Preservatives

 Preservatives are usually added to increase the shelf life of food items. Addition of preservatives is one of the most practiced forms of adulteration at present. Fruits and vegetables, fish and seafood, meat and processed meat, milk and dairy products, and beverages are the most tempting targets.

Formaldehyde is the most reported preservative used in fruits and vegetables. Formalin inhibits the growth of microbes by interacting with the amino groups of adenine, cytosine, and guanine and denaturing them. It also penetrates the interiors of bacterial spores, which makes it capable of preventing microbial contamination and prolonging the shelf life of food. Although there is no set standard for the daily intake of formaldehyde from food, the World Health Organization (WHO) estimated it to be in the range of 1.5–14 mg/d (mean 7.75 mg/d) for an average adult. According to the European Food Safety Authority (EFSA), the daily oral exposure to formaldehyde should not exceed 100 mg formaldehyde per day. In a recent study, the formaldehyde level in fish and seafood were found to be higher than the recognized safety level of 5 mg/kg.

In addition to formalin, wax components, and different forms of esters, are also used to reduce the water loss and surface abrasion. The other purpose is to control internal gas composition and provide the shiny appearance of those fruits and vegetables that lost their natural wax during primary processing. Compared with other lipid and non-lipid coatings, wax coatings provide better resistance to moisture loss. Due to petroleum-based wax containing harmful wood rosins and solvent residues, beeswax, carnauba wax, and shellac are preferable. Fruits and vegetables are dried well before waxing and handling. With the increasing demand and distant transportation of fish and seafood, the addition of low-cost preservatives has been a long-practiced issue. Fish, dry fish, and seafood are usually adulterated with preservatives, such as formalin, chlorofluorocarbon, and DDT powder, to tackle the spoilage and quality deterioration. External parasites of fish egg are also treated with formalin. Since a small quantity of formaldehyde is also naturally produced in fish as a byproduct of amine oxide degradation, artificially added formalin is quite difficult to detect. Increment of shelf life by inhibiting microbial activities is a common form of milk and dairy product adulteration. It is accomplished by adding several preservative chemicals, such as formalin, urea, nitrate or pond water, borax acid, boric acid, cane sugar, sucrose, glucose, caustic soda, salicylic acid, hydrogen peroxide, benzoic acid, hypochlorite, and potassium dichromate. Hydrogen peroxide acts as a preservative for pasteurized milk by activating the natural enzyme lactoperoxidase. On the other hand, a significant reason for adding urea in dairy products is to elongate the shelf life. Preservatives, such as salicylic acid and benzoic acid, are added for preserving cheap wines prone to souring. Citric acid is added for pH adjustment. Beet sugar, cane sugar, concentrated rectified must, grape must, or grape wine are added to increase the natural content of ethanol and overall commercial value.