# Questions and answers: when words are analysed from a chemical and physical perspective, innovation is easy

Hervé This, Vo Kientza

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# Questions and answers: when words are analysed from a chemical and physical perspective, innovation is easy

Hervé This, Vo Kientza

## ► To cite this version:

Hervé This, Vo Kientza. Questions and answers: when words are analysed from a chemical and physical perspective, innovation is easy. International Journal of Molecular and Physical Gastronomy, 2024, 10 (1), pp.1-12. hal-04436143v2

HAL Id: hal-04436143

https://hal.inrae.fr/hal-04436143v2

Submitted on 16 Jul 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Questions and answers: when words are analysed from a chemical and physical perspective, innovation is easy

Hervé This vo Kientza¹

1. Université Paris Saclay, INRAE, AgroParisTech, UMR SayFood, 91120 Palaiseau, France

2. Group of Molecular Gastronomy, Inrae-AgroParisTech International Centre for Molecular and Physical Gastronomy, 22 place de l'agronomie, 91120, Palaiseau, France.

*Correspondence: herve.this@inrae.fr*

**Abstract**

Seven questions sent by a chef about molecular cooking preparations are considered. The scientific and technical analysis of these questions associated with a terminology discussion leads to many technical solutions. This discussion demonstrates that culinary innovation is easier when it is based on molecular and physical gastronomy.

**Keywords**

wording, molecular cooking, solutions.

**Introduction**

In this article, seven questions sent by email by a pastry chef are discussed:

1. What is "xanthan", and how is it used? Is it dangerous?

2. How can "herbal pearls" be made?

3. How can "tomato and date mousse" be made?

4. How can "lemon powder" be made?

5. How can "espuma" be made?

6. How can "vanilla emulsion" be made?

7. What is a "protein batter"?

These questions are about common "molecular cooking" preparations, i.e., culinary preparations that are obtained through the use of modern tools transferred from scientific and technological laboratories to kitchens.

For all of them, (1) the wording will first be analysed, (2) leading to a good understanding, so that (3) various culinary solutions can be proposed.
<figure><img src="image_2.png" /></figure>

Inrae-AgroParisTech
International Centre for Molecular and Physical Gastronomy

International Journal
of
Molecular and Physical Gastronomy

**Authors**

Hervé This vo Kientza

**Title of the work**

Questions and answers: when words are analysed from a chemical and physical perspective,
innovation is easy

Year 2024, 10(1) 1, pp. 1-12

DOI: 10.17180/ijmpg-2024-art01

**Published online:**

22 November 2023,

https://icmpg.hub.inrae.fr/international-activities-of-the-international-centre-of-molecular-gastronomy/international-journal-of-molecular-and-physical-gastronomy/4-edible-ideas/questions-and-answers/ijmpg.-2024-10-1-this-vo-kientza-innovation-is-easy

Questions and answers: when words are analysed from a chemical and physical perspective,
innovation is easy © 2023 by Hervé This vo Kientza is licensed under [Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

<figure><img src="image_3.png" /></figure>
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

**1. What is "xanthan" and how is it used? Is it dangerous?**

Here the question was about "xanthan", and the chef wanted to know what it is, and how it can be used, but it has to be observed that he should have spoken of "xanthan gum", rather than simply "xanthan". Using this more correct terminology, he would have found a large number of Internet pages of different quality, ranging from the very precise to the completely wrong. A reliable source is the *Handbook of Molecular Gastronomy* (Burke et al., 2021).

The word "xanthan" is based on the Greek root *xanthos*, meaning yellow. It comes from the name of the *Xanthomonas* group of bacteria, which sometimes create yellow stains on the leaves of plants. When fermenting corn starch, for example, *Xanthomonas campestris* secrete compounds (see later) that can be recovered by filtration and ethanol precipitation, forming a "gum" called "xanthan gum" (Jecfa, 2016; Edwards-Stuart and Barbar, 2021). This word "gum" is also used for gum arabic, carob bean gum, konjac gum, for example, but there is a difference because these gums are hardened saps from plants (often trees) rather than dried secretions from bacteria.

Contrary to what is sometimes published (Wikipedia, 2023), xanthan gums are not "a" polysaccharide, but mixtures of exo-polysaccharides (Faria *et al.*, 2011), i.e., compounds whose molecules have a high molecular mass (between one and several million), being made of repeats of D-glucose and D-mannose residues, as the dominant hexose units, along with residues of D-glucuronic acid and pyruvic acid. Alternate D-glucose residues have a short, three-sugar branch consisting of a glucuronic acid residue sandwiched between two mannose residues; thus, the overall repeating structure is a pentasaccharide residue (Figure 1). The mannose residues adjacent to the main chain may have an acetyl group (-CH₃) attached to the carbon atom C6, and the terminal mannose residues can be linked through carbons 6 and 4 to the second carbon of pyruvic acid residues. The

<figure><img src="image_2.png" /><figcaption>Figure 1. The chemical structure of xanthan gum molecules.</figcaption></figure>

final xanthan gum products are manufactured in the form of a sodium, potassium or calcium salt, and their solutions are neutral.

Xanthan gums, either native or chemically modified, have thickening properties, and gelling properties in association with other polysaccharides, because of the high number of hydroxyl groups (with an oxygen atom linked to an hydrogen atom, -OH) in their molecules. As such groups can establish hydrogen bonds with water molecules, xanthan gums increase the viscosity of the aqueous solution in which they are dissolved. In association with other polysaccharides (e.g. as galatomannans) or mixture of polysaccharides (e.g. starch), they can make gels.

Xanthan gums are allowed to be used as food additives (European code E415) for their thickening and gelling properties (EFSA Panel on Food Additives and Flavourings, 2023). The acceptable daily intake (ADI) is "not specified", which means that it can used *quantum satis* without risk for the human health.

After receiving this information, the chef to which the information given here was sent asked why
<figure><img src="image_4.png" /></figure>
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

<figure><img src="image_3.png" /><figcaption>Figure 2. The theory of percolation explains the difference between a thickened solution (left) and a gel (right). When monomers that can link are at low concentration (left), they can make a local aggregate that increases the viscosity of the medium in which they are dispersed. When their concentration is higher than the so-called "percolation threshold", a continuous network can be established, making a gel (right).</figcaption></figure>

the same product can be used in two different ways, and indeed there is sometimes confusion between thickeners and gelling agents. Products in these two categories are often polymers, i.e., compounds whose molecules are repetitions of a few basic units, called "monomers". For example, cellulose is a polymer of D-glucose residues. Another example is the material known as gelatine, which is made up of many different "polypeptides" (compounds whose molecules are strings of amino acid residues) of the same kind. The example of gelatine is useful to illustrate the difference between a thickened solution and a gel because it is familiar in classical cooking. When gelatine (powder or sheet) is heated in an aqueous solution (in the culinary context, it can be meat broth, tea, wine, coffee, fruit juice, fish stock, etc.), its molecules disperse among water molecules in the solution; then, on cooling, they slow down and join together at their ends, forming a network whose junction points are small segments of triple helixes. When the gelatine concentration is enough (about > 5%, depending on gelatine quality), the network can be continuous, extending throughout the solution. The water molecules are "trapped" in the gel, i.e.,

unable to flow because of weak chemical bonds with the network. This is a "gel", i.e., a soft solid that does not flow (unless the stress applied leads to its rupture) (Aleman *et al.*, 2007). On the other hand, when the proportion of gelatine is "low" (i.e., less than the proportion required for gelation), gelatine molecules can only form local microscopic aggregates dispersed in the solution, which then flows with high viscosity (Figure 2) (Djabourov, 1991).

