Molecular gastronomy in the chemistry classroom (2022)

Author(s): Johanna Dittmar, Christian Zowada, Shuichi Yamashita, Ingo Eilks

Alginate bubbles are useful in chemistry lessons as well as in molecular gastronomy.

Molecular gastronomy is a new trend in haute cuisine, with chefs providing their guests with novel and strange culinary experiences using liquid nitrogen, gels and foams. One of the techniques that is becoming more well known is the use of alginate spheres containing different fruit juices or flavours. Even if you don’t frequent Michelin-starred restaurants, you may have come across these spheres in bubble tea.

Bubble tea, originally invented in Taiwan in the 1980s, spilled over from Eastern Asia to Western countries some years ago. It consists of a tea-based drink that also contains fruit jellies, tapioca or alginate spheres, filled with fruit juice or syrup.

Making and examining the behaviour of alginate bubbles can be fascinating and can be used in inquiry-based learning in the sciences.

In this article, we suggest how alginate bubbles can be used to teach various scientific concepts, presenting scientific phenomena in an aesthetic fashion. We introduce how to make alginate bubbles and present three example experiments, each of which can be performed in a one-hour lesson: an acid-base reaction, chemo-luminescence with redox chemistry, and thermal convection with a thermochromic effect.

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Forming alginate bubbles

Molecular gastronomy in the chemistry classroom (1)

Alginate bubbles are formed when an aqueous alginate solution (figure 1) comes into contact with a solution containing calcium ions, creating a membrane of calcium alginate where the two solutions meet (figure 2). Alginate is a long polysaccharide that becomes cross-linked in the presence of a divalent cation, such as calcium, to make a water-insoluble gel.

Materials

  • 2 g sodium alginate (Na(C6H806))
  • 100 ml distilled water
  • 10 ml 0.5% calcium chloride (CaCl2) or 1% calcium lactate solution (Ca(C3H5O3)2
  • Two 250 ml beakers
  • Dropper pipette or spoon
  • Glass rod or other stirrer
  • Sieve or spoon

Procedure

Molecular gastronomy in the chemistry classroom (2)
  1. Mix the alginate and water in one of the beakers.
  2. Wait at least 15 minutes until all the alginate has dissolved.
  3. Pour the calcium ion solution into the other beaker.
  4. Add drops of the alginate solution to the calcium ion solution with a pipette or a spoon. Stir the calcium solution as you do this to prevent the alginate spheres sticking together.
  5. The bubbles are stable and can be removed from the calcium ion solution with a spoon or sieve.

When the liquids come into contact, gelatinous calcium alginate is formed, encapsulating the alginate solution in spheres. If other compounds are also added to the alginate solution, such as flavours, colouring agents, or indicators, they are also encapsulated.

Acid–base bubbles

Materials

  • 2 g sodium alginate
  • 500 ml distilled water
  • 10 ml 0.5% calcium chloride or 1% calcium lactate solution
  • Three 250 ml beakers
  • Dropper pipette or spoon
  • Glass rod or other stirrer
  • Sieve (optional)
  • Indicator solution
  • Assorted acids and bases

Procedure

  1. Follow the procedure above for forming alginate bubbles but add an acid–base indicator to the alginate solution just before adding the alginate to the calcium solution.
  2. Remove the bubbles and place them in a beaker containing the rest of the distilled water.
  3. Note the colour of the spheres.
  4. Systematically add different acids and bases to the water and note how the colour of the bubbles changes.

Although the indicator solution is inside the bubbles, the alginate membrane can exchange hydroxide or hydronium ions (hydrated protons) between the bubbles’ contents and the surrounding liquid. Changing the pH value of the surrounding liquid by adding an acid or a base will therefore change the pH of the liquid inside the spheres, and so the indicator will change colour.

While technical indicators can be used in the classroom, pH-sensitive extracts of red cabbage or garden radish peel could be used at home.

