Twenty Years of Molecular Gastronomy

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Twenty Years of Molecular GastronomyHervé This*

　As the 20th anniversary of the scientific discipline called Molecular Gastronomy is being celebrated, the programme of the discipline seems now to be well determined. Also two formalisms for describing the building of dishes are fused into one, called CDS　/　NPOS formalism.

Keywords :　Colloids, dispersed system, formalism, food, cooking.

　*　 INRA Team of Molecular Gastronomy, UMR 214 INRA　/　Institut des sciences et technologies du vivant et de l’environnement （AgroPar-isTech）

Introduction

　　For about 15 years, TV, radio and journals of all over the world give regularly information about a culinary trend called “Molecular Cooking”, frequently confused with “Molecular Gastronomy”. What are they? Why is Molecular Gastronomy different from Molecular Cook-ing? Are they both only temporary trends, or are they here to last? Are they useful ?　　First of all, Molecular Cooking should be defined, be-cause there is much confusion, in particular because of mistakes that we did in the 80’s and 90’s, when the new discipline Molecular and Physical Gastronomy, later shortened Molecular Gastronomy, was created. The issue is solved by the meaning of words :　cooking is... cooking, i. e. the production of food ;　and gastronomy is gastrono-my, i. e. “the intelligent knowledge of whatever concerns man’s nourishment”.1

　　With these definitions in mind, Molecular Cooking was defined as “the use in the kitchen of new methods, ingredients, tools”. On the other hand, Molecular Gastron-omy is a scientific discipline that was formally created in March 1988. The two have nothing in common :　Molecu-lar Cooking produces food, whereas Molecular Gastrono-my produces knowledge.

The issue of so called food sciences

　　Before telling the story of the creation of Molecular and Physical Gastronomy, that became later “Molecular Gastronomy”, let us stop for a while and ask the ques-tion :　what is “food”? Dictionaries give a definition :　“Any substance that can give to living beings the elements nec-essary for their growth or for their preservation.”2 Ac-

cordingly raw, plant or animal tissues should be consid-ered as food as well as dishes, but such a definition is confusing, as human beings very seldom eat non trans-formed tissues or natural products ;　raw material is transformed, so that chemical and physical changes de-termine the final composition of food as well as its bioac-tivity. This leads to a first conclusion :　reagents and prod-ucts of the “culinary transformations” should be given different names, instead of being considered all as “food”. Also there is a main difference between the science of food transformations and the technology of food transfor-mations. Let’s say it differently :　technology uses results from science to improve technique, or craft, whereas sci-ence starts from phenomena to arrive to mechanisms.

Molecular Gastronomy is 20 years old

　　Molecular Gastronomy had ancestors, and many chemical phenomena occurring during culinary transfor-mations were studied before 1988, when Molecular Gas-tronomy was introduced. However it is a fact, first, that in the 1980’s, food science was neglecting culinary pro-cesses in most countries （Japan was an exception with articles published in the Journal of Cookery Science of

Japan and in the Journal of Home Economics of Japan）. For example, “food chemistry” textbooks, such as the classic Food Chemistry3 contained almost nothing about culinary transformation :　in the 1999 edition of the book, less than 0 . 5 percent of the chapter on meat was describ-ing “culinary phenomena” （meat shrinkage during heat-ing because of collagen denaturation）;　most of the chap-ter described either meat composition and structure, or industrial products （sausages, meat extracts...）. Probably because culinary transformations are complex and also because the food industry did not pay for studies out of it’s field, food science drifted slowly toward the science of ingredients and toward technological questions, neglect-

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日本調理科学会誌 Vol. 42，No. 2，79～85（2009）〔総説〕

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日本調理科学会誌　Vol. 42　No. 2（2009）

ing phenomena that occur when cooking cassoulet, gou-lash, hollandaise sauce, etc.　　This is why the late Nicholas Kurti （1908―1998）, for-mer professor of physics in Oxford,4 and me, in March 1988, decided that a “new scientific discipline” was to be created. The situation at that time was about the same as for Molecular Biology some decades before :　“The term “Molecular Biology” was first used by Warren Weaver5 in 1938 to describe certain programs funded by the Rockefeller Foundation, where it simply meant the application of techniques developed in the physical sci-ences to investigate life processes.”6

