Foodstuffs - Various
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Salted peanut
Salted peanuts are cotyledons or Hypogaea sp, either singly or in pairs, which have been roasted in order to break down the cell structure and allow the peanut oil to spread throughout the nut. Even after roasting, remnants of the cell structure are still persistent. Within the cell (marked by arrows), small oil droplets and other organelles can be seen.
Low-temperature SEM is an ideal method of investigating cotyledons, either as a botanical material or in their treated form as a foodstuff. Application of conventional techniques results in considerable extraction of a variety of components, not least of which is lipid.
Frozen hydrated foam (‘head’) on beer
Foams are a mixed blessing to the brewing industry. During early stages of fermentation too much foam can be problematic. However, ‘head’ in the final product is an essential aesthetic to many consumers of the product.
The only available method of examining foam at high resolution is by stabilising the delicate structure through freezing. Important information about bubble size, distribution and the changes in bubble shape during drainage can be derived from frozen hydrated preparations.
When the foam is fractured, often tiny fragments of shattered bubble wall fall onto the fracture surface. Larger fragments can be tapped off, but smaller pieces (marked by arrows) ‘stick’ due to electrostatic attraction.
Bar: 200um (inset 100um)
Rehydrated mashed potato
Potato tubers consist mainly of a mass of parenchyma cells which are filled with simple striated starch grains. When potato is dehydrated its density reduces considerably and much of the cell structure is destroyed.
Bar: 20um
Butter
Butter is a complex colloidal system which is manufactured by churning dairy cream. The cream, which is an emulsion, is foamed and the emulsifiers - mainly protein - become desorbed and spread out onto the surface of the air bubbles. The fat droplets thereby lose their stability and coalesce into much larger drops.
Continued foaming brings about the collapse of the foam structure. Further churning results in the distribution of water (dispersion phase) throughout the fat (continuous phase). On average, butter contains about 82% fat. In the micrograph, water can be seen as both amorphous shaped ice crystals (marked by ‘i’) and spherical droplets (marked by arrows). In places, air bubbles are still obvious (marked by ‘a’).
Bar: 10um
Chocolate bar
Chocolate bar