Food Materials Functionality

John R. Dutcher

University of Guelph, Guelph, Ontario, Canada N1G 2W1 and the Advanced Foods and Materials Network (AFMnet)

E-mail: dutcher@physics.uoguelph.ca

ABSTRACT

Foods have complex properties and behaviors which are determined by the subtle interplay of the interactions between the constituent components. This interplay gives rise to their complex structure and motion, varying dramatically over different length and time scales. We rely on this complexity and diversity for the different types of foods in our everyday diet. To efficiently develop foods and food products, and novel food applications such as the delivery of active functional food components, it is necessary to first obtain a detailed understanding of the complex properties of foods and food materials. Such an understanding is only possible by adopting a truly multidisciplinary approach, incorporating aspects of basic sciences such as chemistry, physics and biology as well as the applied aspects of food science and nutrition. We are using such an approach in the Advanced Foods and Materials Network, a Canadian Network of Centres of Excellence in which we study the natural science and engineering, medical science and social science aspects of advanced foods and bio-materials.

At a molecular level or nanoscale, the building blocks for foods are proteins, polysaccharides, fats and salts, and there are a variety of different possible interactions between these molecules: electrostatic attraction and repulsion, attractive van der Waals interactions, hydrogen bonding, hydrophobic interactions. The strength of these interactions depends on the environment of the molecules, which means that the arrangement and aggregation characteristics of the molecules, and therefore the resulting properties of the material, can change dramatically with changes in temperature and pH.

From a materials perspective, we can classify different foods as various forms of soft matter such as emulsions, foams, polymer networks and liquid crystals, depending on the specific self-assembly or phase separation process that gives rise to the structure. We can then use the concepts that have been developed for the study of soft materials to analyze the complex relationship between the structure, dynamics and function of foods and food materials. In particular, one can use recently-developed, sophisticated experimental and computational tools which probe the properties of soft materials on different length and time scales. One of the main goals of AFMnet is to exploit this knowledge to design and fabricate foods and food products that are responsive to various stimuli for use in, e.g., delivery of active functional food components or antimicrobials.

The wide range of sophisticated techniques that are available make it possible not only to study model systems, in which the interaction between two components of the food matrix are analyzed in detail, but also to study the properties of real food materials at real concentrations.

Our nanoscience activities within AFMnet focus on studies of the nanoscale components of bacterial biofilms and bacterial cell surfaces for use in value-added products, the development of novel cationic antimicrobial peptides, protein and peptide self-assembly on nanostructured surfaces for novel biosensing applications, the use of hydrogels for controlled release and delivery of bioactive components, and the use of prebiotic materials to deliver probiotic bacteria. These studies use complementary microscopy and scattering facilities, together with sophisticated computational techniques, to elucidate the complex properties of these systems.

As an example of the unique types of measurements that can be performed on the nanoscale, we have recently used a unique method to study emulsions (Touhami et al. 2007). Oil droplets in water are immobilized using polycarbonate filtration membranes containing holes with diameters that are comparable to the diameter of the emulsion droplet and the droplets can be imaged using atomic force microscopy (AFM) as shown in Figure 1. We have introduced protein molecules which segregate to the water-oil interface and we can use a functionalized tip on the AFM to bind to and pull on the protein molecules to measure their conformations and unfolding in “near native” conditions at the emulsion droplet surface, and this can be explored as a function of pH, ionic strength and temperature.

Reference

Touhami, A, Alexander, M, Corredig, M and Dutcher, JR . 2007 (in preparation)

Figure 1:(a) Atomic force microscopy (AFM) image of oil droplets immobilized within the pores of a polycarbonate filtration membrane. The image corresponds to an area of 3 m  3 m. (b) Line scans (height versus lateral distance) of the AFM image for the white lines indicated in part (a).