Culinary Chemistry Update

Author: L. A. Briggs // Category:
Posted May 4, 2011 at 2:32pm

It has been really great making blog posts during this semester. I have thoroughly enjoyed it! However, this semester is coming to a close and so is our blog project. I would like to be able to say that I will continue to post new things, but that may not be the case. I hope that I do get the chance to write some more because I love food, but if I don’t then I guess this is goodbye. Thanks for reading! But just remember to keep up the cooking and chemistry!

   ~~ Laura

How Taste Works: From Taste Buds to the Brain

Author: L. A. Briggs // Category: , , , ,

Posted May 4, 2011 at 2:10pm
Food is one of the things that I enjoy immensely. Everything just tastes so different from everything else. So how exactly does that work? How can bananas taste so differently than a steak? And how can the brain distinguish between the two?

The tongue is covered with taste buds, and these allow us to sense the different tastes in food when we eat them. These taste buds are chemoreceptors, which are sensory receptors that detect certain chemical stimuli in the environment and convert it into a useable form within the body. This means they translate the chemical signals that food produce when in contact with the taste buds into an electrical signal that can be sent though the body. These electrical signals are called action potentials, and they travel to the brain through the nervous system. When the signal gets to the brain it is identified by the brain and a certain sensation is experienced.

There are five different distinct tastes that the taste buds detect: salty, sweet,  bitter, sour, and savory. When food enters the mouth, saliva breaks the food down into ions and other chemical molecules that then enter the pores of the taste buds. Each of these tastes is sensed by the taste buds a little bit differently, based on what molecules the food is broken down into.

Salty and sour tastes are sensed through ion channels that are triggered by ions, or electronically charged particles, that are found in salty or sweet foods. Salty foods contain the ion sodium chloride (NaCl), which is commonly called table salt. This molecule is composed of two ions: the positively charged sodium ion and the negatively charged chlorine ion. When the ions are being sensed, the sodium ion triggers the ion channels in the taste buds, which changes the electrical charge of the taste bud cells, causing an action potential. For sour foods, which contain acids, the positively charged hydrogen ions cause the action potential within the taste buds.

Bitter, sweet, and savory foods are sensed through G-protein coupled receptors, which are a more sophisticated mechanism than the ion channels, and one that is not well understood.  Compounds within bitter and sweet foods trigger G-protein coupled receptors to release a messenger protein, gustducin, which triggers molecules to close potassium ion channels, creating an action potential. Sensing savory foods is similar, though it is triggered by the amino acid L-glutamate.

Once the action potential has been created and a signal has been sent through the nervous system, the signal is transferred between nerve cells until the signal reaches the brain where the signal is translated into a taste. The process from ingesting food to having a sensory experience from that food is very fast, happening within a couple of milliseconds, which is good because there are lots of delicious foods out there to try. And the tongue contains an average of 10,000 taste buds that get replaced every two days. That’s a lot of taste buds! Now it’s time to get busy using some!

Water: The Fluid of Life (And Osmosis and Diffusion)

Author: L. A. Briggs // Category: , , , ,

Posted May 3, 2011 at 11:57pm

Water is such an amazing molecule that has many unique features. Without water, life would cease to exist on this planet since life depends on it. Water also has amazing capabilities in the kitchen too. It has great heat transfer properties used when cooking something in boiling water, such as boiling eggs, or when cooling something off with cold water, such as cooling pasta. It is also good for dissolving substances, such as sugar, and for re-hydrating dehydrated foods.

There are two main properties of water that are taken into account in the kitchen: diffusion and osmosis.

Diffusion is the movement of molecules from high areas of concentrations to areas of low concentrations by the random motion of molecules until an equilibrium state has been reached. A good example is the spread of dye within water without being stirred. The random motion of both the water and dye molecules helps the mixture to come to an equilibrium state where the water and the dye are thoroughly mixed.

Osmosis is the diffusive movement of water across a selectively-permeable membrane into a region of higher solute concentration in order to establish an equilibrium of solute to water ratio on both sides of the membrane. A good example is submerging a wilted piece of lettuce in fresh water. The inside of the lettuce leaf has a higher concentration of solute than the water it’s submerged in, so the water diffuses into the leaf in order to equalize the solute concentrations both inside the lettuce leaf and in the water. This essentially causes the wilted piece of lettuce to become rigid again.

The following video is a good example of both diffusion and osmosis. It shows both of the examples that I used above: the diffusion of dye in water, and the osmosis of water into a wilted lettuce leaf.