MOLECULAR GASTRONOMY: Part IV (Completed, THE END)

PART FOUR:  A CUISINE FOR TOMORROW

In Part Four, the author presents some new culinary methods taking advantage of innovative applications of standard chemical laboratory equipment.  One of this is the use of vacuum techniques to facilitate better control filtration methods for clarifying stocks without losing the taste molecules.  Vacuum techniques, at the time of writing, were also tested on culinary preparations that involve foam formation, e.g. meringues.  The vacuum bell jar allows more efficient evaporation of water and expansion of trapped air bubbles.  The innovation does not always result in the best taste or texture as in the case of the meringue which came out too light and airy that “there was nothing to bite into”.  A better application is probably in the preparation of foam-filled food prepared with thicker bubble “walls” as in soufflés.  In addition to mechanical chemical laboratory techniques, the author also explores the potential of chemical manipulation of flavor, aroma, and taste in food by the addition of synthetic flavoring molecules to enhance the flavor contributed by the natural analogue (synthetic flavors for strawberry, rosemary, ginger or addition of glucose to enhance the flavor of the caramelized residue).  For instance, it is known that the Maillard reaction between amino acids and sugars is enhanced by the acidity of the cooking solution.  The author proposes increasing this acidity by adding vinegar whose excess acidic taste can then be neutralized later on by the addition of sodium bicarbonate.  Formation of emulsions and foams features greatly in this part because the chemical composition and the process by which they form are quite well-known.  The author starts with describing the chemical composition of mayonnaise, an emulsion of oil and water containing tensioactive protein and lecithin molecules that help stabilize the oil and water interface.  Another popular emulsion is aioli containing water and tensioactive molecules from garlic and oil.  He then goes to reason that as long as a substance contains some tensioactive molecule (molecules that contain both hydrophilic and hydrophobic parts also called amphiphilic), in theory, one can add oil to it and make an emulsion.  Because both plant and animal cells have cell membranes that contain tensioactive phospholipid molecules, one can technically make an emulsion out of any vegetable or meat.  The author describes making emulsions out of crushed zucchini and oil and crushed beef and oil.  Similar to emulsions but this time a stable mixture of air trapped in water is foam.  They work under the same physical and chemical principle of amphiphilic molecules stabilizing the water-air interface where air is acting like the oil, insoluble in water.  These are another set of examples that illustrate the benefit of knowing the physical and chemical basis of the flavor, taste, smell, and texture of food.  Toward the end of the chapter, the author muses that our cooking methods in relative terms really have not changed much from traditional practices that have been around for several hundred years despite the accumulated knowledge and established technologies that have been achieved in the meantime.  One example he gives is the use of chemical knowledge to create innovations and interventions that could enhance flavor through the addition of known chemical and microbiological aids; but he does concede that perhaps objection to this is more due to devotion to natural sources rather than artificial adulteration.  Based on the knowledge now available as to the physical and chemical basis of foaming and emulsion, he suggests other cooking innovations based on these two techniques.  He also proposes double method cooking based on a table of heating methods and general cooking preparations.  Lastly, at the time of writing, he devotes the last chapter on teleolfaction, the possibility that one day, much like information and images can be telecommunicated electronically, technology can catch up to provide the same medium for gustatory and olfactory sensations.

COOKING IN A VACUUM

·         “New devices can improve traditional culinary techniques.”

·         In this chapter, the author discusses how cooks are looking at chemical lab equipment and methods can be used to carry out similar process in the kitchen.  An example given was in filtering cloudy stocks to clarify it without removing the flavor-giving particles. 

·         The author and a chef tried the vacuum filtration method to filter a tomato consommé using funnel fitted with a fritted glass plate with uniform pore sizes.  The funnel is then placed into a conical vial in which a vacuum has been created using a waterjet pump [I am guessing this is similar to an aspirator attached to running water that pulls air and creates a vacuum].  Compared to the conventional method of filtering the stock, using the new laboratory device resulted in a clear liquid with a more “pronounced taste”.

