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Many products, including food, have a shelf life. A shelf life puts a time limit on how long a product can be stored before it becomes unsuitable for consumption or use.
The UK produced around 9.5 million tonnes of food waste in 2018. Research by the charity Waste and Resources Action Plan (WRAP) revealed that of the 9.5 million tonnes, 1.5 million was wasted by manufacturers and 0.3 million by the retail industry.
If the shelf life of products can be maximised, without compromising on safety, this would benefit businesses, consumers and the planet.
What is a food shelf life?
From the time that all food is manufactured, processed or picked it will begin to degrade. The speed that a product degrades at will vary significantly depending on the product.
Products are often displayed for sale in a retail store on shelves, on counters and in fridges or freezers. Some products will begin their journey a significant distance away from their retail destination. Right from their origin, through the supply chain, if items have been kept under appropriate conditions, they should still be in an ideal state for consumption (or use) until a predetermined date, without impairment to:
Shelf lives of products differ greatly between fresh, frozen and tinned goods. Some products are stamped with a use-by date and others have a best before date.
Typically, we think only of food and drink having a use-by or best before date; however, many other goods will have their own shelf life such as medicines or some cosmetics.
Legislation covers what information has to be printed on a food label. This includes:
1. The name of the food
2. List of ingredients
3. Allergen information
4. Quantitative declaration of ingredients (QUID)
5. Net quantity
6. Storage conditions and date labelling
7. Name and address of manufacturer
8. Country of origin
9. Instructions for preparation
10. Nutritional declaration.
Certain products require additional labelling such as declaring additives, sweeteners or caffeine content. Certain foods that are not prepacked (such as loose items) have reduced requirements for labelling.
What is a food shelf life?
Food technologists test and analyse food items to check they are safe, check their nutritional content and to add guidelines about how and when to store, use and prepare them.
It is important that food that is consumed is safe to eat, because food can provide the ideal conditions for bacteria to grow. Eating contaminated food can make people extremely unwell.
A use-by date indicates how long you have to consume an item before it becomes unsafe; food can be eaten up to and on the use-by date but should not be consumed after this date. Use-by dates relate to food safety.
A best before date indicates the date that the quality and freshness of a product will begin to decrease. Food may still be safe to consume after a best before date, but the texture or taste may be impaired.
The shelf life of a product can be calculated using tests that assess how long a product remains stable during the recommended conditions for storage. The product is monitored over time to see how long it is until the quality product falls below minimum requirements. This gives an indication of shelf life.
The recommended shelf life will only apply if the recommended conditions are maintained. Some foods, for example cut and packed fruit and ready prepared sandwiches or salads, will always have a relatively short shelf life.
Ready-to-eat food is also known as high-risk food. These will normally be accompanied by a use-by date. High-risk foods will provide ideal conditions for bacteria to grow.
Other examples of high-risk foods are:
- Cooked rice
- Cooked meats/poultry
- Dairy products (unpasteurised milk, cream, yoghurt)
- Fish and seafood.
Low-risk foods will often require no refrigeration (prior to opening) and are usually high in salt or sugar content, acidic or have a low water content. These will usually have a best before date.
Low-risk foods include:
- Pickled goods
- Dried pasta
- Jam and preserves
- Uncut fresh fruit and vegetables
- Pasteurised items such as UHT milk or pasteurised juices.
Frozen foods will have a significantly longer shelf life than fresh goods, providing that they are correctly stored. Once thawed, frozen food will not last long before it becomes unsuitable for consumption and should not be refrozen. Although frozen food that has exceeded its shelf life might not be unsafe, it will begin to lack taste, texture or nutritional content.
What factors affect food shelf life
The shelf life of most products can be influenced by factors such as whether food is exposed to light, moisture or heat. Shelf lives can also be affected by mechanical processes, exposure to contaminants (such as microorganisms) and transmission of gases.
Shelf life can be affected by a number of factors during production, supply or sale. These include how and where food is:
The shelf life of food products can also be affected by external factors such as:
- Chemical additives or preservatives
- Production processes.
Food can also be affected by intrinsic factors (those occurring within the food stuff itself), such as:
- pH levels
- Salt and sugar content
- Moisture/water content
- Chemical composition/stability of food
- Oxidation levels.
Extrinsic, external (and to an extent environmental) factors can be assessed, controlled and changed.
Intrinsic factors within the food cannot be controlled, therefore it is important that manufacturing methods, storage and supply chain logistics perform at optimum levels for shelf life to be as long as possible.
This might mean changing processing methods, altering the materials used for packaging or rethinking when and how items are distributed in order to give food items a longer shelf life, reduce waste and increase profitability.
How to determine the shelf life of food products
The concept of shelf life is typically studied by:
- Food scientists
- Food manufacturers
- Food distributors.
More recently, experts who specialise in:
- Reducing food waste.
Have joined in the debate around how food is labelled and how the longevity of a product is defined.
