What is food bleach

According to GB2760 National Standard for Food Safety Standard for the Use of Food Additives, bleach refers to substances that can destroy or inhibit the coloring factors of food, make it fade or save it from browning.

Why do we need to use food bleach to treat food?

Because some food will appear discoloration phenomenon after processing, the color is not ideal, the use of bleach-treated food, white color, better appearance, more popular with consumers, so manufacturers will find ways to bleach food whitening.

There are 3 main reasons for food discoloration:
2.1 Enzymatic browning occurs
Fruits, vegetables, potatoes in the presence of a class of phenol oxidase and polyphenol substances, the two will meet to generate colored substances, plus oxygen will occur enzymatic browning, with the oxidation of the color from red to brown and then black.

Usually this phenol oxidase and polyphenol substances in the cell is tightly separated, but the ingredients a bump or cut, cell damage, separated from the “wall” collapse, all the substances mixed together, the two types of substances will meet and react with the oxygen in the air, resulting in brown substances. For example, cut potatoes left in the air for a period of time will darken on the cut surface.

2.2 Non-enzymatic browning
Non-enzymatic browning is the reaction between carbonyl substances and nitrogenous substances, which generates dark brown substances. Some foods with little moisture, such as dried vegetables, will become darker the longer they are stored, and milk powder and soybean powder will also appear light brown, which are all related to non-enzymatic browning.

2.3 Colored substances in food
Some foods contain natural pigments and colored substances, such as flour in the original carotene and flavonoids, so that the flour shows a light yellow.

Common bleach and its use

According to GB2760, bleaching agents approved for use in food in China include, sulfur dioxide, potassium metabisulfite, sodium metabisulfite, sodium sulfite, sodium bisulfite, sodium hyposulfite, and sulfur. It is a reducing bleaching agent, which mainly releases sulfur dioxide in the process of use, and uses sulfur dioxide to inhibit non-enzymatic browning and enzymatic browning.

1. Sulfur fumigation
Sulfur fumigation is a method of burning sulfur in a closed space to produce sulfur dioxide fumigation, it is an “ancient process”, is allowed as food bleach used for food bleaching, rather than what we have heard of “black hearted practice”.

The principle of sulfur fumigation is that sulfur dioxide can inhibit enzymatic browning, but also inhibit the Meladic reaction to prevent browning. At the same time, sulfur dioxide on fruits and vegetables in the vitamin C has a protective effect, so in terms of nutrition is not harmful. But this method is not good to control the residual amount of sulfur dioxide. In recent years, due to the relevant national standards strictly limit the residual amount of sulfur dioxide, this traditional process has been largely improved, or even eliminated.

So in the future, we will hear so and so fruit smoked with sulfur, do not think it is unsafe, as long as the sulfur dioxide residue in line with the requirements of GB 2760-2014 can be.

2. Direct addition of sulfur dioxide
Sulfur dioxide in food is very wide range of uses, the surface treatment of fresh fruit, dried fruit, candied fruit, dried vegetables, dried mushrooms or mushroom canned, nuts, cocoa products, cookies, bamboo, sugar, fruit and vegetable juices, wine and so on can be added sulfur dioxide.

3. Bleaching effect of sulfites
China’s food production process, the actual use of food bleaching agent mainly sulfite and its salts, such as anhydrous sodium sulfite, sodium sulfite, sodium hyposulfite and sodium metabisulfite. The earliest standard of sodium hyposulfite was called sodium hypodisulfite (commonly known as insurance powder). In addition, due to the unsatisfactory bleaching effect of a single ingredient, there are currently a very large number of compounded food bleaches on the market, of which the combination of sodium hyposulfite + sodium metabisulfite is the most common.