Utilizing Atomic Force Microscopy in Food Research

A. PATRICK GUNNING, ANDREW R. KIRBY, MARY L. PARKER, KATHRYN L. CROSS,

VICTOR J. MORRIS

December 1, 2010

What can a nano technique such as atomic force microscopy (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 micro-scale phenomena. In addition, the importance of structure on the nutritional impact of food is beginning to be understood both in terms of delivering nutrie…

Figure 2. AFM images of the cut surface of dry seeds reveal gross features such as starch granules and cell walls (right).

Figure 3. After hydration, ‘growth-ring’ ultrastructure becomes visible in the starch granules.

Figure 4. At even higher magnification, the growth rings exhibit further substructure known as ‘blocklets.’ Topography images (a,c) and phase images (b,d).

Figure 5. AFM topography image of mixed phospholipid (DPPC)-bile salt films. (a) The bright domains are caused by close packing of the aliphatic tails of DPPC into a close-packed ‘solid phase’ which stands taller than the surrounding background loosely-packed ‘liquid phase’. As more bile salt is added (b) the size of the solid-phase domains decreases.

Figure 6. (a) AFM topography image of lipase-colipase penetration into a mixed phospholipid-bile salt film. (b) Electronic zoom of the lower left region showing the clustering of the enzymes at domain boundaries.

Figure 7. Comparative AFM images of lipase-colipase penetration into a mixed DPPC phospholipid-bile salt film (a) and mixed DGDG galactolipid-bile salt film(b).