Luminescent bubbles

Alginate bubbles can be used to illustrate the phenomenon of luminescence by simply adding a luminescent compound to the alginate solution before the bubbles are formed. One easy way to do this is to use riboflavin (vitamin B2), which fluoresces under UV light. Although you can use pure riboflavin, you can also extract it from a food such as an instant custard powder that contains it.

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Materials

Extracting riboflavin (optional):

  • One pack instant custard powder containing riboflavin (also known as E101)
  • 200 ml distilled water
  • Beaker
  • Stirrer
  • Funnel with filter paper

Making luminescent bubbles:

  • Two spatula tips of riboflavin powder (C17H20NaO6)
  • 2 g sodium alginate
  • 100 ml water
  • 10 ml 0.5% calcium chloride or 1% calcium lactate solution
  • Two 250 ml beakers
  • Dropper pipette or spoon
  • Glass rod or other stirrer
  • Sieve (optional)
  • UV source
  • 15–20 ml saturated sodium dithionite solution (Na2S2O4)
  • 15–20 ml hydrogen peroxide (20%-35%)

Procedure

  1. To extract the riboflavin from the instant custard powder, place about 8 g of powder in 200 ml water. Stir well for about 10 minutes and filter.
  2. Follow the procedure for making alginate bubbles, but add the riboflavin to the alginate solution just before spherification.
  3. Shine UV light on the bubbles that are formed. They should fluoresce, emitting a yellow-green light.
  4. Turn the UV light off and the bubbles will stop fluorescing.
  5. Turn the light back on.
  6. Add the sodium dithionite to the beaker containing the alginate bubbles. You should notice that the luminescence is turned off, because the sodium dithionate crosses the membrane around the alginate bubbles and reduces the riboflavin inside.
  7. Add hydrogen peroxide to oxidise the riboflavin, turning the luminescence on again.

Thermo bubbles

Adding a thermochromic ink to the alginate solution can help to illustrate the phenomenon of convection. In Japan, a special thermo ink based on a lactone of crystal violet (and not to be confused with the thermo inks used in thermo printers) is sold to illustrate heat-related phenomena in physics.

Materials

  • 2 g sodium alginate
  • 100 ml distilled water
  • 10 ml 0.5% calcium chloride or 1% calcium lactate solution
  • Two 250 ml beakers
  • Dropper pipette or spoon
  • Glass rod or other stirrer
  • Sieve
  • 3–5 ml thermochromic ink
  • Heatproof beaker filled with water
  • Heat source

Procedure

  1. Make the bubbles as described above, but add the ink to the alginate solution just before spherification.
  2. Place the resulting bubbles in a heatproof beaker of water.
  3. Heat the beaker until the bubbles start to rise.

The alginate bubbles will move to show convection: rising as they become less dense when heated, and then cooling and sinking back down as they become more dense again. At the same time, the alginate bubbles will change colour, showing that convection is associated with a change in temperature.

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Acknowledgements

Part of this work was funded by the Teaching Enquiry with Mysteries Incorporated (TEMI) project (Peleg et al., 2015), supported by the European Union under the 7th Framework Programme for Research Funding “Science in Society” under Grant Agreement No. 321403.

References

  • Peleg R et al. (2015) The magic sand mystery. Science in School 32: 37-40.

Resources

Author(s)

Johanna Dittmar, Christian Zowada and Professor Ingo Eilks are from the chemistry education research group based at the University of Bremen, Germany. Professor Shuichi Yamashita is a science educator in Chiba, Japan. Each of the authors developed a different activity using alginate bubbles.


Review

Our curiosity is always attracted by changes of colour, position, shape and light. Using such changes in our teaching can help our students to enjoy science more. The first and second activities would be suitable for students aged 15-16, whereas the third activity, involving convection and luminescence, would also be suitable for younger students, aged 11-14.

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After the activities, the teacher could ask why bubbles were used, leading to a discussion of the chemical and physical properties of matter.