·         Another possible application of vacuum techniques is in making meringues.  The vacuum [or low-pressure] environment causes faster water evaporation from the meringue mix while allowing freer expansion of the trapped air.  “The final result is light and airy –like ‘wind crystals’”.  “Too light”, however, “there was nothing to bite into”.

AROMAS OR REACTIONS?

·         “Two ways of imparting flavor to food”

·         Despite the common belief on the aphorism “things ought to taste like what they are” (attributed to gastronome Curnonsky), the author explores the question of whether the aim of cooking is to “transform foods with the purpose of recreating traditional dishes and inventing new ones”.

·         If the goal of cooking is to create specific flavors, he presents two methods for doing this: “adding flavors or organizing chemical reactions in such a way that flavors are formed in the foods themselves” – in this method, natural extracts and synthetic compound mixtures are prepared to provide flavors and familiar scents such strawberry or rosemary.  This method still relies on the “noses” of taste and flavor experts.

·         While many cooks balk at this idea noting that extracting the flavor from the natural source provides a richer results, the author challenges dismissing aromatic engineering altogether for the potential of discovering other palette of flavors, musing, “Why not reinforce the green note of olive oil with hexanal, or add i-octen-3-ol to a meat dish in order to give it an aroma of mushroom or mossy undergrowth (although here one needs to be careful about proportions because in excessive concentrations the small molecule smells a bit moldy)?  Why not use beta-ion-one to give desserts the surprising violet aroma that flowers have such a hard time releasing?”.

·         One can control the flavor of the caramelized residue upon reduction of mixtures of liquid and solid food ingredients by adding glucose, fructose, sucrose, other sugar additions.

·         The author answers the questions of why stocks made by boiling beef or other meats and vegetables retain a strong flavor despite the more volatile aromatic molecules are evaporated upon heating.  Chromatographic analysis showed that even there was a measured reduction in the some volatile flavor-producing molecules, the heating process produces new flavor molecules that help stock retain a strong flavor.

·         The author proposes chemical manipulation to drive reactions to produce more of the desired aroma or flavor.  For example, the Maillard reaction between amino acids and sugars is known to be affected favorably [I am guessing in producing more of the compounds that impart the flavor produced by this reaction] by a more acidic environment.  The author suggests adding vinegar to increase the acidity; the excessive sour taste can then be neutralized to the desired level later on by using sodium bicarbonate.

BUTTER: A FALSE SOLID

·         “How to make it spreadable”

·         Chemical composition of milk:  fat droplets are surrounded by casein protein micelles suspended in the aqueous portion.  The casein molecules are held together by calcium phosphate ions.  “Aromatic molecules [nonpolar]” are dissolved in the fat droplets about a few micrometers in diameter while the vitamins, lactose and other sugars, mineral salts, and other proteins are dissolved in the aqueous liquid surrounding the micelles.

·         The fat portion is constituted by triglycerides containing about 500 different fatty acid residues resulting in more than several thousand types of triglyceride.

·         Because of the diversity of substances in butter, its melting point ranges from -50 C to 40 C:

o   -50 C to 10 C MP: triglycerides with fatty acid residues containing short carbon chains and multiple double bonds [unsaturated]

o   10 C to 20 C MP:  triglycerides with fatty acids containing a single double bond or a short chain

o   20 C to 40 C MP: triglycerides with saturated fatty acids

·         To attempt to separate the different types of triglycerides, the researchers conducted a slow crystallization process, isolating the different components that solidify at the same temperature range one at a time. 

·         To make a more spreadable butter, they then mixed high melting point triglyceride constituents solid at room temperature with low melting point constituents liquid at room temperature.  With the correct proportion between the two, they were able to create a spreadable butter, still considered butter under the law.

LIVER MOUSSE

·         “its aromatic qualities depend on its texture”

·         In an attempt to make liver mousse with lower lipid content, the researchers tested the substitution of starch paste for some of the lipid.  One of the properties tested was meltability.  They found that a 15% starch solution can replace about 2/3 of the lipids without diminishing the overall quality of the mousse.

