MOLECULAR GASTRONOMY: Part I - Secrets of the Kitchen

PART ONE:  SECRETS OF THE KITCHEN

In Part 1, the author devotes mini-chapters first to explore the validity of tradition cookbook recipe tips and instructions and, second, to propose a science-based explanation either based on published studies or by conducting actual experiments.  Some of the more interesting observations and results are listed below:

·         In Making Stock, the author finds that, contrary to traditional recipe instructions, the rate of juice loss by meat is the same regardless of whether it is placed in coldwater first and allowed to boil or it is plunged directly into boiling water.  The author cited an experiment where similar size meat pieces were cooked for an hour, one starting out in cold water the other in boiling water.  After one hour, he found no discernible difference between the mass lost due to liquid loss.

·         In Hardboiled Eggs, the author explores a method to keep the yolk centered after cooking.  The yolk is an emulsion of water and lipids which are less dense than water.  The white is composed of mostly water and proteins and therefore more dense than the yolk.  When left in one position while cooking, the less dense yolk gradually rises to the top.  Rolling the egg around while cooking will keep the yolk centered.

·         Egg white is 90% water and about 10% proteins [by mass, I assume].  Upon heating, the proteins unfold and eventually denature trapping the water and forming a gel-like structure.  The extent of unfolding and denaturation and loss of water determines whether the cooked egg white will remain runny or rubbery.  Most of the proteins in the egg start to coagulate at a temperature below the boiling point of water at 68 C.   In the egg white, the ovotransferrin protein starts to coagulate at 62 C while proteins in the egg yolk remain “liquid” and does not start to harden until 68 C.  Above these temperatures, more water starts to leave the yolk and the egg white resulting in a harder and more rubbery texture. 

·         Quiches, Quennelles, and Puff Pastries:  The puffing up process is mostly due to vaporized water and only little due to expansion of egg.

·         Echaudes and Gnocchi:  In this chapter, the author addresses the question “Is it true that when they float to the surface of the cooking water they are done?”  To answer this question, the author first investigated what makes them rise in the first place and discovered that it must be trapped steam or water vapor that causes its density to decrease causing it to float.  The author then placed two different size dough pieces in water and found that at the point that they have risen to the surface, the smaller dough piece has a higher temperature than the larger dough piece suggesting cooking times that depend on the size and not necessarily signaled by its rising to the surface.

·         The Well-Leavened Souffle:  “Water evaporates upon contact with the heated sides of the ramekin and causes the soufflé to rise.”  Contradictory to common belief, only 20% of the rise in volume of soufflés is due to the expansion of trapped air.  The majority is due to evaporation of water in the milk and eggs that causes the increase in pressure and subsequent rise in volume.  Puncture a soufflé and steam can be seen rising off the top.  Another factor that affects the rising of a soufflé is the degree to which the eggs were whipped. Stiffer egg whites cause more rising because of its better ability to trap the vaporized water within the protein matrix.

·         Quenelles and Their Cousins:  Quenelles are a “small seasoned ball of pounded meat or fish (OAD)”.  In this chapter, the author seeks to find out the best way to cook quenelles, best meaning “the greatest possible tenderness with sufficient firmness”.  Both of these properties rely on the type of gel that forms from the meat or fish protein.  The firmness of a gel is determined by the following parameters:  storage time of the solution, rate of heating, maximum cooking temperature, protein concentration, acidity, and salt concentration.  Some findings that correlate with optimal firmness (firmness was measured using a penetrometer but there was no mention of the quantitative definition using this instrument only that these parameters led to “sufficiently firm and elastic gel” from trout)

o   The maximum protein concentration for optima firmness is about 10 g/L

o   Heating within the temperature range of 70 – 80 C

o   Heating rate of 0.25 C per minute

o   A pH of about 5.6 (the ionization states of the acidic and basic side groups of the amino acids determine bonding of the gel with water)

