Every day, after eating lunch at the FFC, I bring a piece of fruit back with me to the lab and give it to my boss. I figure it’s the least I can do, especially with all the questions I nag him with daily. Being a perfectionist, I always take my time to look for the perfect apple to bring back.
The only problem is the FFC, more often than not, lacks the spotless apple. I can always find some blemish or soft spot that forces me to reject the apple and continue with my search. Same goes for the bananas and oranges. I am reminded of that old saying: one bad apple spoils the bunch. Well, is it true?
Many changes occur as a fruit ripens. Unripe fruit is often hard, odorless, green, sour and tasteless. The ripening process makes the fruit more appealing. Various chemical processes are initiated inside the fruit.
Chlorophyll, a green chemical that allows plants to harness the sun’s energy, breaks down. In some cases, new pigments are made. Acids in the fruit that cause the sour taste decompose. Starches and pectin are converted to sugar, and small molecules are released, which give fruits their aromas. As a result, at the end of the ripening process, fruit becomes soft, sweet, fragrant and colorful.
The entire process is controlled by a group of enzymes that are made on cue. What is the cue? Surprisingly, the signal is a simple molecule called ethylene. Compared to other hormones plants produce, ethylene is an extremely simple and mundane molecule. However, this basic hydrocarbon gas with its two carbons and four hydrogens is able to cause major changes in the developing fruit.
The small molecule is produced by rapidly growing tissue in plants such as the tips of roots, flowers, ripening fruit and damaged tissue. Because a wound can activate ethylene production, the act of picking fruit can initiate the ripening process.
In the cells of plants, ethylene flips the switch and turns on various genes. These genes in turn make enzymes which cause fruit to ripen. Ethylene is unique in that it is the only known airborne hormone used by plants.
By controlling the production of ethylene, farmers can regulate when fruits will begin to ripen. For example, bananas can be harvested when they are still green, shipped to their destination, placed in a ripening room where there is a low concentration of ethylene in the air, and can be ripened on demand.
Refrigeration can also slow the natural process of ripening. The constant flow of air in a refrigerator prevents ethylene from accumulating, thus preventing the fruit from ripening. However, over time fruit can still rot. As a result, you get bananas that are still green on the outside and brown on the inside.
Now back to the original issue. When you damage an apple, it will start producing ethylene. Then you place that bad apple in a barrel of unripe apples.
The ethylene produced by the bad apple will begin to ripen the other apples. Because there is not much airflow in a barrel, the ethylene remains in the barrel. Over time, the apples in the barrel become overripe and spoil. Thus, we get the expression, “one bad apple spoils the bunch.” Now that is some food for thought.
