Shelf life studies

Although the Safe Food for Canadians Regulations (SFCR) came into force on January 15, 2019, other requirements will be introduced in 2020 and 2021 based on food commodity, type of activity and business size. For more information, refer to the SFCR timelines.

Introduction

A shelf life study is the most effective way to determine the durable life or "best before" date of a prepackaged food and obtain evidence showing that the food will remain wholesome, palatable and nutritional until the end of the durable life.

The shelf life of a food can be affected by a variety of factors such as intrinsic factors that relate to the product itself and extrinsic factors that relate to external conditions.

Purpose

The Canadian Food Inspection Agency (CFIA) created this document as guidance to help food businesses comply with the Safe Food for Canadians Regulations.

It's your choice

You may use other guidance developed by provincial governments, industry associations, international partners or academic bodies as long as they can achieve the outcomes identified in the regulations. Always ensure that the guidance you choose is relevant for your particular business, product or products, and market requirements

What's included

The document provides an overview of the process for conducting a shelf life study. It is not exhaustive, the type of shelf life study required will be unique for each business.

The methods used for conducting shelf life studies will depend on the size and complexity of the food business.

Refer to the Tell me more! section for additional sources of information that may help you establish a shelf life for your food.

What's not included

This document does not provide examples of shelf lives you can use for specific food products.

Roles and responsibilities

Food businesses are responsible for complying with the law. They demonstrate compliance by ensuring that the commodities and processes for which they are responsible meet regulatory requirements. If a written preventive control plan (PCP) is required, the food business develops a PCP with supporting documents, monitors and maintains evidence of its implementation, and verifies that all control measures are effective.

The CFIA verifies the compliance of a food business by conducting activities that include inspection, and surveillance. When non-compliance is identified, the CFIA takes appropriate compliance and enforcement actions.

Shelf life studies

Shelf life studies help establish how long a food, under the conditions it is normally handled and stored, can:

  • retain the desired palatability and quality
  • preserve its microbial, chemical and physical integrity
  • remain wholesome and meet nutritional declarations

Shelf life studies do not need to be conducted on every food product. Product lines can be grouped together by considering common intrinsic and extrinsic factors (discussed later).

Types of shelf life studies

The following methods are commonly used to conduct a shelf life study on a food:

Direct or real-time study

  • With a real-time shelf life study, the food is stored under normal conditions for a period of time greater than the estimated shelf life. The state of the food is verified at regular intervals to determine the point at which it deteriorates and no longer has the quality, nutritional value, microbial, chemical and physical integrity it should have

Indirect or accelerated shelf life study

With an indirect shelf life study, the shelf life of a food is predicted using accelerated factors. Acceleration factors such as increased temperatures are applied to the food to increase the rate of deterioration.

  • The data obtained when measuring the accelerated rate of deterioration, such as data on microbial load, can be used in a predictive mathematical model to determine the spoilage rate and bacterial growth under normal conditions
  • Accelerated studies are often used for a food that has a long shelf life. However, you need to fully understand the specific formulation and properties of the food to be able to correctly interpret the data.
  • A commonly used predictive model for assessing pathogen growth over the shelf life of the product is a Combase
  • The use of an indirect study should be validated to be appropriate and effective in predicting the shelf life. Dual studies, where a real-time study is run concurrently to an indirect study, can help validate the predicted shelf life

Determining the shelf life

Step 1: Estimate the shelf life of the food

To estimate the shelf life of a food product:

  • review information and data from scientific journals, industry guides and other publications that may be used to establish the shelf life of the food. For example, information on history of associated illnesses and, outbreaks or potential microbiological growth within the food product type
  • use the information reviewed to propose a shelf life that can be used as a starting point in the process of determining the shelf life

Step 2: Identify the properties of the food which may cause it to deteriorate or become unsafe

In this step, you identify the properties used to determine the shelf life of the food. This information is used to inform the tests needed to assess these properties to determine the point at which the food has passed its durable life.

Depending on the food product, a number of properties (intrinsic or extrinsic) may be considered.