　　As what Kurti and I had in mind was more or less the same, but in another field of knowledge, the name “Molecular and Physical Gastronomy” was chosen. The choice of “gastronomy” in this title was obvious, for rea-sons explained above ;　personally I had the feeling that the “and physical” part of the name was useless, but Kur-ti, being a physicist insisted to keep it because he thought that otherwise too much emphasis would be on chemis-try.　　This full name “Molecular and Physical Gastronomy” was used for international workshops that we both orga-nized every two years or so in Erice （Sicily）, at the Ettore Majorana Centre for Scientific Culture. When Kur-ti died, two years after I was asked to present the first Ph. D in “Molecular and Physical Gastronomy” at the Ecole Supérieure de Physique et de Chimie de Paris （ES-PCI）/University Paris VI,7 and after Jean―Marie Lehn

（Nobel Prize in chemistry, 1987） invited me to create the first Group of Molecular Gastronomy in his Chemistry Laboratory of the Collège de France, the name “Molecu-lar and Physical Gastronomy” was shortened into “Molec-ular Gastronomy”, and Kurti’s name was given to the in-ternational workshops.　　The interest of this new field was and remains scien-tifically clear :　if one wants to discover new phenomena, the exploration of a new field is probably an easier choice than looking to already well considered objects. Of course, as always when new knowledge is produced, there is the possibility to make important technological applications, and indeed since 2000 one “innovation” based on Molecu-lar Gastronomy was introduced every month （frequently, names of famous chemists of the past are given to new “dishes”）.8 But this is technology, not science.　　Here a word should be added to discuss the relation-ship between Molecular Gastronomy and what is called in Japan “cookery science”, or what is called in English

speaking countries “culinology”. First, culinology is a trademark, and this alone shows that it cannot be science. Moreover, according to the Internet site of the University of Pennsylvania, culinology “is the blending of the disci-plines of food science and culinary arts. By combining the knowledge of basic science with the creativity of culinary arts, students develop a unique skill set that will enable them to define the future of food through the creative process of developing new food products.”9 This is a strange definition :　how is it possible to mix science, look-ing for phenomena, and culinary art, producing emotion? Strictly speaking, “cookery science” is also confusing （but this is perhaps a question of translation from Japanese to English?）, as it means the “science of cookery”, and in-deed cookery is no science, but craft. When one looks to the article in this journal, it is very interesting to see how science and technology mix... but it is also important to remember that science and technology don’t have the same goal and should probably be separated.

Program of the Molecular Gastronomy

　　At the beginning of Molecular Gastronomy, the de-sire of rationalization of an old chemical art was also re-sponsible for the creation of the discipline. In Oxford, Kurti was upset by the poor and irrational way of cook-ing, whereas, in France, I began my experimental studies in March 1980 because I thought that it was necessary to collect and to test “old wives tales” and analogous pieces of information. More generally, we thought that culinary tradition should be overcome, and we introduced the fol-lowing program :10，11 （1） collect and test old wives tale ;　

（2） model recipes ;　（3） introduce new tools, products, methods ;　（4） invent new dishes using the 3 previous works ;　（5） use the appeal for food in order to promote science.　　It is easy to see, today, that this “scientific program” was not clear :　if aims （1） and （2） are really scientific,

（3） and （4） are of technological nature, and （5） is an ed-ucational application of the four first. However, this pro-gram being was developed actively. In particular, in France Molecular Gastronomy developed through month-ly seminars, national congresses, courses on molecular gastronomy... The educational effort was also important. In 2001, the Ateliers expérimentaux du goût （Experi-mental workshops on flavor） were introduced in French schools.12 In the following years, new curriculum for culi-nary schools was introduced in Canada and France, with applications of new knowledge obtained from Molecular

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Twenty Years of Molecular Gastronomy

Gastronomy. In 2005, the Institute for Advanced Studies on Gastronomy （IHEGGAT, more recently shortened into HEG） was created,13 with courses in Molecular Gastrono-my, as professorships in various countries were set up

