| Updated: December 14, 2011. The following sites have recently been updated: |
|
• Agrobacterium tumefaciens
• Bacillus thuringiensis • Campylobacter jejuni • Cheese • Yogurt • Talking about EM of Foods • Guest Food Microscopists 3 • Enterobacter aerogenes • Garden compost • Microscopy and Photography • About the author |
A new site on soya foods has been added with information about soybeans and miso and tofu, illustrated with three SEM micrographs.
Information on the preparation of cheese and yogurt for scanning electron microscopy has been added to the Cheese and Yogurt sites.
To answer the questions of several food microscopists concerning the retention of fat globules in milk products for electron microscopy, information on the fixation of fat has been added to the Food Microscopy site.
A new review entitled Microscopy and Hygiene has been published in infocus (The Proceedings of the Royal Microscopical Society), Issue 23 September 2011, pp. 5-32. It is illustrated with bacteria found in various environments such as the human mouth, a toothbrush and dental floss, human hands, bird droppings including those left in bird baths, animal feces, banknotes etc. Until September 2012, the article is not available online. To learn more about it, please contact the author. Ms. Marie Brown noticed that it would be useful to mention restaurants in the article because they are a very important factor in preventing pathogens from spreading among food consumers.
Another review entitled
The Beauty of Milk at High Magnification by M. Kaláb was published in the same proceedings Issue 18 June 2010, pp. 4-37, and is now available in PDF format. The author has explained why electron microscopy findings are important to dairy food manufacturers and that may protect the consumers. The article is illustrated with 22 micrographs in false colours. A transmission electron micrograph of processed cheese (at right) is shown on the cover of the issue.
A review in a similar format entitled Conventional Scanning Electron Microscopy of Bacteria was published by M. Kaláb, A. F. Yang, and Denise Chabot on pages 42-61 of the June 2008 issue of Infocus.
The tables of contents for the Food Microstructure and Food Structure journals are now also accessible at the following URL: http://www.foodsci.uoguelph.ca/dairyedu/journal2.htm
by courtesy of professor Dr. H. D. Goff at the University of Guelph,
Ontario, Canada. The new URL will be available even if this website
ceases to be functional.
Since the last updating of this site, the author
provided electron micrographs of microorganisms 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. In addition to several
examples, 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 here
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 here.
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.
Micrographs of microorganisms may be accessed from the table below. One cell is called a bacterium (e.g., This bacterium is known...), many cells are called bacteria (e.g., These bacteria are found...). Mass media (plural) often make mistakes when dealing with bacteria.
The micrographs are protected by copyright. For technical and scientific information about the images featured please contact the author.
Commercial interest in images of microorganisms should be directed to photo banks such as CMSP, PR, MS, VU, and others.
|
The author
used electron microscopy since the seventies in the past century until the middle of the nineties to
study the development of milk products such as yogurt and cheeses.
To some people, there is a mystery in the ability of milk to form various products such as sour milk, yogurt, kefir, cheeses, butter, ice cream and others. that it became very interesting to study
the ways in which such products are made. It is indeed fascinating to
follow the development of such products under the microscope, particularly because the number of the components is rather small: casein micelles, whey proteins, the milk serum salt system, and fat globules. Various micro-organisms such as bacteria and moulds are like diligent workers introduce profound changes to the entire milk or its fractions during manufacture.
Food Microscopy (Microscopy Handbooks) (Paperback)
by O. Flint
|
|
Disclaimer:
|
| Established under another URL: July 1, 1998. |
That counter has ceased to function after recording over 110,000 new visits.