Between gels and thickened solutions, there are also intermediate systems, such as "debye", which are obtained by blending a gel in oil or in an aqueous solution (This vo Kientza, 2021a). Such systems can have various consistencies, such as "ointments" or "creams" (Mutimer *et al.*, 1956).

Sometimes compounds such as xanthan gum are named "hydrocolloids", but this is incorrect, as colloids are physical systems for which the molecules or polymolecular particles dispersed in a medium (e.g., water) have at least in one direction a dimension roughly between 1 nm and 1 µm, or that in a system discontinuities are found at distances of that order (Everett, 1972; This, 2022). Also such products as xanthan
# Questions and answers: when words are analysed from a chemical and physical perspective, innovation is easy

Hervé This vo Kientza¹

1. Université Paris Saclay, INRAE, AgroParisTech, UMR SayFood, 91120 Palaiseau, France

2. Group of Molecular Gastronomy, Inrae-AgroParisTech International Centre for Molecular and Physical Gastronomy, 22 place de l'agronomie, 91120, Palaiseau, France.

*Correspondence: herve.this@inrae.fr*

**Abstract**

Seven questions sent by a chef about molecular cooking preparations are considered. The scientific and technical analysis of these questions associated with a terminology discussion leads to many technical solutions. This discussion demonstrates that culinary innovation is easier when it is based on molecular and physical gastronomy.

**Keywords**

wording, molecular cooking, solutions.

**Introduction**

In this article, seven questions sent by email by a pastry chef are discussed:

1. What is "xanthan", and how is it used? Is it dangerous?

2. How can "herbal pearls" be made?

3. How can "tomato and date mousse" be made?

4. How can "lemon powder" be made?

5. How can "espuma" be made?

6. How can "vanilla emulsion" be made?

7. What is a "protein batter"?

These questions are about common "molecular cooking" preparations, i.e., culinary preparations that are obtained through the use of modern tools transferred from scientific and technological laboratories to kitchens.

For all of them, (1) the wording will first be analysed, (2) leading to a good understanding, so that (3) various culinary solutions can be proposed.
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

gums are not "plant gelatine": gelatine is very specifically extracted from animal tissues (more precisely collagenic tissue), so that "plant gelatine" is an oxymoron. One should speak instead of "plant gelling agents".

How to use xanthan gums in practice? Examples of use, including concentrations, are given in Lersch (2023) or in Edwards-Stuart and Barbar (2021). It has simply to be added to an aqueous solution, with a proportion at will: with little thickener, little thickening is obtained, but with more thickener, there is more viscosity, as with the classical flour in hot water. For example, a ratio of 0.1-0.3% will make the consistency of a thin sauce, and for thicker sauces, a ratio of 0.3-1% is commonly used (Edwards-Stuart and Barbar, 2021). In order to make gels, one has to mix xanthan gum with other polysaccharides, and the order of magnitude of the minimum quantity of polysaccharides (for xanthan gum mixed with other polysaccharides, but also for other gelling agents) is 1-10% (w/w), depending on the particular gelling agents as well as chemical environment (pH, presence of ions, sucrose, etc.).

Finally, for xanthan gum as for other additives, the question of "hazard" has to be discussed. Here is an opportunity to observe that everything is dangerous, but the issue is reducing the risk, a notion involving exposure to the danger (EFSA, 2016). Among many possible thickeners and gelling agents, some are accepted by regulations after a thorough risk evaluation was performed. Lists of additives are regularly updated by international bodies (European Union, 2008): these include gelatines, pectins, potato starch, corn starch and rice starch, etc., all of which behave in different ways. There are also carob gums, gum arabic, guar gum, etc., as well as products less traditionally used in Western kitchens but introduced a few decades ago: gelling agents such as agar-agar, sodium alginate, certain carrageenans, etc.

At a time when a large proportion of citizens praise "natural products", it is worth observing that strictly speaking xanthan gum and other similar products are "artificial", because they

have been produced. For example, gelatines are extracted from animal tissues, meat, tendon, etc., and pectins are extracted from plant tissues: fruit, vegetables, etc.; some other gelling agents are extracted from algae, such as agar-agar and carrageenans, and there are also thickeners produced by micro-organisms, such as xanthan gums. As a consequence, xanthan gums from different producers have different properties, as for other similar compounds, such as pectins, which are degraded when overheated (Sila et al., 2005), or gelatines, which are different depending on their origin and processing (Eysturskard, 2009). As a consequence of the variability of the products, users have no general rules for determining the exact quantities to be used, and they have to make tests in order to determine how much xanthan gum is to be used in particular culinary conditions (acidity, temperature, etc.).

<figure><img src="image_4.png" /><figcaption>**Figure 3.** Degennes, i.e. spheres with a liquid core and a gelled envelop were formed using calcium lactate dissolved in orange juice; drops of this liquid were then dropped in a solution of sodium alginate. In this picture, the spheres were then inserted in a gel, in order to make a system called a conglomele (This, 2019).</figcaption></figure>
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

<figure><img src="image_5.png" /><figcaption>Figure 1. *The chemical structure of xanthan gum molecules.*</figcaption></figure>

**1. What is "xanthan" and how is it used? Is it dangerous?**

Here the question was about "xanthan", and the chef wanted to know what it is, and how it can be used, but it has to be observed that he should have spoken of "xanthan gum", rather than simply "xanthan". Using this more correct terminology, he would have found a large number of Internet pages of different quality, ranging from the very precise to the completely wrong. A reliable source is the *Handbook of Molecular Gastronomy* (Burke et al., 2021).

The word "xanthan" is based on the Greek root *xanthos*, meaning yellow. It comes from the name of the *Xanthomonas* group of bacteria, which sometimes create yellow stains on the leaves of plants. When fermenting corn starch, for example, *Xanthomonas campestris* secretes compounds (see later) that can be recovered by filtration and ethanol precipitation, forming a "gum" called "xanthan gum" (Jecfa, 2016; Edwards-Stuart and Barbar, 2021). This word "gum" is also used for gum arabic, carob bean gum, konjac gum, for example, but there are differences: gum arabic, tragacanth gum, gum karaya and ghatti gum are

hardened saps from plants; guar gum, carob gum and tara gum come from seeds, konjac gum is extracted from a rhizome, and xanthan is a bacterial secretion.

The molecules of xanthan gums are all built in the same way, with repeats of the same molecular motif, but of different lengths, so that their molecular mass is between one and several millions (Faria et al., 2011; Wikipedia, 2023). The molecular motif is a link of D-glucose residues (as in cellulose molecules), with branches made of a succession of three monosaccharides residues: mannose (substituted by acetic acid), D-glucuronic acid and mannose (substituted by pyruvic acid). (Figure 1). The final xanthan gum products are manufactured in the form of a sodium, potassium or calcium salt, and their solutions are neutral.

Xanthan gums, either native or chemically modified, have thickening properties, and gelling properties in association with other polysaccharides, because of the high number of hydroxyl groups (with an oxygen atom linked to an hydrogen atom, -OH) in their molecules. As such groups can establish hydrogen bonds with water molecules, xanthan gums increase the viscosity of the aqueous solution in which they
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

**2. How can "herbal pearls" be made?**

The second question concerned the production of "herbal pearls". This is a very vague question, again because of words, and more precisely because the word "pearl" is used in a metaphorical sense that can have different interpretations. According to the *Cambridge Dictionary*, a pearl is "a small, round object, usually white, that forms around a grain of sand inside the shell of a sea creature, especially an oyster. Pearls are valuable and are used to make jewellery" (Cambridge Dictionary, 2023).