·         Fondue:  The author tries to find out the best wine and cheese for a non-flapping fondue.  A fondue is just cheese heated with wine.  A “successful fondue is necessarily an emulsion a dispersion of microscopic droplets of fat in water solution”.  Some interesting chemical descriptions:

o   Milk is an emulsion of an aqueous phase, casein proteins, and fast.  The casein are held together by calcium salts (especially phosphates) forming micelles that surround fats with kappa-caseins on the surface interacting with the aqueous phase.

o   The rennet added in cheesemaking contains an enzyme that “detaches a part” of the casein causing the micelles in milk emulsion to aggregate into a gel trapping the fats.

o   WELL-AGED CHEESE:  Peptidases in well-aged cheese help in pre-breaking up of the casein and other proteins into smaller fragments that are more easily dispersed in water.  These proteins stabilize the emulsion process with water causing a smoother, more viscous mixture (“which is why a Camembert fondue will always turn out well”).

o   WINE:  Dry, very acidic, and fruity wines that contain high concentrations of tartaric, malic, and citric acids because their anions are good at chelating calcium ions which help separate the casein micelles, releasing constituent proteins that help stabilize the emulsion.

o   SODIUM BICARBONATE:  Adding this helps in deprotonating the acids in wine to release the basic anions that can chelate more calcium ions.

·         Roasting Beef:  “Allowing meat to rest after cooking causes the juices that have been retained in its center to flow outward to the dry periphery.”

o   At 70 C, ferrous ion in myoglobin is oxidized to ferric iron which turns the meat “pink”. At 80 C, the cell walls break down releasing myoglobin which reacts with oxygen and turns it brown.

·         Seasoning Steak:  In this chapter, the author tries to find out whether it makes a difference to add salt before, during, or after grilling steak.  No discernible differences as far as the retention of water due to osmosis.  During cooking, using x-ray analysis, they found that salt sprinkled on the surface actually “passes out of the meat during cooking”.

·         Wine and Marinades: The author tests whether red wine or white wine marinade results in a more tender beef.  Red wine was the winner.  They tested the hypothesis that the higher concentration of polyphenols which react with protein which presumably leads to a more tender meat.  Using a solution containing tannic acid representing polyphenols, organic acids, and ethanol, they were able to replicate the same result as the red wine.  It is thought that the polyphenols reacting with the protein create a hardened surface that can retain more juices.

·         Color and Freshness:  The author tests different ways to prevent discoloration in fruits and vegetables.

o   Darkening of fruit when exposed to air is caused by the oxidation of polyphenols to quinones by the action of the enzyme polyphenol oxidase producing brown pigment.  The ascorbic acid in lemon and other citrus fruits help reduce the browning because the ascorbic acid is more easily oxidized protecting the polyphenols.  In addition, he following three methods are used to slow the browning process:

§  Refrigeration slows down the polyphenol oxidase enzyme

§  Pasteurization denatures the polyphenol oxidase (may degrade the fruit)

§  Vacuum packing protects prevents contact with oxygen

§  Storing in a nitrogen or carbon dioxide atmosphere removes oxygen (done in food processing industry)

o   Good question for 1B.  Give the following passage to student and ask student to identify what part of the rate equation is affected by each of the techniques given to prevent browning:  “Various methods are used to prevent the darkening of vegetables and fruits that have been sliced or chopped—often their lot in the kitchen. Freezing and refrigeration slow but do not prevent the action of enzymes. Pasteurization, a more radical procedure that inactivates the enzymes, cannot be applied to all fruits and vegetables, for it often degrades their texture and color. Finally, vacuum packing—sealing fruits and vegetables in containers from which the oxygen has been drawn out—prevents the appearance of brown compounds; alternatively, nitrogen and carbon dioxide atmospheres sometimes are used in the food processing industry.”

o   Other chemical ways of reducing the browning:

§  A small amount of naturally occurring salicylhydroxamic acid inhibits the formation of polyphenol oxidase in apples and potatoes.

§  Bentonite, a protein-absorbent clay, also inhibits the enzyme.

§  Gelatin, activated charcoal, and polyvinyl pyrrolidone have been used to extract phenols from wine and beers but can affect the properties of these drinks

§  Sulfites bond with quinones and converts them to colorless sulfoquinones.  In wines, sulfur dioxide and sodium metabisulfite are used to prevent darkening.