The word ‘acceptable’ is often used when discussing shelf life and despite academic studies, tests under laboratory conditions and the collaboration of experts within the fields of food science, there is always an amount of subjectivity around shelf life. This is because the idea of a food being ‘acceptable’ does not have one universal meaning to everyone.
The subjectivity of shelf lives can cause some confusion for consumers and retailers. A more detailed model splits the idea of shelf life into several different stages, which can help to understand shelf life further:
Primary shelf life – the length of time from initial production/packing to where the item will first become unacceptable
Secondary shelf life – the length of time after the packaging has been opened that the item should retain its quality
Required shelf life – the minimum time period that an item has to maintain to be commercially viable (i.e. keeping in mind the time from production to transportation to display to potential purchase)
Maximum shelf life – the maximum amount of time the item has using optimal packaging
Display shelf life – the length of time products can be displayed for retail (under specific conditions)
How to increase the shelf life of food products
It is important that the food we eat is safe and fit for consumption. Unlike with a use-by date, shelf life can refer to the suitability or quality of a product. Consuming an item once it has passed its allocated shelf life may not be dangerous to health.
Depending on the product, a consumer might use their common sense in some instances to decide whether a product is fit to eat or drink once it has exceeded its shelf life.
It is in the interest of businesses to maximise the shelf life of their products and to take all steps necessary to ensure that food reaches consumers in the best condition possible.
The benefits to food manufacturers and retailers of increasing shelf life can include:
- Increased profitability
- Less wastage
- Customer satisfaction
- Being a more sustainable business
- Improved reputation.
Although it will not affect the shelf life of a product, as consumers, it helps to be able to understand the meanings of food labels, including:
- Use-by dates
- Best before dates
- Display until.
This can help us to make informed and sensible decisions about what to buy, what to safely consume and what to discard. This helps to reduce the amount of food that ends up needlessly at landfill and might help to reduce instances of food related ill health from consuming expired items.
To maximise the shelf life of food, it needs to be kept and stored at optimal conditions once packaged. This includes immediately postproduction and at all stages of the supply chain such as during transportation and storage as well as whilst on retail display.
The shelf life that is recommended for food items only refers to them being stored in the recommended conditions. External issues such as extremes in temperature, mishandling by workers or damage to packaging will significantly reduce shelf life.
This means that people working at all stages of food supply and sale should be working safely and competently. Staff should be well trained with clean and tidy working environments and the correct tools for the job in hand.
Five ways to extend shelf life
1. Change or improve packaging – gaps or holes in packaging or problems with the heat sealing processes in factories can lead to food being exposed to air or moisture and an increased chance of bacteria or microbial growth. Shelf-life extending packaging such as Modified Atmosphere Packaging (MAP) works by controlling the gases around an item.
2. Absorbent trays, pads and sheets – these are commonly used within the fresh produce industry. Pads and trays can slow the respiration rate of freshly cut produce, inhibit oxidation and absorb excess juices. Some companies are experimenting with using natural pads and coverings to reduce their use of plastic based items alongside improving shelf life.
3. Acidity – highly acidic environments inhibit the growth of bacteria. The bacterium Clostridium botulinum (botulism) is the most threatening pathogen to food stability and fails to grow below a pH of 4.5. Vinegar and lemon juice have an approximate pH of 2, giving pickled goods such as beetroot, gherkins or fermented items like sauerkraut a long shelf life. Citric acid can also be added to food as it slows the oxidation process substantially.
4. Additives and preservatives – there are many chemical additives that are routinely added to food to preserve them. Sodium benzoate (E211) and potassium sorbate (E202) inhibit the growth of mould and yeast. Nitrites and nitrates (E249 – E252) are used in cured meats and some cheeses. Food additives have to pass robust safety assessments; however, consumers are becoming increasingly sceptical of chemicals in food due to concerns over links to health problems and hyperactivity in children.
5. Natural additives – salt, sugar, alcohol, lemon juice, vinegar and certain herbs/spices have been used to preserve foods naturally throughout history. Many people prefer the use of natural ingredients over synthetic additives due to their perceived health benefits.
There are benefits to increasing shelf life to businesses and manufacturers, as well as to the consumer. These include improved profit margins, better quality products, fresher produce and fewer items being rejected.
Longer shelf life also means the possibility of longer shipments and expanding the geographical area that businesses are able to serve.
There are many ways that businesses can try to increase shelf life to reduce food waste, make a commitment to being more sustainable and improve their output. Consumers can also empower themselves by making sure they read and understand labels on packaging, have knowledge of chemical additives and alternatives and buy from reputable traders.
The particular solutions that a business chooses to extend the shelf life of its products will depend on the specific product and how it is sold.
Food related businesses, including farms, factories and retailers, will find it helpful to keep up with relevant market trends and latest scientific research, changes in legislation (such as certain chemical additives being withdrawn) and best practice around understanding and extending shelf life.
The evolution of food research will mean improvements in food safety and food quality. These innovations should, in turn, influence developments within food manufacturing and retail as well as leading consumers to make more informed choices. As the shelf life of products is increased, less wasted food should be arriving at landfill.