  • Intrinsic properties are those properties that are inherent to the food product
  • Extrinsic properties are the properties of the environment in which the food is stored
  • The intrinsic and extrinsic properties that affect shelf-life may be critical control points
Intrinsic Properties Considerations
Ingredient quality
  • The quality, consistency, level of contamination and storage of ingredients will affect the final food product
  • Variation in the microbiological quality of ingredients can affect the safety and subsequent shelf-life of food products
Formulation/composition
  • Ingredients, and how they behave when combined, influences the number and type of spoilage organisms that can grow. Any changes to the proportions of ingredients, or the ingredients themselves, may affect the shelf life
    • Some spoilage microorganisms that may be present can outgrow pathogens, consume available nutrients and predominate in the food by a process known as competitive inhibition. This results in the product spoiling before it becomes unsafe
  • The presence of certain microorganisms in foods may retard or prevent the growth of pathogens (for example, lactic acid bacteria in yogurt)
    • Microorganisms may excrete antimicrobial substances that retard or prevent the growth of pathogens, increasing shelf life
Water activity (aw)
  • Water activity (aw) is the amount of water in a food that is available to microorganisms
    • Every microorganism has a minimum aw below which it will not grow.
    • Most pathogens will not grow when the aw is below 0.85
  • Ingredients such as salt and sugars and processing techniques such as drying, curing and cooking used in the production of foods influence the aw and therefore the growth of specific pathogens and subsequently the shelf life of the product
  • Water activity can play a significant role in determining the activity of enzymes and vitamins in foods and can have a major impact on the food's color, taste, and aroma
pH
  • The pH is a measure of the acidity or alkalinity and influences the ability of microorganisms to survive and grow
    • Most pathogens will neither grow nor produce toxins at a pH below 4.6
    • Spoilage organisms such as yeasts and moulds are acid tolerant
  • It is important to remember that the pH of some food commodities changes during the shelf life due to microbial activity, composition and formulation
Preservatives
  • Preservatives such as food additives help to control the growth of microorganisms and increase shelf life (for example, nitrates in meat products)
Extrinsic Properties Considerations
Processing
  • The process that the food commodity undergoes affects its shelf life. For example, high pressure processing of packaged meat is used to increase shelf life
Oxygen availability
  • Shelf life may be extended by removing air surrounding the food, by using vacuum packaging or modified atmosphere packaging
  • Some microorganisms grow in environments without oxygen.
    • Production processes, packaging, storage conditions and duration, as well as a label declaration of the storage conditions (such as "keep refrigerated or frozen") can help control these microorganisms
Packaging materials
  • Packaging materials protect the food from contamination during all post packaging steps
  • Some products rely on particular packaging characteristics (for example, a light barrier) to achieve the expected shelf life
Storage
  • Storing food at refrigeration or lower temperatures can slow down the growth of the microorganisms that are important to food safety and quality
  • Certain pathogens can survive and grow at refrigeration temperatures
  • Other storage factors that should be considered include humidity, light, physical handling, placement near other items that could contaminate the food, and protection from rodents, birds and insects
Distribution chain
  • Shelf life is affected by the way a food is handled and stored as it passes through the distribution chain and retail display.
    • Consider all conditions that the food is likely to be exposed to within the distribution chain (for example, temperature abuse)
Consumer practices
  • While consumer practices during purchase, storage and use of foods are outside the control of the manufacturer, these practices (especially when poor) must be taken into account when determining appropriate shelf life
  • Labelling instructions for proper storage and handling are important

Step 3: Identify the tests needed to determine when the food has reached the end it its durable life

The tests conducted for the shelf life study should:

  • indicate whether the food is safe; has the desirable sensory, microbiological, chemical and physical characteristics; and meets any nutritional or other label declarations
  • be suitable for the specific food product
Tests Considerations
Sensory evaluation
  • This type of evaluation should be done by a trained sensory panel to assess a food's odour, appearance, flavour, and texture relative to a reference sample
    • It is recommended that panels consist of a minimum three panelist with established sensory criteria for the food commodity
    • The food commodity should be evaluated under the conditions at which it is normally consumed and should be safe to eat
  • It is used to monitor and record obvious changes that occur over time
Microbiological
  • This type of sampling and testing is used to evaluate both food quality and safety
  • Microbiological tests may be done to estimate:
    • changes in the number and type of spoilage organisms (yeasts, moulds or bacteria) and pathogens occurring over time
    • the level a food borne pathogens can reach, if present in the food.
      • Because the prevalence of food pathogens is normally low, it may be necessary to conduct a challenge study
        • Challenge studies are conducted by inoculating the food with a microorganism known to cause its deterioration in quality and/or safety; if allowed to grow
        • The challenge study should take into account the worst case product /processing parameters and should be performed by trained personnel
        • The Health Canada document Listeria monocytogenes challenge testing of refrigerated Ready-to-Eat foods recommends an experimental design for challenge test studies to determine the potential for growth of Listeria monocytogenes in refrigerated ready-to-eat (RTE). The document Clostridium botulinum challenge testing of Ready-to-Eat foods recommends an experimental design for challenge test studies to determine if Clostridium botulinum can grow and produce toxin in RTE foods
  • The point in time, before the microorganisms reach a level resulting in spoilage or food safety risk can be determined and the shelf life established accordingly
  • Microbial testing may be run concurrently with sensory evaluation to establish correlation between deterioration of product quality/safety and microbial growth
Chemical
  • Chemical tests can detect changes in quality throughout the shelf life. Examples include pH, headspace gas analysis, free fatty acids, and total volatile nitrogen
Physical
  • Physical tests include measuring texture, viscosity, examination of returned packages from "travel tests" and determining the best, worst and average retail conditions. This involves some controlled product abuse, usually by manipulation of storage and handling parameters
    • A "travel test" helps to identify any hazards involved in transport and handling. It involves transporting the food commodity through the expected distribution and storage chain and examining the food commodity at various points along and at the end of the chain
  • A data logger may be used to record the temperature at preset times for analysis. Experimental design should attempt to mimic real life practices (for example, transportation to retail outlets, consumer purchase, and consumer transport)

Step 4: Plan the shelf life study using the estimated shelf life as a starting point

The planning steps of a shelf life study are critical and require that you research the literature available on shelf life studies that have been conducted and are applicable to your specific food product.

