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Amit M. Kheradia
Amit M. Kheradia
Environmental Health and Sanitation Manager

PART 3: Cross-Contamination Control Strategies: Plant Layout and Process Control

In Part 2 of this series, we emphasized the need for hygienically designed equipment and premises necessary for producing safe and quality food. This blog will focus on the importance of laying out an appropriate food processing environment and controlling the processes effectively to minimize the risk of product contamination.


FDA inspectional observations at food sites have revealed that inadequate operational precautions to control pathogen, allergen, or foreign material issues can negatively influence food safety

FDA citation reference Short description Long description
Frequency observations per fiscal year
2019 2020 2021 2022 2023
21 CFR 117.80(c) Manufacturing, Processing, Packing, Holding - Controls The plant did not conduct operations under conditions and controls necessary to minimize the potential for [growth of microorganisms] [allergen cross-contact] [contamination of food] [deterioration of food]
















Designing the Plant Layout

Ensuring a hygienic food processing environment starts with designing a factory with good infrastructure that is easy to clean and maintain and is laid out in a way that minimizes the risk of product cross-contamination.

Food safety begins with the design, construction, and layout of the plant that produces food.

Poor decisions regarding these may lead to an increased risk of food contamination.

  Some key plant infrastructure and layout considerations (illustrated above) are:

  • The buildings (including the walls, ceilings, floors, junctions, fixtures, fittings, equipment, and transport vehicles associated with the food production facility or premises), must be maintained in a sanitary state. The food processing site must also be approved by the relevant authority.
  • The flow of the products (i.e., raw input, work-in-process, and finished outputs) called the process stream, must not create any potential for cross-contamination, i.e., there should be no looped or circular production flows:

High chance of cross-contamination

Some chance of cross-contamination


Negligible or no chance of cross-contamination

  • The air in contact with exposed food needs to be monitored for safety and quality. The flow of air should be from the packed or finished product zone to the exposed or raw materials zone, and not the other way around.
  •  Effective barriers are essential. These include creating zones for different hygiene risk areas, e.g., separation of high-risk production areas from low-risk zones, and pest control measures, including the use of window screens and bottom door seals.
  • The movement and control of traffic and personnel must work to prevent the risk of product contamination and comply with the relevant legislation. For example, it is required by food safety standards and regulations that areas in which high-risk processes are conducted shall only be serviced by trained employees dedicated to that function.
  • Accumulation of waste must not be allowed in food processing, handling, or storage areas. Hence, provisions must be made for the separating, storing, and removing of waste to ensure minimal risk of contact with the food.

* The considerations given above are not an exhaustive list of plant design and layout requirements stated in various food safety regulations and standards.

Implementing Process Controls

Process control, from a food safety perspective, involves managing the plant operations in an effective and efficient way so the risks of product contamination can be significantly minimized. Food safety hazards should be identified, the association risk should be assessed, and appropriate controls should be put in place.

This process starts with the application of risk-based assessment methods, like Hazard Analysis and Critical Control Points (HACCP). HACCP can be used to identify food safety hazards, the Critical Control Points (CCPs) in the process where risk factors must be controlled to minimize risk from the hazard, and the application of appropriate controls to ensure this.

For example, the diagram below shows the process steps involved in the production of cooked, breaded chicken pieces made from raw ingredients:

The CCPs for this process are highlighted in the boxes with the thicker blue borders, i.e., sieving (foreign body hazard control), deep frying (microbial hazard control), blast cooling (microbial hazard control), and metal detection (foreign body hazard control).

For each of these CCPs, the control required and its critical limit need to be defined and continually monitored to ensure they are always achieved.

In the example below, for the CCP of deep frying, the control has been defined as cooking at the correct temperature for the correct time. The time and temperature are then defined in the critical limit, i.e., 320°F for 5 minutes.

Process Step
Deep frying
Hazard & Cause
Survival of pathogens (Salmonella) due to undercooking (low oil temperature or too short a frying time)
Cook at correct oil temperature & for correct time.
Critical Limit
Oil temp 160˚C

Frying time 5 minutes
Fryer operator to check oil temp. and frying time at start-up and every 15 minutes following that and record in frying log
Corrective action
Fryer operator to:
  1. Stop in-feed and divert output.
  2. Dispose of product made since last good check
  3. Inform the production manager & ask an engineer to fix the problem
  4. Record actions in log

HACCP also requires the establishment of corrective actions if monitoring indicates that the critical limits have not been achieved. In the example above, these corrective actions are to stop the product feed; divert the output; dispose of the product since the last good check; inform the production manager; call an engineer to fix the problem; and log the actions taken.

Corrective actions can also include root cause analysis, which will help identify appropriate corrective and prevention actions.

Visualization tools like the Fish-Bone Diagram can help by deep-diving into the variable factors (such as internal and external environments, personnel competencies, equipment, materials, methods, and measurement parameters) responsible for influencing food safety culture in a food processing environment.

Other Cross-Contamination Control Strategies

There are many other ways by which product contamination may happen at a food site. The table below lists some common examples and indicates how the use of color-coded tools and the zoning of production areas by color can both serve as preventive controls to further minimize the risk of product cross-contamination:

Type of contamination Examples of contamination incidents in a processing plant Color-coding recommendations
Cross-contamination: transfer of microorganisms such as pathogens, chemicals, or physical materials from food or a surface to another food or food-contact surface.

Shovel for scooping raw meat was used to handle processed products

Use different colored shovels for raw and cooked product handling


A tube brush for cleaning drains was found on a cookie conveyor

Use different colored tools for drains; hang them on dedicated tool racks or shadow boards of the same color


A white tub trolley for handling rejects was used to store cooked pasta

Use separate colored tubs for different purposes, based on risk

Cross-contact: unintentional incorporation of a food allergen into another food through accidental transfer

Paddle for stirring wheat dough was then used for soy product that should not contain wheat, making it an undeclared gluten allergen hazard

Use different color-coded paddles for use with each controlled allergen

Other important cross-contamination prevention controls to consider are:

  • Equipment used for servicing amenities (e.g., change rooms, toilets, and breakrooms) must not get mixed up with those from the food production zones. For instance, as a critical precaution, tools used for cleaning toilet rooms shall not be used to clean food processing areas.
  • Also ensure that trolleys, vehicles, waste disposal equipment, bins, and trash storage areas are maintained in a serviceable condition and are sanitized regularly to minimize the risk of cross-contamination and prevent them from attracting pests.

Please visit our page on Site Surveys to discover how we can help you develop your color-coded site plan.

Color-coded area zoning can be used as an effective contamination control strategy, to reinforce the message that the people, equipment, and products dedicated to that stay within their own area. This is especially useful if the protective clothing and equipment used are similarly color-coded.

Additional resources on color-coding are available on our website:

Future blogs in this series will offer further support related to the following equipment and facility sanitation challenges:

PART 4: Cross-Contamination Control Strategies: Managing Your Hygienic and Environmental Monitoring Zones

PART 5: Cross-Contamination Control Strategies: Creating Better Sanitation Programs

PART 6: Cross-Contamination Control Strategies: Dealing with the Pest Problem, Product Storage, and Transport Sanitation