Milk is getting harder to drink. Is it my illusion? The truth is...

Today is World Milk Day.

Milk and various dairy products are of great significance to improving the physical fitness of the people and enhancing the nutritional health of the human body. The slogan of this year's National Nutrition Week, "Reduce Oil, Increase Soybeans and Add Milk," also calls on everyone to drink more milk.

However, I often hear people sigh: "I really miss the milk I had when I was a kid. The milk I drink now has less and less milk flavor." "The milk I drank when I was a kid had a thick layer of milk skin after a while. It was very fragrant. Now it tastes like water."...

Why do I always feel that milk nowadays is not as delicious as it was when I was a child? Is it because the "childhood filter" has beautified our memories, or has milk really changed? Let's start with the taste of milk~

How does milk taste like this?

There are three main ways in which flavor substances in milk are formed:

First, feed.

The taste of milk is closely related to what the cow eats. What the cow eats can be absorbed into the blood through the digestive tract, then transferred to peripheral tissues such as the mammary gland, and finally enter the milk, affecting the taste of the milk.

For example, many studies have found that there are dozens of aromatic substances in grass. This is why many companies promote their milk by saying that the grass is lush and green and that it is “grass-fed”.

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Second, the breeding environment.

"Aromatic substances" in the environment can also be inhaled through the nose, enter the blood system through the lungs, and finally enter the milk.

Since "good" taste can enter the milk, "bad" taste can naturally enter the milk. Therefore, in order to obtain the "fragrant" taste of milk, good feed and a clean environment are required. This is also why many milk companies will highlight their dairy farms in good environments, with sunshine and bright weather.

The third is self-metabolism.

The feed that cows eat and the air they breathe enter the digestive tract, respiratory system, and blood, and go through a series of complex metabolic processes in the body to form rich flavor compounds, including fatty acids, alcohols, esters, lactones, aldehydes, ketones, phenols, ethers, sulfur-containing compounds, and terpene compounds.

Why do you feel

"The taste of milk has changed"?

There are several reasons why people feel that the taste of milk has changed and is not as good as before:

1. Bias in personal feelings and memory

People's taste memory is affected by emotions. People tend to beautify their childhood memories, thinking that things in the past were better, so they think that milk tasted better in the past.

Moreover, as people age, their sense of taste changes, and our sensitivity to certain flavors may decrease, causing milk today to not taste as good as it did when we were children.

Especially when we grow up, we eat a variety of foods, and the variety of foods we eat is getting richer and richer, especially the variety of high-sugar, high-salt, high-oil "heavy-tasting" foods, which will also affect people's perception of the natural taste of milk. Under the stimulation of various flavors, we can easily feel that the taste of milk has become lighter and less fragrant. If we are used to eating big fish and meat every day, we will also feel that simple meals are not delicious.

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2. Cow feed and feeding environment

The feeding environment and feed of dairy cows directly affect the quality and flavor of milk.

The taste of milk is closely related to what the cow eats. What the cow eats can be absorbed into the blood through the digestive tract, then transferred to peripheral tissues such as the mammary gland, and finally enter the milk, affecting the taste of the milk. Therefore, the taste of the milk will be different if the cow eats different feed.

In modern farming, in order to make dairy cows eat more nutritionally balanced food, the feed is a scientifically formulated mixed feed (including corn, soybeans, etc.) rather than traditional natural pasture, so the taste of the milk will also be different.

Needless to say, the breeding environment has changed a lot after decades of development. The environment in which we live has changed a lot, and the environment in which dairy cows live has also changed a lot, which will also affect the taste of milk.

3. Impact of production process

Changes in modern milk production technology will also affect the aroma of milk.

The first and most influential process is homogenization.

There is fat in milk, and fat is immiscible with water. Usually, the protein adsorbed on the surface of milk droplets stays quietly in the water. But fat is relatively light, so these milk droplets tend to float to the upper layer of milk, and when they float to the surface, they form a layer of milk skin. Many people think that the milk in the past was rich and fragrant, and often use "whether milk skin will form" as a basis for judgment. In fact, milk skin is formed by fat stratification.

The stratification of milk is not a good thing during processing, as it makes the milk look unbalanced and "stale". Therefore, modern industrialized milk is homogenized, which means using external force to reduce the milk particles, usually reducing the milk particles to about one-tenth of the original size, and the stratification rate is only about one-hundredth of the original. After the homogenization process, the milk usually does not stratify, but the taste will feel much lighter.

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Secondly, sterilization heat treatment will also affect the aroma of milk.

Generally speaking, pasteurization temperature is low, and the milk produced is more fragrant, which is what we often call "fresh milk"; while ultra-high temperature treated (UHT) milk, because of the high temperature, has a greater impact on the aromatic substances, so the resulting "room temperature milk" tastes lighter.

