The Science of J. Kenji López-Alt's Roasted Potato Recipe

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22 Nov 201911:18
EducationalLearning
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TLDRIn this engaging food science video, the host explores the impact of pH levels on the texture of roasted potatoes. Starting with a hypothesis about acidity and basicity, the video delves into the chemistry behind potato starch, specifically the role of amylose and amylopectin, and how they interact with pH to influence the potato's consistency. Through a series of experiments with different pH levels, the host discovers that adding baking soda to the boiling water results in the most desirable roasted potato texture, with a crispy exterior and a soft, non-gummy interior. The video also touches on the Maillard reaction, which contributes to the potatoes' browning and flavor. The host concludes with a surprising revelation that a significant amount of baking soda can be used without compromising the taste, encouraging viewers to experiment with this technique at home.

Takeaways
  • 🥔 The texture of roasted potatoes is influenced by the pH level of the water used to boil them before roasting.
  • 🧪 Potatoes are primarily composed of water and starch, with the latter consisting of amylose and amylopectin polymers.
  • 🔬 Amylopectin's phosphorylation level affects the texture of cooked potatoes; more phosphorylated amylopectin leads to a gummy texture.
  • 🥔 Red potatoes have highly phosphorylated amylopectin, making them ideal for soups and stews, while russets are better for mashed potatoes.
  • 🥔 Yukon Gold potatoes are a middle ground, maintaining shape better than russets but breaking apart more than red potatoes.
  • 🔍 pH affects potato texture through its impact on pectin, which acts as a glue between plant cells; lower pH strengthens this bond.
  • 🧂 Adding vinegar to water lowers the pH, helping to hold the potato structure together, while baking soda raises the pH, causing potatoes to fall apart.
  • 🍽 The Maillard reaction, responsible for the browning of the potatoes, is a complex chemical process that is sped up at higher pH levels.
  • 🥇 The experiment found that adding baking soda to the boiling water resulted in the most preferred potato texture for roasting.
  • 📊 The pH levels were adjusted from most acidic to most basic, with different outcomes in terms of potato texture and crispiness.
  • 📝 The experiment was conducted blind to ensure scientific accuracy, with the person evaluating the potatoes unaware of which pH level was used for each.
Q & A
  • What is the main focus of the video regarding potato cooking?

    -The main focus of the video is to explore how the pH level of the water used for boiling potatoes affects their texture and consistency when making roasted potatoes.

  • What are the two main types of polymers that make up starch in potatoes?

    -The two main types of polymers that make up starch in potatoes are amylose and amylopectin.

  • How does the phosphorylation of amylopectin affect the texture of cooked potatoes?

    -Phosphorylated amylopectins tend to stick together and form a gel as they cool, which can make potatoes gummy and help them hold their shape, suitable for soups or stews.

  • What type of potato is best for making mashed potatoes due to its texture?

    -Russet potatoes are best for making mashed potatoes because they have less well-phosphorylated amylopectin, which results in a fluffier texture when boiled.

  • Why did the team choose Yukon Gold potatoes for their experiment?

    -The team chose Yukon Gold potatoes because they are a good middle ground between red potatoes and russets, maintaining their shape better than russets but breaking apart more easily than red potatoes.

  • What role does pectin play in the texture of potatoes?

    -Pectin acts as a glue between plant cells, and its structure is affected by pH levels. At lower pH, pectin holds cells together well, while at higher pH, the bonds break down, leading to a mushier potato.

  • How does the addition of baking soda to water affect the texture of potatoes?

    -Adding baking soda, a base, to water increases the pH, which can cause phosphorylated amylopectin chains to repel each other, leading to a potato that falls apart more easily.

  • What is the Maillard reaction and how does it affect the roasted potatoes?

    -The Maillard reaction is a complex chemical reaction that occurs when amino acids and sugars in the oil and starchy paste mix are heated. It contributes to the browning and flavor of the potatoes, and it speeds up at higher pH levels.

  • What was the most acidic water solution used in the experiment?

