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Science versus nature: The battle of keeping fruit and veggies fresh and delicious

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Agriculture and Agri-Food Canada
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Many of us enjoy eating fresh, delicious and nutritious fruit and vegetables all year round, but working against us are the microbes and natural processes that break foods down. To tackle this problem, researchers at Agriculture and Agri-Food Canada’s (AAFC) Kentville Research and Development Centre are developing innovative storage techniques and packaging that manipulate the postharvest physiology of crops to extend their shelf life by days, weeks, and even months.

Postharvest physiology is the branch of biology that looks at what happens to crops after they are harvested and are no longer able to absorb nutrients. Once picked from a tree or pulled from the ground, fruits and vegetables start to change chemically, lose water, and break down due to naturally-occurring microbes.

In particular, oxygen drives many reactions in fruits and vegetables. Think of a sliced apple – it is oxygen that reacts with compounds in the fruit that causes it to turn brown, a process called oxidation. Fruits and vegetables, as well as many microorganisms that cause decay, require oxygen to live. Research has found that by increasing crop exposure in storage to carbon dioxide while reducing oxygen can slow the metabolic reactions and decay that degrade the things we like to eat.

By better understanding this metabolic process, researchers have developed techniques and technologies to slow them down.

In the 1930s, Dr. Charles Eaves, a researcher with AAFC, introduced one of the first controlled atmosphere storage facilities for fruits and vegetables in the western hemisphere. His unit extended the shelf life of fruits and vegetables by lowering the amount of oxygen and increasing carbon dioxide to slow the breakdown of produce.

More recently, Dr. John DeLong and Dr. Robert Prange (now retired) introduced a sophisticated sensor and software system called HarvestWatch™ which allows apples to be stored at the lowest possible oxygen level to best preserve the taste and appearance of the fruit.

"What happens in the field up to harvest and what happens to produce after harvest are really two different worlds. If you are eating an apple out of season, and you like it, that’s postharvest physiology in your hand."

– Dr. John DeLong, Research Scientist, Agriculture and Agri-Food Canada

HarvestWatch™ sensors pick up signals directly from the apples where they are stored; if the oxygen level in the room is too low, the sensors let the storage operator know and they can make the appropriate adjustments. This technology has extended the lifespan of picked apples from the traditional two or three months, to eight to twelve months.

On the packaging side, AAFC postharvest physiologist Dr. Charles Forney is looking into compostable plastic for the creation of mini atmosphere-controlled storage environments for produce in the grocery store. These mini-environments have low levels of oxygen and high levels of carbon dioxide to reduce oxidation and bacterial growth.

"Fresh produce is still living and respiring so something like a whole onion or a diced onion needs to breathe. When you seal it up in a package, you change the air around the product."

– Dr. Charles Forney, Research Scientist, Agriculture and Agri-Food Canada

The next time you bite into your apple take a moment to reflect upon the fascinating science and the innovative technologies behind the tug-of-war waged between researchers and nature to keep it crisp, tasty and fresh.

Key discoveries

Photo Gallery

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Dr. John DeLong in the cold storage unit for apples
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A bin of Honeycrisp apples in cold storage at the Kentville Research and Development Centre eight months after harvest.
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Dr. Charles Forney in his lab at the Kentville Research and Development Centre

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