But whether it is "fresh milk" or "room temperature milk", there is not much difference in nutrition. "Fresh milk" needs to be refrigerated and is inconvenient to carry out; "room temperature milk" does not need to be refrigerated and is convenient to store and carry.

4. Impact of nutrients

The flavor substances in milk are mainly concentrated in its fat, followed by protein, lactose, etc., which also affect its flavor. Fat contains most of the flavor substances in milk. Whether the milk is fragrant and delicious has a lot to do with the fat content.

The fat content of ordinary whole milk is mostly 3.3g~3.5g/100ml, and some can reach 4.5g/100ml, which makes it taste better. Therefore, drinking whole milk will feel better, while skim milk is not as good.

Different milks have different nutritional components and naturally different tastes. The taste of dairy cows raised by individual households is usually lighter because of the different feeding environment and feed they eat, while the taste of milk from dairy cows raised on a large scale is generally better because of the higher feed and better environment.

The milk produced by different breeds of cows has different nutritional components and tastes. For example, the milk produced by the common Holstein cows is higher in protein and fat content and tastes better than the milk produced by the Jersey cows that have become increasingly popular in recent years.

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Rich milk flavor

Is the nutritional value higher?

In fact, the taste of milk cannot be completely equated with its nutritional value!

The nutrients in milk, including fat and protein, do affect the flavor of milk. However, whether it is fragrant or not is not the criterion for judging the nutritional value of milk.

In fact, the more fragrant the milk is, the better it is. For example, a lot of the flavor of milk is in the fat. Generally speaking, milk with a high fat content is more fragrant, but now everyone thinks that too much fat is not good and will make you fat.

Moreover, "fragrant and strong" can be easily changed, such as the previous Maiquer milk incident.

This milk can be regarded as an internet celebrity milk. Many people think it tastes good and has a milky flavor. Merchants are also keen to use "fragrance" as a selling point when selling it. However, on June 30, 2022, the Market Supervision Bureau of Qingyuan County, Zhejiang Province announced in the 4th Food Sampling Inspection Report of 2022 that 2 batches of pure milk produced by Maiqiu Group Co., Ltd. (hereinafter referred to as "Maiquer") were unqualified. The unqualified item was propylene glycol. It was later discovered that it was because it added flavors to the milk. Propylene glycol is a solvent for many flavors.

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Therefore, when buying milk, you don’t have to particularly pursue a strong taste.

Drinking milk can help us get rich high-quality protein and calcium. When choosing milk, you really can't just look at the milk flavor. Some milks are particularly fragrant, not necessarily the milk fragrance, but the fragrance of the essence.

The most important thing to choose the right milk is to look at the nutrition label and ingredient list.

How to choose milk?

First, look at protein, which is a particularly important nutrient in milk. According to national standards, the protein content of pure milk should be ≥2.9g/100ml, which is the bottom line. Of course, the higher the protein content, the better the milk will be in theory. Currently, the protein content of major brands of milk on the market is basically around 3.2g/100ml. There are also some milks with protein content of up to 3.6g~3.8g/100ml.

Second, look at the fat content. The milk with a good taste generally has a higher fat content. If you want a good taste, try to choose whole milk.

Third, look at the calcium content. Generally, the calcium content of milk is around 100mg/100ml, and more than 120mg/100ml can be considered high-calcium pure milk.

References

[1] Pan Minghui, Cao Hongfang, Wang Caiyun, et al. Analysis of flavor quality of typical room temperature pure milk at home and abroad [J]. Journal of Chinese Institute of Food Science and Technology, 2022(005):022.

[2] Chi Xuelu, Liu Huimin, Ye Qiaoyan, et al. Research progress in detection technology of flavor substances in milk[J]. China Dairy Industry, 2022(004):050.

[3] Yang Jiyong, Zhang Yangdong, Zheng Nan, et al. Research progress on sensory characteristics and flavor substances of milk[J]. Journal of Animal Nutrition, 2022, 34(05): 2790-2797.

[4] Guo Liya, Wu Jianxin, Zhang Xiaojian, et al. Analysis of differences in milk flavor and taste[J]. China Dairy, 2020(9):4.

[5] Chi Xuelu. Analysis and influencing factors of flavor active substances in raw milk[D]. Xinjiang Agricultural University, 2023. DOI: 10.27431/d.cnki.gxnyu.2023.000003.

Author: Ruan Guangfeng, Director of the Science and Technology Department of the Kexin Food and Nutrition Information Exchange Center

Review丨Zhang Yu, researcher/PhD, Chinese Center for Disease Control and Prevention, national health science expert