Refrigerating Farm Produce

Learn to understand and manage chilling or freezing farm produce - meat, fruit, vegetables, flowers and more.

Course Code: BAG225
Fee Code: S2
Duration (approx) Duration (approx) 100 hours
Qualification Statement of Attainment
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Learn to Manage Chilling or Freezing of Farm Produce


Refrigeration, and the technology behind it, is one of the most important aspects in the food supply chain and paramount in getting food from the farm to the consumer in a fresh, edible and safe state. Not only food, but cut flowers, seeds, extracted oils and other chemicals produced by farms all need to be kept at an optimum temperature; hence an understanding of refrigeration may be very important to farmers, traders and manufacturers of most types of farm produce.

When food is chilled it has an advantageous effect on quality because transport of moisture is minimised through refrigeration – it also extends shelf-life.   When food is frozen it adds another dimension – most bacteria don’t survive temperatures below -12°C and low temperatures also slow the rate of both chemical and enzymic change in foods. Freezing foods promptly after harvest extends shelf-life by preventing deterioration, retains the texture, flavour colour and vitamin C content. This also means that products that are seasonal are available to the consumer all year round and lessens food wastage.

Lesson Structure

There are 8 lessons in this course:

  1. Nature & Scope of Refrigeration
    • Introduction
    • Nature of refrigeration
    • Why refrigerate?
    • Brief History of refrigeration
    • Scope of refrigeration
    • What things are refrigerated and what should not be?
    • Refrigeration Methods
    • Different types of refrigerators
  2. The Refrigeration Process
    • The Refrigeration Process
    • Underlying Principles
    • Definition of Work
    • The Second Law of Thermodynamics
    • The Gas Laws
    • The refrigeration cycle
  3. The Vapour Compression System
    • Refrigeration components in vapour compression systems
    • Compressor
    • Condenser
    • Liquid Receiver
    • Expansion Valve
    • Evaporator
    • Interconnecting pipework
    • Suction Line
    • Discharge Line
    • Liquid Drain Line
    • Liquid Line
    • Refrigerant composition
    • The domestic refrigerator
  4. Heat Load Calculations
    • Heat gain calculations
    • Fabric Heat Gains
    • Product Heat Gains
    • Air Change Heat Gains
    • Occupancy Heat Gains
    • Lighting Heat Gains
    • Mechanical/Electrical Heat Gains
  5. The Refrigeration Cycle: Refrigerants & Components
    • Refrigerant Selection
    • ASHRAE Standards
    • Boiling Point/Evaporating Point
    • Freezing Point
    • Toxicity and Flammability
    • Acute Toxicity Exposure Limit (ATEL)
    • Practical Limit (PL)
    • Global Warming Potential
    • Pressure enthalpy chart
    • Component selections
    • Evaporator Selection
    • Compressor Selection
    • Condenser Selection
    • Expansion Valve Selection
  6. Applied Refrigeration: Farm Produce
    • Fruit
    • General Requirements
    • Pre-treatment
    • Specific Examples
    • Vegetables
    • General Requirements
    • Pre-treatment
    • Specific Examples: Precooling
    • Specific Examples: Storage Life
    • Nuts AND Seeds
    • General Requirements
    • Specific Examples
    • Meat
    • General Requirements
    • Specific Examples
    • Fish
    • General Requirements
    • Specific Examples
    • Dairy
    • General Requirements
    • Specific Examples
  7. Applied Refrigeration: Other Products
    • Cut Flowers
    • General Requirements
    • Duration
    • Shelf Life
    • Post-Harvest Treatments
    • Conditioning for Market
    • Packaging
    • Specific Examples
    • Seed Storage Behaviour
    • Factors Affecting Storage of Seed
    • Types of Seed Storage
    • Cold and Cool Rooms in Seed Banks
    • Chemicals
    • Plant Growth Regulators
    • Storing Plant Growth Regulators
    • Auxins
    • Cytokinins
    • Gibberellins
    • Agricultural Chemicals
  8. Freezing Goods
    • Why Freeze Food?
    • Problems of Freezing
    • Other Frozen Agricultural Products
    • Commercial Freezing Methods
    • Methods
    • Commercial Freezing Equipment
    • Domestic Freezing
    • A few guidelines for freezing
    • Power Failure
    • Other General Considerations
    • Freezing fruits
    • Freezing vegetables
    • Freezing meat and poultry
    • Freezing meat, poultry and fish
    • How to Soften Water

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.


