The Content of Sulfur Dioxide in Cookies

• Sulfur Dioxide

Sulfur dioxide (chemical formula SO₂), also known as sulfite anhydride, has three resonance structures and is the most common sulfur oxide and the main component of sulfuric acid feed gas. At the same time, it is also a very common food additive in the food industry. Sulfur dioxide is a colorless gas with a strong pungent odor and is one of the major pollutants in the atmosphere. It is also a key monitoring target for exhaust emissions.

• The Harm of Sulfur Dioxide to the Human Body

Sulfur dioxide is easily absorbed by the moist mucosal surface to form sulfurous acid and sulfuric acid. It has a strong stimulating effect on the eye and respiratory mucosa. A large amount of inhalation can cause pulmonary edema, laryngeal edema, vocal cords and suffocation. Acute poisoning: Mild poisoning can cause tears, photophobia, cough, and throat burning; severe poisoning can cause pulmonary edema within a few hours; a very high concentration of inhalation can cause reflex glottic sputum and suffocation. Skin or eye contact can cause inflammation or burns. Chronic effects: Long-term low-level exposure may have headache, dizziness, fatigue and other systemic symptoms as well as chronic rhinitis, pharyngitis, bronchitis, smell and taste loss. Other studies have shown that sulfur dioxide can enhance the carcinogenic effects of the carcinogen benzopyrene. According to animal experiments, under the combined action of sulfur dioxide and benzopyrene, the incidence of lung cancer in animals is higher than that of single factor, and squamous cell carcinoma of the lung can be induced in a short period of time.

• The Source of Sulfur Dioxide in Biscuits

The residual sulfur dioxide in the biscuit is mainly the decomposition product of the modifier sodium metabisulfite. At the same time, sulfur dioxide is a long-established food additive commonly used as a food bleach, preservative, antioxidant and anti-browning agent. The source of sulfur dioxide present in biscuit is mainly exogenous, that is, using sulfur-smoked food or pickled food containing sulfur dioxide (sodium sulfite, sodium hydrogen sulfite, sodium thiosulfate, sodium metabisulfite, etc.), resulting that a certain amount of SO₂ remains in biscuit.

Figure 1. Cookies

• Regulations for Sulfur Dioxide

Foods that require sulfite usage above 20 mg/L should be noted by the US FDA. The FDA and WHO Joint Expert Committee on Food Additives assess the risk of sulfur dioxide as a food additive: the daily allowable intake of sulfur dioxide is 0-0.7 mg/kg body weight, which is a 60 kg body weight for adult, and the daily intake of sulfur dioxide does not exceed 42 mg.

• Method for Determining Sulfur Dioxide Content

The determination of the sulfur dioxide content is usually carried out by the reaction of sulfur dioxide with iodine and the iodine is added to the solution to be tested. The content of sulfur dioxide after the end of the reaction can be determined according to the proportionality coefficient of the chemical reaction and the amount of iodine consumed.

• Method for Preventing Excessive Sulfur Dioxide in Biscuits

In order to prevent excessive sulfur dioxide in biscuits, we should first strengthen the management of flour suppliers, and choose flour suppliers with stable product quality and good reputation. Second, sodium metabisulfite should be used according to legal standards to eliminate the problem of excessive sodium metabisulfite. At the same time, ion exchange, chemical oxidation and enzymatic methods can be used to degrade excess sulfur dioxide in biscuit.

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