§  Cysteine and its derivatives, other natural compounds in honey, figs, and pineapple and synthetic compounds are being studied (at the time of the book’s writing) as well.

·         Softening Lentils:  In this chapter, the author looks at the role of bicarbonate in cooking lentils. 

o   Effect of pH: To do this, the author carried out an experiment in which he cooked lentils in three identical pans filled with distilled water, basic water using bicarbonate, and acidic water using vinegar.    The results:  distilled water – lentils just cooked, acidic water – lentils hard as pebbles, and basic water – lentils falling apart.  The hardness of lentils is primarily due to the pectin “glue” holding the tissue together.  To soften this tissue, the pectin must come apart.  Pectin is a protein containing carboxylate side groups  In an acidic solution, these carboxylate groups are protonated and neutral which removes the repulsive forces between the chains.  In a basic solution, the carboxylate groups are deprotonated and negatively charged causing repulsive forces that help keep the pectin chains apart causing tissue deterioration.

o   Effect of calcium ions in hard water:  Experiment done cooking lentils in distilled water (cooked) and in water that has calcium ions added (still hard).  The calcium ions are thought to bind phytic acid molecules and pectin molecules which causes more cohesion.  Monovalent sodium ions do not have the same effect.  Temperature also affects the cooking process, not surprisingly the cooking time is inversely proportional to the temperature.  Plotted data on firmness as function of time, however, shows an elbow which suggests that a rapid preliminary softening as water seeps into the beans followed by a slower rate associated with the gelling of the starch.  Lastly, it has been shown that at temperatures above 86 C, there are more lentils that have fallen apart and those that have softened but retained their form.

·         Souffleed Potatoes:  How to avoid the greasiness of deep frying in making this dish is the topic for this chapter.  Souffleed potatoes are puffed up slices of potatoes deep fried in oil.  The puffing up process results from the vaporization of water in the potatoes.  Potatoes are about 78% water and 17% starch (by mass?) which is denser than oil and water.  When water inside becomes steam, its pressure prevents oil from seeping inside.  The lowered density causes it to rise in the oil.  More oil will adhere to the cooked potato when the surface is rough, the oil is reused, and oil is not removed from the surface (as the water vapor condenses, oil will get sucked inside).

·         Preserves and Preserving Pans:  In this chapter, the author looks at the why unplated copper pans are recommended for cooking fruit preserves.   Fruits used for making jams and preserves can be as acidic as pH 3. 

o   Effect of copper (II) ions:  When cooked in an unplated copper pan, the copper metal is oxidized into copper (II) ions.  Based on an experiment carried out by the author, addition of copper (II) salt results in a firmer preserve gel as the copper (II) ions are thought to help the pectin protein molecules to bond with each other forming a stronger and tighter matrix for the trapped liquid.

o   Effect of other metal ions:  silver salts cause raspberries to turn a little bit white, copper ions cause them to turn red-orange, and tin ions cause a purple tinge.

·         Saving a Crème Anglaise:  To prevent curdling in crème anglaise and similar preparations, add a pinch of flour. The starch molecules in flour swell as they absorb water and release amylase chains which get in the way of protein movement thus stabilizing them and preventing aggregation into clumps.

·         Grains of Salt:  It was found that:  water will take the same amount of time to boil (within experimental precision) with or without salt, meat will lose and absorb about the same amount of liquid (+/- 1 gram, based on mass before and after measurements) regardless of whether the water is salted or not, no effects on eggshells either, nor on vegetables as the surface is covered with a waxy layer that prevents osmosis.

·         Of Champagne and Teaspoons:  The author set out to test whether inserting a teaspoon inside the neck of a bottle prevents bubbles from escaping.  Experiments were done by an interprofessional committee on champagne.  Degassing was measured using weight loss for three different samples under the same conditions:  corked, open, and with a teaspoon in the neck. 

o   Pressure measurement results:  only 10% drop in the pressure for the corked bottles compared to 50% for both the open bottles and the bottles with a teaspoon. 

o   Mass measurement results:  identical mass loss for open bottles and the bottles with a teaspoon and zero for corked bottles. 

o   These experiments showed that the extent of degassing depend on: pressure above the surface of the liquid, the amount of suspended particles, and the roughness of the inner surface of the bottle [both suspended particles and rough surface acting as “nucleation” point for bubbles?]

