Sweetness Lab

In this lab, we asked the question: how does the structure of a carbohydrate affect its sweetness. We found that the monosaccharides are very sweet, and polysaccharides are quite bland; therefore, the fewer the rings, the sweeter the carbohydrate. The monosaccharides fructose and glucose and the disaccharide sucrose were the top three sweetest carbohydrates. Sucrose was used as the standard sweetness at 100. Fructose had a sweetness degree of 115 and glucose had a sweetness degree of 90. The polysaccharides starch and cellulose were extremely bland. Starch had a sweetness degree of 10, and cellulose had no sweetness degree. Since the sweetest carbohydrates were monosaccharides and the blandest were polysaccharides, a carbohydrate is sweeter when it has less rings of carbon, hydrogen, and oxygen.  

Monosaccharides and disaccharides are mainly used as sources of energy for the cell. This is because they are easier to break up since not many rings are bonded together. The polysaccharides are mostly used for forming the cell wall since there are more rings bonded together it is more resistant and cannot be broken apart so easily.  

Not all of the tasters gave the exact same rating. One reason could be that different testers are used to eating different sweetness levels, so someone who eats a lot of sugar will need more sugar for the carbohydrate to be sweet and someone who is accustomed to less sugar needs less for the carbohydrate to taste sweet. Another reason could be that some people are genetically inclined to have more taste buds on their tongue. Therefore, the more tastebuds they have the more flavor they can detect. A third reason is ability smell. It is possible that one person had a cold and a blocked nose, so he or she could not smell very well. Smell helps in identifying flavor.

According to Dr. Robert Magolskee on NPR, the taste bud contains about 50 or 100 taste cells, and maybe a quarter of them are responding to sweetness, and a different percentage of them will respond to salty and sour and bitter. Sweet receptor protein and the sugar encounter each other, they excite the sweet taste cell, and that sends a signal to the brain, to particular centers of the central nervous system that respond to sweetness. In particular for common types of sweet compounds such as sucrose and glucose and fructose, the monosaccharide and disaccharide sweeteners, there are extra pathways, extra mechanisms that allow us to taste something as being sweet. These are sugar transporters and special ion channels, potassium ion channels. The number of tastebuds could play a role in tasters ranking the same samples differently because the more taste buds, the more sweet receptor proteins. Some people will have more proteins to taste all the sweetness.

Sources:

"Getting a Sense of How We Taste Sweetness." NPR. NPR,  Mar. 11  2011. Web.Sept. 16 2015. <http://www.npr.org/2011/03/11/134459338/Getting-a-Sense-of-How-We-Taste-Sweetness>

Carbohydrate	Type of Carbohydrate	Degree of Sweetness	Color	Texture	Other Observations
Sucrose	Disaccharide	100	white	granular	sugar
Glucose	Monosaccharide	90	transparent white	granular	granulated sugar
Fructose	Monosaccharide	115	white	granular	granulated sugar
Galactose	Monosaccharide	50	brownish yellow	powder	powdered sugar
Maltose	Disaccharide	110	white	soft	brown sugar
Lactose	Disaccharide	20	white	soft powder	powdered milk
Starch	Polysaccharide	10	white	sticky powder	potato/corn
Cellulose	Polysaccharide	0	white	soft and sticky	paper