Processed: Food Science and the Modern Meal
By the late 1920s frozen vegetables had entered the consumer food market. Birdseye developed flash freezing to preserve the texture and flavor of frozen foods. (Look)
In addition to breeding delayed ripening into plants, the produce industry also employs chemistry to achieve the same end. For example, the ripening of many fruits, including bananas, tomatoes, apples, melons, apricots, and papayas can be triggered by ethylene, a gaseous plant hormone. Ethylene is what turns bananas from green to yellow and tomatoes from green to red. When fruits sense ethylene, a chain reaction begins: the fruit ripens and produces its own ethylene, which is then sensed by and activates the ripening of nearby fruit.
Ethylene-sensitive fruits are picked green and shipped in closed containers that also hold chemicals, such as potassium permanganate, that can absorb or disable ethylene. Another strategy, approved in the United States and the European Union, is to douse unripe fruit with 1-methylcyclopropene. This molecule blocks the ethylene receptor in many fruits for up to 12 days so that even if some of the ripening hormone is wafting about, the fruits can’t detect it.
Last but not least, pairing vegetables with the proper packaging can maintain freshness. Even off the vine, fruits and vegetables continue to respire, taking in oxygen and releasing carbon dioxide. Put vegetables in a closed environment where no respiration is possible, and they deviate into a different metabolic strategy, one that destroys tissue, thereby producing muck in a bag. To counter this, says Floros, the produce industry has developed plastic packaging that is slightly permeable to oxygen and carbon dioxide, creating a microenvironment that slows down respiration and decay.
In the last century the food industry has figured out how to tweak plant biology in order to control puberty and delay aging. Most of this tinkering was done by trial and error without detailed knowledge of what was happening on a molecular level in plants and their fruits. Over the past decade researchers have sequenced the genome of a variety of plants, including the tomato, and they’ve figured out the three-dimensional structures of many of the receptors in plants that detect ripening hormones. This knowledge is allowing plant biologists to figure out, in retrospect, how some of their tinkering has interfered with ripening and led to flavor loss—a loss that most consumers accepted in exchange for the convenience of out-of-season vegetables. Yet consumers are now increasingly demanding it all: fresh fruit and veggies year-round that truly do taste vine ripe, even if they are not. If the food industry can figure out a way to give people what they want, it will require a lot more tinkering with plant biology, certainly more chemical interventions, and possibly some genetic engineering. Whether future consumers would buy into the outcome is anyone’s guess.
Sarah Everts is the European correspondent for Chemical & Engineering News and has also written for Smithsonian, Economist, New Scientist, and Scientific American.