·         They also found through sensory tests that the perception of fattiness is not correlated with the lipid content.

IN PRAISE OF FATS

·         “Whatever else may be said about them, fats are to be welcomed in cooking.”

·         Fats and oils are essential in cooking:

·         French fries and fritters will not crisp unless cooked in hot oil that reaches a temperature of 200 C

·         Researchers have also found that fats are important components in Maillard reactions and achieving the desired flavor from the reaction of sugar and amino acids

·         Butter starts to have a different smell in the refrigerator because many odorant molecules are soluble in it.  In this capacity, butter is a good medium with which to dissolve herbs in as a flavor carrier and distributor.

MAYONNAISE

·         “The art of mixing oil and water”

·         Mayonnaise is a seemingly homogeneous mixture of vinegar, mustard, egg yolk, and salt but under a microscope it is composed of large droplets dispersed in an aqueous solution of vinegar, mustard, and salt.  The amphiphilic proteins and lecithin (the author refers to this property as tensioactive) in egg yolk help stabilize the oil and water emulsion.

·         The author makes the point that any ingredient that has tensioactive or amphiphilic molecules in theory can help stabilize the oil and water emulsion in “mayonnaise” but without the egg yolk at least at 8%, at least in France, it can no longer be called mayonnaise.

AOILI GENERALIZED

·         “Delicious emulsions that can be made from any vegetable, meat, or fish.”

·         Aioli is an emulsion of water from crushed garlic and olive oil.  Garlic contributes tensioactive molecules that stabilize the oil and water emulsion.

·         Similarly, adding oil to crushed shallots or onions also result in an emulsion because both release tensioactive molecules.

·         Many vegetables can in fact be mixed with oil to make an emulsion.  As the author reasoned, these vegetables contain cells that have cell membranes composed of tensioactive phospholipid molecules.  The author tried this with zucchini and mustard seeds have also been used to make a vinaigrette emulsion with oil.

·         Crushed beef can also release enough tensioactive phospholipid molecules to make an emulsion with oil.

·         Mousses work in the same way as they contain foams which are also stabilized by tensioactive molecules.  Cheese and chocolate mousses are examples.  Cheese contains casein proteins and other tensioactive molecules that can stabilize an air and water layer mixture to form stable foams.

ORDERS OF MAGNITUDE

·         “Dispersed systems make it possible to get a lot from a little”

·         The amount of tensioactive molecules in egg yolk, about 5 grams of proteins and phospholipids, is enough to “cover a football field with a monomolecular layer and when these molecules cover oil droplets whose radius is on the order of a micrometer, as in the case of mayonnaise, they suffice to stabilize several liters of sauce”.

·         Whipped egg white is a mixture of two substances that normally won’t mix, water and air (instead of oil in mayonnaise).  The result is foam instead of an emulsion.  The tensioactive proteins in egg whites stabilize the interface between these two (air is not very soluble in water just like oil).  Order of magnitude calculation estimates that several cubic meters of meringue can be made from a single egg yolk (micrometer scale of foam bubble).  To turn one egg yolk to this much meringue, one has to add more water.  As the size grows however, the less stable the foam becomes because the stability of the foam depends on the viscosity of the liquid which decreases as more water is added.

·         In making flan (like in quiche), an order of magnitude calculation estimates that about a liter of flan (with enough water added) can be made from one egg yolk.

HUNDRED YEAR OLD EGGS

·         “Experiments with acids and bases”

·         Recipes for preserving eggs fall into three classes:  just egg alone, in a basic environment, and in the acidic environment of vinegar.

