The Chemistry of Food Additives and Preservatives

Kate Onissiphorou

by Kate Onissiphorou

5th October 2022

Food additives are substances that are added to food to improve it in some way. This could be to enhance the flavour, colour, texture or appearance, for instance. Meanwhile, preservatives – a subset of food additives – are commonly used to extend the shelf life of certain food products.

Food additives have been used by our ancestors since ancient times for a variety of purposes. For example, vinegar is one of the first and most common food additives independently invented or discovered by various ancient civilisations. Ancient Babylonian scrolls even mentioned the use of vinegar as early as 7,000 years ago!

Food additives were developed along with the invention of cooking and different recipes. From condiments to spices and fermented homemade additives to mass-produced varieties, food additives now play a vital role in culinary and food processing.

What are food additives?

Food additives are either organic or inorganic compounds that are added to food to improve its characteristics, such as making it more palatable or appetising to look at. 

Scientist using a magnifying glass to look at a donut decorated with tablets with the names of E. food additives.

Some of the main ways food additives can be used to improve food include the following:

  • Flavour enhancement – food additives can amplify the natural flavour of food, such as in the case of umami 
  • Artificial flavouring – some food products, especially processed food, have a bland taste that requires artificial flavouring. Artificial flavourings include fruit flavours for sweets and meat or barbeque flavours for crisps
  • Colour enhancement – natural or artificial food colourings may be added to enhance the colour of food. For example, atsuete (also known as annatto) is a natural red food colouring that comes from the seeds of the achiote tree Red annatto (achiote) seeds in a black bowl.
  • Artificial colouring – artificial colouring is often added to processed foods that have an unattractive natural colour. Common examples of products that need artificial colourings include ice creams and condiments
  • Odour modifiers – these can either enhance, suppress, or add odours to food products. Some also function as food flavourings
  • Food preservative – bacterial and fungal growths are the two main enemies of food longevity. Food products that are stored for long periods, either for commercial or personal use, require preservatives to extend their shelf life
  • Additional nutrients – as processed foods can lose some of their nutrients, supplementary vitamins and minerals may be added
  • Texture modifiers or preservers – anticaking agents, for example, are often added to prevent ingredients from becoming lumpy.

There are many different types of food additives. Some may be used at home, whereas others are designed for commercial, large-scale food production. Some specific examples are outlined below.

Vinegar

Vinegar is an ancient (maybe even prehistoric) invention or discovery. There are at least 15 common types of vinegars that vary depending on the raw materials used during manufacturing. Today, vinegars serve as a food flavouring and preservative.

As a byproduct of the fermentation of sugar using yeast, vinegars can be considered failed or sour wine. From a chemical point of view, they’re diluted aqueous solutions of acetic acid at 4% to 6% concentration. Although vinegars contain identifiable impurities (determined by the source), the active ingredient is acetic acid, which has the chemical formula CH₃COOH.

Table sugar

Table sugar, otherwise known as sucrose, has the chemical formula C12H22O11. It’s commonly derived from sugar canes, sugar beets, and sugar maple saps. Like vinegar, table sugar is one of the ancient discoveries of humans.

As a flavouring, sugar is added to beverages like fizzy drinks and pastries. It’s also used as a preservative in jams and canned products.

Table salt

Table salt or sodium chloride (NaCl) is used both as a flavouring and a preservative. It’s abundant because it can either be mined or derived from seawater. Another ancient discovery with culinary applications, table salt has mainly been used to preserve fish and meat.

Saltpetre

Saltpetre or potassium nitrate (KNO3) is mainly used in preserving meat. It can be derived from natural mineral sources or synthetic processes using nitric acid. The compound is also used in manufacturing gunpowder and fertiliser.

Baking powder

Baking powder or sodium bicarbonate (NaHCO3) is commonly used as a leavening ingredient in baking. It produces carbon dioxide bubbles that make the dough rise and expand. As a base or alkaline substance, sodium bicarbonate is also used for other purposes such as neutralising acidic solutions.

Close-up of sourdough dough

Why are additives added to food?

Additives are added to food mainly for flavouring, preserving, colouring, and maintaining or modifying the appearance and texture. 

For several millennia, food additives have been developed along with the invention of cooking and various recipes from across different cultures. While modern food additives share a similar purpose to traditional additives, the primary aim today is to extend the shelf life of various products.

The difference between additives and preservatives

The main difference between additives and preservatives is in terms of category; all preservatives are food additives but not all additives are preservatives. Some food additives have other roles such as flavouring and artificial colouring.

Different types of food preservation

Various food preservation techniques have been invented over the years. Here are some of the most common:

  • Cooking – exposing food directly to fire or heat kills the bacteria that causes fresh food to deteriorate quickly. The process can therefore extend the shelf life of food for several hours or even days, depending on the ingredients.
  • Pasteurisation – this is a mild heat treatment designed to kill the bacteria in milk. The temperature is typically below the boiling point of water.
  • Drying – fish drying has been practised for thousands of years. Fish or other seafood is dried by exposing it to sunlight to remove moisture. Salt may also be added.
  • Salting – commonly used in preserving seafood and meat, this technique removes the cellular moisture content. Hams are prepared partly through salting.
  • Smoking – meat and fish such as smoked salmon are commonly preserved using this method. Aside from killing the microorganisms and drying the food, smoking also adds flavour.
  • Pickling – this technique typically uses vinegar to kill microbes and thereby preserve foods like fruits and vegetables. Four kilner jars of pickled foods.
  • Canning and bottling – the food is cooked and put into cans or bottles that have been thoroughly cleaned and sterilised.
  • Jellying – fruits are commonly preserved using this method. The pectin in fruits turns gelatinous when boiled at certain temperatures for specific periods of time.
  • Vacuum sealing – the food may first be sterilised through irradiation before it is vacuum sealed in plastic containers.

In summary

Various food additives, including preservatives, are added to food to extend its shelf life and improve properties such as taste and colour. 

Many common additives have been around for centuries. Today, additives and preservatives are designed to increase the commercial value and attractiveness of food.

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