Application: Food

A wide range of instruments used for polymer analysis and their applications

Foreign Material Analysis

Analysis of Aroma

Texture / Morphology Observation

Component Analysis

Oxidative Deterioration

Instrumental analysis is mainly conducted for quality control and research and development purposes in food analysis.

Quality control includes foreign material analysis, bacteria contamination test, agrichemical contamination test, and analysis of food content elements.

These analyses are performed for quality control at food factories and for addressing complaints, and exporting/importing.

For research and development activities for food, qualitative and quantitative analyses of components that contribute to human perception of taste and aroma are conducted as analyses to pursue tastefulness. Analyzing physical factors, such as texture, are also analyzed. Further, for the development of healthier food, the antioxidant capacity may be checked further.

Here, we introduce the food analysis examples using JEOL products, and an analysis example of plants that are closely related to food.

Foreign Material Analysis

Instruments used for foreign material analysis in food vary depending on the purpose. As the XRF and SEM-EDS of JEOL products can determine the elements of the inorganic system, they are often used in foreign material analysis in food.

Flow of foreign material analysis using analytical instruments

Application example: Analysis of foreign materials on the surface of a rice cake with SEM-EDS

Foreign materials on the surface of a rice cake were observed with SEM, and the area in the yellow box was analyzed. The result was the detection of many Fe (iron) and O (oxygen). Among the materials that can be mixed in as foreign material, a black-colored oxygen absorber containing a large amount of irons was observed and analyzed in the same way as the foreign materials. A result was obtained which was similar to that of the oxygen absorber; in terms of shape and analysis result spectrum. We could assume that the foreign materials on the surface of the rice cake were an oxygen absorber.

SEM-EDS is an instrument that allows for observation of shape by using the SEM and elemental analysis. For a typical EDS case, elements from Be (beryllium) or B (boron) to U (uranium) can be analyzed. Visual confirmation of foreign materials and pinpoint elemental analysis are the key features.

Visual confirmation of foreign materials and pinpoint elemental analysis are the key features.

Analysis of aroma component / off-flavor

Mass spectrometry (MS) x Sensory Test (Sniffing)

Sniffing-GC-MS is an instrument combining a sniffing analysis method (a sensory evaluation method) and MS (mass spectrometry) of components separated with GC simultaneously. By separating components emitted from the sample by GC, followed by sniffing of each component as well as the MS analysis at the same time, the results can be linked to each other. Simultaneous measurement of a sensory index of aroma and identification of chemical substances can estimate the substances that are the source of specific off-flavors.

Application example: Analysis of the off-flavor of the wrapping of picked Chinese cabbage with sniffing GC-MS

Here is an attempt to identify off-flavor components, generated from a wrapping of commercial-pickled Chinese cabbage, using sniffing-GC-MS. Aromas that were separated with the GC were sniffed sequentially, and the MS analysis results were confirmed at which odor was sniffed. As a result, we could assume that the off-flavor component was dimethyl trisulfide. Thus, by utilizing sniffing-GC-MS, the components responsible for characteristic aromas can be inferred from both the perceived aroma sniffed and the corresponding mass spectrometry analysis results.

Texture / Morphology Observation

When observing the shape of food using an electron microscope (TEM/SEM), the distribution of minerals as well as fat balls and air bubbles, can be confirmed. Soft samples, whose shapes are difficult to retain, and liquid samples can be observed by performing an appropriate pre-treatment.

μCT is the instrument to analyze the micro structure of 2D/3D inside the sample from the surface without destruction. It can perform a quantitative evaluation of particle diameter and void, etc. of components that can impact the texture.

TEM observation of liquid food

Soft or liquid specimen is frozen and fractured under high vacuum and a replica film made on the fractured surface is observed by using TEM.

TEM observation example of a single-serving creamer packet

Single-serving creamer packet

Fat globule in single-serving creamer packet

TEM observation example of oil in liquid

This is an observation example of sesame oil. The crystal structure in liquid can be observed.

Sesame oil

SEM observation of a variety of cheese containing water

Observing cheese with a scanning electron microscope (SEM) can lead to specimen deformation due to moisture loss from the vacuum environment and heat generated by electron beam irradiation. These deformations can be reduced by cooling the specimen.

Observing cooled cheese can reveal the distribution of moisture, fat globules, and mineral components, enabling the evaluation of its texture.

Mozzarella cheese

Gouda cheese

Processed cheese

Inner structure analysis example of cheese with μCT

This is the measurement example of processed cheese of different textures by using Micro Focus X-ray CT analysis system (μCT). Through data processing based on the density difference of containing components, information of low-density organic components (fat and protein) is removed, and a 3D image was constructed from the information of high density inorganic components. Based on this, we compared the existing state of inorganic salt particles. It became clear that with processed cheese A of rough texture, the inorganic salts are scattering as an aggregate of 70 to 150 µm in size. On the other hand, the processed cheese B with a smooth texture, the inorganic salt particles of about 10µm in size are scattered almost evenly.

3D distribution image and its distribution graph of high-density particles (inorganic salt particles) in processed cheese A.

3D distribution image and its distribution graph of high-density particles (inorganic salt particles) in processed cheese B.

Component Analysis

Component analysis of bonito broth with NMR

NMR is used for qualitative and quantitative analysis because of its ability to observe the nuclei in molecules directly. Since the analysis can be performed non-destructively, with the analyte in an original state, without any preparation like component separation, it can be used for comprehensive analysis as well as the so-called screening assay. The measurement result of bonito broth is shown below. The only sample preparation was making an aqueous solution.

From the spectrum pattern, it is possible to confirm the presence of amino acids, sugars, inosinic acid and guanylic acid all at once. Since the signal intensity on the NMR spectrum is proportional to the number of moles, by using a comparison of the integrated values it was found that the ratio of alanine and glutamic acid was 1:6.

The measurement time for an acquisition of the NMR spectra is a few minutes for an automated measurement. Therefore, it is possible to perform a screening assay in an analytical sample in a short amount of time.

¹H-NMR of broth solution

Oxidative deterioration/antioxidation

ESR: Evaluation of peroxide deterioration of vegetable oil

It is known that oils are susceptible to oxidative deterioration due to the presence of unsaturated fatty acids. Vegetable oils contain natural antioxidants such as Vitamin E (VE), but depending on storage conditions, oxidation can progress gradually and peroxides can accumulate, resulting in the degradation of flavor. The peroxide value (POV) method is used as an evaluation method. Here, we will introduce an application using ESR as a method to evaluate oxidative deterioration earlier.

ESR has high sensitivity and can evaluate earlier oxidative deterioration than the POV method.

Lipid peroxide is decomposed by light irradiation to produce peroxide radicals, which quickly form VE radicals (VE・) when VE coexists. ESR, which selectively detects radicals, can measure VE・ without sample pretreatment. The left figure shows an ESR spectrum obtained before light irradiation (green), in which no radicals were observed, but after irradiation, the characteristic VE・ radicals (black) were observed. The higher intensity of this signal indicates a higher oxidative degradation of the oil.

The figure on the right shows the results of evaluating samples with different mixing ratios of old and new canola oils. The VE・ and signal increased as the amount of old oil mixed increased, but no difference was observed when the same sample was evaluated using the POV method. Thus, it demonstrates that ESR can evaluate oxidative degradation earlier than the POV method due to its high sensitivity.