（France, Denmark...）.14 The expression “Molecular Cook-ing” was introduced in 2002, because the press began publishing that some chefs were “molecular gastrono-mists”, which is not possible, because chefs are not doing science.　　As it was clear from the beginning between Kurti and me that Molecular Gastronomy was science, and not technology, a new program had to be designed. It ap-peared in 2003 that any traditional recipes are made of three parts. The first one is all the technically useless material. The second one is a “definition” :　for example, a soufflé is a foamy product that swells during cooking, and deflates as it is opened （otherwise it’s a cake）;　mayon-naise sauce is an emulsion obtained with only egg yolk, salt, pepper, vinegar and oil ;　etc. Generally these defini-tions are given as protocols, and they are mixed with the third part, called “culinary precisions”, i. e. old wives tales, lore, ways of doing, tricks, sayings, adages, maxims...　　Accordingly, the scientific program was made clear-er when it was reduced to :　（1） model definitions ;　（2） collect and test precisions. However this new program was discovered insufficient, because the main point in cu-linary practice is to produce “good” dishes :　this is art, and not technique ;　and as good dishes thrown to the face of the customers are not “good”, in spite of art, it was un-derstood that the “social component” of culinary practice was also to be considered. Of course, science cannot have the last word on such topics, but Evolution biology, for example, can explain a lot about human behaviors, and, accordingly, about culinary practice.　　Today, the scientific program of Molecular Gastrono-my is then :　（1） explore scientifically the technical part of cooking ;　（2） explore scientifically the art component of cooking ;　（3） explore scientifically the “social link” component of cooking.With this scientific program, what is the most rational way of exploring the field of culinary phenomena? As culinary transformations are dynamic processes involving systems with structure,15 it’s natural to make complementary descriptions of the physical state, on one hand, and of the chemical state on the other. The bioactivity （organoleptic, nutritious, toxic） of such systems is later considered, as the result of the two.

The CDS　/　NPOS formalism, a tool for studying culinary processes

　　Let’s focus first on the question of structure. A CDS （“complex disperse system”） formalism was introduced in 2002 for the description of the “matter” from which the various parts of dishes are made. Later, in 2003, another formalism called NPOS （“non periodical organization of space”） was proposed for the overall description of dish-es, and distribution of matters described by the CDS for-malism, but it was recently recognized that indeed these two formalisms could be mixed into a more comprehen-sive description called CDS　/　NPOS.　　As other formulated products such as paints, cos-metic or drugs16，17, dishes are often made of parts which are colloids.18，19 In particular plant and animal tissues, made of cells whose smallest dimensions is of the order of 10－6 m, are colloids according to the IUPAC definition :　cells aggregation in tissues make formally non connected gels, contrary to gelatin gels, which are connected gels, water forming a continuous phase in the continuous solid phase due to collagen molecules associations by triple he-lixes.20，21 Emulsions are also frequent in the kitchen （let’s think of mayonnaise, aioli, or wine sauces with butter...）.22

　　When more complex systems are considered, physics generally focused on the interface, i. e. local descriptions of macroscopic systems, or on some thermodynamic properties.23，24 However this has two main disadvantages. First the global description of the systems is lost. Then, in more complex ― but familiar―systems, such as potato tissues or ice creams, the denomination are rather com-plicated. Potatoes, for example, are mainly “suspensions dispersed in gels”, as amyloplasts （solid starch granules of size less 20 m）,25 are dispersed into the cytoplasm of cells （water or gel, depending on the description level）, this phase being itself dispersed into the network of cell walls responsible for the “solid” behavior of the whole po-tato. Ice cream is another example of food complex sys-tem that should be called “multiple suspension　/　foam　/　emulsion”, as gas （air） bubbles, ice crystals, proteins ag-gregates, sucrose crystals, fat （either crystals or liquid droplets）, etc. （depending of the “recipes” and of the pro-cesses used） are dispersed in an aqueous solution.26 On the other hand, the names “potato” or “ice cream” are probably not admissible names in physics textbook be-cause they are imprecise and restricted to food.　　This is why the CDS formalism was introduced at the 2002 European Congress on Interface Science

