Preventing cross-contamination

Introduction

Cross-contamination is often a contributing factor in outbreaks of foodborne illness.

Preventing cross-contamination is an important part of a Preventive Control Plan (PCP). Sources of cross-contamination are identified during the hazard analysis and control measures are put in place to prevent the cross-contamination of a food.

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 is included

The document provides information on:

• Factors that can result in cross-contamination
• How to prevent cross-contamination

What is not included

The information provided to reduce cross-contamination is not exhaustive. The hazards, potential for cross-contamination and procedures to prevent cross-contamination are unique for each business.

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 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.

Preventing cross-contamination

In order to prevent cross contamination, you have to first:

• Conduct a hazard analysis to identify all hazards that present a risk of contamination to a food. Be sure to consider each input and step in the production
• Establish control measures to prevent hazards or reduce them to an acceptable level

The document Conducting a hazard analysis provides guidance on the identification of hazards.

In addition to the control measures you implement to prevent hazards from contaminating a food, you should consider the factors that can result in cross-contamination of a food and apply good practices to prevent it.

Factors that can result in cross-contamination

Understanding how cross-contamination can occur is the best way to prevent cross-contamination.

The following provides examples of factors to consider that can result in cross-contamination.

Establishment or equipment design:

• cross-connections between unprocessed and processed food processing lines
• residues of cleaning chemicals from the clean-in-place (CIP) system
• conveyance equipment such as forklifts or line conveyors that can harbor and transport dirt within a food manufacturing environment
• pest activity
• the accumulation of waste and the manner it is stored and disposed
• use of the same preparation areas, equipment or utensils for raw and cooked food
• exposure to allergens

Cleaning/sanitizing:

• allergen residues that can remain on equipment surfaces if not cleaned effectively
• splashing of water contaminated with pathogens in food processing areas
• residues from cleaning chemicals that can remain on food contact surfaces

Employee practices:

• not respecting traffic flows between raw product areas and finished product areas
• failure to apply proper hygienic practices
• movement of employees from one processing area to another
• soiled clothing or failure to wear protective clothing

Storage

• exposing ready-to-eat food to raw food
• leaky boxes

Quick tip

Look for direct and indirect points of contact between finished products, raw products, allergenic ingredients, packaging materials, waste, inedible products, non-food products, contaminated air, food contact surfaces, employees and visitors.

How to prevent cross-contamination

The following provides examples of practices that can help you prevent cross-contamination.

Premises

• Physical separation of the areas dedicated to handling and preparing raw food from the areas dedicated to handling and preparing cooked Ready-to-Eat (RTE) food, including marking the equipment and utensils dedicated for each area
• Having clean filtered air flowing from finished product or packaging areas to raw product handling areas

Equipment

• Install equipment and pipelines in a way that does not jeopardize the integrity of the CIP systems, resulting in cross-connections
• Use colour coding or other designations to identify equipment and utensils by use and location within the establishment
• Ensure that there are no opportunities for cross-contamination from common equipment, e.g., weigh scales, kettles, mixers, grinders, slicers, table tops, curing injection equipment, conveyor belts, utensils, or knives
  • Equipment should not have "harbourage sites" such as cracks or seams where water and debris can collect and result in small niches where pathogens such as Listeria monocytogenes can persist and multiply
• Avoid repairing equipment during processing operations unless the work can be done without creating a cross-contamination hazard

Quick tip

Avoid cross connections that could result in one material contaminating another. For example: avoid cross connections between:

• allergenic and non-allergenic ingredients
• cleaning solutions and food or potable water
• waste materials and food

In complex food manufacturing process designs, for example, mix proof valves are used to shut off, open, or change over pipe paths to guarantee there is no intermixing or cross-contamination of incompatible products at intersection points.