·         Coffee, Tea and Milk:  How best to cool down a hot beverage?  Heat transfer can take place by convection, conduction, or radiation.  Radiation of heat by a body per unit time is proportional to the 4^th power of the body’s absolute temperature (Stefan’s law): the hotter the coffee, the more heat is radiated per unit time.  Some experimental results: 

o   Using the addition of 7.5 cL room-temperature milk to cool down 20 cL of 100 C coffee:

o   10 minutes to go from 100 C to 55 C.

o   4 minutes to 55 C if milk is added only after coffee has cooled down to 75 C

o   Placing a teaspoon to facilitate heat radiation: no significant effect.

o   Stirring has two effects: 1) the movement of liquid exposes more surface area for heat transfer to cold air to take place and 2) accelerates the expulsion of the higher kinetic energy molecules (they are not recycled back into the liquid) lowering the average kinetic energy and thus the temperature.

o   Blowing is more efficient than stirring:  6 C/minute loss versus 3.5 C/minute loss for stirring.

MOLECULAR GASTRONOMY: Introduction

INTRODUCTION TO THE ENGLISH LANGUAGE EDITION

·         “…Generally speaking, it is correct to say that food science deals with the composition and structure of food, and molecular gastronomy deals with culinary transformations and the sensory phenomena associated with eating.”

·         Two prominent chemists, Count Rumford and Justus von Liebig, did some experimental work related to the chemistry of food and cooking.  Another well-known name in Chemistry that did some work related to food chemistry is Louis Camille Maillard, after whom the Maillard reaction was named, carried out the experiments on reactions involving glycerol and sugars with amino acids.  The Maillard reactions taking place in cooking give grilled meats, bread crust, roasted chocolate, and many other foods their characteristic smells and flavors.

·         One of the primary motivators for the author conducting cooking science workshops and publishing this book is his belief that “whoever understands the reasons for the results he or she obtains in the kitchen can improve on them”.

MOLECULAR GASTRONOMY: Introduction and Part I

INTRODUCTION TO THE ENGLISH LANGUAGE EDITION

• “…Generally speaking, it is correct to say that food science deals with the composition and structure of food, and molecular gastronomy deals with culinary transformations and the sensory phenomena associated with eating.”
• Two prominent chemists, Count Rumford and Justus von Liebig, did some experimental work related to the chemistry of food and cooking.  Another well-known name in Chemistry that did some work related to food chemistry is Louis Camille Maillard, after whom the Maillard reaction was named, carried out the experiments on reactions involving glycerol and sugars with amino acids.  The Maillard reactions taking place in cooking give grilled meats, bread crust, roasted chocolate, and many other foods their characteristic smells and flavors.
• One of the primary motivators for the author conducting cooking science workshops and publishing this book is his belief that “whoever understands the reasons for the results he or she obtains in the kitchen can improve on them”.



