Production principle: Utilizing the characteristics of "protein gel" of eggs in "alkaline solution", it can become an elastic solid. However, if the formula of preserved eggs is poorly controlled, the protein will be hydrolyzed in the alkaline solution, and the protein will be denatured and turned into albumen, making it inedible. If there are cracks in the eggshell or the formula is not well controlled, the hydrogen sulfide in the egg will escape and turn golden yellow. Normal preserved eggs are "dark green", "pine-flowered" and "elastic". Preparation method Preserved eggs are a unique processed egg product in China and are also an alkaline food. The materials required for pickling preserved eggs include salt, tea and alkaline substances (such as quicklime, plant ash, sodium carbonate, sodium hydroxide, etc.). The reason why preserved eggs have a special flavor is that after the action of a strong alkali, the original sulfur-containing amino acids are decomposed to produce hydrogen sulfide and ammonia. Together with the smell of the ingredients in the dipping solution, the unique taste is produced. The color of preserved eggs is due to the fact that under the action of strong alkali, the protein part will turn reddish brown or dark brown, and the yolk will turn dark green or orange red. Where did the pine flowers on the preserved eggs come from? In fact, it is produced through a chemical reaction: the main chemical component of protein is a protein. When eggs are left for a long time, part of the protein in the egg whites will break down into amino acids. Its chemical structure has a basic amino group -NH2 and an acidic carboxyl group -COOH, so it can interact with both acidic and alkaline substances. So when people are making preserved egg designs, they deliberately add some alkaline substances to the mud. Such as lime, potassium carbonate, sodium carbonate, etc. They pass through the pores on the eggshell and combine with amino acids to form amino acid salts. These amino acid salts are insoluble in protein, so they crystallize out in certain geometric shapes, forming beautiful pine flowers. Why is the yolk of preserved eggs bluish black? In fact, this is also caused by a chemical reaction: the main chemical component of preserved eggs is another protein, which contains sulfur. Over time, the egg yolk will decompose into amino acids and release hydrogen sulfide, a gas that we usually call rotten egg smell. The egg yolk itself contains many minerals, such as iron, copper, zinc, manganese, etc. Hydrogen sulfide can react with these minerals to form sulfide. Therefore, the bluish-black color of egg yolk is due to the production of these sulfides. Most of these sulfides are extremely insoluble in water, so they are not absorbed by the body. In addition, because a lot of protein in the yolk of preserved eggs is decomposed into amino acids, the yolks of preserved eggs taste much fresher than those of ordinary eggs. Although preserved eggs are rich in nutrients and delicious, they are too alkaline, so it is not advisable to eat too much. Suggestion: When eating preserved eggs, add a little vinegar. Vinegar can sterilize and neutralize part of the alkalinity of preserved eggs, making them taste more delicious. Category 1. Lead-free preserved eggs: In my country’s traditional preserved egg processing formula, lead oxide is added, and the peeled preserved eggs (yellow red powder) are banned from sale in some countries because lead is a toxic heavy metal element. , which has affected my country’s export sales of preserved eggs. For this reason, the relevant scientific research departments are studying substitute substances for lead oxide, among which EDTA and FWD have better results. When using EDTA (ethylenediaminetetraacetic acid), the other auxiliary material formulas and processing techniques remain unchanged, as long as the lead oxide is eliminated and then replaced with EDTA. Generally, when processing 1,000 duck eggs, the dosage is 0.12 to 0.13 kg. FWD is a substance synthesized from trace elements such as magnesium and manganese. Its usage is to dissolve 0.5 kilograms of FWD in 75 kilograms of cold boiled water and soak 1,500 duck eggs. The formulas and processing methods of other auxiliary materials are the same as when using lead oxide. same. 2. Colored preserved eggs: The main raw materials are fresh duck eggs, white lime, secondary tea, salt, flour alkali, yellow red powder, plant ash, loess, and rice husk. Equipment and utensils such as cylinders, basins, etc. Preparation method: Weigh 25 grams of tea, 100 grams of salt, 165 grams of flour alkali, 400 grams of white lime, 10 grams of yellow red powder, 300 grams of plant ash, 1500 grams of loess, and 2500 grams of rice husk. First, pour 1500 grams of hot water into a large vat, put the tea leaves, salt, noodle base, and yellow red powder into the vat and mix well. Then put the sifted white lime, loess, and plant ash into the vat, and stir evenly. Material mud. Purchase 35 fresh and unbroken duck eggs, put on rubber gloves, wrap them one by one with the prepared mud, wrap them evenly, put them in a tank, seal them tightly with plastic film, and store them at room temperature of 15°C to 30°C. The finished product will be ready in 30 to 40 days. The process flow includes weighing → ingredients → covering → storage → finished product. Inspection process: The finished egg shells are easy to peel off without sticking, the egg whites are translucent brown solids, the surface of the egg whites has pine branch-like patterns, the yolks are dark green solids, and some have sugar centers. The egg pieces are very colorful after being cut into pieces. The food is cool and refreshing, fragrant but not greasy, and tastes delicious. The quality inspection and grading of preserved eggs is the last important process for manufacturers and should be carried out in accordance with relevant national regulations. When consumers purchase goods, they also need to make selections. Quality of Preserved Eggs The commonly used methods for testing preserved eggs after peeling are: one look, two weighs, three shakes, and four photos. First observation: Check whether the packaging material is moldy, whether the eggshell is complete, and whether the color of the shell is normal (green color is preferred). Second weighing: Put the egg in your hand, gently throw it up, and throw it several times. If it feels elastic and vibrating, and it is heavier, it is a good egg, otherwise it is a poor quality egg. Three shakes: Pinch both ends of the egg with your thumb and middle finger, shake it up, down, left and right by your ear, and listen for any sound of water or impact. If no sound is heard, the egg is good.

Four photos: Use light to see through, if most of the egg is black