·         Eggs placed in vinegar:  the calcium carbonate shell first reacts and dissolves in the acid releasing bubbles of carbon dioxide.  The egg begins to swell and the white starts to coagulate as the protein dentatures.  The swelling occurs because the water concentration in vinegar is 95% but only 90% in water.  Acetic acid molecules can permeate the coagulated layer causing the solute concentration to further increase inside the egg while the egg proteins cannot diffuse to the vinegar solution.  [I WILL USE THIS AS A 30A, 31, AND 1A DEMO]

·         Eggs placed in caustic soda (sodium hydroxide):  the egg white initially coagulates. Then, a nauseating sulfurous gas is released and the egg turns clear again.  The base dissociates the proteins after first causing them to precipitate.  Ash [mostly potassium hydroxide] and lime are basic but have lower pH levels and do not cause the same immediate and dramatic chemical transformation as sodium hydroxide [concentration dependent of course].

SMOKING SALMON

• “Sugar and an electrical field can be used to accelerate smoking.”
• In this method developed by French researchers the processes of osmosis and electrostatic smoking are used to shorten the time it takes to create smoked salmon without sacrificing flavor.
• Salting, drying, and smoking are all food preparation processes wherein as much water is removed from the food stuff to prevent the growth or further proliferation of microorganisms.  With modern refrigeration techniques, less salt can be used but the food must be kept within 0 and 2 C.
• In the new method:
•  Salting and drying: a solution of 10-30% sugar and 70-90% salt is used.  Less salt permeates the flesh while the high solute particle concentration outside causes water to enter the flesh.  Because sugar molecules are too big to enter the flesh (while keeping the colligative concentration high), there is still a net flow of water out of the fish flesh without too much salt entering the flesh.  Overall, fish filets lose about 10% of water when immersed in a solution containing 350 g salt and 1900 g sugar per liter of water.
• Smoking “without fire”:  Smoke is created by pyrolysis (dry heating) of sawdust.  The smoke is then injected into the chamber containing the salted and dried fish filet at a temperature of 40 C.  At this temperature, carcinogenic aromatic polycyclic hydrocarbons are condensed and removed.  The smoke and the fish filet are subjected to several tens of thousands of volts; the electric potential “impress upon” the fish filet the smoke particles that impart the flavor.  The process takes 15 minutes rather than 3.5 hours.

METHODS AND PRINCIPLES

• “On the invention of new recipes”
• In this chapter, the author makes the point that our current cooking methods are still very much like the traditional cooking methods passed on in the last several hundred years.
• Cooking, transformation of food substance using heat, has always been done through conduction; the only thing that has changed is the material used to transport the heat.  Ways that heat can be transferred to the food: 
• contact with a hot solid:  e.g. stones heated by embers, cast iron plate heated by fire, inside a layer of heated salt, in a mold heated by fire or placed in an oven
• hot liquid:  e.g., meat in boiling water, poaching in sauces, frying in oil
• hot air:  e.g., dry heated air (usually above 100 C) in roasting, heated moist air in braising or steaming
• Use of electromagnetic radiation:  indirect transmission of heat through infrared rays using a laser, for example, used in classic French cuisine, high frequency visible rays, microwave
• Acids can also be used to cook food by denaturing proteins as in seviche.
• This chapter presents a table listing all the possible methods of cooking food which can be used to design double cooking methods.

PURE BEEF

• “A textural additive for restructuring meats.”
• In this chapter, the author looks at ways that the meat industry has tried to restructure leftover meat cuts by looking at the chemical and structural composition of meat.  Previously, they have used, for example, sodium alginate (a gelatinizing substance extracted from algae) to enhance the binding power to “restore cohesiveness to destructured” meat pieces. However, the addition of the sodium alginate binder prevents these processing industries to call he restructured product beef.
• Researchers have looked at sourcing these binding additives from the leftover meat itself.  In particular, researchers have looked at myosin in the lab as a possible binding agent.
• Meat muscle is composed of three different types of proteins:  myofibrillary proteins, sarcoplasmic proteins, and connective tissue proteins.
• Myosin is the principal protein of the myofibrillary class.  Its thick fibers combine with actin in the presence of calcium ions and adenosine triphosphate (ATP, energy fuel) to execute muscle contraction.
• Myosin has better gelatinizing effects than actin, examples of which are used in preparing cooked hams, pates, sausages, etc.
• Different myosin solutions prepared from two different types of muscles and at different concentrations were studied for their thermal gelatinization properties.  Some findings:
• Gelatinization occurred even at very low myosin concentrations of 0.1 – 0.5%.
• The firmness of the gel formed is strongly directly correlated with myosin concentrations.
• The firmest gels were found to form from myosin from fast white muscles, at a pH of about 5.8, and with salt.
• Gels were firmer if the myosin is extracted just after slaughter.
• These myosin were later found to be suitable for restructuring meat, which when cut into thin pieces, were able to retain their cohesiveness and reduce the loss of juices.

