Analyzing Texture and Flavor During Same Process: An Application Note

Food knows no boundaries. As people move around the world, they bring with them their culture and favorite recipes. Food companies not only try to duplicate these recipes but also look to offer some advantages, such as meal preparation time, cooking time, cost, or some combination of these. In many cases though, the recipes aren’t quite right as the texture and flavors are slightly off.

This relates to the perceived taste of food, which is related to both the flavor of the food and as well as the texture. The human mouth is able to ascertain and describe food texture in terms of hardness, adhesiveness, cohesiveness, brittleness, elasticity, gumminess, and chewiness. These parameters can be defined using a mechanical testing machine (shown in first figure). At the same time, the flavors of food released during the chewing process are detected subjectively by the nose. Each discrete “chew” may release different types of aromatic flavors as well as different concentrations, depending on the type of food.

The mouth can detect five unique tastes, which are sweet, sour, salty, bitter, and umami (savory); however, it has been estimated the nose can detect anywhere from 10,000 to a trillion different odors. This has led research and development departments to focus more attention on the evaluation of the flavors released during chewing.

Flavor Release Evaluation

For such purposes, the EZ Test Flavor Release Evaluation Kit has been developed to evaluate the subjective texture of a food product, and simultaneously collect aromatic compounds that are released during the chewing process. The evaluation tool seals the sample, the sample holder, and plunger in a dedicated sample bag. It is able to perform the texture evaluation test in the sealed sample bag, and capture the released flavor and aroma compounds for subsequent analysis during the texture testing process.

Flavor-release measurements can be made before and after each texture test. The amount and composition of the flavors and aromas released by each “chew,” or series of “chews,” can then be compared. The flavor compounds are collected by solid-phase micro-extraction (SPME). The SPME unit is then inserted into a heated injection port of a gas chromatograph-mass spectrometry (GC-MS) where the flavors are released and analyzed.

Application Example

Texture and flavor are important factors in the taste of foods. In this application, a piece of an apple was evaluated for the flavor released during the “chewing” process. The results of flavor analysis of the apple by GC-MS are shown in second figure. The gray chromatogram shows the flavor analysis before the texture test, and the red chromatogram is after the texture test. By comparing the gray and red chromatograms, it can be seen that some peaks increased in intensity whereas others remained the same. The peaks that increased in intensity are marked with green circles above them. This indicates that some flavors were released by destroying or “chewing” the apple sarcocarp during the texture test. The increased peaks were determined to be alcohols and esters by a mass spectrum library search.

As indicated earlier, there are a number of texture characteristics that can be tested. In this example, the apple’s brittleness was tested. The third figure shows the mechanical characteristic curve of the apple by a texture test. During this test, five different “chews” of the apple were tested in different sampling positions, indicated by the five peaks. The first peak expresses the texture characteristics. The chromatograms in second figure show the cumulative aromas released during the five “chews.”

Below shows the compounds from the library search and the percent increase from the “chewing” process. The nine compounds released with the percent increase in concentration in parentheses are as follows.

1. 2-Methylbutyl acetate (96%)

2. sec-Butylcarbinol (16%)

3. Ethyl hexanoate (108%)

4. n-Hexyl acetate (130%)

5. n-Hexanol (43%)

6. n-Hexyl butyrate (202%)

7. Hexyl 2-methylbutyrate (192%)

8. 6-Methyl-5-hepten-2-ol (58%)

9. Farnesene (264%)

Looking at the first example of these compounds, the 2-Methylbutyl acetate is listed as a food and flavor ingredient according to Sigma-Aldrich, and can be purchased as an additive to foods. The second compound, sec-Butylcarbinol, can be produced during the distillation of alcohol and can be grouped with the fusel oil compounds, which are predominately C3, C4, and C5 aliphatic alcohols. n-Hexyl acetate is an additive in many foods because of its fruity odor. It is present in many fruits and alcoholic beverages and is known to be found in apples and plums. The last example compound, Farnesene, is an essential oil found on the coating of apples and is commonly used in flavoring food and drink.

The fourth figure shows a comparison of two different apples with the first (A) being firm and crispy and the second (B) being soft and juicy. This can be deduced by the sharper, larger first “chew” in the mechanical characteristic curve for apple species A. Subsequent “chews” two through five indicate apple species A to be more firm and crispy.

In addition to the different textures, the compounds released were also different. The last figure shows the compounds released in apple species B as well as the percent increase in these compounds with “chewing.” Apple species B contained two compounds: Butyl acetate and p-Allylanisol, not found in apple species A. p-Allylanisol is a natural organic, phenylpropene

Peak No.	Compound Namme	Rate of Increase (%)
1	Butyl acetate	73
2	2-Methylbutyl acetate	99
3	n-Hexyl acetate	128
4	n-Hexanol	33
5	n-Hexyl butanoate	241
6	Hexyl 2-methylbutyrate	240
7	6-Methyl-5-hepten-2-ol	49
8	p-Allylanisole	139
9	Farnesene	192

compound found in herbs and used in preparation of fragrances. In addition, compounds sec-Butylcarbinol and Ethyl hexanoate found in apple species A were not identified in apple species B. Thus, the texture and flavor of these two apples will be quite different.

Conclusion

In this application note the apple texture and flavor were determined simultaneously by a “chewing” process. It was found that apples released mostly alcohols and esters. A flavor release evaluation kit can be used as an effective tool for food development. The texture/flavor test can be performed on many different types of foods to copy that homemade cooking feel—regardless of which part of the world “home” originates.

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Dr. Clifford is the food and consumer products business unit manager at Shimadzu Scientific Instruments. He can be reached at [email protected]. Dr. Yamaki is an analytical applications development engineer at Shimadzu Corp. He can be reached at [email protected].