Shelf life studies
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.
The Canadian Food Inspection Agency (CFIA) created this document as guidance to help food businesses comply with the Safe Food for Canadians Regulations.
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
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
|Water activity (aw)
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
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
|What test(s) should be used?
|Where are the samples collected?
|Duration of the study?
For direct shelf life studies:
|At what frequency should samples be tested?
|How many samples are required?
|What are the storage conditions?
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.
- Combase online tool for quantitative food microbiology
- Health Canada's Clostridium botulinum challenge testing of ready-to-eat foods, 2010
- Health Canada's Listeria monocytogenes challenge testing of refrigerated ready-to-eat foods, 2012
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