FOODS UNDER THE MICROSCOPE

Table of Contents:

Microscopy Cheese Yogurt Milk
Foods & bacteria Bacteria in foods Bacterial filters SEM of Bacteria
Hygiene & Microscopy Guest
Food Microscopists 2
Guest
Food Microscopists 3
Surface replication
Anaglyphs - 3-D SEM micrographs Food Structure J.
1. Dairy products
Food Structure J.
2. Fats and oils
Sticky tape
The Beauty of Milk
at High Magnification
Talking about Electron
Microscopy of Foods
History of Publishing
Food Structure
FM, FS, SFMS
Tables of Contents


Updated: March 2, 2014.

Food Structure Journal 1982-1993
Beauty of Milk
Hygiene & Microscopy
SEM of Bacteria
Talking about EM of Foods
Guest Food Microscopists 3
About the author



WHAT'S NEW?

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 micro­structure 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.


   The tables of Contents for the Food Microstructure and Food Structure journals are now also accessible at the following URL: http://www.uoguelph.ca/foodscience/dairy-science-and-technology/structure-milk-and-dairy-products/food-structure-journal-tables-content by courtesy of professor Dr. H. D. Goff at the University of Guelph, Ontario, Canada. They are also accessible at the Food Structure and Funtionality Forum. These URLs 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. It shows how to make anaglyphs using a scanning electron microscope. A practical example may be found here in Fig 4 (p. 58).

   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.

Links to Images of Microorganisms

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, SS, VU, and others.

Agrobacterium tumefaciens Alcaligenes faecalis Alcaligenes viscolactis
Bacillus brevis Bacillus cereus Arcobacter species
Bacillus megaterium Bacillus subtilis Bacillus thuringiensis
Bifidobacteria Campylobacter jejuni Clostridium difficile
Enterobacter sakazakii Erwinia carotova Escherichia coli
Enterobacter aerogenes Kefir micro-organisms Infected chicken meat
Lactobacillus acidophilus Lactobacillus bulgaricus Lactobacillus casei, L. rhamnosus
Leuconostocs Listeria monocytogenes Mycobacterium smegmatis
Saccharomyces cerevisiae Salmonella spp. Serratia marcescens
Shigella sonnei Staphylococcus aureus Root nodule bacteria
Streptococcus thermophilus Yersinia enterocolitica Compost micro-organisms

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.

Studies of food microstructure help to understand some of very important physical properties of foods such as elasticity or firmness and sensory attributes such as grittiness. Industrial production of foods and, in particular, the development of new foods can use the information collected and analyzed by food microscopists.

There are several interesting topics featured on this website as the table at the top shows. Work of several food microscopists is featured under the titles of "Guest Food Microscopists "2" and "3". Titles of scientific papers published in the Food Microstructure and Food Structure journals are also available. Some links to other sites on food microscopy are listed below:

Food Microscopy (Microscopy Handbooks) (Paperback) by O. Flint
Food Microscopy by J. G. Vaughan (Editor) (Hardcover)
Microstructural principles of food processing and engineering - by Josť Miguel Aguilera, David W. Stanley
Images from the Microscope
Books on food microscopy
Molecular Expressions Photo Gallery: Burgers 'n Fries



Disclaimer:
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.

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