Enrico Capaccio, Istituto Superiore S Bellarmino, Montepulciano (Siena), Italy

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CC-BY

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FAQs

How does molecular gastronomy relate to chemistry? ›

Introduction. The field of “Molecular gastronomy” was developed to investigate the physical and chemical transformation of food ingredients during cooking. It deals with the enrichment of the organoleptic properties (taste, color, odor, and feel) of different cuisines by comprehending modern technology with cooking.

What is molecular gastronomy answer? ›

molecular gastronomy, the scientific discipline concerned with the physical and chemical transformations that occur during cooking. The name is sometimes mistakenly given to the application of scientific knowledge to the creation of new dishes and culinary techniques.

What is the point of molecular gastronomy? ›

Molecular gastronomy is important because it bridges the social, artistic, and technical ramifications of food and food preparation. By studying the science behind different culinary processes or commonly used methods, chefs and scientists can understand why certain outcomes occur.

Who introduced molecular gastronomy? ›

Molecular gastronomy was born in 1988, when two scientists, Nicholas Kurti and Herve This, created a new scientific discipline to investigate culinary transformations, specifically the chemistry and physics behind the preparation of food (This, 2006).

Is cooking like chemistry? ›

Cooking is chemistry

Cooking itself is really just chemistry. Heating, freezing, mixing and blending are all processes used in the laboratory and the kitchen. When we cook food, a myriad of different physical and chemical processes simultaneously take place to transform the ingredients (i.e. chemicals) involved.

What are the 14 examples of gastronomy? ›

14 Examples of Gastronomy
  • Cultivation. Gastronomy isn't farming but involves knowledge around how food is cultivated including terroir, appellation and what processes and chemicals are involved.
  • Selection. ...
  • Nutrition & Diet. ...
  • Sustainability. ...
  • Preparation. ...
  • Molecular Gastronomy. ...
  • Technical Gastronomy. ...
  • Presentation.
May 11, 2018

Why is it called gastronomy? ›

The word is a compound of Greek γαστρ(ο)- 'stomach' ἀστρονομία and νόμος lit. 'custom', modeled on 'astronomy'. It was revived in 1801 as the title of a poem by Joseph Berchoux. It was Brillat-Savarin, in his Physiologie du goût (1825) who systematized the study of food and cooking under this name.

What can you say about gastronomy? ›

Gastronomy is the study of food and culture, with a particular focus on gourmet cuisine. Modern gastronomy has its roots in several French texts published in the 1800s, but the idea of relating food, science, society, and the arts has been around much longer.

What are the impact of molecular gastronomy toward the modern cuisine? ›

The knowledge that has been gained through molecular gastronomy has given chefs the ability to transform the tastes and textures of foods in revolutionary ways – something that would not be possible without knowing why ingredients behave in certain ways.

Who is the father of gastronomy? ›

Legendary chef Paul Bocuse has died aged 91.

The death of the man referred to as the father of gastronomy was announced by the French interior minister today (20 January).

What is the chemistry behind cooking meat? ›

When you sear your meat, proteins and sugars within the meat break down, creating the Maillard reaction. About 3,000 to 4,000 new chemical compounds are formed during this process, giving the meat a more complex flavor.

How is food related to science? ›

Food science draws from many disciplines, including biology, chemical engineering, and biochemistry to better understand food processes and improve food products for the general public. As the stewards of the field, food scientists study the physical, microbial, and chemical makeup of food.

What term is used to describe a contemporary culinary movement that explores the chemistry and physics of food? ›

The term "molecular and physical gastronomy" was coined in 1988 by Hungarian physicist Nicholas Kurti and French physical chemist Hervé This.

What are the elements of gastronomy? ›

The following are common elements of gastronomy.
  • Cultivation. ...
  • Selection. ...
  • Nutrition & Diet. ...
  • Sustainability. ...
  • Preparation. ...
  • Molecular Gastronomy. ...
  • Technical Gastronomy. ...
  • Presentation.
May 11, 2018

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