Clearly, the chef who asked the question was thinking of another object. In the kitchen, for example, chefs are familiar with "Japanese pearls", tapioca, so that "herb pearls" could be obtained by cooking tapioca in a sauce with herbs (e.g. chopped parsley): the compounds responsible for the flavour, odour or colour of the herbs would migrate into the starch pearls, by diffusion or by capillarity (Aguilera *et al.*, 2004).

However, in molecular cooking, the word "pearl" has also been used for designing "degennes" (This vo Kientza, 2023), i.e. gelled or liquid spheres, bounded by a gelled membrane, formed by the reaction of sodium alginate with calcium ions Ca²⁺ (Figure 3). Two main techniques are commonly used to produce these spheres with liquid inside: direct spherification and reverse spherification (Soprani *et al.*, 2021). In the first case, about 5% (w/w) sodium alginate is dissolved in an aqueous solution (in this case, a herbal solution), and drops of this liquid are deposited in an aqueous solution containing calcium ions (by dissolving calcium lactate in water, for example): contact between the sodium alginate and calcium ions leads to gelation, and immediate rinsing prevents excess calcium ions from migrating into the spheres formed, and causing the spheres to gel entirely. In the reverse process, sodium alginate is dissolved in water, and drops of the herbal sauce with calcium ions are added to the alginate aqueous bath.

Many other interpretations of "herbal pearls" can

be envisioned: gelatine can be used to gel a "herbal solution", or herbal balls can be made from a herb omelette, using a melon spoon.

**3. How can “tomato and date mousse” be made?**

The third question concerns a "tomato and date mousse". How can such a food preparation be produced?

Again there are countless ways of achieving this. One possibility is to cook tomatoes with dates, to process all the ingredients in a food blender, to add proteins (e.g. powdered egg whites) and to whip: the result is a mousse. Gelatine also can be used: it has to be dissolved in the heated solution, and the foam that is created through whipping sets when it is stored at temperatures lower than about 36 °C. Another technique is to start by crushing the tomatoes with the dates, possibly while cooking, filter to recover a liquid, add egg proteins or a whole egg, put the liquid in a siphon and produce the mousse.

Contrary to a popular idea based on visual appearance, siphons produce foams rather than emulsions. Foams are colloidal systems in which gas bubbles are dispersed in a liquid (e.g. whipped egg white), whereas emulsions are dispersions of droplets of one liquid in another liquid (e.g. sauce mayonnaise, made of oil droplets dispersed in the aqueous mixture of egg yolk and vinegar).

A simple optical microscope establish that the products delivered by siphons are indeed foams. Often the gas is nitrous oxide (N₂O) if an N₂O cartridge is used), but it can also be carbon dioxide (CO₂), in which case the final product has a pleasant little fizz. Sometimes, the system can be both an emulsion and a foam if the liquid processed by the siphon is already an emulsion.

Other mousses can be obtained with less modern tools, e.g. by mixing the tomato and date purée with Italian meringue or whipped cream, for example, or by making a sabayon from
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

<figure><img src="image_6.png" /><figcaption>Figure 2. The theory of percolation explains the difference between a thickened solution (left) and a gel (right). When monomers that can link are at low concentration (left), they can make a local aggregate that increases the viscosity of the medium in which they are dispersed. When their concentration is higher than the so-called "percolation threshold", a continuous network can be established, making a gel (right).</figcaption></figure>

are dissolved. In association with other polysaccharides (e.g. as galatomannans) or mixture of polysaccharides (e.g. starch), they can make gels.

Xanthan gums are allowed to be used as food additives (European code E415) for their thickening and gelling properties (EFSA Panel on Food Additives and Flavourings, 2023). The acceptable daily intake (ADI) is "not specified", which means that it can used *quantum satis* without risk for the human health.

After receiving this information, the chef to which the information given here was sent asked why the same product can be used in two different ways, and indeed there is sometimes confusion between thickeners and gelling agents. Products in these two categories are often polymers, i.e., compounds whose molecules are repetitions of a few basic units, called "monomers". For example, cellulose is a polymer of D-glucose residues. Another example is the material known as gelatine, which is made up of many different "polypeptides" (compounds whose molecules are strings of amino acid residues) of the same kind.

The example of gelatine is useful to illustrate the difference between a thickened solution and a gel

because it is familiar in classical cooking. When gelatine (powder or sheet) is heated in an aqueous solution (in the culinary context, it can be meat broth, tea, wine, coffee, fruit juice, fish stock, etc.), its molecules disperse among water molecules in the solution; then, on cooling, they slow down and join together at their ends, forming a network whose junction points are small segments of triple helices. When the gelatine concentration is enough (about > 5%, depending on gelatine quality), the network can be continuous, extending throughout the solution. The water molecules are "trapped" in the gel, i.e., unable to flow because of weak chemical bonds with the network. This is a "gel", i.e., a soft solid that does not flow (unless the stress applied leads to its rupture) (Aleman et al., 2007). On the other hand, when the proportion of gelatine is "low" (i.e., less than the proportion required for gelation), gelatine molecules can only form local microscopic aggregates dispersed in the solution, which then flows with high viscosity (Figure 2) (Djabourov, 1991).

Between gels and thickened solutions, there are also intermediate systems, such as "debye",
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

tomato juice, date juice, sugar (sucrose) and
whole egg.

In short, here again there are many ways to
answer the question, because the name of the
dish includes only three constraints: to include
tomatoes, which are essentially water, to include
dates, which are mainly made of water, and to
include gas bubbles. In all cases, molecules are
needed to stabilize the bubbles: egg proteins, for
example, or proteins extracted from meat, plants
or milk, or many other agents from the additive
family.

**4. How can lemon powder be made?**

In order to make lemon powder, the fastest is
probably to dip lemons in liquid nitrogen
(indeed liquid dinitrogen, because the
molecules N₂ are made of two nitrogen
atoms), and then break the brittle frozen
lemons. However not all chefs have liquid
nitrogen. Dehydrators or freeze dryers are
now more common types of equipment: a
powder is obtained by placing slices of lemon
on the trays. And when no such tools are
available, lemon skins can be first put to in
boiling water (three times), then cooked with
a sugar (sucrose) syrup, before drying in an
oven at 100 °C for some hours; after cooling,
they can be ground into powder.

Different kind of solutions are to give the
lemon flavour to powders such as starch, or
"plating agents" (powders made of porous
particles) such as *Pine Flow* or *N-Zorbit
2144*. The first one has a higher porosity and
intrusion volume than the second and was
found to have a greater capacity to hold oil:
the oil holding capacities of *N-Zorbit 2044*
and *Pine Flow* are about 100 and 400%,
respectively (Domian and Cenker, 2013). The
impregnating oil can be produced by
macerating cut lemons in ordinary oil, or
adding to oil a lemon flavouring (there many
different kinds of such flavourings in the
perfume and flavouring industry) and deposit

the flavoured oil on a powdery base, such
as starch: a "lemon powder" would be
obtained.

It could have been discussed also for the
previous and the next questions, but let us
observe now that the names of food products
are sometimes defined by regulations (wine,
bread, meat, milk, etc.) or institutions such as
the *Codex alimentarius* (FAO UN-WHO, 2023).
Often, in order to know which product is
designated by a name, consulting the regulatory
texts is necessary: what is "corned beef", what is
"white sugar", which ingredients are allowed in a
marketed "mango chutney", etc.