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（ECIS）.27 The physical nature rather than the chemical composition is considered described. For food, where liq-uids are mostly water and mixtures of triacylglycerols, symbols G, O, W, S respectively stand for “gas”, “oil”, “wa-ter”, “solid” ;　of course, other symbols such as E （for eth-anol） could be added if necessary （this would be useful in other fields than food）. The distribution of the various phases can be geometrically or topologically described by operators. As recommended by the IUPAC, the “@” sym-bol describes inclusion （topology）:　e. g. O@W applies to some oil phase included into a water phase. Physical chemistry also uses traditionally the symbol “/” to de-scribe the random dispersion of a large number of struc-tures of one phase into another phase, such as in W　/　O

（emulsion）.28 And as many phases can be dispersed into another, the “ ” symbol is needed, such as in （G O）　/　W for describing aerated emulsions, with gas G and oil G dispersed in the continuous water phase W. For opera-tors as for phases, other symbols could be added if neces-sary to fully describe complex disperse systems, but up to now no addition was needed.

　　Some rules give more coherence to the formalism.　　◯　　Some simplifications can be done. For exam-ple, G　/　G and W　/　W are respectively equal to G or W.　　◯　　The various components of a sum （ symbol） should be written in alphabetical order. For example, cus-tard （it is not an emulsion O　/　W, contrary to what was frequently published in culinary textbooks29） is made of oil droplets O （from milk）, air bubbles G （introduced dur-ing the initial whipping of sugar and egg yolks） and small solid particles S （due to egg coagulation during thermal processing30） and should be described as （G O S）/　W. This rule is the key to uniqueness of formulas associated to physical systems.　　◯　　Repetitions can be described by exponents.

For example, egg yolks are made of concentric layers called light and deep yolk, deposited respectively during the day and the night ;　their number is about 9, as shown on ultrasound scan pictures.31 As each layer is composed of granules （S） dispersed into a plasma （W）,32 the full yolk could be described as （S　/　W）@9 .　　The basic formula can be increased to give more precise descriptions of systems.　　◯　　For example, the quantity of each phase can be added as a subscript. For example, O95　/　W5 would de-scribe oil into water emulsion at the limit of failure, with 95 g of oil dispersed into 5 g of water （then, the oil drop-lets have a polyhedral shape）.33 Using such subscripts, conservation laws can be used. For example, the overall making of a mayonnaise could be written as:

O95　　W5　EW――→　O95　/　W5

　　◯　　As the size of structures is important, they can be indicated into brackets, such as in the emulsion formula : O95［10－6－10－5］/　W5,　　where the powers of 10 indicates the minimum and maximum radii of dispersed oil droplets （in international units）.　　◯　　At the end of formulas, the smallest struc-tures considered can be given, if necessary, as a “size cut―off”, inside brackets :　the last brackets in a mayon-naise formula such as O［10－5, 10－4］　/　W［>10－5］ shows that the structures considered are larger than 10－5 m, i. e. that granules of egg yolk are not taken into account as their size is between 0 . 3 and 2 micrometers.34 This particulari-ty of the CDS formalism is a way to take into account with different formula the various scales in systems.　　Describing objects is only a first step ;　as we said above, the main point is studying the mechanisms of transformations （here physical transformations）. For ex-ample, for mayonnaise sauce with regular addition of oil starting from one egg yolk and one tablespoon of vinegar

（the parameter t could be time）: 35，36

O（6 374*t）, t 0..1　/　W20.

　　Another example would be the foaming an emulsion, which can both be described as: O　/　W G ―→ （G O）/　W　　Or using kinetic parameters t, the equation can be reduced for only one formula （here the gas would be in-troduced at regular pace ;　subscripts give volume instead of mass）: （Gt 0..5 O30（100－t）　/　100）　/　W70（100－t）　/　100.

Objects GOWSOthers :　such E...

Gaz“oil”, i. e. any hydrophobic liquid“water”, i. e. any aqueous solutionSolidE for ethanol, other solvants

Operators /

@

Others if necessary

Dispersed intoMixed withIncluded inSuperposed...

Fig. 1．　The main objects of the CDS formalism.

