Throughout much of my life I have had access to a variety of fresh fruits and vegetables either by good fortune or good planning. I have learned that the concept of “fresh” has a very real meaning in terms of flavor. Whether I was popping cherry tomatoes into my mouth while working on a farm, or planning my commute home in order to pass by the farms with the most recent harvests, I have always appreciated the unique taste and texture qualities of fruits and vegetables just minutes or hours after harvesting. Some of my friends have pointed to this as an obsession. However there is a scientific explanation why fruits and vegetables taste significantly different the closer they are to harvest. It all comes down to respiration.
Plants of all kinds exist with one purpose in their sometimes brief lives; creating offspring so that their species may continue to survive over time. In order to procreate, plants carryout two primary functions; photosynthesis and respiration. Photosynthesis is the most widely known process of the plant. The process combines water and carbon dioxide using the power of the Sun to create glucose, which is a very simple sugar. This part of plant growth creates the sugars we taste when we eat a harvested fruit or vegetable.
Photosynthesis only stores sugar as potential energy. It gives the plant the potential to use sugar to carryout growth and the creation of future offspring which we know as seeds, leaves, or fruits. The plant must have the ability to convert the sugars into energy which it does through the process of respiration. The respiration process takes the stored sugar molecule and combines it with oxygen, creating water, carbon dioxide and energy. This energy allows the plant to carryout its primary functions.
These two processes are inextricably intertwined. When a fruit, vegetable or leaf is harvested these two processes are interrupted. Cut off from the source of water the harvested item can no longer carry on photosynthesis. This fixes the amount of sugar in the fruit or vegetable. However the portion that is harvested still carries on respiration in order to preserve the life of the plant for procreation of the species. The respiration process very quickly uses up all the sugar in the fruit or vegetable. The result is that the harvest can very quickly taste very bland.
Fruits and vegetables have a wide range of respiration rates which affect the amount of sweetness we taste after harvest. For example sweet corn has one of the highest rates of respiration. For most varieties the sugar in the corn is reduced completely to starch within twenty-four hours. Much of the corn we see in the grocery store is a very bland substitute for the fresh-picked variety. Other fruits and vegetables with high respiration rates include asparagus, broccoli, and peas.
Science has tried to slow the respiration process of harvested fruits and vegetables. These items are often packed in plastic bags designed to reduce the amount of oxygen surrounding the harvest. These modified atmospheric packages (MAP) are able to slow the process of respiration. This prolongs the amount of time the product can retain its sugar for slightly longer periods. Scientists have also modified the genetics of certain fruits and vegetables to prolong their shelf life. Shelf life unfortunately pertains primarily to looking good not necessarily tasting good. In fact many of the genetically modified varieties of fruits and vegetables begin with lower sugar content than their heirloom variety counterparts.
The solutions to finding the freshest fruits and vegetables are fairly limited depending on location and time of the year. Buying items that are locally grown can yield good results. A fruit or vegetable harvested within a few hundred miles of your location can usually be trusted to be very fresh tasting. Herbs and greens grown in your own garden are a sure bet for the freshest tasting salads.
Most of us do not live near farms or we are limited by seasonal selections. Items with lower respiration rates such as carrots, celery, grapes, onions, and apples can travel well over long distances and still maintain their flavor quality. Items with high respiration rates including green beans, asparagus, broccoli, peas, and especially sweet corn are either best eaten within a day or two of harvest or eaten using the frozen variety. Most freezing operations process vegetables within twenty-four hours in order to preserve the sweetness of the products.
It is worth the extra trouble to seek out fresh sources of fruits and vegetables. There is simply no flavor comparison between freshly picked items and those found in the grocery store. My so called obsession leads me to stop at farm stands and ask to pick my own fruits and vegetables. There is just nothing like picking your own produce and eating it raw in the field.