This is not to say that such norms are perfect,
far from it. For example, about flavours and
flavourings, the *Discussion Paper for Flavouring
Agents* recognized that "Natural flavours and
natural flavouring substances are preparations
and single substances respectively, acceptable
for human consumption, obtained exclusively by
physical processes from vegetable, sometime
animal, raw materials either in their natural state
or processed, for human consumption" (Codex
Committee on Food Additives and
Contaminants, 2004). However here the
definition of the *Codex alimentarius* contradicts
the common one: a flavour has always been
and will remain as a synthetic sensation based
on taste, odour, consistency, trigeminal
stimulations (This vo Kientza, 2021b). Also the
use of the word "natural" is misleading, as it
means indeed "what was not transformed by
human beings": odorant preparations being
prepared by the flavouring industry or by chefs,
either extracted or synthesized, are indeed
artificial.

Finally discussing flavourings calls for
observing that "lemon flavourings" can be
formulated in many different ways: the
flavouring companies sell a variety of liquid
products, or powders, with various flavours,
depending on the particular mixture of odorant
compounds used; users can choose between
"fresh lemon", "baked lemon", "sweet lemon",
"sour lemon", etc.
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

which are obtained by blending a gel in oil or in an aqueous solution (This vo Kientza, 2021a). Such systems can have various consistencies, such as "ointments" or "creams" (Mutimer et al., 1956). Sometimes compounds such as xanthan gum are named "hydrocolloids", but this is incorrect, as colloids are physical systems for which the molecules or polymolecular particles dispersed in a medium (e.g., water) have at least in one direction a dimension roughly between 1 nm and 1 µm, or that in a system discontinuities are found at distances of that order (Everett, 1972; This, 2022). Also such products as xanthan gums are not "plant gelatine": gelatine is very specifically extracted from animal tissues (more precisely collagenic tissue), so that "plant gelatine" is an oxymoron. One should speak instead of "plant gelling agents".

How to use xanthan gums in practice? Examples of use, including concentrations, are given in Lersch (2023) or in Edwards-Stuart and Barbar (2021). It has simply to be added to an aqueous solution, with a proportion at will: with little thickener, little thickening is obtained, but with more thickener, there is more viscosity, as with the classical flour in hot water. For example, a ratio of 0.1-0.3% will make the consistency of a thin sauce, and for thicker sauces, a ratio of 0.3-1% is commonly used (Edwards-Stuart and Barbar, 2021). In order to make gels, one has to mix xanthan gum with other polysaccharides, and the order of magnitude of the minimum quantity of polysaccharides (for xanthan gum mixed with other polysaccharides, but also for other gelling agents) is 1-10% (w/w), depending on the particular gelling agents as well as chemical environment (pH, presence of ions, sucrose, etc.). Finally, for xanthan gum as for other additives, the question of "hazard" has to be discussed. Here is an opportunity to observe that everything is dangerous, but the issue is reducing the risk, a notion involving exposure to the danger (EFSA, 2016). Among many possible thickeners and gelling agents, some are accepted by regulations after a thorough risk evaluation was performed. Lists of additives are regularly

updated by international bodies (European Union, 2008): these include gelatines, pectins, potato starch, corn starch and rice starch, etc., all of which behave in different ways. There are also carob gums, gum arabic, guar gum, etc., as well as products less traditionally used in Western kitchens but introduced a few decades ago: gelling agents such as agar-agar, sodium alginate, certain carrageenans, etc.
At a time when a large proportion of citizens praise "natural products", it is worth observing that strictly speaking xanthan gum and other similar products are "artificial", because they have been produced. For example, gelatines are extracted from animal tissues, meat, tendon, etc., and pectins are extracted from plant tissues: fruit, vegetables, etc.; some other gelling agents are extracted from algae, such as agar-agar and carrageenans, and there are also thickeners produced by micro-organisms, such as xanthan gums. As a consequence, xanthan

<figure><img src="image_7.png" /><figcaption>**Figure 3.** Degennes, i.e. spheres with a liquid core and a gelled envelop were formed using calcium lactate dissolved in orange juice; drops of this liquid were then dropped in a solution of sodium alginate. In this picture, the spheres were then inserted in a gel, in order to make a system called a conglomele (This, 2019).</figcaption></figure>
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**Section Questions and Answers (Part 4: Edible Ideas)**

**5. How can "espuma" be made? How can hot
foam be made?**

In Spanish, the word espuma simply means foam, or scum, or froth, and there is no reason to use the word espuma, as such systems were not invented in Spain. In molecular cooking, techniques of expansion using pumps or siphons were proposed to restaurants during the European FP5 Inicon program, as a technology transfer from the food industry, and chefs from many European countries began then using such systems.

As said before, a foam is a "dispersion in which a large proportion of gas by volume in the form of gas bubbles, is dispersed in a liquid [liquid foams], solid [solid foams] or gel [aerated gels]. The diameter of the bubbles is usually larger than 1 µm, but the thickness of the lamellae between the bubbles is often in the usual colloidal size range. The term froth has been used interchangeably with foam. In certain cases froth may be distinguished from foam by the fact that the former is stabilized by solid particles (as in froth flotation q.v.) and the latter by soluble substances" (IUPAC, 1972).

Culinary preparations are seldom pure foams, except for such systems as whipped egg, because the initial ingredients are generally not simple aqueous solution, but can be emulsions (e.g. oil droplets dispersed in the solution) or suspensions (with solid particles dispersed in a liquid). These complex systems are said to be "aerated", and they can be better described using the "dispersed systems formalism" (This vo Kientza, 2021c).

Some aerated food products are classic, such as sabayons, meringues, certain sauces (béarnaises, hollandaises), but also soufflés, hot cakes or breads. The foaming is performed thanks to the natural foaming agents that are in the plant and animal tissues, such as proteins (from egg white, from animal or plant tissues) or phospholipids such as lecithins. Hence, there is no need for molecular cooking techniques to make hot foams, even if some tools, such as

siphons, can be used.

Important information, in discussing aerated systems is the size of gas bubbles. Various tools produce foams with different bubbles. For example, stirring a rotating paddle can generate > 1 cm diameter bubbles, while siphons produce foams whose bubbles are invisible with the naked eye (radius < 0.2 mm). Finally one can observe that pumps with small nozzles, such as the ones used by pastry chefs to spray colorants, would be more sustainable than siphons, for which cartridges are seldom recycled.

As a conclusion of the answer to this question of hot foams, we have to observe that (1) knowing more chemistry and physics - in particular understanding the meaning of words borrowed from these fields - helps in recognizing unsuspected systems in traditional dishes, but also gives more control on their production; (2) the molecular and physical gastronomy analysis of food systems is the key of reasoning in terms of functionality of ingredients. For example, observing that gelatine is a protein, one can start from any aqueous solution (e.g. raspberry juice), heat it to dissolve gelatine, and whip while cooling: the foam that is produced will gel into a food system called a "würtz" (This, 2009). This is a cold gelled foam, but replacing gelatine by thermocoagulable proteins such as animal proteins (actin, myosin, ovalbumin, etc.) will lead to hot aerated gels, still with the flavour that one wants.

**6. How to make a “vanilla emulsion”?**

The expression "vanilla emulsion" is as imprecise as the previous systems that were discussed before. As an emulsion (see above) is a colloidal system made of droplets of one liquid dispersed in another liquid, no "vanilla emulsion" can exist stricto sensu because vanilla is not an oil, and it is not an aqueous emulsion either. In the question from the chef, "vanilla emulsion" should be replaced by "emulsion with vanilla
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gums from different producers have different
properties, as for other similar compounds,
such as pectins, which are degraded when
overheated (Sila *et al.*, 2005), or gelatines,
which are different depending on their origin
and processing (Eysturskard, 2009). As a
consequence of the variability of the products,
users have no general rules for determining
the exact quantities to be used, and they have
to make tests in order to determine how much
xanthan gum is to be used in particular
culinary conditions (acidity, temperature, etc.).