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　　Whereas the CDS formalism describes the matter of which food and formulated products are composed, these formulated products are frequently highly organized sys-

tems, made of many parts. Moreover, this organization is frequently very important for bioactivity. In order to get a full description of systems, another formalism seemed to be needed. As crystallographic descriptions apply only for periodical organization37, they cannot be used for the description of man made systems, which are non―periodic in space or even irregular.　　The same idea as above （using “objects” and “opera-tors”） was proposed, but in the “non periodical space or-ganization” formalism （NPOS）, it was found useful to de-scribe parts as objects of particular dimension :　D0, D1, D2 and D3. A “reference dimension” being chosen （see be-low）, D0 stands for objects of zero physical dimension

（“dots”）, i. e. objects whose size in the three directions of space is more than one order of magnitude lower than the “reference size”. D1 stands for “lines” （with only one dimension of the same order of magnitude as the refer-ence dimension）, D2 for surfaces （with two dimensions of the same order of magnitude as the reference dimen-sion）, D3 for volumes. If necessary, Dx objects could be

Fig. 2．　 This product called a “gibbs”, in honor of the physical chemist Josiah Willard Gibbs, is based on the formu-la （O　/　W）/　S. It is obtained by whipping oil O in an egg white W, and heating the emulsion obtained so that proteins at the interface coagulate and make a gel trapping the emulsion.

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Fig. 3．　 Different kinds of systems that are considered as gels :　（a） gelatine gel ;　（b） animal muscular tissue ;　（c） plant tis-sues. These systems can be described by different CDS　/　NPOS formula.

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considered, x being non integer, and these objects being then fractals38. Reference size has to be defined more pre-cisely :　for food systems, it would be the size of the plate, but more generally, reference size, being the scale where the full object is considered, can be added in brackets, when needed. For example, D1［10－5］ would indicate a lin-ear structure whose length is of the order of magnitude of 10－5 m （and, accordingly, whose radius is more than one order of magnitude lower）. The direction of sheets and fibers is sometimes usefully added, using the Carte-sian equation in the same bracket.　　Again the various objects Dk are included in formu-las using operators :　here again the operator @ repre-sents inclusion ;　geometrical operators such as x, y, z represent respectively superposition in the direction x, y and z （but any particular direction could be given by the Cartesian coordinates of a vector, such as in （u, v, w）, or even other coordinates systems such as ｛ , , ｝ for spherical organization）. However in many systems, some disorder has to be described, and this is why new opera-tors should be used instead. In particular, the “/　” opera-tor is again useful for the description the disordered ac-cumulation of objects in space. Other operators could be added when needed.　　Using this new formalism, only topology is consid-ered, and the geometrical shape of formulated products is not described :　a square has the same “formula” as a disk. And as the two previous formalisms use the same opera-tors, they can be mixed easily in order to get a more pre-cise description of formulated systems （the name “CDS　/　NPOS formalism” was proposed）. For example, meat, be-ing formed of aligned muscular fibers full of a jellified so-lution39 could be described as D1,x（W）　/　D3（S）, if x repre-sent one arbitrary direction. And an oil―into―water emulsion could be described by D0（O）　/　D3（W）.

Conclusion

　　How useful are these formalization? Do they apply to all food? And how can they be used for studies of Mo-lecular Gastronomy? This will be the topic of another ar-ticle in the next issue of this journal.

References1　Brillat―Savarin J. A., （1825）, in Molecular Gastronomy, This, H., （2006）, Columbia University Press.2　Trésor de la langue française, （2006）, electronic version, http://atilf.atilf.fr/tlf.htm, access 01/10/2006.3 Belitz H. D., and Grosch W., （1999）, Food Chemistry, Spring-er.

