Cleaning In The Food Industry
Reprinted by permission of Wesmar Company Inc. from 
"Basic Principles of Sanitation", Andy Bishop, 1997.

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Cleaning Water

Knowing the water source available to a food processing plant is a must when designing a sanitation program.  An analysis of the raw water should be regularly conducted two to four times a year.  The analysis should include total alkalinity, calcium hardness, iron, pH, silica, total dissolved solids, and standard plate count.
Selection of the chemical compounds used for proper equipment cleaning will be influenced by the constituents of the plant raw water supply.  For instance, if there are high levels of calcium hardness in the water a regular acid rinse may be desired to prevent mineral film buildup.  If iron is present, chelants may be needed to prevent equipment staining.  Often problems in plant sanitation programs are a direct result of the raw water supply.  These sanitation problems can be prevented or minimized through advanced knowledge of the raw water quality.  When water has permanent hardness additional cleaners are required because minerals precipitate out with the alkali cleaners and will require more cleaners.  A water softener may be used in hard water areas to reduce the amount of cleaners needed.  If the raw water is not considered, films can manifest over a long period of time, making removal very difficult.

Types of Soils

The table below shows the four basic food soil residues left on processing equipment.  Depending upon the food product being manufactured and the process equipment used, varying degrees of food soil will be deposited on the equipment during production.  These food soils will require complete removal during the cleaning process and will affect the cleaning compound used, along with the method of cleaning.
Deposit Solubility Removal Process Heat Effects
Sugars Water Soluble Easy Caramelization makes removal more difficult
Fats Water Insoluble
Alkaline Soluble
Difficult Polymerization makes removal more difficult
Proteins Water Insoluble
Alkaline Soluble
Slightly Acid Soluble
Very Difficult Denaturation makes removal more difficult
Minerals Water Soluble
Acid Soluble
Easy to Difficult Reaction with other soils

Factors Influencing Cleaning

There are four interrelated factors which effect the overall cleaning process.  When designing cleaning procedures these factors need to be carefully considered.
  1. Time: The longer a cleaning solution remains in contact with the equipment surface, the greater the amount of food soil that is removed. Increasing time reduces the chemical concentration requirements.
  2. Temperature: Soils are affected to varying degrees by temperature.  In the presence of a cleaning solution most soils become more readily soluble as the temperature is increased.
  3. Chemical Concentrations: Chemical concentrations vary depending upon the chemical itself, type of food soil, and the equipment to be cleaned.  Concentration will normally be reduced as time and temperature are increased.
  4. Mechanical Force: Mechanical force can be simple hand scrubbing with a brush or as complex as turbulent flow and pressure inside a pipeline.  Mechanical force aids in soil removal and typically reduces time, temperature, and concentration requirements.

Methods of Cleaning

  1. Foam: Foam is produced through the introduction of air into a detergent solution as it is sprayed onto the surface to be cleaned.  Foam cleaning will increase the contact time of the chemical solutions, allowing for improved cleaning with less mechanical force and temperature.
  2. High Pressure: High pressure cleaning is used to increase the mechanical force, aiding in soil removal.  In high pressure cleaning chemical detergents are often used along with increased temperature to make soil removal more effective.
  3. Clean in Place (CIP): CIP cleaning is utilized to clean interior surfaces of tanks and pipelines of liquid process equipment.  A chemical solution is circulated through a circuit of tanks and or lines then returned to a central reservoir allowing for reuse of the chemical solution.  Time, temperature, and mechanical force are manipulated to achieve maximum cleaning.
  4. Clean Out Of Place (COP): COP cleaning is utilized to clean tear down parts of fillers and parts of other equipment which require disassembly for proper cleaning.  Parts removed for cleaning are placed in a circulation tank and cleaned using a heated chemical solution and agitation.
  5. Mechanical: Mechanical cleaning normally involves the use of a brush either by hand or a machine such as a floor scrubber.  Mechanical cleaning uses friction for food soil removal.

Fundamental Cleaning Procedure

The following is the typical procedure used when cleaning food processing equipment.  The factors that influence cleaning (time, temperature, chemical concentration, and mechanical force), the method of cleaning, and the food soils to be removed will ultimately determine the cleaning procedures selected for use.
  1. Pre-Rinse: Soiled equipment surfaces are rinsed with warm water to remove the gross amounts of loose food soils.
  2. Cleaning Cycle: Removal of residual food soils from equipment surfaces through manipulation of the four basic cleaning factors and the method of cleaning.  Typically alkaline chemical solutions are used for the cleaning cycle.
  3. Rinse: Rinsing of all surfaces with cold to hot water, depending upon the temperature of the cleaning cycle, to thoroughly remove all remaining chemical solution and food soil residues.
  4. Acid Rinse: A mild acid rinse of the equipment neutralizes any alkaline residues left and removes any mineral soil present.
  5. Sanitize: All equipment surfaces are rinsed or flooded with a sanitizing agent.  Time and concentration are critical for optimum results.

Cleaning Compound Composition

There are two classes of cleaning compounds, alkaline and acid.  Chemical formulations for alkaline and acid compounds vary widely providing for selection flexibility when considering sanitation procedures, types of processing equipment to be cleaned, chemical dispensing, and method of cleaning.

Reprinted by permission of Wesmar Company Inc. from "Basic Principles of Sanitation", Andy Bishop, 1997.

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