PART ONE:  SECRETS OF THE KITCHEN

• In Part 1, the author devotes mini-chapters first to explore the validity of tradition cookbook recipe tips and instructions and, second, to propose a science-based explanation either based on published studies or by conducting actual experiments.  Some of the more interesting observations and results are listed below:
• In Making Stock, the author finds that, contrary to traditional recipe instructions, the rate of juice loss by meat is the same regardless of whether it is placed in coldwater first and allowed to boil or it is plunged directly into boiling water.  The author cited an experiment where similar size meat pieces were cooked for an hour, one starting out in cold water the other in boiling water.  After one hour, he found no discernible difference between the mass lost due to liquid loss.
• In Clarifying Stock,
• In Hardboiled Eggs, the author explores a method to keep the yolk centered after cooking.  The yolk is an emulsion of water and lipids which are less dense than water.  The white is composed of mostly water and proteins and therefore more dense than the yolk.  When left in one position while cooking, the less dense yolk gradually rises to the top.  Rolling the egg around while cooking will keep the yolk centered.
• Egg white is 90% water and about 10% proteins [by mass, I assume].  Upon heating, the proteins unfold and eventually denature trapping the water and forming a gel-like structure.  The extent of unfolding and denaturation and loss of water determines whether the cooked egg white will remain runny or rubbery.  Most of the proteins in the egg start to coagulate at a temperature below the boiling point of water at 68 C.   In the egg white, the ovotransferrin protein starts to coagulate at 62 C while proteins in the egg yolk remain “liquid” and does not start to harden until 68 C.  Above these temperatures, more water starts to leave the yolk and the egg white resulting in a harder and more rubbery texture.
• Quiches, Quennelles, and Puff Pastries
• Echaudes and Gnocchi:  In this chapter, the author addresses the question “Is it true that when they float to the surface of the cooking water they are done?”  To answer this question, the author first investigated what makes them rise in the first place and discovered that it must be trapped steam or water vapor that causes its density to decrease causing it to float.  The author then placed two different size dough pieces in water and found that at the point that they have risen to the surface, the smaller dough piece has a higher temperature than the larger dough piece suggesting cooking times that depend on the size and not necessarily signaled by its rising to the surface.
• The Well-Leavened Souffle:  “Water evaporates upon contact with the heated sides of the ramekin and causes the soufflé to rise.”  Contradictory to common belief, only 20% of the rise in volume of soufflés is due to the expansion of trapped air.  The majority is due to evaporation of water in the milk and eggs that causes the increase in pressure and subsequent rise in volume.  Puncture a soufflé and steam can be seen rising off the top.  Another factor that affects the rising of a soufflé is the degree to which the eggs were whipped. Stiffer egg whites cause more rising because of its better ability to trap the vaporized water within the protein matrix.
• Quenelles and Their Cousins:  Quenelles are a “small seasoned ball of pounded meat or fish (OAD)”.  In this chapter, the author seeks to find out the best way to cook quenelles, best meaning “the greatest possible tenderness with sufficient firmness”.  Both of these properties rely on the type of gel that forms from the meat or fish protein.  The firmness of a gel is determined by the following parameters:  storage time of the solution, rate of heating, maximum cooking temperature, protein concentration, acidity, and salt concentration.  Some findings that correlate with optimal firmness (firmness was measured using a penetrometer but there was no mention of the quantitative definition using this instrument only that these parameters led to “sufficiently firm and elastic gel” from trout)
o The maximum protein concentration for optima firmness is about 10 g/L
o Heating within the temperature range of 70 – 80 C
o Heating rate of 0.25 C per minute
o A pH of about 5.6 (the ionization states of the acidic and basic side groups of the amino acids determine bonding of the gel with water)
• Fondue:  The author tries to find out the best wine and cheese for a non-flapping fondue.  A fondue is just cheese heated with wine.  A “successful fondue is necessarily an emulsion a dispersion of microscopic droplets of fat in water solution”.  Some interesting chemical descriptions:
o Milk is an emulsion of an aqueous phase, casein proteins, and fast.  The casein are held together by calcium salts (especially phosphates) forming micelles that surround fats with kappa-caseins on the surface interacting with the aqueous phase.
o The rennet added in cheesemaking contains an enzyme that “detaches a part” of the casein causing the micelles in milk emulsion to aggregate into a gel trapping the fats.
o WELL-AGED CHEESE:  Peptidases in well-aged cheese help in pre-breaking up of the casein and other proteins into smaller fragments that are more easily dispersed in water.  These proteins stabilize the emulsion process with water causing a smoother, more viscous mixture (“which is why a Camembert fondue will always turn out well”).
o WINE:  Dry, very acidic, and fruity wines that contain high concentrations of tartaric, malic, and citric acids because their anions are good at chelating calcium ions which help separate the casein micelles, releasing constituent proteins that help stabilize the emulsion.
o SODIUM BICARBONATE:  Adding this helps in deprotonating the acids in wine to release the basic anions that can chelate more calcium ions.
