Are all Potatoes created the same?

Are all Potatoes created the same?

Raw potatoes corresponding to their respective food dye colors--Blue--Yukon Gold, Red--Red Bliss,and Green--Sweet Potato.

Potatoes cooking on the stove, in their respectively dyed water.

Just for fun. All the potatoes placed together, once data was collected.

Yukon Gold potatoes cut open, after they were cooked for 10 mins. As you can see the dye was absorbed all the way to the core of the potato, thus showing their high starch content.

Red Bliss potatoes cut open, after cooking. As you can see the dye was absorbed only 2mm into the outside of the potato, which formed a small red ring around the outside.

All the potatoes, on plates, before they were cut open, and data gathered.

Sweet potatoes cut open, after cooking for 10 mins. As you can see, the green dye only traveled 1mm into the potatoes. This demonstrated that Sweet potatoes also have a very low starch content. 

For my third mini-experiment, given the fact that I had kind of ran out of ideas for things to test, and because I wanted to start to test something’s that might not be so obvious as the concepts I had already tested, I decided to explore the chapters in my The Science of Good Cooking text book for some ideas. In addition, I also wanted an experiment idea that would produce a large sample size than a 1 on 1 comparison, as well as a test that would be quantifiably measurable. One of the categories that caught my eye was the sections on potatoes. When I saw the word potatoes, I immediately thought “hey I could get a lot of samples out of those potatoes, for a relatively inexpensive price, and no matter what I was going to do it wouldn’t take very much time.” The first experiment I read up on dealt with the temperature of hot oils used for frying. However, that was something that was somewhat obvious, and I wanted to test a concept that I really had never heard about before and that was more interesting. With that said, I settled on the experiment that explored the density of different varieties of potatoes in terms of their starch content.

According to concept 25 (chapter 25), all potatoes are not created equal. While potatoes consist of 2 main components—starch and moisture—the density of each particular type of potato is directly correlated to the amount of starch it has, which can range from 16% to 22% (Editors of Cook's Illustrated & Crosby, 2012). Furthermore, the amount of starch each potato possesses affects a variety of things with its two most important characteristics being the potato’s ability to hold shape and fluffiness (Editors of Cook's Illustrated & Crosby, 2012). When potatoes are cooked, the granules inside them absorb water from within the potato, which causes the potato to swell similar to that of a balloon, which in in turn causes the cells inside the potato contain the granules to expand, separate, and burst (Editors of Cook's Illustrated & Crosby, 2012). And with continued cooking, the swollen granules that have not let burst, end up bursting, which in turn release some of the entrapped starch (Editors of Cook's Illustrated & Crosby, 2012). In the end, the more starch a potato contains, the more burst potato cells potato will have (Editors of Cook's Illustrated & Crosby, 2012). And one of the ways to test how much starch a potato has is to dye the water it is being cooked in with food coloring.

My hypothesis for this experiment was that if we tested the amount of starch in 3 types of potatoes—Yukon Gold, Red Bliss, and Sweet Potato—by cooking them in colored dye, then potatoes with a higher starch content would absorb more food coloring than potatoes with a lower starch content, because potatoes with a higher starch content would have more burst granules, and would therefore be able draw in more liquid during the cooking process.

My null hypothesis was that the amount of starch in each type of potato would have no effect on the amount of food coloring drawn into each potato.

My independent variable for this experiment was the type of potato used—Yukon Gold, Red Bliss, or Sweet Potato.

My dependent variable for this experiment was the amount of starch each potato contained, which translated into the amount of food dye color that was absorbed by each potato.

My standard variables for this experiment included: the size of the potato cubes being cooked (30mm x 20mm x 5mm), the temperature of the boiling water (210.5 degrees Fahrenheit),  the number of potato cubes tested (5), the amount of cook time and rest time (15 minutes and 10 minutes respectively), the measuring instrument (a 12 inch ruler with metric marks), the amount of potato cubes per each type of potato (5 cubes), and finally the food dye colors used for each potato (blue-Yukon, red- Red Bliss, and green-Sweet potato).

