Foods Under the Microscope
Two new sites (Food Structure Journal. 1. Dairy Products and Food Structure Journal. 2. Fats and Oils) have been created to bring attention to papers on the micro-structure of milk products and fats and oils, which were published more than 20 years ago. Emphasis is on papers published in the Studies of Food Microstructure and in the journal Food Microstructure which was published in 1982-1989 (Vol. 1-8) and was renamed Food Structure in 1990 (Vol. 9). Volunteers willing to review other foods such as cereals, meat products, legumes, etc. in a similar format are welcome to discuss their potential contributions with the former editor-in-chief. Another site, The History of Food Structure, presents personal reminiscences of the former Editor-in-Chief. Essential information about the journal is available in Wikipedia.
The defunct journal has now been succeeded by a new journal under the same title, Food Structure, published by Elsevier. The first issue will appear at the beginning of 2014, thus providing food scientists with a needed forum.
Since the last updating of this site, the author provided electron micrographs of micro-organisms and blood cells to other colleagues, for example, Staphylococcus epidermidis forms biofilms under simulated platelet storage conditions.
A presentation on various electron microscopy subjects includes an explanation how to calculate the magnification of a micrograph from the width of the image in micrometers or from the micrometer marker.
Fresh spinach was removed from food stores in North America in 2006 because it was contaminated with toxigenic bacteria. Also lettuce was found to have caused food poisoning - similar to some other leaf vegetables which are consumed raw. SEM shows Escherichia coli bacteria on the leaves in the Talking about electron microscopy of foods.
Some 20 years ago, when research findings were published in journals, pairs of SEM stereograms were printed on paper if there was a need to show the three-dimensional structure of the specimen. They were then examined visually using a simple optical stand, but some researchers have been able to cross their eyes and see the 3-D structures directly. This was relatively easy if the two images were properly spaced with respect to the distance between human eyes of about 68 mm. It is still possible but not as easy nowadays when micrographs are shown on monitors or projected on a screen. Yet it is sometimes useful to show the 3-D structure, particularly where minute particles are interacting with each other - not necessarily in foods, e.g., blood platelets with bacteria or bacteria with magnetic beads, etc.
Anaglyphs are pairs of stereograms within a single frame - one image is red and the other is cyan, green, or blue. They have to be viewed through (plastic) glasses of the corresponding colours. If you have them, you may find the new contribution interesting. It shows how to make anaglyphs using a scanning electron microscope.
Images of microorganisms shown in bold letters in the pink table below are available for viewing. Restoration of these sites has been slower than anticipated
One of the earlier additions to this site is a finding that a double sticky tape is not as good a mounting material as it has been believed to be. After a few days, bacteria on Nuclepore filters could not be examined again because they seemed to be obscured by some unknown material. Something oozing was through the filter...
In the past few months, the author of this site used SEM to photograph bacteria adhering to chicken intestines. There was a need to retain the mucus in which and below which the bacteria live. Ruthenium red provided better results than Alcian blue. A note and a micrograph may be found at the Foodmiblog.
Examination of rice grains and rice starch has produced interesting results particularly concerning so-called red yeast rice. The yeast in this case is Monascus purpureus. It disintegrates the rice grains to some extent and partially digests the starch granules inside. At the same time, it produces minute crystals of statins (substances known to reduce cholesterol in humans) on the rice grain surface. A note and 3 micrographs may be found at the Foodmiblog.
At present, the author is an Honorary Research Associate at Agriculture and Agri-Food Canada in Ottawa, where he provides assistance in electron microscopy to his colleagues and occasionally adds new information to his talk about food microscopy.
Is it possible to obtain SEM images of stainless steel surfaces used in the manufacture of foods? Such surfaces get into contact with a variety of food ingredients and unless they are frequently cleaned, they could become sources of food-borne pathogens. Could scratches in smooth surfaces provide hiding places for some hardened microorganisms? Although it is not possible to place large subjects into electron microscopes, it is possible to replicate surfaces of interest and examine the replicas of small surface areas. A replication procedure now added to these Web sites makes it possible to show the details of steel surfaces including bacterial contamination.
Does cryofixation of hydrated foods produce more accurate images of their structures than chemical fixation? It may, under certain conditions, which, however, are not easy to meet. Otherwise the structure of the sample may be distorted by the development of ice crystals.
You can also view images of microorganisms.
The author of this set of articles on the microstructure of foods is not a health care professional of any kind and assumes no liability for any health effect which would result from using information on the foods mentioned without personally checking first with a health specialist.
Illustrations (micrographs and diagrams) are protected by copyright.
Established under another URL: July 1, 1998.