Xinjiang red raisins are a snack that people like, and many people claim that it is "nutritive" and "iron content is five times that of fresh grapes." But recently, many WeChat groups have circulated a video of "Grape soaking desiccant to make raisins". In the video, the fruit farmers soaked baskets of grapes in a brown liquid, and then the video footage captured a packaging bag labeled "Grape desiccant". The videographer said: "Don't buy raisins bought on the market, don't take them out directly. There is a desiccant in it, and eating them directly will burn the intestines and stomach."

This can scare netizens who love raisins. Do you really want to give up your favorite raisins because of the desiccant? To this end, a reporter from Science and Technology Daily interviewed Wu Jihong, a doctoral tutor at the School of Food Science and Nutritional Engineering, China Agricultural University, and deputy director of the Fruit and Vegetable Processing Technology Research Center of the Ministry of Education. The expert's words relieved netizens who love raisins. "The residual amount of the desiccant on the raisins is very low, and there is no need to worry about the potential risks of the raisins that have used the desiccant, such as excessive alkali.

Can speed up drying and improve the quality of dried fruits

When making raisins, people always want the grapes to lose water and dry as soon as possible. Drying as soon as possible not only shortens the production cycle, but also reduces the possibility of the raisins depositing dust, being eroded by bacteria, and oxidized and discolored during the drying process.

Wu Jihong said: "Traditional raisin production process mainly includes two kinds of drying and drying in the shade. The dried raisins made by the drying process are sour and easy to brown. At present, the drying of raisins is generally used, but the drying cycle of the dried raisins takes longer, the short period is 30-45 days, and the longer It takes 60 days and is susceptible to climate change." To reverse this situation, researchers have developed desiccants. It can be used not only on grapes, but also on other fruits such as wolfberry and apricot.

So, what are the ingredients in the desiccant?

Wu Jihong said: "The desiccant is a powdered chemical preparation used for the drying of fresh fruit. Put it into water to form a desiccant water emulsion, which is essentially a strong alkaline solution that can destroy the skin of the fruit. The toughness of the waxy layer and peel."

In recent years, Chinese researchers have developed a series of fruit desiccants, the main components of which include alkaline bases, esters and emulsifiers. "The most common alkaline substrates are potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate. These substances can decompose or destroy the waxy layer of the fruit skin. Commonly used esters are ethyl oleate and propyl oleate. , Butyl oleate, etc., after the wax layer of the peel is destroyed, its components (long-chain fatty acids, esters, alkanes, etc.) can be dissolved by the esters." Wu Jihong said that the emulsifier makes the desiccant water emulsion more stable and can be more Good infiltration on the surface of the waxy layer, commonly used are ethanol, sodium dodecyl sulfonate, fatty alcohol polyoxyethylene ether and so on.

Wu Jihong said: "With the desiccant, you only need to immerse the fresh grapes in a 3.5% concentration desiccant water emulsion for 1 minute, take it out and wash it with clean water, and let it dry for 15-20 days, you can harvest crystal clear Raisin. The use of desiccant greatly shortens the drying cycle, get rid of the limitation of climate factors to the greatest extent, and also can make the sugar content of raisins up to 60%-70%, and the quality is improved by one or two grades. Application prospects."

Therefore, the desiccant is of great significance to accelerate the rate of fresh fruit drying, improve the quality of dried fruit, and even reduce the loss of fresh fruit after harvest.

The desiccant is non-toxic and the residue is very low

Although the desiccant is beneficial to the drying of fresh fruit, people are more concerned about whether it is harmful to human health. Therefore, for many years, researchers have conducted a series of tests on the safety of desiccant.

In 1992, the Institute of Nutrition and Food Hygiene of the Chinese Academy of Preventive Medicine made a report on the evaluation of the safety of grape desiccant, which concluded that it was non-toxic.

In 2005, the inspection report of the Xinjiang Center for Disease Control and Prevention showed that the grape desiccant was non-toxic.

In 2009, the inspection report of the Xinjiang Center for Disease Control and Prevention reached the same conclusion for the improved desiccant.

Not long ago, the science public tadpole stave under the Beijing Science and Technology Association also issued a document saying that researchers have used acute oral toxicity tests and genotoxicity tests to carry out toxicological evaluation of the food safety of grape driers. The test results show that the grape desiccant is a non-toxic and non-genotoxic food additive, and its maximum concentration is 7.0%. The driers water soaked with raisins only needs a concentration of about 3%, which is much lower than this maximum concentration.

In addition, Wu Jihong said that after the fresh grapes were soaked in the desiccant water emulsion for a short time, the fruit farmers washed the grapes. The strong alkaline solution attached to the grape skin was easily washed away by water, so the residual amount of desiccant on the raisins Very low. Researchers have conducted a pH test on 7 randomly selected raisins on the market. After soaking these raisins separately, the pH value of their aqueous solutions showed neutrality, so there is no need to worry about the potential risks of raisins that have used a desiccant and exceed the standard. .

Wu Jihong emphasized that by consuming raisin products purchased from regular channels, there is no need to worry about excessive residues of the desiccant to burn the stomach or cause other health risks.

Is the white cream on the raisins a desiccant?

Some people pointed out that the white frost on the raisins is the residual desiccant.

Wu Jihong said: "The white frost on the raisins is the same as the white frost on the skin of fresh grapes. It is a sugar alcohol substance (also called fruit powder) secreted by the fruits and vegetables itself. It is a biosynthetic natural substance that is completely harmless to the human body. Fruit powder It is insoluble in water and only soluble in organic solvents such as chloroform. Therefore, during the desiccant soaking and water rinse process, it survives on the grape skin, so there will be such a layer of white frost on the raisins."

Some experts pointed out that fruit powder may be rubbed off during long-term transportation and storage. Therefore, grapes covered with this white fruit powder can prove that it is fresh.