    -The most acidic water solution was achieved by adding three tablespoons of vinegar followed by an entire cup of extra vinegar, resulting in a pH level around four.

  • How did the crew correct Sam's guess regarding the pH levels of the potatoes?

    -The crew corrected Sam by stating that the potato labeled 'E' was the most basic, not 'A' as Sam had guessed.

  • What was the recommended method for achieving the best roasted potato texture in the video?

    -The recommended method for achieving the best roasted potato texture was to use baking soda when boiling the potatoes to increase the pH of the water.

  • What other PBS Digital Studios show is mentioned for those interested in more food science?

    -The show mentioned for those interested in more food science is 'Serving Up Science', hosted by Sheril Kirshenbaum.

Outlines
00:00
🧪 Exploring pH and Potato Consistency

The video begins with Sam guessing the pH levels of different water samples, suspecting that sample A is the most basic and B the most acidic. The crew corrects him, leading to a discussion about making roasted potatoes with a unique twist inspired by J. Kenji López-Alt's recipe. The focus is on how varying the pH level of the water used to boil potatoes can affect their texture. Sam explains the composition of potatoes, the role of starch, amylose, and amylopectin, and how phosphorylated amylopectins contribute to the texture of cooked potatoes. Different potato varieties are compared based on their amylopectin phosphorylation levels. The experiment aims to achieve a balance between a soft interior and a crispy exterior by adjusting the pH. Pectin's role in cell cohesion and how it's affected by pH levels is also discussed. Sam outlines the plan to test five different pH levels to determine the optimal texture for roasted potatoes, starting with the most acidic water by adding vinegar.

05:02
🥔 Boiling, Roasting, and the Maillard Reaction

After a secretive preparation, Sam checks the potatoes for doneness and adds olive oil to each pot, explaining the importance of this step for the Maillard reaction, which enhances the flavor and color of the potatoes. The potatoes are seasoned only with oil for the sake of the experiment. They are then roasted at a high temperature, flipped halfway through, and cooked until they achieve a crispy, golden brown appearance. Sam tastes the potatoes in the order of their pH levels, finding that the most basic one (E) is his favorite. He notes the differences in texture and hardness among the samples, with some being too mushy, too hard, or just right. Based on the taste test, he awards E the gold star, C the silver, and is undecided between D or A for the bronze. Sam's final guess about the pH levels is corrected by the crew, revealing that E was the most basic. He concludes with a recommendation to use baking soda in the boiling water for the perfect roasted potato texture.

10:05
📚 Final Thoughts and Additional Resources

Sam summarizes the experiment's findings, emphasizing the surprising effectiveness of using baking soda in boiling water to achieve the ideal texture for roasted potatoes. He encourages viewers to try this method and share their results in the comments. The video concludes with a promotion for 'Serving Up Science,' a PBS Digital Studios show hosted by Sheril Kirshenbaum, which offers science-based answers to various food-related questions. Sam invites viewers to explore more food science by watching 'Serving Up Science' on the PBS Food channel.