**2. How can "herbal pearls" be made?**

The second question concerned the production of "herbal pearls". This is a very vague question, again because of words, and more precisely because the word "pearl" is used in a metaphorical sense that can have different interpretations. According to the *Cambridge Dictionary*, a pearl is "a small, round object, usually white, that forms around a grain of sand inside the shell of a sea creature, especially an oyster. Pearls are valuable and are used to make jewellery" (Cambridge Dictionary, 2023).

Clearly, the chef who asked the question was
thinking of another object. In the kitchen, for
example, chefs are familiar with "Japanese
pearls", tapioca, so that "herb pearls" could be
obtained by cooking tapioca in a sauce with herbs
(e.g. chopped parsley): the compounds
responsible for the flavour, odour or colour of the
herbs would migrate into the starch pearls, by
diffusion or by capillarity (Aguilera *et al.*, 2004).

However, in molecular cooking, the word "pearl" has also been used for designing "degennes" (This vo Kientza, 2023), i.e. gelled or liquid spheres, bounded by a gelled membrane, formed by the reaction of sodium alginate with calcium ions Ca²⁺ (Figure 3). Two main techniques are commonly used to produce these spheres with liquid inside: direct spherification and reverse spherification (Soprani et al., 2021). In the first case, about 5% (w/w) sodium alginate

is dissolved in an aqueous solution (in this
case, a herbal solution), and drops of this
liquid are deposited in an aqueous solution
containing calcium ions (by dissolving
calcium lactate in water, for example):
contact between the sodium alginate and
calcium ions leads to gelation, and
immediate rinsing prevents excess calcium
ions from migrating into the spheres formed,
and causing the spheres to gel entirely. In
the reverse process, sodium alginate is
dissolved in water, and drops of the herbal
sauce with calcium ions are added to the
alginate aqueous bath.

Many other interpretations of "herbal pearls" can
be envisioned: gelatine can be used to gel a
"herbal solution", or herbal balls can be made
from a herb omelette, using a melon spoon.

**3. How can “tomato and date mousse” be made?**

The third question concerns a "tomato and date
mousse". How can such a food preparation be
produced?

Again there are countless ways of achieving this.
One possibility is to cook tomatoes with dates, to
process all the ingredients in a food blender, to
add proteins (e.g. powdered egg whites) and to
whip: the result is a mousse. Gelatine also can
be used: it has to be dissolved in the heated
solution, and the foam that is created through
whipping sets when it is stored at temperatures
lower than about 36 °C. Another technique is to
start by crushing the tomatoes with the dates,
possibly while cooking, filter to recover a liquid,
add egg proteins or a whole egg, put the liquid in
a siphon and produce the mousse.

Contrary to a popular idea based on visual
appearance, siphons produce foams rather
than emulsions. Foams are colloidal systems in
which gas bubbles are dispersed in a liquid
(e.g. whipped egg white), whereas emulsions
are dispersions of droplets of one liquid in
another liquid (e.g. sauce mayonnaise, made of
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<figure><img src="image_5.png" /><figcaption>Figure 4. When an egg white is first whipped, and then oil is added while whisking, an emulsified foam can be obtained. Here, the system is observed using an optical microscope. The dark spheres are air bubbles, and the smallest transparent spheres are oil droplets. The diameter of the biggest dispersed structures is about 0.1 mm.</figcaption></figure>

flavour". And this new question has no answer, because the flavour of an emulsion will never be the exactly the same as the flavour of vanilla, with exactly the same odour, taste, trigeminal sensations, and others orosensory compounds (Schwartz and Hofmann, 2009). The best that can be made is an emulsion with a flavour similar to vanilla, as a photo of a painting is similar to the painting, more or less closely.

In order to make such an emulsion, "oil" (by oil, physical chemists mean any hydrophobic liquid), "water (any aqueous solution) and surfactants are needed. In the vanilla context, a vanilla aqueous extract can be made by macerating vanilla pods in water, extraction

hydrophilic compounds. And a "vanilla oil" can be produced by maceration, infusion or decoction of vanilla pods in oil or in any other liquid fat (e.g. melted butter), extraction hydrophobic compounds, including odorant ones.

Concerning surfactants, the list of accepted additives contain many candidates, such as lecithins, diphosphates, polysorbates, carrageenans, guar gum, polysorbates, celluloses and cellulose derivatives, mono- and diglycerides, sucrose esters and sucroglycerides (European Commission, 2023). In the kitchen, proteins or phospholipids are often used because they are naturally present
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oil droplets dispersed in the aqueous mixture of
eyg yolk and vinegar).

A simple optical microscope establish that the
products delivered by siphons are indeed
foams. Often the gas is nitrous oxide (N₂O) if
an N₂O cartridge is used), but it can also be
carbon dioxide (CO₂), in which case the final
product has a pleasant little fizz. Sometimes,
the system can be both an emulsion and a
foam if the liquid processed by the siphon is
already an emulsion.

Other mousses can be obtained with less
modern tools, e.g. by mixing the tomato and
date purée with Italian meringue or whipped
cream, for example, or by making a sabayon
from tomato juice, date juice, sugar (sucrose)
and whole egg.

In short, here again there are many ways to
answer the question, because the name of the
dish includes only three constraints: to include
tomatoes, which are essentially water, to include
dates, which are mainly made of water, and to
include gas bubbles. In all cases, molecules are
needed to stabilize the bubbles: egg proteins, for
example, or proteins extracted from meat, plants
or milk, or many other agents from the additive
family.

**4. How can lemon powder be made?**

In order to make lemon powder, the fastest is
probably to dip lemons in liquid nitrogen
(indeed liquid dinitrogen, because the
molecules N₂ are made of two nitrogen
atoms), and then break the brittle frozen
lemons. However not all chefs have liquid
nitrogen. Dehydrators or freeze dryers are
now more common types of equipment: a
powder is obtained by placing slices of lemon
on the trays. And when no such tools are
available, lemon skins can be first put to in
boiling water (three times), then cooked with
a sugar (sucrose) syrup, before drying in an
oven at 100 °C for some hours; after cooling,
they can be ground into powder.

Different kind of solutions are to give the
lemon flavour to powders such as starch, or
"plating agents" (powders made of porous
particles) such as *Pine Flow* or *N-Zorbit
2144*. The first one has a higher porosity
and intrusion volume than the second and
was found to have a greater capacity to hold
oil: the oil holding capacities of *N-Zorbit
2044* and *Pine Flow* are about 100 and
400%, respectively (Domian and Cenker,
2013). The impregnating oil can be
produced by macerating cut lemons in
ordinary oil, or adding to oil a lemon
flavouring (there many different kinds of
such flavourings in the perfume and
flavouring industry) and deposit the
flavoured oil on a powdery base, such as
starch: a "lemon powder" would be
obtained.

It could have been discussed also for the
previous and the next questions, but let us
observe now that the names of food products
are sometimes defined by regulations (wine,
bread, meat, milk, etc.) or institutions such as
the *Codex alimentarius* (FAO UN-WHO, 2023).
Often, in order to know which product is
designated by a name, consulting the regulatory
texts is necessary: what is "corned beef", what is
"white sugar", which ingredients are allowed in a
marketed "mango chutney", etc.

