Scallions can remove the mutton smell and are effective whether eaten by sheep or humans!

Audit expert: Wang Guoyi

Postdoctoral fellow in Nutrition and Food Safety, China Agricultural University

The cold winter is the season for hotpot. Sitting in front of a steaming hotpot and eating mutton is one of the greatest pleasures of winter.

Source: CHINADAILY

When it comes to mutton, the mutton smell is unavoidable. Some people think that the mutton smell is too strong to eat, while others think it doesn’t matter. When people talk about mutton, they always say: “You go to so-and-so’s house, his mutton doesn’t smell stinky.”

So, what exactly is mutton smell? Do different types of sheep have different mutton smells?

1Why does mutton have a strong smell?

The smell of mutton refers to the stench of meat. The smell of mutton has been recorded in Zhuangzi as early as the Qing Dynasty: "Mosquitoes adore mutton, because mutton smells stinky." For thousands of years, the smell of mutton has made diners love and hate it. The reasons for its formation are complex, but the root cause is inseparable from this substance in the stomach - 4-alkyl branched-chain fatty acids.

4-Methylnonanoic acid

4-alkyl branched-chain fatty acids are a class of fatty acids with specific structural characteristics, characterized by one or more methyl (-CH3) groups at position 4 of the carbon chain (counting from the carboxyl end). In mutton, 4-methyloctanoic acid, 4-methylnonanoic acid, and 4-ethyloctanoic acid in 4-alkyl branched-chain fatty acids are the main sources of mutton odor. At the same time, 3-methylindole (skatole) and 4-methylphenol (p-cresol) produced by pasture will also increase the mutton odor.

Source: Pexels

As a special smell, the smell of mutton is related to the chemical properties of these fatty acids - the flavor threshold. The flavor threshold of these fatty acids is low, which means that it can be detected by the human olfactory system at a lower concentration.

The picture shows the flavor threshold of beer contents

Source: Beer sensory tasting

The fatty acids mentioned above often appear in the rumen of ruminants. Microorganisms convert volatile fatty acids in feed into saturated fatty acids through fermentation, and some unsaturated fatty acids are isomerized during the hydrogenation process to form branched fatty acids. These branched fatty acids are deposited in the meat and milk of ruminants, creating a unique smell.

Ruminant stomach origin丨Internet

As common ruminants, beef has a much lighter mutton smell than mutton because of the different types of fatty acids in beef and mutton. The 4-alkyl branched-chain fatty acids in mutton are branched-chain fatty acids, which are saturated fatty acids; the fatty acids in beef are mainly long-chain fatty acids, such as oleic acid and linoleic acid, which are unsaturated fatty acids. Unlike the branched-chain fatty acids in mutton, the long-chain fatty acids in beef have a milder smell during cooking and are more easily accepted by people.

2Is the smell related to the breed of sheep?

The root cause of the mutton smell is the branched-chain fatty acids in mutton. The generation and content of these branched-chain fatty acids are closely related to the type, living conditions, feeding conditions, and age of the sheep. There are many varieties of sheep in my country. The meat-type (edible) sheep can be divided into the genera of sheep and goat in biology.

Source of Sunite Sheep丨Baidu Encyclopedia

In the sheep genus, my country can basically be divided into three types: Mongolian sheep, Kazakh sheep, and Tibetan sheep. Among them, the famous small-tailed Han sheep, Tan sheep, Sunite sheep, and Chahar sheep belong to Mongolian sheep. In the goat genus, there are Guizhou Matou goats, Hainan Dongshan goats, Yimeng black goats, etc., which are almost distributed throughout the country from south to north.

Source: Sohu

Goats and sheep belong to different genera in biological classification, so what is the difference in flavor when they are served on the table? People who love to eat may find that the smell of sheep and goats is different. The fundamental reason is the difference in the content of branched-chain fatty acids in the body. When people eat goats, they basically feel that the smell of goats is stronger than that of sheep. This can be seen from the fact that in the south, goats need to be seasoned with more spices to remove the smell, while in the north, sheep can be eaten directly in hot pot.

Studies have shown that the content of 4-methyloctanoic acid in goat meat is usually higher than that in mutton, and it contains more branched-chain fatty acids than sheep. This means that if the same processing mode is adopted for the ingredients, the unique smell of branched-chain fatty acids in goat meat is easier for diners to taste than that in mutton, and the smell will be more obvious.

3 Is the mutton smell in the north obviously lighter than that in the south?

When it comes to eating mutton, we have to mention the differences between the north and the south. The south likes to make mutton stew and add more spices to remove the mutton smell. The north likes to shabu-shabu or eat with hands to enjoy the original flavor of mutton. The different ways of eating are related to the differences between mutton in the north and south. Especially the mutton in Inner Mongolia, its mutton smell is milder than that in the south. The fundamental reason for the difference in mutton smell mentioned above is the same for mutton in the north and south, and the reason for this difference comes from the different breeding conditions and habits of sheep in the north and south. Take the famous Mongolian sheep as an example. The breeding area of ​​Mongolian sheep is the northwest region, which is basically sulfur-rich grassland. The representative forage grass of sulfur-rich grassland is sand onion. The sulfide in sand onion can help decompose the branched-chain fatty acids that give mutton a strong mutton smell.

Sand onion Source: Tencent News

Experiments have shown that adding Allium mongolicum polysaccharides, Allium mongolicum and filter residue to the feed can significantly reduce the content of medium-chain mutton-flavored fatty acids in the longissimus dorsi muscle of sheep, which are important substances that cause the mutton odor.

Evaluation of mutton quality in different provinces and regions

Source: "A Preliminary Study on the Effect of Sulfur on the Odor of Lamb" by Ye Hong, Wang Xingchun, Kou Xiangning

In addition, the content of carbonyl compounds in mutton plays a decisive role in the mutton's mutton smell. When the feed lacks enough sulfur-containing organic matter to maintain metabolism, the content of carbonyl compounds in the sheep's tissues and organs increases, and the sulfur-containing amino acids decrease.

If the feed can provide enough sulfur-containing organic matter during the sheep's digestion process, the conversion process can be completed, the volatile carbonyl compounds can be reduced, and the sheep odor can be reduced or even eliminated. It can be seen that sulfur-rich land or sulfur-rich plants are very important for reducing the sheep odor.
Of course, it is not only northern sheep that have a light smell. Southern sheep also have a light smell, such as Hainan Dongshan sheep. Its meat is fat and tender, with a light smell, and it has the characteristics of northern sheep.

People's acceptance of the smell of mutton varies. Some people love that unique taste, while others like the sweetness of mutton.

Different types of sheep do have different mutton smells, but this difference is also part of the characteristics of mutton cuisine in different places. Whether it is roasted whole lamb in Inner Mongolia, hand-pulled lamb in Xinjiang, or beach lamb chops in Ningxia, in this cold winter, let us sit around the table together and enjoy the warmth and deliciousness that mutton brings us.