4　This H., 1999, Froid, magnétisme et cuisine :　Nicholas Kurti （1908―1998, membre d’honneur de la SFP）, Bulletin de la So-ciété française de physique, 119, 24―25.5　Weaver W. T., （1970）, Molecular Biology, Origins of the Term, Science, 170, 591―592.6　Baltimore D. （Ed. ）, （1977）, Nobel Lectures in Molecular Biology 1933―1975. Elsevier, viii.7　This H., （1996）, La gastronomie moléculaire et physique, Université Paris VI.8　http://www.pierre―gagnaire.com, see “Art et Science”.9　http://university―pennsylvania.edu.10　This H., （1995）, La gastronomie moléculaire, L’Actualité chimique, 42―46.11　This H., （2002）, Molecular Gastronomy, Angewandte Che-mie, International Edition in English, 41（1）, 83―88.12　http://crdp.ac―paris.fr/index.htm?url d_arts―culture/gout―intro.htm （last access 03/07/07）.13　HEG, （2006）, http://www.iheggat.com/, last access 03/07/07.14　http://www.agroparistech.fr15　Dickinson E., （2006）, Colloid Science of Mixed Ingredients, Soft Matter, 2, 642―652.16　Cotte J., （1992）, Introduction, in Martini M.―C., and Seillier M., （Eds.）, Actifs & Additifs en cosmétologie, Technique & Documentation Lavoisier, XIII―XVI.17　Teisseire J., （1991）, Chimie des substances odorantes, Technique & Documentation Lavoisier.18　http ://old . iupac .org/reports/2001/col lo id_ 2001/manual_of_s_and_t/node33.html19　Dickinson E., （1994）, in Nishinari, K., and Doi E., （Eds.）, Food Hydrocolloids, Structure, Properties and Functions, Ple-num Press.20　Djabourov M., （1988）, Architecture of Gels. Contemp. Phys, 29（3）, 273―297.21　Lehn J.―M. Chimie supramoléculaire, De Boeck :　Paris, 1999.22　Hunter R. J., （1986）, Foundations of Colloid Science, Ox-ford University Press.23　Israelachvili J., （1992）, Intermolecular & Surface Forces, 2 nd Ed., Academic Press.24　Dickinson E., （1994）, in Food Hydrocolloids, Structure, Properties and Functions, Nishinari K., and Doi E., （Eds.）, Ple-num Press.25　Bowes B. G., Structure des plantes, INRA Editions :　Paris, 1988.26　Sztehlo A., （1994）, Ice Cream Microstructure, European Microscopy and Analysis, 5, 17.27　This H. La gastronomie moléculaire. Sciences des ali-ments. 2003, 23（2）, 187―198.28　Hunter R. J., （1986） Foundations of Colloid Science, Oxford University Press :　Oxford.29　Maincent M., （1993）, Cuisine de référence, BPI.30　This H., （2003）, La gastronomie moléculaire. Sciences des aliments, 23（2）, 187―198.31　This H., （2003）, La gastronomie moléculaire. Sciences des aliments, 23（2）, 187―198.32　Anton M., （1998）, Structure and Functional Properties of Hen Egg Yolk Constituents, Recent Res. Devel. in Agricultur-al& Food Chem., 2.

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33　Bibette J., Morse D. C., Witten T. A., and Weitz D. A., （1992）, Stability Criteria for Emulsion, Phys. Rev. Let., 69（16）, 2439―2442.34　Causeret D., Matringe, E., and Lorient D., （1991）, Ionic Strength and pH Effects on Composition and Microstructure of Yolk Granules, J. Food Sci., 56, 1532―1536.35　Anton, M., and Gandemer J., （1997）, Composition, solubility and emulsifying properties of granules and plasm of egg yolk, J. Food Sci., 62（3）, 484―487.36　Belitz H. D., and Grosch W., （1999）, Food Chemistry,

Springer Verlag, 915.37　Kettle S. F. A., （1999）, Physico―chimie inorganique, De Boeck Université, 440―444.38　Mandelbrot B., （1982）, The Fractal Geometry of Nature, W. H. Freeman and Co.39　Kopp J., （1986）, Le rôle du collagène dans les phénomènes de restructuration des viandes, in Dumont B. L., Ed., La re-structuration des viandes, Erti, 55―77.

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和文抄録　分子美味学と呼ばれる科学的研究分野の 20 周年が記念されるに伴い，研究分野の概念もよくまとまって来ているように思われる。また，調理の構成を表現しうる CDS〔Complex disperse system；複合分散系（複雑な分散状態を説明する考え方）〕と NPOS〔Non periodical organization of space；非周期的空間組織（不規則な空間構成を説明する考え方）〕という 2 つの公式論も CDS/NPOS と呼んでいる一つの公式論に融合されている。そこで，本稿では分子美味学がどのように開始され，定義されるかを概説したい。

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Twenty Years of Molecular Gastronomy