Smart Consumer: The hard truth about avocados
You fancy an avocado to put in your salad and head to your local grocers to buy one. Except the avocado you buy is rock hard.
So you leave the avocado on a table and wait for it to ripen. Your avocado salad can wait. A few days later you're ready for that fruit, but the avocado is now so ripe it's black. You can't eat it and the money you spent has gone in the bin along with the avocado. What the hell happened?
The avocado may be a tropical fruit but we're so used to having all fruit and veg available at all times of the year that we want to buy it. And when we do, we want to be able to eat it.
Nutritionist Paula Mee says "sometimes supermarkets get it wrong and forget to test and taste the produce so it can be too hard and unripe to eat immediately".
She adds: "Good supermarkets have specialised personnel called agronomists and quality control personnel to test sugar levels in the produce to make sure the right fruit is on the shelf at the right time".
For those of you with unripe fruit at home, Paula Mee's trick is to put it in a brown paper bag. "Ethylene is a natural gas that the fruit gives out and the brown paper bag collects and confines the ethlyene so the fruit will ripen faster".
Dr Paula Bourke, Head of Research and Learning Development at DIT's Faculty of Tourism and Food, also suggests putting the fruit beside another ripe fruit, like a banana with brown specks on it.
"The proximity and exposure to the ethylene gas emitted from the ripe fruit will help the unripe fruit to ripen more quickly," explains Bourke. She says that "ethylene gas is naturally produced by many fruits when they are ripening and it triggers the production of enzymes that ripen the fruits, including the conversion of starch to sugars, increasing the aromas associated with fruits and also colour changes associated with ripe fruit".
Besides avocados and bananas, examples of high ethylene producing fruit are apples, melons, pears and tomatoes. But don't put your hard avocado beside your broccoli, cabbage, cauliflower or lettuce, as these do not produce ethylene.
Of course, you can find perfectly ripe exotic fruit that has been transported thousands of miles to get to our local shelves. So how is it done?
Tesco says it sells both firm and ripe fruit in order to provide a choice. "We import them firm and then our expert ripeners use heat, time and humidity to encourage the natural ripening process of the fruit," a Tesco spokesperson says. When the product has reached ripeness, they then package them and send to their stores.
For Marks & Spencer it's all about managing the process. "From the point of harvest, through grading, shipping and storage at the importer the fruit is kept at about 5 degrees Celsius", explains a spokesperson for M&S.
"For longer sea voyages Controlled Atmosphere containers are also used to slow the levels of oxygen and carbon dioxide. Unripe product is then selected for forced ripening in specially designed ripening chambers using temperature (16-22°C) and/or an external ethylene source".
Dr Jesus Frias, Head of Department of Food Science at DIT also describes another method that supermarkets employ. "Most Irish supermarkets now offer packagings where they mix one or two matured fruits with another one or two unripe ones.
"The mature fruits provide the ethylene in a closed environment so that the unripe one matures faster. This is the same solution as putting a ripe banana in your fruit bowl, just with the advantage of the closed package that will increase the ethylene exposure."
So with all this science going on, and what you could call "interference" in the development of the fruit, is that avocado still good for you?
Dr Bourke says it should be. "If the product has been stored properly and was in good condition when it was harvested, the eating and nutritional quality should be maintained. In fact, much research has focused on minimising post-harvest quality losses and to extend shelf-life to ensure good eating and nutritional quality on arrival."
She adds that in the case of the avocado, they do not generally ripen on the tree anyway but ripen when picked. "However, in common with many tropical fruits," continues Dr Bourke, "they can be subject to chilling injury if too low temperatures are used for transport".
"The use of post-harvest technologies, such as storing the fruit in controlled atmosphere chambers or using modified atmosphere packaging," she cautions, "can not improve the original quality of the product. This depends on the initial quality of the product when it was harvested".
This is a lot of science to consume when perusing the shelves for your fruit so Paula Mee suggests that if in doubt you should ask for a taste or sample of a fruit or vegetable you consider unripe.
"Give feedback including any complaints if the fruit is inadequately ripened," recommends Mee. "This will alert the retailer and supplier that they need more stringent checks on produce."