Shelf life factors Considerations
What test(s) should be used?
  • The test chosen depends on the food commodity to be tested and, at a minimum, must comply with the applicable food safety/quality standards
  • You may consider consulting competent third party companies (for example, a laboratory or food process authority) for guidance on applicable tests and associated criteria for food products
Where are the samples collected?
  • Samples for shelf life studies are collected from the same production run after final packaging
  • Consideration should be given to testing finished products which represent the least favourable scenario within the process limits established (for example, with the highest pH within the limits established for the food)
    • This helps ensure that the test results are representative of the average values found in the product on the market
Duration of the study?

For direct shelf life studies:

  • The initial shelf life testing period should be based on the estimated "best before" date
    • If the qualifying criteria (for example, the microbiological criteria for pathogens) are still being met after this period, the shelf life study may continue until they are exceeded
    • If the qualifying criteria are not being met by the estimated "best before" date, the shelf life study is terminated
      • the product formulation may need to be adjusted to achieve the desired shelf life
      • the shelf life testing period is decreased and a shorter shelf-life is established
  • A margin of safety should be applied to the shelf life determined
At what frequency should samples be tested?
  • The frequency of sample testing is based on the estimated shelf life for the food
    • In general products with a short shelf life of 7 to 10 days (perishable products) should be sampled and tested daily
    • Products with a longer shelf life should be sampled and tested at the start of the estimated shelf life, mid-way, at the end of the estimated shelf-life and, at a minimum, one point beyond the estimated shelf life
How many samples are required?
  • At a minimum, duplicate containers should be tested at each sampling interval to account for variability
    • Once a sample is tested, you should discard that sample

    Note: The more samples tested at each interval, the higher degree of confidence in the validity of the shelf life study outcome

  • The size of the production batch should also be considered when determining the number of samples to be taken
What are the storage conditions?
  • During the study, the product samples should be stored under the least favorable conditions (for example, the highest temperature, lighting level and humidity level) that could reasonably be expected to occur for the duration of its shelf-life
  • The temperature and humidity of storage should be checked and recorded regularly

Note: If unrealistically low storage temperatures are used to establish the shelf life there may be an underestimation of microbial growth, particularly pathogens, and an overestimation of the safe shelf life of the food commodity.

Step 5: Conduct the study

Conduct the shelf life study in accordance with what you have established in the planning steps.

  • Document your plan and record all the activities conducted and results obtained

Step 6: Evaluate the data and determine the actual shelf life of the food

  • A point will be reached, sometime during the sampling and testing period of the shelf life study, when the food no longer meets safety, nutritional or quality standards. Evaluate the data gathered to determine how long the food can be kept and remain safe, nutritionally adequate and of an acceptable quality
    • The interpretation of the data gathered is only reliable if the analysis is designed and implemented correctly (for example, appropriate microbiological criteria is used)
  • The shelf life of a food is based on the minimum amount of time it takes for the product to fail any one of the qualifying criteria, regardless of whether it relates to quality or safety
  • Establish the actual shelf life of the product (the point at which the product no longer meets the requirements for quality and/or food safety)
    • The declared shelf life ("best before" date stated on the product label) should be the actual shelf life with the inclusion of a safety margin (for example, the actual shelf life minus one or more days as a safety margin)

Note: A longer shelf life can be reached by modifying the intrinsic properties where possible, and repeating the study.

Step 7: Establish conditions for verifying the declared shelf life

It is important to ensure that the food continues to meet standards for safety and quality for the duration of the declared shelf life.

  • It is recommended that you conduct the shelf life tests two or three times a year. The frequency depends on the shelf life of the food. To gather ongoing data as evidence showing that established shelf life is valid
    • The process involves taking samples from various points within the distribution and retail system and testing for the factors that the shelf life study indicated were the most important, such as acidity, flavour and spoilage
  • A shelf life study is repeated after any change made to the formulation, ingredient quality, packaging, production methods, processing equipment or sanitation
  • If testing shows that the declared shelf life is no longer appropriate, it is adjusted accordingly. Another indication that the declared shelf life might need to be adjusted is if customers complain about poor quality of the food commodity before the "best before" date on the label

Tell me more! Further reading

The following references contain information that helps explain food safety controls, demonstrates how to develop them, and provides examples. The CFIA is not responsible for the content of documents that are created by other government agencies or international sources.

CFIA references

Other references

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