This is not to say that such norms are perfect, far
from it. For example, about flavours and
flavourings, the Discussion Paper for Flavouring
Agents recognized that "Natural flavours and
natural flavouring substances are preparations
and single substances respectively, acceptable
for human consumption, obtained exclusively by
physical processes from vegetable, sometime
animal, raw materials either in their natural state
or processed, for human consumption" (Codex
Committee on Food Additives and
Contaminants, 2004). However here the
definition of the Codex alimentarius contradicts
the common one: a flavour has always been and
will remain as a synthetic sensation based on
taste, odour, consistency, trigeminal stimulations
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in plant or animal tissues: any ground plant or animal tissue releases water and surfactants, so that oil can be emulsified. This is the mechanism of the traditional sauce aioli, made of crushed garlic into which olive oil is emulsified, and this is the principe of “ollis”, i.e. generalizations of aoili, but with any ground plant or animal tissue (This, 1997).

Finally, energy is needed to make emulsions, dividing the oil in tiny droplets that are dispersed in the aqueous solution. Traditionally forks, whisks, mortar and pestle are used, but mixers make firmer emulsions because they give more energy and overcome better surface tension, generating smaller droplets. In chemistry laboratories, ultrasonic probes are common, but in spite of proposals made for decades, they remain very rare in kitchens.

Let us end this long paragraph by considering a proposal that was made in the 1990s, of a system that was named "geoffroy" (This, 1997): an egg white is used as it contains water (90%) and proteins (10%, around 370 kinds) (Shi et al., 2023); if oil is added in while whisking, air bubbles are first introduced with oil droplets, and an emulsified foam is obtained (Figure 4).

Adding more oil makes the bubbles disappear; the emulsified foam turns into a white - somehow aerated - emulsion. The preparation is very smooth, white and flavourless, so it can be given any flavour, such as vanilla. The emulsion can be turned into a dessert, adding sugar: sucrose dissolves in water, up to a limit of 960 g of sucrose per kilogram of water. The vanilla geoffroy can be served as it is, but it can also be cooked in a microwave oven until expansion is observed, so that the proteins in the egg white coagulate, producing an expanded, chemically gelled emulsion known as "gibbs" (This, 2009).

**7. What is a "protein batter"?**

Finally about "protein batters", again the name

does not describe only one particular product, but allows imagining many possibilities. For example, adding 10 g of egg white powder in 100 g of water makes a batter that has the properties of egg white: it can be whipped into a white foam, or cooked, producing a result very similar to cooked egg white. With a higher proportion of water, the batter becomes less viscous, but still coagulates, until the proportion of proteins is less than 5%; with more proteins (20%), thermocoagulation generates products that can have the hardness of meat. This batter behaves like the one that would be made from flour and water, except that proteins are present instead of polysaccharides.

So far, only egg proteins were mentioned, but there are proteins in many other products, both in animal tissues or products (e.g. milk proteins) and in some plants tissues, such as pulses (Shevkani et al., 2019). Today plant proteins again can be found under the form of powders (white powders when they are pure) and they can often be used as explained for egg white.

It was not part of the question, but how can a protein batter be used? If it is put in a syringe and deposited in a hot medium (boiling water, hot oil), some "spaghetti" are obtained from the protein batter; if deposited as a layer that

<figure><img src="image_6.png" /><figcaption>Figure 5. This green "dirac" was obtained by frying a 20% protein aqueous solution, added with oil salt, glutamate monosodium, piperine, green food colorant, D-glucose, and 1-octen-3 ol (This vo Kientza, 2021).</figcaption></figure>
Section Questions and Answers (Part 4: Edible Ideas)

(This vo Kientza, 2021b). Also the use of the word "natural" is misleading, as it means indeed "what was not transformed by human beings": odorant preparations being prepared by the flavouring industry or by chefs, either extracted or synthesized, are indeed artificial.

Finally discussing flavourings calls for observing
that "lemon flavourings" can be formulated in
many different ways: the flavouring companies
sell a variety of liquid products, or powders, with
various flavours, depending on the particular
mixture of odorant compounds used; users can
choose between "fresh lemon", "baked lemon",
"sweet lemon", "sour lemon", etc.

5. How can "espuma" be made? How can hot
foam be made?

In Spanish, the word espuma simply means foam,
or scum, or froth, and there is no reason to use
the word espuma, as such systems were not
invented in Spain. In molecular cooking,
techniques of expansion using pumps or siphons
were proposed to restaurants during the
European FP5 Inicon program, as a technology
transfer from the food industry, and chefs from
many European countries began then using such
systems.

As said before, a foam is a "dispersion in which a
large proportion of gas by volume in the form of
gas bubbles, is dispersed in a liquid [liquid foams],
solid [solid foams] or gel [aerated gels]. The
diameter of the bubbles is usually larger than
1 µm, but the thickness of the lamellae between
the bubbles is often in the usual colloidal size
range. The term froth has been used
interchangeably with foam. In certain cases froth
may be distinguished from foam by the fact that
the former is stabilized by solid particles (as in
froth flotation q.v.) and the latter by soluble
substances" (IUPAC, 1972).

Culinary preparations are seldom pure foams,
except for such systems as whipped egg,
because the initial ingredients are generally not
simple aqueous solution, but can be emulsions

(e.g. oil droplets dispersed in the solution) or
suspensions (with solid particles dispersed in a
liquid). These complex systems are said to be
"aerated", and they can be better described
using the "dispersed systems formalism" (This
vo Kientza, 2021c).

Some aerated food products are classic, such as
sabayons, meringues, certain sauces
(béarnaises, hollandaises), but also soufflés, hot
cakes or breads. The foaming is performed
thanks to the natural foaming agents that are in
the plant and animal tissues, such as proteins
(from egg white, from animal or plant tissues) or
phospholipids such as lecithins. Hence, there is
no need for molecular cooking techniques to
make hot foams, even if some tools, such as
siphons, can be used.

Important information, in discussing aerated
systems is the size of gas bubbles. Various tools
produce foams with different bubbles. For
example, stirring a rotating paddle can generate
> 1 cm diameter bubbles, while siphons produce
foams whose bubbles are invisible with the
naked eye (radius < 0.2 mm). Finally one can
observe that pumps with small nozzles, such as
the ones used by pastry chefs to spray
colorants, would be more sustainable than
siphons, for which cartridges are seldom
recycled.

As a conclusion of the answer to this question of
hot foams, we have to observe that (1) knowing
more chemistry and physics - in particular
understanding the meaning of words borrowed
from these fields - helps in recognizing
unsuspected systems in traditional dishes, but
also gives more control on their production; (2)
the molecular and physical gastronomy analysis
of food systems is the key of reasoning in terms
of functionality of ingredients. For example,
observing that gelatine is a protein, one can start
from any aqueous solution (e.g. raspberry juice),
heat it to dissolve gelatine, and whip while
cooling: the foam that is produced will gel into a
food system called a "würtz" (This, 2009). This is
a cold gelled foam, but replacing gelatine by
thermocoagulable proteins such as animal
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**Section Questions and Answers (Part 4: Edible Ideas)**

is heated, coagulated sheets can be produced, etc. If the proteins have been chosen in such a way that they can coagulate, then the equivalent of meat (a "dirac") can be made, at least from the point of view of consistency (Figure 5) (Gagnaire, 2021). Such "pancakes" can be improved, for example by spreading the protein batter, strewing it with a fork, cooking it, rolling it on itself into a sheet and obtaining a kind of surimi, as was done in 2012 by the chefs Ismail Osorio, Erik Ayala-Bibriesca, and their students from the Institut technique du Québec (ITHQ), in Montréal (Canada).

Any flavour can be given to all these products. In the experiment described above, "water" was used as the liquid, but any aqueous solution will do: tea, coffee, orange juice, tomato juice, wine, stock, etc. And moving to "synthetic cooking" (the technique used by the culinary art called "note by note cooking) gives even more possibilities (This, 2014). Indeed flavour is the synthetic sensation including colour, consistency, temperature, tastes, odours, and spiciness and freshness, etc. One should therefore not forget, before cooking or before use, to add compounds to the protein batter in order to create colour, flavour, odour, etc.

