Produced by: Popular Science China
Produced by: Lu Wensheng (Institute of Chemistry, Chinese Academy of Sciences)
Produced by: Computer Network Information Center, Chinese Academy of Sciences
< p> Golden and crispy fried dough sticks are a common food on the breakfast table. In recent years, there have been reports that the fried dough sticks contain alum (potassium aluminum alum, potassium alum) and that the aluminum content in the fried dough sticks exceeds the standard [1], which once confused people who love eating fried dough sticks. . Today we will start with the aluminum element and talk about this topic.Fried dough sticks (picture source: taken by the author)
What is "aluminum"?
The symbol for aluminum is Al, and its atomic number is 13 in the periodic table of elements. The content of aluminum in the earth's crust ranks third after oxygen and silicon. It is the most abundant metal element in the earth's crust. Aluminum is silvery white, light in weight, and has good ductility, electrical conductivity, and thermal conductivity. Widely used in important industrial fields such as aviation, construction, automobiles, and electric power.
Aluminum element (picture source: produced by the author)
Aluminum compounds include alumina, aluminum chloride, potassium aluminum vitriol, etc. Some aluminum oxide crystals are transparent and have a distinct color due to impurities. For example, rubies are red because they contain very small amounts of chromium oxides. Sapphire is blue due to the oxides of iron and titanium it contains [2].
Potassium aluminum vitriol can be used to prepare aluminum salts and is a food additive.
Where does the aluminum in fried dough sticks come from?
Fried dough sticks are a kind of fried flour product. Its crispy texture is not only related to the frying process, but also closely related to the ingredients. Many people have experience steaming steamed buns and steamed buns, and they must be familiar with the fluffy feeling caused by fermentation of steamed buns after adding yeast. Similarly, the dough of fried dough sticks should also be added with ingredients to make it fluffy. Unlike yeast, which uses fermentation to produce carbon dioxide and other gases to make the dough soft. In the making methods of some processing points, baking powder containing potassium alum, baking soda (sodium bicarbonate) and other ingredients is usually added to the dough sticks as a leavening agent. During the processing of dough sticks, they produce gas through chemical reactions ( Mainly carbon dioxide), which makes the dough rise and produce a porous structure, thereby achieving the foaming effect that makes the dough sticks fluffy and crispy. The reaction between potassium alum and baking soda is as follows:
Using aluminum-containing baking powder can quickly foam, which is very efficient and eliminates the need for traditional fermentation. The long time required is an important reason why people favor this kind of baking powder in the process of making fried dough sticks. Another reason is its low price. In this way, in the process of using aluminum-containing baking powder, aluminum is introduced into the dough sticks.
The impact of aluminum on human health
At first, people did not care about the aluminum in fried dough sticks when enjoying delicious food, because aluminum was once considered harmless to the human body. However, with the advancement of science and technology and the improvement of people's living standards, people's understanding of aluminum has gradually deepened. Typically, people's main sources of aluminum intake are water, food, and pharmaceuticals. Research by Moore and others has shown that excessive exposure and accumulation of aluminum may be one of the causes of Alzheimer's disease [3]. Of course, some researchers have expressed different opinions [4, 5]. Especially for some aluminum-containing antacid drugs, there are almost no clear research results linking them to neurotoxicity [6].
Although the relationship between aluminum and Alzheimer’s disease is still a controversial issue, from the perspective of residents’ health, some countries and organizations have issued regulations on the use of aluminum-containing food additives. Corresponding guidance documents. The World Health Organization and the Food and Agriculture Organization of the United Nations (WHO/FAO) have provided detailed explanations on the safety assessment and contamination of aluminum-containing food additives, and set the tentative weekly tolerable intake (PTWI) of aluminum at 2 mg/kg. bw[6].
my country’s national food safety standard for the use of food additives GB2760-2014 (implemented on May 24, 2015) stipulates that the residual amount of aluminum in fried noodle products shall not exceed 100 mg/kg. Comparing this standard with GB2760-2011 (which has been replaced), it can be seen that in GB2760-2014, potassium aluminum sulfate (potassium alum) and ammonium aluminum sulfate (ammonium alum) are used as leavening agents and stabilizers. More stringent.
The National Food Safety Standard for the Use of Food Additives (GB2760-2014) is about aluminum potassium sulfate (58 pages) [7]
The National Food Safety Standard for the Use of Food Additives (GB2760-2014) 2011) About potassium aluminum sulfate (pages 49-50) [8]
From this point of view, the use of food additives containing potassium alum and ammonium alum is allowed. However, in the process of making fried dough sticks, the amount of aluminum-containing food additives must be strictly controlled and the corresponding regulations must be followed. After all, food safety is no small matter. Although the country has promulgated corresponding standards, it cannot be ruled out that individual businesses use it illegally, resulting in fried dough sticks with excessive aluminum on the dining table.
Do the fried dough sticks we eat still contain aluminum?
If you use aluminum-free baking powder, then the fried dough sticks we eat will basically not contain aluminum. As mentioned earlier, baking powder is added mainly to produce a fluffy effect. The baking powder sold on the market is a compound leavening agent. In addition to aluminum-containing baking powder, there is also an aluminum-free baking powder. The author’s investigation found that the market The aluminum-free baking powder above has a variety of formulas, some are suitable for making bread, cakes and biscuits, etc., and some are specially used for making fried dough sticks.
Compound leavening agent (picture source: taken by the author)
The main ingredients of an aluminum-free formula are sodium bicarbonate, calcium carbonate, sodium dihydrogen phosphate, tartaric acid, and starch wait. Using aluminum-free baking powder, fried dough sticks can avoid the use of aluminum introduced by alum. Naturally, there is no need to worry about food additives causing excessive aluminum in the dough sticks.
However, as a fried food, fried dough sticks have higher calories, contain more oil, are greasy, and are not easy to digest. From a health perspective, it is not recommended to eat too much.
References:
[1]/a/211471688_100011028
[2] Editor, Inorganic Chemistry Teaching and Research Section, Dalian University of Technology, Inorganic Chemistry, Volume 2, Higher Education Publishing House, 3rd edition 1990.
[3]P. B. Moore, J. P. Day, G. A. Taylor, I. N. Ferrier, L. K. Fifield, J. A. Edwardson. Absorption of Aluminum-26 in Alzheimer's Disease, Measured Using Accelerator Mass Spectrometry, Dementia and Geriatric Cognitive Disorders, 2000 , 11, 66-69.
[4]S. A. Virk, G. D. Eslick.Brief Report: Meta-analysis of Antacid Use and Alzheimer's Disease: Implications for the Aluminum Hypothesis.Epidemiology, 2015, 26 (5) , 769-773.
[5] Yu Shenghao, Xiang Yu, Peng Shaojie. Risk monitoring and exposure assessment of aluminum content in commercially available fried dough sticks in Shanghai, Shanghai Preventive Medicine, 2018, 30(6), 450-453.
[6]Joint FAO/WHO Expert Committee on Food Additives. Safety Evaluation of Certain Food Additives and Contaminants. WHO Food Additives Series 65. http://whqlibdoc.who.int/publications/2012/9789241660655_eng .pdf.
[7] National Standards of the People's Republic of China, National Food Safety Standards for the Use of Food Additives (GB2760-2014).
[8] National Standards of the People's Republic of China, National Food Safety Standards for the Use of Food Additives (GB2760-2011).
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