• Roasting Beef:  “Allowing meat to rest after cooking causes the juices that have been retained in its center to flow outward to the dry periphery.”
o At 70 C, ferrous ion in myoglobin is oxidized to ferric iron which turns the meat “pink”. At 80 C, the cell walls break down releasing myoglobin which reacts with oxygen and turns it brown.
• Seasoning Steak:  In this chapter, the author tries to find out whether it makes a difference to add salt before, during, or after grilling steak.  No discernible differences as far as the retention of water due to osmosis.  During cooking, using x-ray analysis, they found that salt sprinkled on the surface actually “passes out of the meat during cooking”.
• Wine and Marinades: The author tests whether red wine or white wine marinade results in a more tender beef.  Red wine was the winner.  They tested the hypothesis that the higher concentration of polyphenols which react with protein which presumably leads to a more tender meat.  Using a solution containing tannic acid representing polyphenols, organic acids, and ethanol, they were able to replicate the same result as the red wine.  It is thought that the polyphenols reacting with the protein create a hardened surface that can retain more juices.
• Color and Freshness:  The author tests different ways to prevent discoloration in fruits and vegetables.
o Darkening of fruit when exposed to air is caused by the oxidation of polyphenols to quinones by the action of the enzyme polyphenol oxidase producing brown pigment.  The ascorbic acid in lemon and other citrus fruits help reduce the browning because the ascorbic acid is more easily oxidized protecting the polyphenols.  In addition, he following three methods are used to slow the browning process:
 Refrigeration slows down the polyphenol oxidase enzyme
 Pasteurization denatures the polyphenol oxidase (may degrade the fruit)
 Vacuum packing protects prevents contact with oxygen
 Storing in a nitrogen or carbon dioxide atmosphere removes oxygen (done in food processing industry)
o Good question for 1B.  Give the following passage to student and ask student to identify what part of the rate equation is affected by each of the techniques given to prevent browning:  “Various methods are used to prevent the darkening of vegetables and fruits that have been sliced or chopped—often their lot in the kitchen. Freezing and refrigeration slow but do not prevent the action of enzymes. Pasteurization, a more radical procedure that inactivates the enzymes, cannot be applied to all fruits and vegetables, for it often degrades their texture and color. Finally, vacuum packing—sealing fruits and vegetables in containers from which the oxygen has been drawn out—prevents the appearance of brown compounds; alternatively, nitrogen and carbon dioxide atmospheres sometimes are used in the food processing industry.”
o Other chemical ways of reducing the browning:
 A small amount of naturally occurring salicylhydroxamic acid inhibits the formation of polyphenol oxidase in apples and potatoes.
 Bentonite, a protein-absorbent clay, also inhibits the enzyme.
 Gelatin, activated charcoal, and polyvinyl pyrrolidone have been used to extract phenols from wine and beers but can affect the properties of these drinks
 Sulfites bond with quinones and converts them to colorless sulfoquinones.  In wines, sulfur dioxide and sodium metabisulfite are used to prevent darkening.
 Cysteine and its derivatives, other natural compounds in honey, figs, and pineapple and synthetic compounds are being studied (at the time of the book’s writing) as well.
• Softening Lentils:  In this chapter, the author looks at the role of bicarbonate in cooking lentils.
o Effect of pH: To do this, the author carried out an experiment in which he cooked lentils in three identical pans filled with distilled water, basic water using bicarbonate, and acidic water using vinegar.    The results:  distilled water – lentils just cooked, acidic water – lentils hard as pebbles, and basic water – lentils falling apart.  The hardness of lentils is primarily due to the pectin “glue” holding the tissue together.  To soften this tissue, the pectin must come apart.  Pectin is a protein containing carboxylate side groups  In an acidic solution, these carboxylate groups are protonated and neutral which removes the repulsive forces between the chains.  In a basic solution, the carboxylate groups are deprotonated and negatively charged causing repulsive forces that help keep the pectin chains apart causing tissue deterioration.
o Effect of calcium ions in hard water:  Experiment done cooking lentils in distilled water (cooked) and in water that has calcium ions added (still hard).  The calcium ions are thought to bind phytic acid molecules and pectin molecules which causes more cohesion.  Monovalent sodium ions do not have the same effect.  Temperature also affects the cooking process, not surprisingly the cooking time is inversely proportional to the temperature.  Plotted data on firmness as function of time, however, shows an elbow which suggests that a rapid preliminary softening as water seeps into the beans followed by a slower rate associated with the gelling of the starch.  Lastly, it has been shown that at temperatures above 86 C, there are more lentils that have fallen apart and those that have softened but retained their form.
• Souffleed Potatoes:  How to avoid the greasiness of deep frying in making this dish is the topic for this chapter.  Souffleed potatoes are puffed up slices of potatoes deep fried in oil.  The puffing up process results from the vaporization of water in the potatoes.  Potatoes are about 78% water and 17% starch (by mass?) which is denser than oil and water.  When water inside becomes steam, its pressure prevents oil from seeping inside.  The lowered density causes it to rise in the oil.  More oil will adhere to the cooked potato when the surface is rough, the oil is reused, and oil is not removed from the surface (as the water vapor condenses, oil will get sucked inside).

