Food preservatives are substances ‘that are added to food items in order to inhibit, retard or arrest the process of fermentation, acidification, and decomposition of food items’. Or, in other words, preservatives in food help keep the food safe, without spoiling, for longer.
Food preservatives are classified as:
Class I preservatives or the natural preservatives such as salt, sugar, vinegar, syrup, spices, honey and edible oil; and
Class II preservatives or the chemical preservatives such as benzoates, sorbates, nitrites and nitrates of sodium or potassium, sulfites, glutamates, glycerides and the like. The food standards regulations require that not more than one class II preservative to be used on one particular food item.
Both, natural and chemical preservatives are categorized into 3 types: Antimicrobials
that destroy or delay the growth of bacteria, yeast and molds. E.g. nitrites and nitrates prevent botulism in meat products. Sulfur dioxide prevents further degradation in fruits, wine and beer. Benzoates and sorbates are anti-fungals used in jams, salads, cheese and pickles.
that slow or stop the breakdown of fats and oils in food that happens in the presence of oxygen(Oxidation) leading to rancidity. Examples of anti-oxidants include BHT, BHA, TBHQ, and propyl gallate. Anti-enzymatic preservatives
that block the enzymatic processes such as ripening occurring in foodstuffs even after harvest. E.g. Erythorbic acid and citric acid stop the action of enzyme phenolase that leads to a brown color on the exposed surface of cut fruits or potato.
The following table shows the type of food preservatives used, the type of food products they are used in, and the permissible limits for their use.
: Permissible limits for use of food preservatives vary depending on the food product, from country to country.