“Eat it fresh!” is a common saying. In most cases, this is true; for most foods, the fresher they are, the higher their nutritional value and the better their taste. However, for the following foods, “fresh” can often mean a potential risk of food poisoning. For these foods, the saying might have to be changed to “Eat it not-so-fresh!”
I. Milk
Some people prefer to drink milk “fresh from the cow,” believing it is fresher and more nutritious. In reality, this greatly increases the risk of the milk being contaminated. This contamination can come from several factors: the health of the milker; the hygiene and disinfection of the milker's hands; the cleanliness of the milking environment; the disinfection of the milk container; and the health of the cow (whether it is infected with pathogenic microorganisms such as *Brucella*, *Mycobacterium tuberculosis*, *Staphylococcus aureus*, foot-and-mouth disease virus, etc.).
II. Fresh Daylilies
Fresh daylilies contain colchicine, which can cause a toxic reaction in the human body after consumption, leading to nausea, vomiting, headaches, and abdominal pain. A large intake can result in hematuria, bloody stools, and even death. In dried daylilies that have been steamed and cooked, the colchicine is leached out, and therefore does not cause poisoning.
III. Fresh Jellyfish
Fresh jellyfish contains toxins and is not edible. It must be dehydrated several times with salt, iodized salt, and alum to remove all the toxins.
IV. Fresh Wood Ear Mushrooms
Fresh wood ear mushrooms contain a photosensitive substance called porphyrin. After consumption, exposure to sunlight can cause skin itching and edema; in severe cases, it can lead to skin necrosis. If edema occurs in the pharyngeal mucosa, it can cause difficulty breathing. Dried wood ear mushrooms are a finished product that has been sun-dried. During this process, most of the porphyrins are broken down. Before eating, dried mushrooms are soaked in water, which dissolves the remaining toxins. Therefore, rehydrated dried wood ear mushrooms are non-toxic.
V. Bucket Water
Bucket water is often treated with ozone before being bottled. Therefore, newly filled bucket water contains a relatively high concentration of ozone, which poses a potential health risk. It is best to let the bucket water sit for 2 days for the ozone to dissipate naturally before drinking.
VI. Fresh Pickles and Sauerkraut
Fresh pickles and sauerkraut contain a considerable amount of nitrates. A few hours after salting, the nitrite content begins to increase significantly, peaks after two weeks, and then gradually declines. Nitrites can cause symptoms of hypoxia (such as cyanosis) and can combine with secondary amines in food to form carcinogenic nitrosamines. Therefore, fresh pickled foods should not be eaten; it is best to consume them after four weeks of pickling.
VII. Fresh Spinach
Spinach contains a large amount of oxalic acid, and excessive intake can be harmful to health. The oxalic acid in spinach is mainly in the form of calcium oxalate and potassium oxalate. Calcium oxalate is insoluble in water and gastrointestinal fluids and is not absorbed, so it has little impact on health. However, potassium oxalate is highly water-soluble; 1 gram of potassium oxalate can dissolve in 3 ml of water. Therefore, when spinach is boiled in soup, a large amount of potassium oxalate dissolves into the broth. After entering the body, potassium oxalate combines with calcium to form insoluble calcium oxalate, which precipitates in the digestive tract, hindering calcium absorption and potentially causing kidney stones.
Therefore, it is best to blanch spinach in hot water before cooking to reduce its oxalic acid content.