**8. Conclusion**

The chemical and physical analysis of culinary systems not only makes it possible to understand the constitution of classic culinary preparations, but it is also the basis for innovations, demonstrating that the results of natural sciences are a condition for fruitful technological work. Often it is useful to use the right names for objects and mechanisms, in order to ask more precise questions and find the answers to these questions more easily.

**References**

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Alemán JV, Chadwick AV, He J, Hess M, Horie K, Jones RG, Kratochvíl P, Meisel I, Mita I, Moad G, Penczek S, Stepto RFT. 2007. Definitions of terms relating to the structure and processing of sols, gels, networks, and inorganic-organic hybrid materials (IUPAC Recommendations 2007), *Pure and Applied Chemistry*, 79(10), 1801-1829. DOI: 10.1351/pac200779101801.

Burke R, Kelly A, Lavelle C, This vo Kientza H (eds.). 2021. *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida. ISBN 9781466594784.

Cambridge Dictionary. 2023. Pearl, https://dictionary.cambridge.org/dictionary/english/pearl, last access 2023-12-14.

Codex Committee on Food Additives and Contaminants. 2004. Discussion paper on flavouring agents, https://www.fao.org/fao-who-codexalimentarius/sh-proxy/en/?lnk=1&url=https%253A%252F%252Fworkspace.fao.org%252Fsites%252Fcodex%252FShared%2BDocuments%252FArchive%252FMeetings%252FCCFAC%252Fccfac37%252FFA37_15e.pdf, last access 2023-12-14.

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Edwards-Stuart R, Barbar R. Hydrocolloid usages as gelling and emulsifying agents for culinary and industrial applications, In Burke R, Kelly A, Lavelle C, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

<figure><img src="image_8.png" /><figcaption>Figure 4. When an egg white is first whipped, and then oil is added while whisking, an emulsified foam can be obtained. Here, the system is observed using an optical microscope. The dark spheres are air bubbles, and the smallest transparent spheres are oil droplets. The diameter of the biggest dispersed structures is about 0.1 mm.</figcaption></figure>

proteins (actin, myosin, ovalbumin, etc.) will lead to hot aerated gels, still with the flavour that one wants.

**6. How to make a “vanilla emulsion”?**

The expression "vanilla emulsion" is as imprecise as the previous systems that were discussed before. As an emulsion (see above) is a colloidal system made of droplets of one liquid dispersed in another liquid, no "vanilla emulsion" can exist *stricto sensu* because vanilla is not an oil, and it is not an aqueous emulsion either. In the question from the chef, "vanilla emulsion" should be replaced by "emulsion with vanilla flavour". And

this new question has no answer, because the flavour of an emulsion will never be the exactly the same as the flavour of vanilla, with exactly the same odour, taste, trigeminal sensations, and others orosensory compounds (Schwartz and Hofmann, 2009). The best that can be made is an emulsion with a flavour similar to vanilla, as a photo of a painting is similar to the painting, more or less closely.

In order to make such an emulsion, "oil" (by oil, physical chemists mean any hydrophobic liquid), "water (any aqueous solution) and surfactants are needed. In the vanilla context, a vanilla aqueous extract can be made by macerating vanilla pods in water, extraction hydrophilic compounds. And a
**International Journal of Molecular and Physical Gastronomy**
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**Section Questions and Answers (Part 4: Edible Ideas)**

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FAO UN-WHO. 2023. *Codex alimentarius (international food standards)*, https://www.fao.org/fao-who-codexalimentarius/pu

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Gagnaire P. 2021. Culinary constructivism and note by note cooking. In Burke R, Kelly A, Lavelle C, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 743-749.

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Jecfa. 2016. Xanthan gum, https://www.fao.org/3/br568e/br568e.pdf, last access 2023-12-13.

Lersch M. 2023. Khymos, https://khymos.org/recipe-collection/, last access 2023-12-15.

Schwarz B, Hofmann T. 2009. Identification of novel orosensory active molecules in cured vanilla beans (*Vanilla planifolia*), *Journal of agricultural and food chemistry*, 57, 9, 3729–3737.

Shevkani K, Singh N, Chen Y, Kaur A, Yu L. 2019. Pulses proteins: secondary structure, functionality and applications, *Journal of food science and technology*, 56(6), 2787-2798.

Shi D, Su W, Mu Y. 2023. Quantitative proteomics study on the changes of egg white of yellow preserved primary chicken eggs soaked in alkali solution, *Food Research International*, 165, 112346, 1-11.

Sila DN, Melbourne F, Smout C, Van Loey A, Hendrickx M. 2005. beta-Elimination of carrot pectin: towards a better understanding of carrot texture during thermal processing, *Communications in Agricultural and Applied Biological Sciences*, 70(2), 19-22.

Soprani L, Querciagrossa L, Cistofaro S, Muccioli L, Orlandi S, Strocchi E, Arcioni A, Berardi R. 2021. Ionic diffusion in sphérified
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

"vanilla oil" can be produced by maceration, infusion or decoction of vanilla pods in oil or in any other liquid fat (e.g. melted butter), extraction hydrophobic compounds, including odorant ones.

Concerning surfactants, the list of accepted additives contain many candidates, such as lecithins, diphosphates, polysorbates, carrageenans, guar gum, polysorbates, celluloses and cellulose derivatives, mono- and diglycerides, sucrose esters and sucroglycerides (European Commission, 2023). In the kitchen, proteins or phospholipids are often used because they are naturally present in plant or animal tissues: any ground plant or animal tissue releases water and surfactants, so that oil can be emulsified. This is the mechanism of the traditional sauce aioli, made of crushed garlic into which olive oil is emulsified, and this is the principe of "ollis", i.e. generalizations of aoili, but with any ground plant or animal tissue (This, 1997).

Finally, energy is needed to make emulsions, dividing the oil in tiny droplets that are dispersed in the aqueous solution. Traditionally forks, whisks, mortar and pestle are used, but mixers make firmer emulsions because they give more energy and overcome better surface tension, generating smaller droplets. In chemistry laboratories, ultrasonic probes are common, but in spite of proposals made for decades, they remain very rare in kitchens.

Let us end this long paragraph by considering a proposal that was made in the 1990s, of a system that was named "geoffroy" (This, 1997): an egg white is used as it contains water (90%) and proteins (10%, around 370 kinds) (Shi et al., 2023); if oil is added in while whisking, air bubbles are first introduced with oil droplets, and an emulsified foam is obtained (Figure 4).

Adding more oil makes the bubbles disappear; the emulsified foam turns into a white - somehow aerated - emulsion. The preparation is very smooth, white and flavourless, so it can be given any flavour, such as vanilla. The

emulsion can be turned into a dessert, adding sugar: sucrose dissolves in water, up to a limit of 960 g of sucrose per kilogram of water. The vanilla geoffroy can be served as it is, but it can also be cooked in a microwave oven until expansion is observed, so that the proteins in the egg white coagulate, producing an expanded, chemically gelled emulsion known as "gibbs" (This, 2009).

**7. What is a "protein batter"?**

Finally about "protein batters", again the name does not describe only one particular product, but allows imagining many possibilities. For example, adding 10 g of egg white powder in 100 g of water makes a batter that has the properties of egg white: it can be whipped into a white foam, or cooked, producing a result very similar to cooked egg white. With a higher proportion of water, the batter becomes less viscous, but still coagulates, until the proportion of proteins is less than 5%; with more proteins (20%), thermocoagulation generates products that can have the hardness of meat. This batter behaves like the one that would be made from flour and water, except that proteins are present instead of polysaccharides.

