Why use 75% alcohol to disinfect food

Differences among edible alcohol, industrial alcohol, medical alcohol and anhydrous ethanol

Edible alcohol: aqueous alcohol refined by fermentation and distillation with grains,potatoes, molasses or other edible crops as the main raw materials and used in the food industry. (quoted from GB 31640-2016 national food safety standard edible alcohol). 

Medical alcohol: it is made from starch plants through saccharification,fermentation and distillation,which is equivalent to the process of making wine. However,the distillation temperature is lower than that of wine, the distillation times are more than that of wine, the alcohol degree is higher, the output of finished products is higher, and there are more ether and aldehyde components other than alcohol than wine. It can notbe drunk, but it can touch human medical alcohol.

Industrial alcohol: alcohol used in industry, also known as denatured alcohol and industrial fire wine. The purity of industrial alcohol is generally more than 95%. It is mainly produced in two ways: synthesis and brewing (corn or cassava), which contains a certain amount of methanol, aldehydes, organic acids and other impurities, which greatly increases its toxicity. Industrial alcohol can not be used for human body disinfection, because methanol will lead to poisoning, and some will be absorbed by the skin for skin disinfection. Serious poisoning can lead to blindness or even death. GB / T394.1-2008 industrial alcohol methanol content (superior grade) ≤ 800mg / L, which is much higher than the methanol content ≤ 150mg / L specified in edible alcohol GB31640-2016.

Absolute ethanol: chemical reagent commonly used in the laboratory, with ethanol content of 99.5%. GB / T 678-2002 chemical reagent ethanol (absolute ethanol)analytical purity grade stipulates that the mass fraction of methanol is ≤ 0.05%,accounting for ≤ 500mg / L, which is far greater than the methanol content ≤ 150mg/ L specified in edible alcohol GB 31640-2016.

Summary: After disinfection, the hands or operating table of food factory employees may directly or indirectly contact with food materials, and the alcohol that may remain on the hands or operating table will be introduced into the food. Therefore, it is the best choice to use edible alcohol from the perspective of safety and compliance.

Why use 75% alcohol for disinfection?

The strength of the sterilization and disinfection ability of alcohol plays a key role inits concentration, which is neither too high nor too low. Too high concentration of alcohol will form a protective film on the surface of bacteria to prevent it from entering the bacteria, which is difficult to kill the bacteria completely. If the alcohol concentration is too low, although it can enter the bacteria, it can not coagulate the protein in its body,nor can it completely kill the bacteria.

After determination, the best effect is that the concentration is 75%, which candenature the protein in bacteria. The osmotic pressure of 75% alcohol is similar to thatof bacteria. It can gradually and continuously penetrate into the bacteria before the protein on the surface of bacteria is denatured, so as to achieve the concentration and dose of killing, dehydrate, deform and solidify all bacterial proteins, and achieve the purpose of complete disinfection. Therefore, the best concentration of alcohol fordisinfection should be 75%. In addition, the higher the concentration, the greater the damage to the skin or human body.

How to configure 95% alcohol into 100 ml of 75% alcohol?

Universal formula: 95% * a = 75% * B requires pure water C = b-a. in the formula, a and B are the total volume of 95% and 75% alcohol respectively, which is the key totheir mutual preparation.
Substitute into the universal formula, because B = 100ml, so 95% * a = 75% * 100,then a = 75% * 100 / 95% = 78.95ml (total volume of 95% alcohol), and the required pure water is 100-78.95 = 21.05ml. That is, 78.95ml of 95% alcohol plus 21.05ml of pure water is 75% alcohol.

How to prepare 100 ml of 95% alcohol into 75% alcohol?

95%*A=75%*B，A=100ml，B=95%*100/75%=126.66ml
This 126.66ml is the total volume of 75% alcohol, including water and 95% alcohol.Therefore, 126.66-100 = 26.66ml pure water is required for preparation, plus the original 100ml of 95% alcohol.