As a kind of food additive, sodium metabisulfite is mainly used as bleaching agent, preservative, loosening agent, antioxidant, color-protecting agent and preservative in the food industry due to its special physical and chemical properties. Sodium metabisulfite is used in different foods The functions they play are also different, and in summary, the main functions can be divided into these three types.
1. The role of antiseptic and preservative
The internal tissue of the fruit or vegetable after picking does not stop moving immediately, but can usually carry out normal activities and decompose the oxygen in the tissue. There will be a large number of multiplied microorganisms in the injured part, and these microorganisms can decompose the nutrients in the tissue produce harmful substances, which in turn leads to the rot of fruits and vegetables.
Therefore, the use of food-grade sodium metabisulfite can play a good role in slowing down the rot of fruits and vegetables. After picking the grapes are fumigated with sulfur dioxide, the respiration of the grapes will be reduced, reducing the respiration substrate, thereby reducing the activity of oxidase, so that during the entire storage period, the respiration of the grapes has been at a low level. Obviously, ethylene release is also less. Its action process is: when sulfur dioxide meets water, it undergoes a combination reaction to generate sulfurous acid. The substance has a strong anti-oxidation property, can consume oxygen in tissues well, and hinder normal processes such as the reproduction, respiration and fermentation of microorganisms. Sodium metabisulfite undergoes a decomposition reaction under this condition, and the reaction produces hydrogen ions, which can hydrolyze proteins and nucleic acids on the surface of bacteria, thereby eliminating a large number of microorganisms. There are a lot of oxidase in the grape tissue, this enzyme destroys nutrients and changes the color of the tissue, and the role of sodium metabisulfite in decomposing oxygen can just slow down the effect of this enzyme, thus playing a role in keeping fresh.
2. Antioxidant and bleaching effect
In food processing, it is often used as a food bleaching agent. The reason why sodium sulfite has strong anti-oxidation is that in sodium sulfite, the valence of sulfur is +4, which is reducing and can react with oxygen or oxidizing agents to form sulfate, so it has anti-oxidation effect. Sodium sulfite can bleach the color of anthocyanins. The principle of bleaching is: an addition reaction between sodium sulfite and anthocyanin molecules causes damage to the conjugated system in the anthocyanin molecules, forcing the color of the product to disappear, resulting in bleaching Effect. When sodium metabisulfite reacts with colored substances, the stability of the product is weak and it is easy to decompose. The substances produced after decomposition lose their function due to oxidation, which will cause discoloration of food. Therefore, sodium metabisulfite often remains in food processing.
3. Inhibitors to reduce food browning
Enzymatic browning is generally found in fresh plant foods, such as fresh fruits and vegetables. Sodium metabisulfite can inhibit the activity of phenolase, and can undergo addition reaction with carbonyl, thereby reducing the polymerization reaction of carbonyl compounds. Sodium metabisulfite can inhibit enzymatic browning in an acidic environment. In the process of food storage, sodium metabisulfite is usually mixed with citric acid and ascorbic acid, which can maintain the color of the original substance for a long time.
Sodium Metabisulfite has a stronger reducing property than bisulfite, and its effect is similar to that of sodium sulfite. my country stipulates that it can be used in candied fruit, biscuits, sugar, rock sugar, maltose, candy, glucose, liquid glucose, bamboo shoots, mushrooms and canned mushrooms, with a maximum usage of 0.45g/kg. The residues of candied fruit, bamboo shoots, mushrooms and canned mushrooms, grapes and black currant juice concentrate (calculated as SO2) are less than 0.05g/kg; the residues of biscuits, sugar, vermicelli and other varieties are less than 0.1g/kg; the residues of liquid glucose The amount shall not exceed 0.2g/kg. In the food industry, it is used as bleaching agent, preservative, loosening agent, antioxidant, color-protecting agent and fresh-keeping agent.
Safety and Environmental Impact of Sodium Metabisulfite
As a widely used chemical, sodium metabisulfite has attracted much attention for its impact on human health and environmental safety. Generally speaking, sodium metabisulfite is safe to use within the specified dosage range. However, if it is used excessively or exposed to high concentrations of sodium metabisulfite for a long time, it will have a certain impact on human health, such as skin irritation, breathing difficulties, and allergies. In addition, sodium metabisulfite may also produce pollutants such as SOx (sulfur oxides) during the process of decomposition to generate sulfur dioxide, which will have a certain negative impact on the environment. Therefore, when using sodium metabisulfite, control and safety considerations should be taken to avoid possible hazards and environmental impacts.
What is sodium metabisulfite, and why is it used in food?
Sodium metabisulfite (or sodium pyrosulfite) is a white, crystalline powder used in food as a preservative, antioxidant, and antimicrobial agent. Its primary purpose is to extend the shelf life of various food products.
Is sodium metabisulfite safe for consumption?
Sodium metabisulfite is generally recognized as safe (GRAS) when used in accordance with established food safety regulations. However, some individuals may be sensitive or allergic to sulfites, so food labeling regulations require its presence to be disclosed.
What foods commonly contain sodium metabisulfite?
Sodium metabisulfite can be found in a variety of foods, including dried fruits, wine, beer, some fruit juices, processed vegetables, and certain baked goods. It is also used during the production of some cheeses and meat products.
How does sodium metabisulfite act as a preservative in food?
Sodium metabisulfite helps preserve food by inhibiting the growth of spoilage microorganisms and preventing enzymatic browning and oxidation. It achieves this by releasing sulfur dioxide gas, which has antimicrobial and antioxidant properties.
Can sodium metabisulfite cause allergic reactions or sensitivity in some individuals?
Yes, sodium metabisulfite can trigger allergic reactions, especially in individuals with sulfite sensitivity or asthma. Symptoms may include skin rashes, breathing difficulties, or digestive issues. Food products containing sulfites are often labeled to alert sensitive individuals.
How does sodium metabisulfite prevent enzymatic browning in fruits and vegetables?
Enzymatic browning in fruits and vegetables is caused by the enzyme polyphenol oxidase. Sodium metabisulfite inhibits this enzyme, preventing the browning reaction and helping maintain the visual appeal of food products.
Can sodium metabisulfite be used to sanitize or disinfect food contact surfaces?
Sodium metabisulfite is not typically used for sanitizing or disinfecting food contact surfaces. Instead, it is primarily employed to preserve and protect the quality of food products themselves.
Are there alternatives to sodium metabisulfite as a food preservative and antioxidant?
Yes, there are alternative preservatives and antioxidants available, such as ascorbic acid (vitamin C), tocopherols (vitamin E), and rosemary extract. These alternatives may be used in foods to achieve similar preservation and antioxidant effects.
Is there a maximum allowable limit for sodium metabisulfite in food products?
Regulatory agencies, such as the FDA in the United States and the EU in Europe, specify maximum allowable limits for sodium metabisulfite in various food products to ensure consumer safety. These limits vary depending on the type of food and its intended use.
Can consumers reduce their exposure to sodium metabisulfite in food?
Consumers who are concerned about sulfite exposure can look for food labels that disclose the presence of sodium metabisulfite and choose products without sulfite additives. Additionally, fresh and minimally processed foods are less likely to contain sulfites.
Always check food labels for ingredient information, especially if you have known sensitivities or allergies to sulfites. Consulting with a healthcare professional is advisable for individuals with specific dietary concerns.