<figure><img src="image_9.png" /><figcaption>Figure 5. This green "dirac" was obtained by frying a 20% protein aqueous solution, added with oil salt, glutamate monosodium, piperine, green food colorant, D-glucose, and 1-octen-3 ol (This vo Kientza, 2021).</figcaption></figure>
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

calcium alginate gels : a laboratory experiment, In Burke R, Kelly A, Lavelle C, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 689-701.

This H. 1997. *Révélations gastronomiques*, Belin, Paris (France).

This H. 2009. *Science, technologie, technique (culinaires) : quelles relations ?, Cours de gastronomie moléculaire N°1*, Quae/Belin, Paris (France).

This H. 2014. *Note by Note Cooking*, Columbia University Press, New York, USA.

This H. 2019. Des perles pour contrôler la jutosité et la tendreté, *Pour la Science*, 513, 96.

This H. 2022. Pourquoi éviter le terme « hydrocolloide », Encyclopédie de l'Académie d'agriculture de France, https://www.academie-agriculture.fr/sites/default/files/publications/encyclopedie/final_08.01.q21_hydrocolloides.pdf.

This vo Kientza H. 2021a. Debye. In Burke R, Kelly A, Lavelle C, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 743-744.

This vo Kientza H. 2021b. The right words for improving communication in food science, food technology and between food science and technology and a broader audience. In Burke R, Kelly A, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 627-644.

This vo Kientza H. 2021c. Dispersed system formalism. In Burke R, Kelly A, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 627-644.

This vo Kientza H. 2023. *Calculating and problem solving through culinary experimentation*, CRC Press, Boca Raton, Florida.

Wikipedia. 2023. Xanthan gum, https://en.wikipedia.org/wiki/Xanthan_gum.

This article is published in the section *Questions and Answers* of the part *Edible Ideas*

**Received :**

20 August 2023

**Accepted :**

23 January 2024

**Published :**

2 February 2024

**Editor:**

Anonymous

**Reviewers :**

1. Anonymous

2. Anonymous

**Cite as:**

This vo Kientza H. 2024. Questions and answers: when words are analysed from a chemical and physical perspective, innovation is easy, *International Journal of Molecular and Physical Gastronomy*, 10(1), 1-12.
**International Journal of Molecular and Physical Gastronomy**
(Mol Phys Gast)

**Section Questions and Answers (Part 4: Edible Ideas)**

So far, only egg proteins were mentioned, but there are proteins in many other products, both in animal tissues or products (e.g. milk proteins) and in some plants tissues, such as pulses (Shevkani et al., 2019). Today plant proteins again can be found under the form of powders (white powders when they are pure) and they can often be used as explained for egg white.

It was not part of the question, but how can a protein batter be used? If it is put in a syringe and deposited in a hot medium (boiling water, hot oil), some "spaghetti" are obtained from the protein batter; if deposited as a layer that is heated, coagulated sheets can be produced, etc. If the proteins have been chosen in such a way that they can coagulate, then the equivalent of meat (a "dirac") can be made, at least from the point of view of consistency (Figure 5) (Gagnaire, 2021). Such "pancakes" can be improved, for example by spreading the protein batter, strewing it with a fork, cooking it, rolling it on itself into a sheet and obtaining a kind of surimi, as was done in 2012 by the chefs Ismail Osorio, Erik Ayala-Bibriesca, and their students from the Institut technique du Québec (ITHQ), in Montréal (Canada).

Any flavour can be given to all these products. In the experiment described above, "water" was used as the liquid, but any aqueous solution will do: tea, coffee, orange juice, tomato juice, wine, stock, etc. And moving to "synthetic cooking" (the technique used by the culinary art called "note by note cooking) gives even more possibilities (This, 2014). Indeed flavour is the synthetic sensation including colour, consistency, temperature, tastes, odours, and spiciness and freshness, etc. One should therefore not forget, before cooking or before use, to add compounds to the protein batter in order to create colour, flavour, odour, etc.

**8. Conclusion**

The chemical and physical analysis of culinary

systems not only makes it possible to understand the constitution of classic culinary preparations, but it is also the basis for innovations, demonstrating that the results of natural sciences are a condition for fruitful technological work. Often it is useful to use the right names for objects and mechanisms, in order to ask more precise questions and find the answers to these questions more easily.

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Schwarz B, Hofmann T. 2009. Identification of novel orosensory active molecules in cured vanilla beans (*Vanilla planifolia*), *Journal of agricultural and food chemistry*, 57, 9, 3729–3737.

Shevkani K, Singh N, Chen Y, Kaur A, Yu L. 2019. Pulses proteins: secondary structure, functionality and applications, *Journal of food science and technology*, 56(6), 2787-2798.

Shi D, Su W, Mu Y. 2023. Quantitative proteomics study on the changes of egg white of yellow preserved primary chicken eggs soaked
**International Journal of Molecular and Physical Gastronomy**
*(Mol Phys Gast)*

**Section Questions and Answers (Part 4: Edible Ideas)**

in alkali solution, *Food Research International*, 165, 112346, 1-11.

Sila DN, Melbourne F, Smout C, Van Loey A, Hendrickx M. 2005. beta-Elimination of carrot pectin: towards a better understanding of carrot texture during thermal processing, *Communications in Agricultural and Applied Biological Sciences*, 70(2), 19-22.

Soprani L, Querciagrossa L, Cistofaro S, Muccioli L, Orlandi S, Strocchi E, Arcioni A, Berardi R. 2021. Ionic diffusion in sphérified calcium alginate gels : a laboratory experiment, In Burke R, Kelly A, Lavelle C, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 689-701.

This H. 1997. *Révélations gastronomiques*, Belin, Paris (France).

This H. 2009. *Science, technologie, technique (culinaires) : quelles relations ?*, Cours de gastronomie moléculaire N°1, Quae/Belin, Paris (France).

This H. 2014. *Note by Note Cooking*, Columbia University Press, New York, USA.

This H. 2019. Des perles pour contrôler la jutosité et la tendreté, *Pour la Science*, 513, 96.

This H. 2022. Pourquoi éviter le terme « hydrocolloide », Encyclopédie de l'Académie d'agriculture de France, https://www.academie-agriculture.fr/sites/default/files/publications/encyclopedie/final_08.01.q21_hydrocolloides.pdf.

This vo Kientza H. 2021a. Debye. In Burke R, Kelly A, Lavelle C, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 743-744.

This vo Kientza H. 2021b. The right words for improving communication in food science, food technology and between food science and

technology and a broader audience. In Burke R, Kelly A, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 627-644.

This vo Kientza H. 2021c. Dispersed system formalism. In Burke R, Kelly A, This vo Kientza H (eds) *Handbook of Molecular Gastronomy*, CRC Press, Boca Raton, Florida, 627-644.

This vo Kientza H. 2023. *Calculating and problem solving through culinary experimentation*, CRC Press, Boca Raton, Florida.

Wikipedia. 2023. Xanthan gum, https://en.wikipedia.org/wiki/Xanthan_gum.

This article is published in the section *Questions and Answers* of the part *Edible Ideas*

**Received :**

20 August 2023

**Accepted :**

23 January 2024

**Published :**

2 February 2024

**Editor:**

Anonymous

**Reviewers :**

1. Anonymous

2. Anonymous

**Cite as:**

This vo Kientza H. 2024. Questions and answers: when words are analysed from a chemical and physical perspective, innovation is easy, *International Journal of Molecular and Physical Gastronomy*, 10(1), 1, 1-12. DOI: 10.17180/ijmpg-2024-art01.