Sensation determines what food we consume. We have many senses, such as vision, olfaction, gustation, etc, and we have an apparatus for each of these senses that sends interpretable information to our brain to be process and interpreted. There has been evolutionary pressure on preferred sensation for food in the human population. Sensation emerged through evolution with rules from our interaction with the food supply. Our senses tell us if the food is safe to eat, and we are very good at determining this from our senses. Although our senses are not very good at telling us if the food is nourishing, since the only nutrient we can detect as a sense is water, because we can detect thirst. Our senses can tell us the quality of the food product. There are many sensory attributes of food that we can detect using our senses, such as appearance, taste, texture, temperature, aroma, etc. These sensory attributes help us determine whether we like a food or not.
Humans are very visual animals; we make most of our profound decisions about food based on sight. We are really good visual animals because we are exceptionally good at interpreting the visual spectrum from our apparatus (eye ball), and the secret is in the retina.
We have all these cells placed in our retina in a particular fashion where they are able to absorb the spectrum that enters the eye, and transduce it so it is able to send a signal to the optic nerve in the brain. Vision has to do with the assumptions of your brain as well as what you are actually seeing. Sometimes you brain can force you into seeing something that is not actually there, therefore our brains are very coded in its expectation of what it is going to see. The brain is very important in vision. The brain’s part in vision is learned through experience, considering if one was exposed to some color constantly over time their brain will silence the stimuli. For example, if you look at a picture of an American Flag for about a minute constantly, and look at a blank canvas you will still see that flag for some sort period of time, considering your brain thinks that it is still looking at the stimuli.
This works for all senses, since if you are exposed to a constant sense you over time ignore that stimuli. For example, we have salty saliva although we cannot detect the saltiness due to being exposed to this for a long period of time. Our visual apparatus can only detect a certain range of colors in the visual spectrum. We can only determine the quality of foods based on experience, taking into account we can tell if a strawberry is immature, ripe, or spoiled. Although, if you were to ask an average American if they know if a melon found in Southeast Asia is of good quality, they would not know because they have never encountered this melon in past experiences. The plant pigments tell us a lot about food. Multiple conjugated double bonds associated with ionizable subgroups gives a food a particular color. For example, the blue color of blueberries results from a compound called anthocyanin that has many conjugated double bonds. The plant’s color is held in the vacuoles of the cells that make up a food product. The vacuole maintains a particular pH in which allows the plant pigment to persist. When the vacuole breaks, like when cooking or processing or after the plant has gone bad, the vacuole gets broken and the color changes because there is a change in the environment’s pH. Therefore, the plant color can give an accurate representation of the plant’s quality, which tells the consumer if that plant is safe to eat. Colored plants are very unstable because the color can change whenever the food has been broken down chemically or enzymatically.
There are an abundance of functions colored plants can complete; such as they can turn light into energy with the assistance of the green colored chlorophyll. In addition, they can show injury with brown colored melanins hence showing the food is not as good of quality, as well as they can have camouflage by utilizing their protein carotenoid complexes, which give the plant an array of orange colors. Animal products also have pigments that give an accurate representation of the quality of that food product. The fat-soluble pigments are stored in adipocytes, and the water-soluble pigments are stored in the blood of the animal and in the aqueous (watery) parts of the animal. These pigments are similar to plant pigments in that if the compartment that holds the pigments break the pH changes, and therefore the color changes as well. Frequently nitrites are added to meat to preserve the red color of the meat and counteract the unwanted color change of the meat from the salt. If one were to not to add these nitrites to a hotdog it would be almost gray in color. Although consumers unanimously choose to eat the red meat and believe that it is of better quality, even though it contains unfavorable preservatives (nitrites), and the gray meat is exactly the same minus the nitrites. The red color comes from the nitrite that is added to the meat reacting with the heme in the meat to form a red colored compound called nitrosomyoglobin. There are three pigments that can be expressed in meat.
Oxymyoglobin is a pigment that is bright red and is the color of meat that one expects to see in a grocery store/supermarket, since this is the color that results from the fresh meat’s heme being exposed to oxygen. Myoglobin is a pigment that is purple and is the color of meat when it is freshly cut and not yet exposed to oxygen. People rarely see meat in this purple color state because the meat is usually exposed to oxygen before packaging. Metmyoglobin is a pigment that causes the meat to be brown, which results from the heme in the meat reacting with hydroxide, therefore showing that the meat has been oxidized and is of lesser quality. Since people already knew that food color is a big aspect of what people evaluate to determine if they want to consume that food or not, in the 19th century chemists learned how to make artificial pigments. After this it was easier for the food industries marketers to color foods to make them seem fresh, without the food products actually being fresh. Although the food industry attempted to stop this from happening with the use of taxes, for example in 1886 the US passed a law that taxes butter substitutes that use artificial pigments to make the compound look more like butter. Then in 1906 the US Government passed the Pure Food and Drug Act which “prevent[s] the manufacture, sale, or transportation of adulterated or misbranded or poisonous or deleterious foods, drugs, medicines, and liquors, and for regulating traffic therein, and for other purposes” (Pure Food and Drug Act). This Pure Food and Drug Act set in place the basis for food regulations for the next hundred years. Food pigments are a very important aspect in the reasons why people like certain food products. Pigmentation can occur during the processing stage of a food product, such as bread undergoes the Maillard reaction and this is responsible for the visual characteristics of bread having the crust. Chemists have figured out how to separate the pigments and make artificial pigments, therefore being able to add them back into different food products to give those foods a particular pigmentation. Chemists found a way to make artificial pigments because the natural pigments were highly unstable. Hence, the natural pigments would degrade in the food product very readily, unlike the artificial pigments.
Resources:
Pure Food and Drug Act (1906). United States Statutes at Large (59th Cong., Sess. I, Chp. 3915, p. 768-772; cited as 34 U.S. Stats. 768
Learning in the Kitchen 