FORTIFIED CHEESES

• “The right bacteria can strengthen the flavor of cheeses”
• Some known chemistry about cheeses:
• The flavor of cheeses primarily develops from the action of microorganisms on different chemical substances in cheese in the process of maturation.
• Proteins are broken down into amino acids, some of which impart unique flavors:  tearic and valine produce compounds that give a cheese note and phenylalanine, tyrosine, and tryptophan are precursors to compounds that give floral and phenolic [?] notes (as they described by trained testers).
• Direct addition of free amino acids did not result in any enhanced flavors
• Addition of lactic bacteria genetically engineered for increased ability to decompose proteins did not produce any measurable changes either.
• A group of researchers concluded later that it must be the transformation of amino acids to flavor [the author uses the word aromatic but I am not sure if he meant the word to refer to aroma or if he is referring to the molecules having an aromatic arrangement of carbon atoms] molecules that limits the development of flavor.
• In the Netherlands, researchers found that adding tearic to lactic bacteria without milk produced a Gouda cheese flavor, identifying the two enzymes responsible for the transformation.
• Other researchers found (in vitro) that lactic bacteria transform certain amino acids to aldehydes and carboxylic acids.  The first step is transamination.  In this step, an amine group is transferred from the amino acid to ketoglutarate producing a keto acid and glutamate (responsible for the umami taste)
• In a study, researchers seeded warm pasteurized milk with lactic bacteria and then added rennet.  The curdled product is then pressed and immersed in a brine enriched with ketoglutarate.  Using trained testers, the transformation of the amino acids was monitored during the aging process.  Findings:
• The odor was weak and few amino acids were dissociated in the control cheeses that did not have the added ketoglutarate.
• The odor of the cheese was increased with the formation of “powerfully aromatic compounds” such as isovalerate from tearic and benzaldehyde [almond flavor?] from phenylalanine in the sample with added ketoglutarate.
• Effects of using genetically modified lactic bacteria into which a gene for producing dehydrogenase glutamate is inserted: 
• transamination occurred at the same rate as samples to which ketoglutarate was added
• more highly “aromatic” carboxylic acids were produced

CHANTILLY CHOCOLATE

• “How to make a chocolate mousse without eggs”
• In this chapter, the author proposes a way to use chocolate to make tearic, with the cocoa butter forming the “cream” base that can then be whipped into the foamy texture of tearic.  Without eggs, however, something else needs to be added to provide the tensioactive molecules needed to stabilize the foam.  These tensioactive molecules can be gelatin (chocolate has some lecithin which is also tensioactive but there is not enough).

EVERYTHING CHOCOLATE

• “How to introduce chocolate into all kinds of pastry.”
• 80% of cocoa butter is composed of triglycerides that contain tearic, tearic, and oleic acid in varying proportions.  Because of this variable composition:
• the melting point for cocoa butter can range from -7 C to 34 C
• 75% of cocoa butter melt between 20 and 34 C
• almost 50% melt between 30 and 34 C
• knowing the chemical composition and the melting point temperatures provide information for how the chocolate composition can be modified to target a certain melting point temperature for various uses.