Mindmap
Keywords
💡pH
pH is a scale that measures how acidic or basic a substance is, with a lower value indicating higher acidity and a higher value indicating more basic or alkaline properties. In the video, the experimenters manipulate the pH of water to understand its effect on the texture of potatoes. They use vinegar to lower the pH and baking soda to raise it, which in turn impacts the potato's texture when boiled and roasted.
💡roasted potatoes
Roasted potatoes are a popular dish made by cooking potatoes at high temperatures, typically resulting in a crispy exterior and soft interior. The video's theme revolves around achieving the perfect texture for roasted potatoes using chemistry, specifically by altering the pH of the water in which they are boiled before roasting.
💡amylose and amylopectin
Amylose and amylopectin are two types of starch molecules found in potatoes. They are polymers that serve as stored fuel for the plant. The video explains that the texture of cooked potatoes is related to the phosphorylation of amylopectin. When potatoes are boiled, the starch granules swell, and the amylopectin can form a gel upon cooling, affecting the potato's texture.
💡pectin
Pectin is a polymer found between plant cell walls that acts as a glue, holding cells together. In the context of the video, pectin's behavior in response to different pH levels is discussed. At lower pH levels, pectin polymer chains hold together well, while at higher pH levels, the bonds linking pectin start to break down, leading to a mushier potato texture.
💡phosphorylated amylopectins
Phosphorylated amylopectins are starch molecules in potatoes that have had phosphate groups added to them, giving them a negative charge. The video explains that when a base like baking soda is added to the water, it increases the negative charge, causing the phosphorylated amylopectin chains to repel each other, which can cause the potato to fall apart.
💡Maillard reaction
The Maillard reaction is a complex, multi-step chemical reaction that occurs when amino acids and sugars are heated together, as in the cooking process. It is responsible for the browning of the potatoes when they are roasted. The video mentions that this reaction speeds up at a higher pH, which is why potatoes boiled in baking soda water appear more brown.
💡Yukon Gold potatoes
Yukon Gold potatoes are a variety of potato that is chosen for the experiment because they are intermediate in their texture properties. They hold their shape better than russets but disintegrate more easily than red potatoes, making them suitable for the texture experiment described in the video.
💡russet potatoes
Russet potatoes are mentioned as a variety that does not have well-phosphorylated amylopectin, leading to a fluffier texture when boiled. This characteristic makes them ideal for dishes like mashed potatoes, but not as suitable for the roasted potato texture experiment conducted in the video.
💡red potatoes
Red potatoes are highlighted as having very well-phosphorylated amylopectin, which results in a gummy texture when cooked. This trait makes them hold their shape well, making them a good choice for soups or stews but less ideal for the roasted potato experiment aimed at achieving a specific texture.
💡baking soda
Baking soda, or sodium bicarbonate, is used in the experiment to increase the pH of the water in which the potatoes are boiled. The video concludes that adding baking soda to the water results in the most preferred texture for roasted potatoes, making them crispy on the outside and soft on the inside without falling apart.
💡vinegar
Vinegar is used to lower the pH of the water, making it more acidic. In the context of the video, adding vinegar to the water helps to maintain the structure of pectin and results in potatoes that hold together better. The experiment explores how varying the pH with vinegar affects the final texture of the roasted potatoes.
Highlights

The experiment aims to find the perfect texture for roasted potatoes using chemistry and pH manipulation.

Potatoes are primarily composed of water and starch, which includes amylose and amylopectin polymers.

The texture of cooked potatoes is related to the degree of phosphorylation of their amylopectins.

Red potatoes have well-phosphorylated amylopectin, making them ideal for soups or stews.

Russet potatoes have less phosphorylated amylopectin, resulting in a fluffier texture suitable for mashed potatoes.

Yukon Gold potatoes are chosen for their intermediate texture properties between red and russet potatoes.

pH affects potato texture by influencing pectin, a polymer that acts as a glue between plant cells.

Lower pH levels help maintain the structure of pectin, while higher pH levels cause it to break down, leading to mushier potatoes.

The addition of baking soda to water increases the pH, causing phosphorylated amylopectin chains to repel each other and the potato to fall apart.

Acidic water helps hold potatoes together, while basic water makes them fall apart.

Five different pH levels are tested to determine the best consistency for roasted potatoes.

Vinegar is added to water to achieve the most acidic environment, while baking soda is used for the most basic.

The use of pH strips helps to measure and adjust the acidity or alkalinity of the water.

Boiling potatoes in different pH levels of water reveals how each affects the final texture.

The Maillard reaction, responsible for the browning of potatoes, is influenced by pH levels.

Potatoes boiled in baking soda water are expected to brown more due to the acceleration of the Maillard reaction at higher pH.

The experiment concludes that adding baking soda to the boiling water results in the preferred roasted potato texture.

The most basic pH (E) was identified as the favorite, with a crispy outside and very soft inside.

The recommendation is to use baking soda when boiling potatoes to achieve the perfect roasted potato texture.

Transcripts
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