The trouble with transpiration

When you think about it, fresh fruit and vegetables are essentially water in fancy packaging! Most fresh produce contains between 80% and 95% water, with even the “low water” produce such as avocados, bananas and potatoes made up of about 70% water.

When they’re first harvested, the water content of fresh produce is at its highest, and the fruit and vegetables appear crisp and plump. But from that moment on, the natural process of transpiration, or water loss, begins and is the main cause of weight loss in agricultural products post-harvest. It can affect saleable weight, appearance and texture.

As little as a 5% reduction in water can cause wilting or shrivelling – sometimes within just a few hours after picking if the weather is warm and dry. Water loss also weakens plant cells, making them more susceptible to pathogens, which may result in greater ethylene production and a loss of chlorophyll, causing the produce to yellow.

The point at which water loss affects quality differs depending on the type of fruit or vegetable. Leafy vegetables, for example, have a thin skin with many pores and will wilt quickly after losing between 3 and 5% of their water. Nectarines, on the other hand, can lose up to over 15% before starting to shrivel. Even the same types of produce in a box can deteriorate at different rates depending on where they are in the box.

The real cost of fresh produce transpiration.

Loss of water means loss of weight, which can have an immediate and significant economic impact. For example, a 3% loss in weight in blueberries may not affect their outward appearance, but in a pallet containing 500kgs of blueberries, this translates to a 15kg loss. At approximately R240 a kilo retail, this means a loss of over R3500 per pallet.

The key to reducing moisture loss – and thus weight loss – is to reduce the levels of transpiration. Methods which are rapidly becoming outdated and undesirable include covering the produce in a waxy coating and placing it in airtight packaging. Modern-day science, however, has proven that the most effective way to slow the rate of transpiration is to increase the relative humidity of the environment immediately surrounding the harvested produce.

PerfoTec is a game changing, scientifically designed packaging that contains micro perforations which help control the atmosphere inside the pack, reducing water and weight loss and the overall rate of decay. PerfoTec slows respiration and transpiration, delays decay, increases shelf-life, and decreases waste.

Mapflex is a joint venture between international companies and is a recognised specialist in PerfoTec packaging. We ensure the right films and packaging methods are used to maximise the benefits of equilibrium modified atmosphere (EMA). Contact us for tailored packaging solutions and modified atmosphere packaging products specifically suited to your fresh produce needs.