importance of structure on the nutritional impact of food is beginning to be understood both in terms of delivering nutrients to the body, and also in terms of its potential to exert protective effects against chronic diseases. In this article we will illustrate these areas using two examples of the AFM work being carried out at the Institute of Food Research (IFR) using the MFP-3D™ AFM from Asylum Research.
Interactions Between Oil Droplets Probed by Force Spectroscopy with the MFP-3D™ AFM
Understanding the interactions between the colloidal particles found in emulsions is important to a range of applications from the food and pharmaceutical industries through to oil recovery and mineral flotation. The interactions which occur between emulsion droplets are of huge importance in determining the functional properties of such systems. These interactions can be modified by the adsorption at the oil-water interface of surface-active species such as small molecule surfactants, proteins or polymers. However, the physical interactions which occur between emulsified oil droplets have traditionally been a difficult area to study, with work historically being carried out on model rigid colloidal particles. This has changed recently following the development of methods to attach oil droplets to atomic force microscope (AFM) cantilevers. These methods have demonstrated that the measurements are sensitive to the nature of the interfacial film and have allowed detailed study of the force interactions between single pairs of droplets, including recent mathematical modeling.4 In this application note we will illustrate the advantages of studying a real fluid droplet system, capturing effects in the AFM data which are unique to deformable particles with a mobile interfacial layer. All work for this note was performed with an MFP-3D-BIO™ AFM from Asylum Research.
Asylum Research Image Gallery
C. V. L. Giosafatto, P. D. Pierro, P. Gunning, A. Mackie, R. Porta, and L. Mariniello, "Characterization of Citrus pectin edible films containing transglutaminase-modified phaseolin," Carbohydr. Polym. 106, 200-208 (2014). doi:10.1016/j.carbpol.2014.02.015
A. Gromer, and A. Patrick Gunning, "Atomic Force Spectroscopy of Interactions between Oil Droplets in Emulsions," Microscopy and Analysis 25, 9-12 (2011). link to magazine
A. P. Gunning, A. R. Kirby, C. Fuell, C. Pin, L. E. Tailford, and N. Juge, "Mining the "glycocode"--exploring the spatial distribution of glycans in gastrointestinal mucin using force spectroscopy," The FASEB Journal 27, 2342-2354 (2013). doi:10.1096/fj.12-221416
S. U. Kadam, S. Pankaj, B. K. Tiwari, P. Cullen, and C. P. O'Donnell, "Development of biopolymer-based gelatin and casein films incorporating brown seaweed Ascophyllum nodosum extract," Food Packaging and Shelf Life 6, 68-74 (2015). doi:10.1016/j.fpsl.2015.09.003
D. Middendorf, A. Juadjur, U. Bindrich, and P. Mischnick, "AFM approach to study the function of PGPR's emulsifying properties in cocoa butter based suspensions," Food Structure 4, 16-26 (2015). doi:10.1016/j.foostr.2014.11.003