After acquiring my 3 types of potatoes from the grocery store, I took 3 pots out of my kitchen cabinets, filled them with water, and placed them on top of my stove over high heat to boil. While the water started to boil, I rinsed each potato under cold water, to clean any remaining dirt off the outside of the potato. Following this, I cut each type of potato into 30mm x 20mm x 5mm cubes , and placed them next to their corresponding dye color that I had selected. Before dying the water, I took the temperature of the water in each pot to ensure that they were all roughly about the same, which was indeed the case as the water in each pot had reached 210.5 degrees Fahrenheit. At this point I dyed the water in each pot a different color—blue, red, and green—and placed the corresponding potatoes in each pot—Yukon Gold, Red Bliss, and Sweet potatoes respectively. At this time, I left the potatoes to boil over high heat for 15 minutes. Upon completion of the 15 minute boil time, I removed all pots from the stove and allowed the potatoes to cool for 10 minutes. Once the potatoes had cooled, I removed each type of potato from their pots, and placed them on separate Styrofoam plates. At this time I cut each potato open and measured how far the colored dye had traveled into the potato. The results were as followed:

Yukon Gold	Red Bliss	Sweet Potato
5mm	2mm	1mm
5mm	2mm	1mm
5mm	2mm	1mm
5mm	2mm	1mm
5mm	2mm	1mm

This graph displays how far the food coloring traveled (in millimeters) into each type of potato after being boiled for 15 minutes, and cooling for 10 minutes. As one can observe from the graph, the dye traveled the farthest in the Yukon Gold potatoes at 5 millimeters, followed by Red Bliss at 2 millimeters, and lastly Sweet potatoes at 1 millimeter. The distance traveled correlates to the amount of starch in each type of potato. Thus, Yukon Gold potatoes have the highest starch content of the three types tested above, followed by Red Bliss and then Sweet potatoes respectively. The error bars are not displayed on the chart, because there was no variation or deviation among the samples collected for each type of potato.  

Yukon Gold potatoes appear to have the most amount of starch as the food dye had traveled completely into the potato all the way to the core. The next highest starch content appears to be in the Red Bliss Potato, as the dye had formed a 2mm ring of coloring around the outside of the potato. While this indicates that there is very little starch in the Red Bliss potato compared to the Yukon Gold potato, in comparison of the 3 types, it was the second highest starch content. Finally, the food coloring had only managed to travel 1mm inside the sweet potato, leaving a 1mm green ring around the outside of the potato, which indicated that sweet potatoes had the least amount of starch out of the 3 types of potatoes. 

The science behind this experiment is as follows: The first important aspect deals with the ratio of starch to moisture that each potato has (Editors of Cook's Illustrated & Crosby, 2012). The more starch a potato has, the more dense it is, and the great the propensity it has to absorb liquid (Editors of Cook's Illustrated & Crosby, 2012). This is because the starch granules have a greater propensity to absorb water as they are cooked, which causes them to swell, and also causes the other cells in the potato to separate from one another, and even burst, thus drawing in the food coloring (Editors of Cook's Illustrated & Crosby, 2012). Thus, the higher starch potatoes absorbed more food dye than the lower starch potatoes (Editors of Cook's Illustrated & Crosby, 2012).

Secondly, the ratio of each type of starch each potato has—amylose and amylopectin—determines the internal consistency of the potato (Editors of Cook's Illustrated & Crosby, 2012). Amylose is a long chain of starch that separates from swollen granules when exposed to heat, thus allowing for more fluid movement into the potato, and is also responsible for the fluffier texture of Yukon Gold potatoes (Editors of Cook's Illustrated & Crosby, 2012). The starch amylopectin, helps hold the potato tightly together when exposed to heat, thus diminishing the amount of outside moisture that is drawn into the potato when cooked (Editors of Cook's Illustrated & Crosby, 2012).

With that said, Yukon Gold potatoes had more overall starch compared to Red Bliss and Sweet potatoes in general, but Red Bliss and Sweet potatoes had a higher ratio of amylopectin starch compared to amylose starch, with Sweet potatoes possessing the highest ration of amylopectin. This was evident by the amount of dye that was absorbed by each potato. 

At this time, I am unsure of what I would do differently if I had to do this experiment over again. This was the smoothest any of my experiments have gone, and was actually quite simple. If I had to pick one thing, I would have to say that I would have cut the potatoes into larger cubes. The size I chose ended up being rather small after they were cooked, and it was a little hard to measure how far the dye had traveled. Thus, increasing the size of the cubes would have allowed me to make more accurate measurements, thus allowing me to detect minor differences.

Citation:
Editors of Cook. , & Crosby, G. (2012). The science of good cooking. Brookline: Cook's Illustrated