How to identify the "beauty" after the high-faced white lotus?

Original title: How to identify the "beauty" after the high-faced white lotus?
is an important aquatic vegetable in China, with a cultivation history of more than three thousand years, mainly in the Yangtze River Delta, Pearl River Delta and Dongting Lake area. The fat lotus is delicious and nutritious and is loved by many people. However, when harvesting white and tender lotus due to high water content, not resistant to storage and transportation, often blackened at the first place, not only affect the value of the face, but also affect the quality. Recently, the market everywhere can be seen some "white rich beauty" lotus, looks clean and refreshing, very happy, and can withstand storage, buy home for several days will not turn black, so soon became the darling of the lotus market.
but some consumers can not help but have doubts, the common lotus seems to be "dirty", this kind of white lotus how to come? Will you use any special beauty method? You're right! According to the investigation, this high-value lotus is soaked with citric acid solution.
Citric acid is an important means to prevent the color change of lotus
lotus is the main reason for color change, is an enzyme-driven browning, is the polyphenol oxygen also enzyme (PPO) catalytic phenolic compounds in the lotus oxidation reaction, the formation of tanned tan, tan, and then automatic polymerization, the formation of dark substances. So the lotus grows dark spots.
inhibition of PPO activity in lotus is the key to preventing the browning process. PPO is a kind of copper-containing enzyme, citric acid can reduce pH, but also can chelate part of the metal ions, so it can significantly reduce the activity of PPO, inhibit enzymatic browning, play a color protection effect.
In the use of citric acid to protect the lotus is not a strange thing, but has long been used in a fruit and vegetable chemical preservation method, especially for freshly cut lotus, the use of a certain concentration of citric acid with other ingredients, is an important means to prevent browning, some ready-to-eat packaging in the flakes added citric acid and other substances inhibiting PPO activity.
Rational use of citric acid is not obvious harm to the human body
citric acid (CA), also known asacid, is an organic acid widely distributed in nature, common fruits including lemons, citrus, pineapples, grapes, etc. contain citric acid, especially in lemons and green lemons are very high content. Citric acid is also an important compound in the body's metabolic process of sugars, proteins, and fats, a series of metabolic reactions known as the "citric acid cycle" or "tricarbonate cycle".
citric acid is also an important food additives, is the most commonly used acid flavor agent, China's national food safety standards "food additives use standards" (GB2760-2014) stipulates: citric acid can be used in various types of food according to the production needs of the appropriate amount of food additives, but also can be used in various types of food processing processing processes, residues do not need to limit the amount of processing aids.
are added to many common foods, such as beverages (carbonated beverages, fruit juice drinks, lactic acid drinks, etc.), jams, sweets, frozen foods, etc. Citric acid is also allowed as an acidity regulator in infant formula and infant ancillary foods. The kettle descaling agent used in daily life is also made of citric acid.
from this point of view, citric acid is not a major health hazard. But why should the use of citric acid to bubble lotus attract the attention of consumers and regulators? Mainly because the citric acid used is not qualified or used too much.
Industrial citric acid and excess citric acid will harm health
citric acid is a commonly used browning inhibitor, with the appropriate concentration of citric acid solution to treat lotus, potatoes, fruits and other easily browned food is not a big problem, but some traders in order to reduce costs, with industrial citric acid to bubble lotus.
industrial citric acid and food grade citric acid, although the main ingredients are the same, but the quality specifications of different requirements. The national standard for food safety, the food additive citric acid (GB1987-2007), specifies in detail the quality requirements for citric acid used in food products, and there are strict limits on the impurities and harmful ingredients contained therein, of which arsenic must not exceed 1 mg/kg and lead shall not exceed 0.5 mg/kg.
industrial-grade citric acid, as the name suggests, is for industrial use, not for people to eat, so some indicators are less stringent, such as heavy metals and other harmful substances content is significantly higher than food-grade citric acid. Soaking lotus with industrial citric acid will cause harmful ingredient residues in lotus, harming consumer health.
In addition, because the greater the use of citric acid, the better the color protection effect of the lotus, so many vendors in order to enhance the effect, a large number of citric acid, which will inevitably cause too much citric acid residue in the lotus, affecting its taste and flavor. Although citric acid is more safe, high intake can irritate the digestive tract and cause discomfort, especially in people with stomach ulcers and excess stomach acid.
In short, it is difficult to judge whether the vendors are using industrial citric acid or food-grade citric acid, in the end how much to use, insurance, or to buy "the color of the person" lotus is better. Unprocessed lotus slightly with sediment, dark color, the surface is not smooth, there is a smell of soil rather than sour taste.
kitchen to prevent the lotus from turning black has a trick
so usually we buy lotus after how to prevent it from turning black? The enzymatic browning of lotus is a chemical process involving enzymes and oxygen, which can be slowed by cutting off any of these links.
1. Steaming or boiling lotus: If you want to steam or cook lotus, need a soft taste, you can first boil the lotus water hot for more than 70 seconds, so that PPO inactive, thereby preventing browning.
2. Stir-fry or mix lotus: if you want to fry or mix lotus, need a crisp taste, it is not suitable for earlyhot, you can put it in clean water soaked, isolated air, but also to slow oxidation blackening. Add vinegar to the water, reduce pH, but also inhibit the activity of PPO, further delay browning, and can make lotus more crisp.
3. Use casserole, not iron pot: it is best to use casserole when cooking lotus, not iron pot. Because the polyphenols contained in the lotus can be combined with iron ions to form a purple or blue-black compound, so that the made lotus becomes black, vegetable soup is like ink, although there is no harm, but very affect appetite.
/Ma Guansheng (Director
Department of Nutrition and Food Hygiene, Peking University School of Public Health)