Process Design/Flow

• Separate raw and unprocessed food, either physically or by time, from processed foods.
• Separate foods containing allergens, either physically or by time, from allergen-free foods, and check that cleaning is effective. For example:
  • schedule foods containing allergens as the last product of the day or after running foods that do not contain allergens
  • minimize the amount of equipment that comes into contact with allergenic ingredients by adding allergenic ingredients near the end of the process, or by isolating the point where an allergenic ingredient is added to the food (if possible)
  • carefully control the use of rework that contains allergens
• Evaluate areas of shared equipment or physical cross-over to ensure they are not cross-contamination points. For example, products containing an allergenic ingredient do not travel on a conveyor belt above a product that does not contain allergens
• Use dedicated lines whenever possible
  • this could prevent cross-contamination of a RTE food by another food prepared in which low levels of pathogens can occur. For example, a raw food that needs to be cooked before consumption or another RTE food in which a low level of Listeria monocytogenes can occur and does not present a health risk
• Prepare RTE food at the beginning of the operation, before preparing food in which low levels of pathogens can occur without presenting a health risk, or after a full clean-up and sanitation
• When designing the process, consider the proximity of equipment to other machines, avoid line cross-over, allow sufficient space to perform wash downs, and reduce the creation and spread of dust
• Identify sanitary and restricted access zones to help control traffic flow patterns and equipment between the incoming ingredients and the finished products
• Establish a flow of operations that prevents employees working in the raw processing area from accessing the RTE area
• Don't place containers or boxes that may have been stored on the floor onto food contact surfaces
• Use different utensils for raw and pre-prepared foods
• If you use the same facility or common equipment to produce more than one Listeria monocytogenes risk category of RTE food, consider potential cross contamination. The cross-contamination can be prevented by using dedicated production lines/equipment or by processing Listeria monocytogenes risk Category 1 RTE products at the beginning of the operation or after full clean-up and sanitation

Cleaning and Sanitation

• Clean up spills immediately to reduce opportunities for cross-contamination
• Thoroughly clean and, where necessary, sanitize food contact surfaces, utensils, equipment, fixtures, and fittings after contact with raw foods
• Do not begin operations until sanitation requirements have been met
• Use colour-coded cleaning utensils for different sections of the plant
• Avoid cleaning during processing operations unless the work can be done without creating a cross-contamination hazard

Don't forget

Potential sources of cross-contamination include pumps, pipe connections, valves, and dead spots in product lines and or other "difficult to clean areas" where product, extraneous material, or residue from cleaning agents may persist.

Personnel and visitors

• Control the flow of personnel or visitors such as contractors to minimize the likelihood of cross-contamination. Limit employees to designated task areas where possible. For example:
  • have personnel enter processing areas via a changing facility where they are required to put on clean protective clothing, including footwear, and wash their hands
  • post traffic control charts of pre-identified routes
  • post signs and cautions in the allergen handling areas
• Ensure personnel in food handling areas maintain personal cleanliness and take precautions to prevent cross-contamination. For example:
  • require employees to wear protective clothing, hair coverings, footwear and gloves as appropriate to the operation, and to maintain the sanitary condition of these items
  • prohibit employees from eating in food handling areas, using undesignated containers in food manufacturing, and other behaviours that can cause cross-contamination of food
  • store personal effects and street clothing away from food handling areas
  • change smocks and dip or change boots before entering a RTE area

Best practice

Cross-contamination may result in food products not meeting applicable microbiological, chemical and physical standards. Monitor applicable microbiological, chemical and physical parameters to identify any cross-contamination in your food manufacturing processes.

Storage

• Store ingredients containing Health Canada's priority allergens below or away from allergen-free ingredients (for example: do not store loose bags of nuts over an open bin of flour)
• If raw and RTE products are stored in the same refrigerator, store RTE foods above raw foods
• Keep food products covered and off the floor during storage
• Store cleaning materials and other chemicals separately from food products
• Consider dedicated receiving storage areas, or storing incompatible products separately, either physically or by using a same space-different time approach. Another good practice is to store allergen ingredients on shelves below non-allergen ingredients, in case of spills
• Keep bags, boxes, and containers sealed when not in use

Tell me more! – Further reading

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

CFIA references

• Conducting a hazard analysis
• Preventive controls for food allergens, gluten and added sulphites

Other references

• Codex Alimentarius Commission, General Principles of Food Hygiene, CXC 1-1969, 2020
• Food allergies