Reprinted from zhihu
Author / Qian Cheng
What kind of special flavor substances does lard have compared to vegetable oil that makes those who like to eat lard stir-fry feel that lard stir-fry is more "fragrant"?
Let me answer this question head-on.
This question involves an area of study in flavor chemistry , lipid flavor chemistry.
First of all, everyone may have such a life experience: pig fat itself is actually not "fragrant", and the special aroma of lard is actually produced during the boiling process or the stir-frying process. This shows that in the process of lard boiling, some complex chemical reactions must have occurred, and eventually some small molecules of volatile organic compounds were generated, which were detected by our sense of smell to form a fragrance.
Kenji Watanabe and Yasushi Sato systematically studied various volatile organic compounds in lard in the 1960s and 1970s, and found that lactones (such as γ-heptane, γ-capryllactone, γ-nonolactone, etc.) played a large role in the flavor of lard.[1][2] And what is particularly interesting is that they are almost undetectable when not boiled, and increase significantly after boiling.
The two scientists speculated that it is possible that the aldehyde substances originally possessed in lard (hexanal, nonaldehyde, etc.) have undergone some chemical reaction in heating, and finally formed lactones.
In addition, there is a substance called "2,4-decadienoal" that is also closely related to the aroma emitted by various fats and oils after frying food, and this substance was also found in their research. It is therefore possible that this substance also contributes a part of the attractive aroma of lard. [3]
In addition to the research of two Japanese scientists, Hwang and Chen compared the differences in the amount of volatile organic compounds in lard using different boiling methods [4]. In the end, it was concluded that the lard, which was boiled dryly, had the highest content of volatile organic compounds, in other words, it was directly boiled without adding water, and the lard that came out was "the most fragrant".
Moreover, the refining step will lose the fragrance component to a certain extent. Therefore, if you buy those refined lard in the market and go home to cook, it is far less fragrant than the lard that you can directly take the fat pork and boil it.
One might ask, what is the use of such research other than interesting?
In fact, the use is very large.
For example, now that we know which chemical components of lard are key sources of "lard flavor", it is possible to directly combine these chemical components in the same ratio as lard to mimic the flavor of lard.
At present, many flavors in the food industry are actually obtained through this method.
(Of course, most of the flavors in the direction of lard are now reactive flavors.) But these studies can also guide the entire production process of reactive flavors, optimizing production by monitoring key flavor substances.
When we get the "lard flavor", add a little "lard flavor" to the food, it will have the flavor of lard.
Lard itself contains a lot of saturated fat, and it is not healthy to eat more. But as we all know, "true incense" is one of the three essences of human beings, and people's pursuit of more incense is endless. Replacing lard with lard flavor can not only achieve the aroma of lard, but also achieve the pursuit of health. Why not kill two birds with one stone?