From Farm to Fork: The Importance of Pre-Cooling and Proper Handling of Fresh Fruits and Vegetables

Pre-cooling of fruits and vegetables has been practised for many years and is the key step in post-harvest operations. Important for the preservation of the quality of perishable produce, pre-cooling is closely related to handling and storage. However, many growers do not use this method and the reasons may include misconceptions about the cost, deciding which pre-cooling technique will work for them, and not being aware of how to set up a pre-cooling process. 

So, let’s dive deeper into understanding the pre-cooling methods as well as the proper handling and storage of fresh fruits and vegetables. 

What Does Post-harvest Handling Involve 

Proper post-harvest handling of fresh fruits and vegetables will enable you to sell high-quality products and extend the shelf life of your produce. Here are some common steps involved. 

Post-Harvest Handling of Fruits and Vegetables 

In the later sections, we will primarily focus on the pre-cooling step and why farms and businesses should not ignore it. 

What Is Pre-Cooling and Why It Is Important? 

Pre-cooling is the rapid removal of heat from freshly harvested fruits and vegetables. This process is usually performed before the produce is taken to the market or cold storage facilities. 

Why You Need to Pre-Cool Your Produce 

It is no surprise that as soon as the produce is harvested, it starts to deteriorate. Respiration which occurs due to enzymatic oxidation results in the release of heat, carbon dioxide, and other gases. If this heat is not removed, the respiration process further gets accelerated. Additionally, heat also results in the growth of molds and the loss of moisture. 

Bruising can also accelerate these processes and lead to loss of texture, colour, flavour, appearance, and nutritional value. With these losses, it is considered that the produce has lost its quality and freshness.  

That is why quick lowering of temperature and maintenance at a uniform temperature reduce enzymatic processes and the associated loss. Therefore, pre-cooling is an effective and practical method for maintaining the optimum quality of the produce, especially for those with higher respiration rates.  

                                                   Common Causes of Post-Harvest Losses

Methods for Pre-Cooling Produce

Here are some common methods used for pre-cooling.

• Room cooling

In this method, the produce cools passively inside a cool room. The temperatures can take hours or days to approach the room setpoint, depending on air circulation and container venting. This method is effective for smaller quantities or those which do not deteriorate rapidly. 

• Forced air-cooling

During forced air-cooling, the air is pulled rapidly through bins or cartons of fruits and vegetables. This increases the effective surface area from that of the bin or cartons to that of the produce inside. This increases the rate of cooling and avoids condensation. Forced air cooling can, thus, reduce cooling time by ten times or more, compared to room cooling.

Forced Horizontal Air Flow 

Forced Vertical Air Flow 

• Hydro-cooling

It is known that water is a better conductor of heat than air. Hydro-cooling method can provide fast cooling so long as the water chiller has enough capacity to remove the heat from the dip or drench water. However, it is not suitable for all products, and it is important to include a sanitiser to avoid the spread of human or plant pathogens.

• Ice cooling

Packing products with crushed or fine granular ice can provide ‘insurance’ against poor cold chain practices and may be expected by customers or retailers for certain commercial products. However, using ice is an inefficient method of cooling fruits and vegetables.

• Vacuum cooling

Vacuum cooling involves reducing pressure inside a sealed chamber. The water

inside the vegetables turns to vapour, absorbing heat energy. Vacuum cooling

works best for products that lose water easily, such as lettuce and baby leaf crops. 

Proper Handling of Fruits and Vegetables: Blast Freezers  

Blast freezers are also known as shock freezers or flash freezers as they rapidly bring down the temperature of fresh produce as well as cooked food, and freeze it to lock the nutritional value and taste. This method is based on air blast freezing. 

In fact, rapid freezing prevents the formation and growth of harmful micro-organisms

in the food by naturalising them. The blast freezer preserves the food at extremely

low temperatures [-18⁰ C to -45⁰ C] and for a long duration.

Pros and Cons of Blast Freezing

• Blast freezers arrest contamination of food, helping preserve food’s integrity, quality and flavour and safeguarding their nutritional values.  
• It also pre-empts the growth of harmful bacteria and other microorganisms, ensuring 100% food safety. 

There are seemingly no cons to blast freezing. 

Proper Handling of Fruits and Vegetables: Ripening Chambers

The ripening chamber is one of the components for completing the ripening process of some fruits. However, there are still misconceptions about the reopening process in these chambers. Let’s address those. 

Ripening chambers can help improve the quality and flavour of fruits. In fact, ripening is a crucial part of the maturation process. Since these chambers provide a controlled environment, the ripening of the fruits can be accelerated or slowed down by adjusting the humidity, temperature, carbon dioxide concentration and the supply of ethylene gas. 

How does it work?

Ethylene, a natural ripening agent, is pumped into the room (at 1 ppm) and left for 24 hours. The ethylene is then ventilated out of the room and the fruits are left to ripen for three to four days depending on their initial condition and the ripening level the customer would like. It improves the texture and flavour and extends the shelf-life, eliminating the use of toxic substances (carbide) traditionally used in ripening.

Proper Handling of Fruits and Vegetables: Refrigerated Transportation

Transporting fresh produce presents several business challenges and requires completeness and adherence to all sanitary regulations. 

Transporting fresh products has always faced many challenges due to temperature sensitivities and perishability. The temperature and humidity of fresh produce during transportation should be monitored carefully. Refrigerated vehicles are commonly used for shipping. A safe temperature range between 35 and 45 °F is accepted for most fresh fruits and vegetables. 

A cold environment can damages bananas, avocados and mangoes, so they should be kept between 13 and 15 °C, with humidity levels between 85% and 90%. A temperature and humidity data logger is one of the new tools for monitoring temperature and humidity during transportation.

Thus, appropriate temperatures should be maintained throughout the food chain. 

Final Words 

Post-harvest handling operations are critical for maintaining the quality and freshness of the produce. Pre-cooling, which is an important step in this entire process is important for most fruits and vegetables. Apart from removing field heat, pre-cooling also reduces bruise damage from vibrations during transportation. 

Rinac offers a range of world-class solutions to enable the proper handling of fruits and vegetables, so you get the best price for the produce. Explore our well-designed pre-coolers, ripening chambers, eco-friendly refrigerated transportation, and blast freezers for all your needs!