PLAYING WITH TEXTURE

• “Gelatinizing emulsions produces a new kind of chocolate cake”
• The author begins the chapter by saying, “Emulsions are an inexhaustible source of culinary discoveries”.
• Variations on mayonnaise, a classic emulsion:
• Yolkless mayonnaise uses egg whites to provide the tensioactive molecules needed to stabilize the oil and water emulsion.  Egg white contains albumen which is 90% water and 10% proteins.
• Eggless mayonnaise can be made by using gelatin to provide the tensioactive molecules.

CHRISTMAS RECIPES

• “A few ideas for modernizing holiday meals”
• Adding ethyl alcohol or ethanol to egg white denatures the protein and, in essence, cooks the egg white.  But ethanol alone does not taste very good. The author suggests using a flavored alcoholic beverage such as plum brandy to make an egg dish.
• Transformation taking place in turkey meat flesh as the temperature increases:
• 40 C—proteins unfold, become denatured, and the meat loses its transparency
• 50 C – collagen fibers contract
• 55 C – myosin coagulates and the collagen begins to dissolve
• 66 C – sarcoplasmic proteins making up collagen coagulate
• 79 C – actin coagulates
• the author suggests cooking different parts of turkey meat at different temperatures to produce meats with different textures.
• The author makes other suggestions for unique cooking innovations: using fructose instead of shallots in caramelizing for the French dish chavignol.

THE HIDDEN TASTE OF WINE

• “Adding enzymes to grape juice releases its flavors”
• Grapes contain in great amounts terpenic glycosides which do not contribute much to flavor as much as the odorant volatile molecules belonging to the class of terpenols: linalool, geraniol, nerol, citronellol, alpha-terpineol, linalool oxides, and terpenic polyols.
• Terpenic glycosides are terpenol molecules attached to sugars.   Researchers looked into whether dissociating terpenic glycosides could result in the dissociated terpenols and sugars “intensifying” the “aromatic quality” of wine.
• 34 commercially developed enzymatic preparations including pectinases, cellulases, and hemicellulases were tested in their ability to hydrolyze terpenic glycosides.  Findings:
• 5 enzymes all containing beta-glucopyranosidase and alpha-rhamnopyranosidase or alpha-arabinofuranosidase resulted in producing either linalool or geraniol.
• In vitro tests of the same five enzymes resulted the release of not just the desired odorant terpenols but also norisoprenoids, volatile phenols, and benzylic alcohol, “all compounds with very low perception thresholds and an agreeable smell”.
• The grape’s own glucosidase is ineffective in glycosidic hydrolysis because it is not stable and active at the high level of acidity in must and in wine.
• Plant enzymes hydrolyze only the glycosides of primary alcohols such as geraniol, nerol, and citronellol [LOOK UP STRUCTURES TO CONFIRM].
• Only 2 of the enzymes tested were able to hydrolyze the beta-glycosides of tertiary alcohols such as linalool and alpha-terpineol. [LOOK UP STRUCTURES TO CONFIRM]

TELEOLFACTION

• “Waiting for a new form of telecommunication”
• The binding of odorant and sapid molecules to receptor cells in the nose and mouth is what produces gustatory and olfactory sensations.  In this chapter, the author presents some ideas proposed for methods by which odor, flavor, taste, etc. can be telecommunicated
• By means of deciphering, encoding, and sending electrical signals (by means of electrodes) to the brain that produce the desired gustatory and olfactory sensations.
• Analyzing mixtures of odorant and taste molecules and associating them with selected stimuli than can be sent electronically as encoded information.  Upon receipt, the relevant molecules can be combined to reproduce the same sensation.
• The author also delves into new technologies that act as “artificial noses”:
• Mass spectrometry, a very sensitive spectrometric instrument that can detect and produce a signal even for very low concentrations of compounds, producing a unique fingerprint spectrum representing the different molecules making up the mixture of odorant and taste molecules.
• Selective adsorption of odorant and taste molecules on doped semiconductors, producing a distinctive electronic signature even for very low concentration molecules.

THE END OF PART IV AND THE BOOK