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Microscopy in Food Development and Testing

The physical structure and composition impacts quality and safety

Mike May, PhD

Mike May is a freelance writer and editor living in Texas.

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When sitting down for a family meal, someone often says, “This looks good!” Although a casual diner makes an eye-level assessment, food scientists look deeper. “Microscopy is an essential tool in food science and product development,” says Hans Tromp, senior scientist at NIZO food research. “Microscopy is used to understand how ingredients work together to form a certain food structure or mouth feel.”

Microscopy can be applied to foods in many ways. “Examples of subjects of food science for which microscopy is frequently used are emulsions, novel plant-based products, and mouth-feel studies,” Tromp explains. For instance, the size and consistency of oil droplets in emulsion-based foods indicate the level of stabilization. As Tromp puts it: “Microscopy can, therefore, predict creaming on the shelf,” which is like cream coming to the top of raw milk.

In some of today’s new plant-based foods, the solubility of proteins can create a problem. For example, microscopic protein aggregates can reduce the stability of a product and its appeal to customers. As Tromp explains, “Mouthfeel is dominated by, among other factors, the droplet size in emulsions and the shape and size of fibers and aggregates.” Humans can sense particles as small as 10 micrometers.

Today’s scientists use a wide range of microscopic techniques to analyze many things. Plus, studies can consider the fate of that food in different parts of its lifecycle, from a field to a store shelf. To resolve so many features of food, many studies require multiple forms of microscopy. 

An arsenal of equipment

Any lab dedicated to the development or testing of foods likely applies various forms of imaging. As examples, Tromp notes that NIZO often uses standard, classical microscopy with contrast-enhancing techniques such as phase contrast and interference contrast. “For further contrast and observation of ingredients in different colors, confocal microscopy is used in autofluorescence mode or in combination with fluorescent staining agents highlighting certain ingredients,” he says. Electron microscopy can be used to study structures smaller than a micrometer, such as tiny parts of foods that stick to surfaces during processing, which can cause shutdowns to clean the equipment.

Making better mayonnaise

A variety of characteristics can be explored when analyzing a particular food. The shelf life of mayonnaise, for instance, depends on the oxidation of proteins and lipids. In the laboratory of biophysics at Wageningen University & Research in the Netherlands, Johannes Hohlbein, PhD, and his colleagues studied the oxidation and aggregation of low-density lipoprotein (LDL) particles, which serve as key emulsifiers in mayonnaise.¹ As Hohlbein and his colleagues noted, manufacturers struggle to reduce oxidation of various components of mayonnaise, which can reduce its shelf-life and its nutritional profile.

Microscopy is an essential tool in food science and product development.

In this work, Hohlbein’s team used two types of imaging: bright-field light microscopy and cryogenic transmission electron microscopy (cryo-TEM). When asked about these choices, Hohlbein points out that each type of microscopic technology offers benefits. “Bright field microscopy is very simple—just a lamp, an objective, and a camera,” he says. “No staining is necessary.” He and his colleagues used this form of microscopy to monitor the aggregation of LDL particles over several days with a relatively coarse resolution. 

To look more closely, the scientists switched to cryo-TEM. As Hohlbein notes, this form of microscopy is complicated, but its nanometer resolution can resolve single LDL particles. With this technique, he says, “We showed that the LDLs before aggregation have a size of around 30 nanometers that cannot be picked up with brightfield microscopy.”

So, analyzing food at a finer grain can require a more complex form of imaging. In general, the specific question about a food determines the best form of microscopy for the task.

Searching for silicon in supplements

When asking someone to name the most common nutritional supplements, silicon might not be on the list. Nonetheless, Guido Kickelbick, PhD, professor for inorganic solid state chemistry at Saarland University in Saarbrücken, Germany, and his colleagues noted: “In the human body, [silicon] is the third most abundant trace element and contributes to many biological functions.”² Those functions include strengthening bones, hair, and nails. Plus, silicon can be found in structures ranging from the aorta to the trachea and beyond. Consequently, Kickelbick’s team stated: “A silicon balance in the body is therefore most likely important for human health.”

Although silicon appears in a wide variety of foods and beverages, vendors make a range of silicon supplements. Consuming silicon, though, only makes a difference if it comes in bioavailable compounds, like silicates or orthosilicic acid. So, Kickelbick and his colleagues analyzed commercially available supplements for their silicon form and content. They examined the samples with TEM, along with various analytical techniques. When asked about this choice of microscopy, Kickelbick says, “We used TEM because it works well as a method for the silica-based materials we studied.” That’s not the case for all supplements, though. “For many organic-based supplements, one cannot use TEM, or it does not provide helpful information,” he added.

For Kickelbick, however, TEM provided just what the scientists wanted. “In our TEM study, we were interested in the general morphology of the material at the nanoscale, such as the radii of the primary particles, which we could not determine using another method,” he says. By using cryogenic TEM, they showed that freeze-drying compresses the overall structure, but the primary particles remain separated.

In a supplement, the bioavailability of silicon depends on its concentration and chemical composition, as well as the processing of the product. Determining how a person might take up silicon from a food or supplement depends on work like that performed by Kickelbick’s team.

Analysis in the field

For many foods, safety starts with the associated agricultural crops. As one example, scientists at the East China University of Science and Technology in Shanghai searched for a faster, easier way to harvest crops when the level of pesticides on the plants meets safety guidelines. First, they developed a portable NIR imager that could be taken to the fields. Next, they tested various forms of image analysis on leaves of Chinese cabbage. The kind of pesticide being analyzed impacted the best method of image analysis and the resulting accuracy. For example, analyzing NIR images with a support vector machine algorithm accurately identified trichlorfon sprayed at one gram per liter in nearly 97 percent of the tests.

As the scientists concluded, “The pesticide residue rapid detection system developed in this work offers guidance for agricultural producers on harvesting agricultural products at an appropriate time while ensuring that the pesticide residues do not exceed the national limit.”³

Given the expanse of foods, the various structural characteristics that can impact quality, and the wide range of potential contaminants, various forms of microscopic analysis are required in testing. Only a range of analytical techniques, including microscopy, can determine if food will taste good and be safe.


1. Yang, S., Takeuchi, M., Friedrich, H., et al. “Unravelling mechanisms of protein and lipid oxidation in mayonnaise at multiple length scales.” Food Chemistry, 402:134417. (2023).

2. Curto, Y., Koch, M., Kickelbick, G. “Chemical and structural comparison of different commercial food supplements for silicon uptake.” Solids, 4(1):1¬21. (2023).

3. Sun, H., Zhang, L., Ni, L., et al. “Study on rapid detection of pesticide residues in Shanghaiqing based on analyzing near-infrared microscopic images.” Sensors, 23(2), 983. (2023).