Beautiful summer vacation, fresh food

Author: Li Haijie, School of Public Health, North China University of Technology

Reviewer: Yan Shengguang, Professor of School of Public Health, North China University of Technology

"A horse gallops through the dusty streets, and the concubine smiles. No one knows that lychees are coming." In ancient times, only the rich and powerful could enjoy the "freshness" of food. Today, people all over the country can enjoy lychees in early summer. With the rapid development of my country's economy, people's requirements for "eating" are also constantly increasing. In the past, we completed the transition from "eating enough" to "eating well", and now we pursue "safe" and "fresh" eating. Summer vacation is here, and summer is usually a high incidence period for foodborne diseases. Today, let's talk about the relationship between the "freshness" of food and food safety.

What are some “fresh” foods?

When it comes to the word "fresh", most people may think of the various fresh fruits, vegetables, livestock and poultry meat, and aquatic products in the supermarket. In fact, fresh food refers to primary products that have not been cooked or made, and are only sold after necessary preservation and simple arrangement on the shelves, as well as bread, cooked food and other processed products. Fresh products mainly include fruits, vegetables, meat, aquatic products, dry goods, daily necessities, cooked food and cakes. Usually, the storage conditions of fresh food are basically the same, the shelf life is relatively short, and it needs to be preserved, refrigerated, and frozen.

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Why does food need to be “fresh”?

1. The fresher the food, the better .

In life, we all know that most food is fresh, so what is the good of fresh food? The 2022 edition of the "Dietary Guidelines for Chinese Residents" recommends that vegetables be included in every meal, ensuring a daily intake of no less than 300g of fresh vegetables; eat fruit every day, ensuring a daily intake of 200-350g of fresh fruit. Why should we pay special attention to the freshness of fruits and vegetables? This is because fresh fruits and vegetables are rich in a variety of vitamins necessary for the human body. As the freshness decreases, the content of some vitamins will also be lost. Fresh fruits and vegetables are the most abundant in vitamins such as vitamin C and carotene. Vitamin C, also known as ascorbic acid, has the functions of maintaining the body's immune function, promoting the absorption of folic acid, calcium, and non-heme iron, participating in cholesterol metabolism, anti-oxidation, scavenging free radicals, and increasing resistance. Carotene is the main source of vitamin A, which mainly exists in three forms: a, β, and γ. The most important of these is β-carotene, which can activate vitamin A, prevent night blindness and vision loss, improve eye problems such as macular degeneration, cataracts, dry eyes, and eye fatigue, and also prevent dry skin, maintain and promote immune function.

2. Not fresh ≈ bad taste, unsafe .

First, unfresh food tastes worse. For example, fruits and vegetables that have been picked for too long will lose their crispness due to loss of moisture, and meat products that have been stored for too long will lose their elasticity and affect their taste. Secondly, unfresh food is more likely to decompose substances that are harmful to the human body. For example, nitrates in overnight meals and nitrites in unfresh vegetables can be converted into nitrites. Excessive intake of nitrites can easily cause food poisoning. Finally, food that has been stored for a long time can cause food poisoning even if there are no obvious changes on the surface. For example, Salmonella does not decompose protein or produce indigo. Meat products do not change in sensory properties after being contaminated by Salmonella, but they can still cause food poisoning.

If food loses its "freshness"

The process of food going from fresh to spoiled is a process in which microorganisms use the nutrients in food to grow and multiply in large quantities, which not only reduces the nutritional value of food, but also produces various metabolic products that are harmful to the human body. When food is spoiled, it can generally be seen from its appearance, which mainly includes three types of changes:

1. Color change . Green vegetables may turn yellow, and some fruits and meat may become darker or lighter. When rotting and spoiling occurs, fruits may develop brown spots, and meat may turn dark green.

2. Changes in smell . Stale fruits have a very light or even no fruity aroma. Slightly rotten fruits will produce the smell of alcohol fermentation. Stale aquatic products and livestock and poultry meat will produce a foul odor, which is the smell of the decayed products produced by the decomposition of proteins by microorganisms. Histamine, cadaverine, putrescine, etc. produced by bacteria decomposing proteins in meat and meat products not only produce bad odors, but also cause food poisoning.

3. Texture changes . Fruits or vegetables first lose moisture, the skin or surface of the fruit or vegetable becomes wrinkled, and the whole thing wilts, then softens, becomes sticky, and begins to ooze juice, or even rots in the fruit or stems and leaves. Meat products begin to soften and lose elasticity, and the meat becomes sticky when it is spoiled.

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How to keep food fresh?

With the rapid development of the logistics industry, we can eat lychees from Lingnan, apricots from Xinjiang, mutton from Inner Mongolia, and prawns from Qingdao without leaving home. Convenient transportation provides a way to eat "fresh", and advanced preservation technology provides support for locking in "freshness". This is the dual result of the country's economic and technological development. What can we do to keep the food "fresh"? First of all, we must purchase on demand and eliminate waste. According to the recommendations of the latest version of the "Dietary Guidelines for Chinese Residents 2022", we purchase food in combination with the actual situation of the family, with balanced nutrition and reasonable matching to ensure that every fresh food can contribute to our health in the best time. Secondly, in order to lock the "freshness" of food as much as possible, we must pay attention to the storage method. In order to extend the storage period of vegetables, salting is often used in northern regions, which makes the nitrite content in vegetables higher and increases the incidence of gastric cancer and esophageal cancer. Dried fruits and vegetables are prone to a large loss of water-soluble vitamins during production and processing, so short-term refrigeration and long-term freezing are often used to store food in family life. Finally, appropriate cooking methods can maximize the "freshness" of food. For example, you can reduce the loss of vitamin C in vegetables by stir-frying them quickly over high heat, and you can use stewing, braising, simmering, and boiling instead of roasting, baking, frying, and deep-frying to reduce the formation of heterocyclic amines in food.

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As the old saying goes, "A country is based on its people, people depend on food for their survival, and food safety comes first." Food safety is related to the health and life safety of all of us. The continuous innovation of food science and technology and the well-connected transportation network have enabled us to eat not only "safely" but also "freshly." This summer, safety is "fresh" to know, food is "fresh" to eat, and "fresh" to accompany, "safety" to follow.

References

[1] Liu Yan. Review of the current status and future prospects of fruit and vegetable juice beverages in China [J]. Modern Food, 2018 (06): 25-27.

[2] Sun Changhao. Nutrition and Food Hygiene[M]. Beijing: People's Medical Publishing House, 2017.