  • Explain the nature and scope of refrigeration by providing a general overview of the concepts.
  • Outline what happens to the physical properties of substances during refrigeration and different refrigeration methods, especially vapour compression.
  • Describe the vapour compression refrigeration system and its components.
  • Describe the nature of cooling and freezing items and outline how to calculate the heat load to be removed in order to carry out these processes.
  • Outline the principles behind the basic refrigeration cycle, and selection of refrigerants and components.
  • Explain refrigeration and chilling techniques for a range of edible products.
  • Explain refrigeration and chilling techniques for a range of products other than edible produce.
  • Outline the difference between freezing and refrigerating and how freezing methods can be used to store a range of goods.

What things are refrigerated and what should not be?

The majority of items belonging to the overall categories of fruit, vegetables, meat, fish, cut produce and flowers can all be refrigerated, however not all items should be refrigerated. Refrigerating certain foods can actually change their flavour and not in a good way. It can even reduce their nutritional quality of accelerate the spoiling/decaying process.

The following are items that should generally not be chilled:

  • Bread: it is fine to freeze bread, but chilling bread causes it to dry out.
  • Herbs: chilling herbs can cause them to wilt faster.
  • Potatoes: storing loose potatoes in a fridge can adversely affect their flavour. If they are going to be stored in a fridge, then either store them loose or in a paper bag as a plastic bag can promote moisture and speed up the decaying process.
  • Fruits: some fruits can lose their flavours and textures if stored in fridges.

Generally, if unsure, consult the food preservation label that you will generally find on the items.


As seen in the brief history of refrigeration, there are a number of natural and mechanical methods available which are all used in today’s society.

Ice Refrigeration

In this method, ordinary ice is used for keeping the space at a temperature below the surrounding temperature. The temperature of ice is generally 0oC and therefore can be used to maintain temperature of about 5-10oC. To use ice as a refrigeration method, a closed and insulated chamber is required. On one side of the chamber ice is kept whilst on the other side there is a space which is to be cooled or where the items to be cooled are placed. If a temperature below 0oC is required, then an ice/salt mixture can be used which lowers the freezing temperature of the ice mixture.

Dry Ice Refrigeration

Dry ice is solid carbon dioxide. It has a temperature of -78oC. Dry ice converts directly from a solid state to a gaseous state in a process called sublimation. Dry ice can be formed into various different shapes of blocks so that it can be packed in with frozen food that has to be kept frozen for long periods of time. When the dry ice gets converted to the gaseous state, it produces a refrigeration effect keeping the product frozen.

Mechanical Refrigeration

Mechanical refrigeration consists of a variety of methods, the Vapour Compression cycle, the absorption cycle, the adsorption cycle, the gas cycle and many others. What distinguishes these from the natural methods is that some form of mechanical input is required to drive the process and the processes are cyclical meaning that they do not require topping up as the natural methods would. These methods can be used over a variety of temperature ranges from high temperatures to cryogenic temperatures and the method chosen will be dependent upon the application required.



  • To understand the physics and engineering that makes refrigeration work.
  • When you understand how temperature is physically manipulated, you then have the basis for maintaining and managing refrigeration equipment.
  • Learn to choose what equipment you need to do the job at hand.
  • Learn how to chill, refrigerate or freeze different types of farm produce.
  • Be more capable as a farmer, produce processor, manufacturer or marketer of agricultural products.
  • As a farmer, value add to your products to increase cash flow.
  • Teach, Consult, Write better, as an agricultural or production horticulture expert.



ACS Distance Education holds an Educational Membership with the ATA.
ACS Distance Education holds an Educational Membership with the ATA.
Member Nursery and Garden Industry Association.
Member Nursery and Garden Industry Association.
ACS is a Silver Sponsor of the AIH; and students studying designated courses are given free student membership. ACS and it's principal have had an association with AIH since the 1980's
ACS is a Silver Sponsor of the AIH; and students studying designated courses are given free student membership. ACS and it's principal have had an association with AIH since the 1980's
Long-term member since 1986.
Long-term member since 1986.
ACS is an organisational member of the Future Farmers Network.
ACS is an organisational member of the Future Farmers Network.
UK Register of Learning Providers, UK PRN10000112
UK Register of Learning Providers, UK PRN10000112

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