Recently, the 2019 Food Flavor Chemistry and Sensory Evaluation and Quality Innovation Academic Forum was held in Shanghai. Numerous experts and scholars on site discussed three topics: food sensory and flavor chemistry, processing technology and quality control technology, and intelligent sensory analysis technology and application promotion, sharing many new technologies in the field of food flavor analysis.



Food research emphasizes color, aroma, and scientific instruments to assist flavor studies

Just as Chinese cuisine emphasizes the combination of color, aroma, and taste, professionals studying food should also pay attention to color, aroma, and taste. In terms of terminology, that is food flavor. With the improvement of economic level and the change of lifestyle and dietary concepts, people not only require food to have high nutritional value, but also require food to have good flavor. The former developed food nutrition, while the latter gave rise to another discipline - food flavor studies, which mainly study the chemical nature of food flavor composition and their generation pathways and methods.

Although the flavor of most foods cannot be fully described and subjective factors are mixed in when evaluating flavor, resulting in vastly different evaluations of food flavor, some flavor compounds can already be extracted and analyzed using scientific instruments to present them objectively. For example, at this forum, some companies used gas-phase ion migration spectroscopy to study food flavor and sensory evaluation, which is the application of analytical instrument technology in this field.

How to extract flavor compounds? Extraction technology shows great potential

You should know that the reason why food flavors differ is because there are differences in the composition and content of flavor substances. To understand these, chemical analysis of the substance is necessary. There is an important step before this, which is to extract the substance. For example, the discovered flavor compound ben formaldehyde in the world was extracted by scientists from bitter almonds and then analyzed and identified. With the continuous progress of science, the extraction technology of flavor compounds is also advancing rapidly. At present, popular extraction methods mainly include headspace sampling technology, solid-phase microextraction technology, simultaneous distillation extraction technology, stirring rod adsorption extraction technology, and supercritical fluid extraction technology.

Among them, headspace sampling technology is a relatively simple and practical method. The basic principle is to place the sample in a closed container and use a gas chromatograph to analyze the headspace gas in the container after the sample components have evaporated. This technology can also be divided into static headspace sampling technology (SHS) and dynamic headspace sampling technology (DHS). SHS technology is easy to prepare samples without the need for other reagents, and the possibility of false analysis is relatively small. It can be well applied to the analysis of meat flavor. However, if the food has poor volatility and low substance content, then this technology is not very applicable. Unlike SHS, DHS technology requires continuous blowing of the sample with inert gas until all volatile components are blown out. This method has a small sampling volume, high enrichment efficiency, minimal matrix interference, and convenient online detection, but it is also not suitable for flavor compounds with low volatility.

Solid phase microextraction technology, born in the last century, currently has a wide range of applications in the field of analytical chemistry. At first, this technology was applied to environmental chemical analysis, but now it has expanded to the field of food research. It mainly uses fused silica fiber coated with stationary phase to adsorb and enrich flavor substances in samples, and then analyzes them with gas chromatograph. Unlike the headspace sampling technique mentioned above, solid-phase microextraction technology does not use solvents, has a faster detection speed, and can also reduce the loss of flavor compounds. However, as the key to this technology lies in the adsorption effect, it is greatly influenced by the adsorption head.

Later, let's talk about the new technology currently being compared - supercritical fluid extraction technology. As early as a hundred years ago, it was discovered that supercritical fluids have solubility, but they have not been applied in production and daily life. It was not until the 1970s that gradual exploration and research began, applied in laboratories and in the extraction of some expensive products. Now, it can also replace conventional solvents to extract and separate flavor compounds from food. The advantage of this technology is that it can extract substances in an environment close to room temperature, prevent partial material pyrolysis, and also avoid pollution, ensuring the properties of the extracted substances. Of course, supercritical fluid extraction technology also has certain limitations, as the extracted material is prone to blockage during transportation.

Although these extraction techniques are different and have advantages and disadvantages, they will not destroy, produce, or mask the original flavor of the food. It is precisely because of the continuous advancement of extraction technology that food flavor research can develop towards quantification. However, due to the complex composition of food, many substances have low content or are easily volatile and destroyed, so the extraction of flavor compounds needs to be more refined and faster. In the next article, the editor will talk about how to use analytical instruments to detect these extracted flavor substances and savor the human flavor carefully.