Home > Guideline on Validation of Product Shelf-life

Introduction:

Shelf-life is the period of time over which a food maintains its safety and/or quality under reasonably foreseeable conditions of distribution, storage and use1-2. The shelf-life of a food begins from the time the food is produced and/or packed.

Validating product shelf-life is obtaining and documenting any evidence that proves that the shelf-life of a food is accurate and that the food will maintain its safety and/or quality until the end of that shelf-life.

While the overarching responsibility for food safety rests with food business operators3-5, there is no generic method to estimate and set food shelf-life. This is because many different conditions can affect product safety and quality. As such, this document outlines good practice for food business operators to estimate, set and verify the safety of food over its shelf-life.

Scope:

The setting and validation of shelf-life as it relates to food safety is within the scope of this document. In most circumstances, these foods will require a ‘use-by’ date to indicate the end of shelf-life.

The setting and validation of shelf-life as it relates to food quality and sensory issues are outside the scope of this document. In most circumstances, these foods will require a ‘best-before’ date to indicate the end of shelf-life.

Legal Requirements & Responsibilities for Shelf-life:

General Food Law

General food safety requirements are that food must not be placed on the market if it is unsafe, i.e. injurious to health, or unfit for consumption.

Responsibility

Generally, the manufacturer of a food (with some exceptions) is responsible for setting and validating the shelf-life. However, this responsibility may also fall to secondary manufacturers (co-packers), re-packers, food caterers, food retail outlets etc. depending on specific circumstances.

Microbiological Criteria

Food should “not contain microorganisms their toxins and metabolites in quantities that present an unacceptable risk for human health”.

Furthermore, some food business operators may be required to demonstrate that foods they manufacture comply with specified microbiological criteria throughout the foods shelf-life under reasonably foreseeable conditions of distribution, storage and use.

Labelling

Shelf-life is defined in European legislation as the ‘date of minimum durability’ and means the date until which a food retains its specific properties when properly stored. The date of minimum durability provides for two different indicators of food shelf-life.

• ‘Use-by’ date – Used for food which from a microbiological point of view, is highly perishable and therefore, likely after a short period to constitute an immediate danger to human health. After the ‘use-by’ date has passed, a food is deemed unsafe and must not be sold or consumed.
• ‘Best-before’ date – The date until which a food retains its specific properties when properly stored, i.e. quality characteristics such as appearance, odour, texture, flavour etc.

Setting & Validating Shelf-life of Food:

Many different factors will affect the safety of food and lead to variation in shelf-life. As such, there is no simple answer to how long a shelf-life should be and how that shelf-life should be set and validated. However, there are good practice guides available for food business operators to follow which will help them to accurately estimate, set and validate the shelf-life of foods.

In estimating and setting shelf-life, the primary objective should be food safety. Therefore, an accurate shelf-life is essential. If the shelf-life is too long or food business operators assume that food is going to be produced, distributed and stored under unrealistic conditions there is an increased risk of food safety issues arising, people becoming ill and damage to the food business operator’s brand and reputation.

With this in mind, shelf-life should always be an integral part of a food business operator’s procedures based on HACCP and good hygiene practice and should always take into account, reasonably foreseeable conditions of distribution, storage and use of the food including consumer practices where applicable.

It is strongly recommended that food business operators document all work related to estimating, setting and validating food shelf-life. This will allow the food business operator to link together documented work to support and provide objective evidence that the declared shelf-life is accurate. It will also allow customers and inspectors alike to verify the validity of the shelf-life declared. The documentation which relates to shelf-life should be filed together and kept by the food business operator as a part of its procedures based on HACCP.

The shelf-life of food ideally should be estimated during product development and set before the food goes on sale to consumers. The estimate of shelf-life should be made at the point in the product development process where the food business operator is confident that it can consistently produce the same food from batch to batch under real processing conditions.

Other circumstances where the shelf-life should be estimated, set and validated include:

• The absence of supporting evidence for the shelf-life of an existing food
• Modification or reformulation of a food or its production
• Where there is a legal requirement

Describe the Food

Typically, when a food business operator is developing a food product, a preliminary product specification will be drawn up to outline all details relating to the food and its manufacture. It is important that food business operators include as much information as possible in this specification.

Establish the Characteristics of the Food

All foods have their own unique characteristics which will affect food safety and shelf-life. The characteristics of the food’s entire lifecycle from choice of ingredient through processing and distribution to final consumer, will affect shelf-life.

Some characteristics prolong shelf-life while others decrease it. Describing, measuring and understanding these characteristics will allow food business operators to identify what characteristics will cause food to become unsafe and affect the shelf-life.

All foods can have their characteristics broadly divided into intrinsic and extrinsic characteristics. Intrinsic characteristics are those characteristics inherent to the composition of the food such as its ingredients and formulation. Extrinsic characteristics are those characteristics which relate to the external processing environment which impact on the food such as storage temperature and packaging.

Predictive Microbiology

Predictive microbiology uses mathematical models (built with data from laboratory testing) and computer software to graphically describe the responses of microorganisms to intrinsic or extrinsic characteristics.

Predictive microbiological models are initially useful to help estimate food safety and shelf-life having established the food’s intrinsic and extrinsic characteristics. In product development, a predictive microbiological model may allow a food business operator to evaluate the safety and stability of new formulations and identify those which may give a desired shelf-life. They are also useful when food with an established shelf-life is subject to a minor process or formulation change. A predictive microbiological model can then be used to establish if the change might have any effect on the safety and shelf-life of the food.

However, predictive microbiological models do not replace laboratory analysis or the training and judgement of an experienced food microbiologist. Food business operators should never rely solely on any predictive microbiological model to determine the safety of food or its shelf-life.

Predictive microbiological models are normally developed assuming that microbial responses are consistent. While predictive models can provide a cost-effective means to minimise microbiological testing in determining shelf-life, there may be occasions when the model’s predictions may not be accurate, due to inconsistent microbial responses and variations in the growth media. Research has indicated that this is often why some predictive microbiological models fail to accurately predict the survival, growth or inactivation of pathogens in food products.

Laboratory Testing

The next step in a shelf-life study is often the planning and design of laboratory testing of the food. In this regard, microbiological tests are predominately used to make the critical decisions regarding food safety and shelf-life.

Microbiological tests are also used to estimate food quality over the shelf-life and are often carried out in conjunction with tests to establish safety. However, the quality aspects of shelf-life are not discussed here.

Two types of laboratory testing, durability studies and challenge testing can be used in relation to shelf-life.

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