Food preservatives are chemicals that are added to foods and beverages, to preserve them. They prevent decay from occurring either by microbial development or by unwanted chemical changes. Preservatives can either be obtained from natural sources or be manufactured synthetically. Various chemical preservatives are added to food to extend their shelf-life and inhibit factors that could trigger food spoilage. Preservatives are mainly used for foods processed or manufactured in the food industry.
Different chemical preservatives have different functions ranging from antimicrobial, antioxidants or a combination of both as well as preserving the sensory attributes of those foods i.e. appearance, texture, flavour etc. Preservatives contain compounds such as sulphites, sorbates, nitrates and nitrites, benzoates etc:
Antimicrobials preservatives e.g. sulphites destroy micro-organisms. Examples of antimicrobial preservatives include:
- Benzoates-The common benzoate used is sodium benzoate (a whitish crystal-like substance) that dissolves in water to become acidic. The acidic conditions it creates hinders microbial development and promote a longer shelf-life of a food. Benzoate and benzoic acid are used to preserve confectionery e.g. sweets, chocolate
- Sorbic and sorbates-They are anti-microbials used to preserve foods such as processed vegetables and fruits, bakery goods e.g. bread, pastries, and cheese.
Antioxidants
- Ascorbic acid/ ascorbate and citric acid – Are also antioxidants that prevent oxidation of food thus reducing the browning of foods. They are mainly used to preserve drinks, sauces, jellies, cheese, jams, canned vegetables etc.
- Tocopherol (form of vitamin E) -It is also an anti-oxidant used in fats , oils and meat products.
- Butylated hydoxyanisole (BHA) or Butylated hydroxytoluene (BHT)-They are anti-oxidants mainly contained in margarine, oils and fats. These preservatives prevent the oxidation of oils and fats.
Preservatives that act as both antimicrobials and antioxidants
- Nitrites and nitrates-They are mainly added to meat and meat products such as sausages, ham, bacon etc. In addition to hindering the development of bacteria and fungi, these chemicals maintain the flavour and pinkish -red appearance of processed meat and meat products.
- Sulphur dioxide and sulphites-Sulphites applied to processed fruits, vegetables e.g. potatoes, processed fish and its products, wines. Are antioxidants and as such prevent the oxidation process of the foods it preserves hence reducing browning that results from oxidation.
Kitchen ingredients such as salt and sugar also act as preservatives. In the post on Salting Food Preservation, we focussed on how salting preserves certain foods. Similarly, sugar has the same effect where it reduces the moisture content of foods, particularly sweetened foods such as jellies, jams, chutney etc . Both can be used at home or on a larger scale, in the food industry. The foods are put into a concentrated sugar solution, causing water to be drawn out of the cells of microorganisms and the food; hence, destructing microorganisms as the conditions no longer favour their development.
Are food preservatives harmful?
Preservatives are generally safe for most consumers. Though, whether or not they are harmful is an issue of concern for most individuals.
Indeed, there have been several claims among certain individuals that the consumption of foods with preservatives triggered some digestive discomfort i.e. bloating and others stating that they caused them allergic reactions, particularly after consuming foods containing sulphites. Moreover, adequate research ascertains an increased risk of developing cancer as a result of consuming foods with chemicals, particularly food products that contain nitrates and nitrites.
Therefore, it is probably best to limit their intake and instead opt for a variety of natural foods including vegetables, fruits, seeds, wholegrains, fish and nuts etc.