04.Shopping for the most nutritious fruit and vegetables
There are a mind-boggling array of factors affecting
the freshness, nutrition and taste
of your food.
Most fruit and veggies
are 70-90% water, and once harvested
immediately start losing moisture and
degrading in quality and nutritional
value. So the less time between
harvest and plate there is, the better.
Although time since harvest is
important, there are other
factors influencing quality, including
the particular variety, soil health,
growing methods (fertilisers high
in nitrogen can reduce vitamin C
levels), changes in temperature
and humidity during transport,
and storage methods.
- The nutrient content and
taste is optimised if produce
is picked ripe.
- Bruising leads to a loss of
nutrients, so produce should be gently
handled. Handpicking is less likely to
damage produce than mechanical.
- Soft or leafy fruit and veg have
high levels of water-soluble C
vitamins that are unstable, so the
fresher they are when you eat
them, the better. Shrivelling
and yellowing is a sign
of ageing and
- Minerals and
tomatoes their red
colour) are more
stable than water-soluble
are the nutrients in
root veggies, so time
since harvest is
Birthday apple is a term for apples that are one year old before they hit the stores. Most apples are harvested between February and April, so it’s standard for them to be placed in a controlled atmosphere storage straight off the tree and distributed gradually throughout the year.
The combination of reduced oxygen levels and temperature, plus an increase in carbon dioxide, stops the apple’s production of ethylene, effectively putting it to “sleep”. Once removed from cold storage, the apples “wake up” and start ripening again.
Exact conditions in the rooms are set according to the apple variety, but incorrect storage can cause flavour loss or a brown core. Storage has little effect on apple nutrients; the way the fruit is treated before and after storage is more important.
“People may not like the idea of cold storage, but would they prefer to eat Australian apples all year or to eat imported apples?” asks Colin Gray from the NSW Chamber of Fruit & Vegetable Industries.
How is early-picked fruit ripened?
In order to get fruits to market without damage, they’re usually picked before ripening, transported and then exposed to ethylene gas.
Ethylene occurs naturally in fruit and veg and naturally triggers the ripening process. Fruits such as bananas, tomatoes, avocados, apples, mangoes, pears and peaches continue to ripen after harvest as they produce their own ethylene.
There doesn’t appear to be any evidence that exposure to ethylene is harmful to crops, but if crops are picked too early they may not ripen completely. They can reach full colour, but not necessarily full nutrition.
Other fruit such as raspberries, cherries, grapes, lemons, oranges, pineapples and strawberries don’t ripen after harvest, but oranges and lemons can be made to look less green by exposure to ethylene gas.
With a structure similar to ethylene, 1-methylcyclopropene (1-MCP) is used to block the fruits and veggies’ ethylene receptors, slowing the ripening. It’s used in cold storage and controlled atmosphere for tomatoes, pears, plums, avocados and kiwifruit.