Passing by the fresh food sections of farmers' markets and supermarkets countless times, your eyes are more likely to be drawn to the lights that emit a slightly eerie light than meat and vegetables.
This kind of lamp is called "fresh lamp" and is essentially an LED light source. At the same wattage, LED lamps use more than 80% more energy than incandescent lamps and have an average lifespan of 20 times longer[1]. In addition, LED lights produce less heat and do not accelerate the spoilage of food when used for a long time [2].
However, in June this year, the State Administration for Market Regulation (SAMR) promulgated the Measures for the Supervision and Administration of the Quality and Safety of Edible Agricultural Products Market, which explicitly banned the use of fresh lamps, and the relevant regulations came into effect on December 1[3].
What crime did the fresh lamp commit and should be "driven out and killed"?
Meat, vegetables and fruits show "two faces" at the farmers' market and at home, and the color changes from full to dull in an instant, which is the way that merchants use fresh lights to create for you.
On the one hand, the color rendering index of fresh lamps is generally low, which is easy to cover for stale ingredients and achieve shoddy results.
The color rendering index indicates how well an object's true color is restored under illumination. The International Commission on Illumination sets the color rendering index of sunlight at 100, and the rest of the light sources use it as a reference. The higher the color rendering index of the light source, the more the object will show its true texture and luster [4].
Different areas of the shopping mall have different requirements for the lighting color rendering index, among which the requirements of the ** area are the highest, and clothing stores, department stores and supermarkets need to be equipped with qualified lights
According to China's "Architectural Lighting Standards", the color rendering index of lighting fixtures in farmers' markets, supermarkets, and shops should not be lower than 80 [5]. However, before the introduction of the new regulations, the color rendering index of most fresh lamps did not meet the national standard.
During a visit by the Dinghai District Procuratorate in Zhoushan City, Zhejiang Province, in February this year, it was found that the color rendering index of fresh lamps used in some farmers' markets and supermarkets in Dinghai District was far below 80, and some even had only single digits [6].
Under the illumination of these fresh lights, the food is like "grinding skin", not only the surface is smooth and flat, but also the spots, insect eyes and other defects that are disliked by consumers are also covered up one by one. If you want to distinguish the quality of food with the naked eye under this kind of fresh light, I am afraid that you must become a detective and not let go of any clues on the surface of the food.
When you go to the market at night, not only can you not see the flaws on the surface of the ingredients with the help of daylight, but the ingredients you buy are the least fresh of the day.
In addition to texture and shine, the color of the food can also affect your judgment, which gave new inspiration to the lamp manufacturer, and thus, the infamous "color-changing lamp" was born.
When different colors of light hit the food, it will be reflected and appear different colors in people's eyes, which is the premise of the "discoloration" of the food. LED lights have a wide range of color temperatures, which can emit both warm reddish and cool blue light [7], so they can meet the needs of merchants to "color" different foods.
Taking pork as an example, with the extension of time, the oxidation of pork will produce methemoglobin, and the meat color will gradually darken or even brown [8].
Many restaurants will also use warm yellow tones to make the food look more delicious and attractive, and increase the appetite of customers.
In addition to meat, red and white light fresh lamps are also used in the cooked food area, such as braised vegetables and mixed vegetablesGreen and white light is used in the vegetable area, yellow light is used in the baking area, and blue light [4......] is used in the seafood area
Under the "beauty" of various fresh lights, no matter whether the meat is fresh or not, the vegetables are healthy, they all look so ruddy and green, and you who are Xi to judging the freshness and deterioration of food by the color of food [9][10] are inevitably easily confused by their appearance.
Sometimes, merchants will also use other auxiliary means to match the fresh lights. Meat products are equipped with mosquito repellent fans, and the vegetable and fruit area is "full of fairy energy" and sprays water from time to time, and the atmosphere is also paid attention to when selling vegetables.
Some fruit shops will also cut different kinds of fruit directly and sell them by cups to deal with leftover fruit that is not fresh enough.
However, the swirling water mist does reduce the ambient temperature, and the water droplets on the surface can prevent the loss of water and prolong the shelf life of fruits and vegetables [11], but do fresh lamps have the same preservation effect?
To be sure, the light from LED lights does extend the storage time of fruits and vegetables, slow down the breakdown of pigments, and even improve the ability of fruits and vegetables to resist pests and diseases.
Studies have found that the red and blue light of LED lights can delay the ripening and aging of fruits and vegetables by controlling the production of ethylene. Among them, red light can inhibit the formation of ethylene and prolong the storage period of broccoli;Blue light can promote the production of ethylene, prolong the hardness and storage time of green tomatoes [12].
In addition, under certain temperature conditions and light intensity, blue light can also increase the anthocyanin content in apples and cherries, enhancing their ability to resist diseases and low temperaturesRed light can delay the degradation of chlorophyll in broccoli, allowing it to remain "green and glowing" [13][14].
Vegetables and fruits are detached from nutrients after harvesting**, and their physiological metabolism will be significantly different from the growth period
Even if the fruit has been cut, LED lights still have a place to play. Researchers at Southwest University found that continuous irradiation of blue light could inhibit the growth of microorganisms in fresh-cut mangoes and prolong the shelf life [13].
The bad news is that the studies were conducted in laboratories with strict controls on temperature, humidity, light intensity, and other factors, and the stalls at farmers' markets and supermarkets may not be able to meet these demanding conditions.
And compared to laboratories, there are more microorganisms in public places such as farmers' markets and supermarkets. Cutting boards for dividing pork, spit splashing when people talk, and dust kicked up while walking can all harbor bacteria and contaminate food.
In the farmers' market, the amount of meat is large, the air is turbid, and the temperature is high, and the hot fresh meat will quickly enter the autolysis and spoilage process, breeding all kinds of bacteria.
However, after the implementation of the new regulations, local market supervision bureaus and farmers' market staff are inspecting and replacing substandard fresh lights, and the food is gradually returning to its original color.
But if you order takeout every day, you may not care about this. After all, after all, they all eat pre-made dishes, who still works with the ingredients are new or not?