Microscopy Image Gallery

Exploration of the Month

October 1997

The end of October is celebrated by the feast of Halloween. Particularly in the USA children go out trick-or-treating, and collect large quantities of candy. Here we have a closer look at some of this seasonal booty.

Bite sized candy ... ... unwrapped

Everyday we all eat food. We may smell it or look briefly at it before we eat it (to check that it is OK to eat), but often it goes straight into our mouth without a second thought. Usually when we examine some food it is with our mouth; what does it feel like - crunchy or smooth for example, what does it taste like - salty, spicy, or nothing much at all like soggy cereals. But most of the things we eat have a microscopic texture that makes them interesting to look at under the microscope.

Slice through candy

Chocolate is made from the beans of the Theobroma Cacao   tree. To change the cocoa bean into the dark, rich, delicious substance we know as chocolate, it goes through a series of involved steps and processes.

First, the ripened cocoa beans are removed from their protective pods. Once the beans are cleaned, they are allowed to ferment naturally to bring out the characteristic chocolate flavor from the beans. Next, the beans are dried, blended, and roasted to further develop the flavor and color. During roasting, the bean's outer shell is loosened, cracked and removed; a process known as winnowing. This separates the cocoa bean shell from its center or nib. It is the nib that contains both cocoa solids (that will become chocolate) and cocoa butter. After further refining a rich chocolate with a satiny smooth texture is produced.

Close-up of Chocolate layer Close-up of Caramel Close-up of filling

In the first Image above, we see a magnified view of the chocolate layer of the candy. Next are the caramel and nougat layers at the same magnification.

In the manufacture of caramel or toffee sweetened, condensed, or evaporated milk is usually added to syrup. Fats, either butter or vegetable oil, preferably emulsified with milk are added to the mixture. Because milk and fat are present, the texture is plastic at normal temperatures (this means that it can flow, not that it can be made into plastic toys!). It is the action of heat on the milk solids and the sugar ingredients which creates the typical caramel flavour and colour. This process is therefore called caramelization.

Nougats usually do not contain milk. They are aerated by vigorously mixing a solution of egg albumin (or other similar protein) into boiled syrup; a less sticky product is obtained by mixing in some vegetable fat.

Since both of these layers contain air, they do not make very good samples to put in an electron microscope. The microscope needs a vacuum around the sample, but since the air can't easily get out of the caramel, the caramel swells up: just like popcorn :(

The chocolate, however, is much better behaved, as you can see below. The first two images show the difference between appearance of the chocolate on a freshly broken edge, and the flat surface of the bottom of the candy. Both were originally photographed at 300 times magnification (300X), The third image is at 1000X and shows some texture in the chocolate. This is the very fine chocolate particles in the candy. They are so small that, to our tongues they have only a very smooth texture.

SEM image of broken chocolate 300X SEM image of flat chocolate 300X Higher magnification 1000X

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Last Update: 12/13/97