Knowing how to handle fruit during the production process is important, and so is understanding the basics of post-harvest plant physiology.
The 3 enemies of fruit and vegetables are bad handling, time and high temperatures.
Time is the critical factor in the race to extend the shelf-life of your fresh produce. The longer it takes from “farm to fork”, the better the chances for damage and wastage.
This means that, on the farm, fruit and vegetables should be harvested, packed and transported as quickly as possible.
WHEN TO PICK
- When the fruit is hanging on the tree it converts starches made by photosynthesis from sunlight into fructose – fruit sugars.
- These sugars are what the plant uses to feed the fruit hanging on its branches.
- Fructose gives the fruit its sweetness and can be measured (Brix) with an instrument called a refractometer.
- The Brix reading helps the farmer determine the maturity (sugar development) of the fruit and the optimum time to pick.
- The higher the fructose level, the riper the fruit, and the quicker it will decay.
- Conversely, if sugar development is too low the fruit won’t ripen properly after picking and become shrivelled.
- Remember that most fruit is only 100% good immediately after picking (provided that it is picked at optimum ripeness) and from that point on it will decay.
- Some fruit decays faster than others – we can’t stop the process, but we can slow it down through correct storage and careful handling.
- Temperatures fluctuating between hot and cold are one of the main causes of fruit decay.
- Severe, frequent temperature changes – in and out of cold rooms – cause havoc inside fruit.
- Always keep your fresh produce as cool as possible.
- Fruit are living organisms and they breathe – just like us – except that they don’t use lungs but respire (breathe) through tiny holes in their surface called stomata.
- Plants absorb carbon dioxide (CO2) from the air and give off oxygen (O2); this respiration process is what ages (decays) the fruit.
- Temperature influences respiration, which influences dehydration.
- The higher the temperature, the faster the respiration, the faster the dehydration and the faster the decaying process.
- Relative humidity (RH) means the percentage of moisture in the surrounding air, which will also affect the respiration rate.
- The drier the air, the faster the respiration rate will be.
- During respiration fruit dehydrates (loses water) which also speeds up decaying.
- If you don’t have a cold room, it doesn’t mean you don’t have to be responsible for how and where you store your fresh produce.
- Not all fresh produce needs cold storage – pumpkins, butternut and potatoes, for example, do not – but they do like to be kept cool.
- Select a suitable place where you can build a simple storeroom, such as under the shade of trees or behind another building where it will be cool.
- This storeroom should be clean, well-ventilated, secure, cool and easily accessible for product flow (in and out).
- All fruit gives off ethylene, a plant hormone that influences ripening when fruit is in storage.
- No two fruit give off the same quantity of ethylene, so one has to be very careful when storing them not to mix high-ethylene producers with low-ethylene producers, as this will cause them to ripen quicker.
- To make matters even more complicated, no two fruit types have exactly the same storage requirements (temperatures) or characteristics, so many cannot be mixed in a cold room.
Your objective should be to keep the fruit as close to the 100% mark as possible, for as long as possible. That’s what the consumer wants!
Fresh fruit and vegetables need specialised care; do it right and you’ll reap (harvest, pick) the benefits. Do it wrong and they’ll cost you a lot of money. The choice is yours.
- This article was written by Michael Cordes and first appeared in Farming SA.