Next book? Life's Ratchet or Molecular Gastronomy

I started two books yesterday to follow Stuff Matters which I have finished.

I read 40 pages of Life's Ratchet, authored by a physicist turned biophysicist.  So far, there has not been a lot of chemistry as the author explores answers to the question "What is life?".  The premise of the book, however, is good promising to give accessible explanations to how random motions get filtered through molecular machines that act as a ratchet, organizing these random steps toward one cohesive, purpose-filled action.

I read 100 pages of Molecular Gastronomy by Herve This, a popular TV show persona and also the first person to have received a Ph.D. in Molecular Gastronomy.  The book starts off explaining the difference between food science and molecular gastronomy.  He devotes each of the first few chapters to a particular food or type of food for which he analyses the validity of instructions for preparation and their given explanation on the basis known chemical and physical principles.  So far, not much chemistry, some physics, in varying depths of coverage.

STUFF MATTERS: Annotation

Miodownik, M.  Stuff Matters: Exploring the Marvelous Materials that Shape Our Man-made World.  London: Penguin, 2013.

This book, 272 pages in length (paperback version), provides several examples of material to illustrate the special relationship between human and civilization and material use: their discovery and the drive it took to get there, their uses, and their cultural significance. In the introduction, he points out that our civilization owes much to material wealth, so much so that different historical epochs have been named after the material that facilitated its human progress.  In each chapter devoted to a certain material, the author tries to “uncover the desire that brought it into being, decode(s) the materials science behind it, marvel(s) at our technological prowess in being able to make it, but most of all, tr(ies) to express why it matters”.   Many of the interesting stories and descriptions from this book are a good source of examples that I can use in my classes.  Each chapter is rich with anecdotes, metaphors, analogies, and interesting facts useful for engaging students' interest in the chemistry behind the simplest things we take for granted.  Material after material, chapter after chapter, the author clearly makes the point that each one has an interesting human story to tell and the adjective that the author gives as a title for each one represents his personal relationship with the material world.  The author is very well versed in the science but also has the depth and breadth of analysis to illustrate the cultural and human impact of each type of material, capturing the essence of, not just what motivates humans to explore creative and practical uses for natural materials and invent new ones, but also what these materials motivate in humans to achieve.

The author is materials scientist who received his Ph.D. in Materials Science at Oxford University.

STUFF MATTERS: Chapters 9-11 (the end)

CHAPTER 9: REFINED
• On ceramics
• Some properties of ceramics noted by the author:
o Relatively chemically inert and not degraded by UV [because it does not absorb UV?]
o Impervious to scratching
o Non-stick surface except for tannins and a few others which can be removed by bleach or acid
o Material strength
• Because of these properties, the author thinks that “for real sustainability, we must look to ceramics”.
• Because of its high melting point ceramics cannot be melted and poured unlike metals, plastics, and glass.
• Clay is a mixture of small mineral crystals and water.  Terra cotta is made from clay containing mostly quartz, alumina, iron hydr/oxide crystals (thus the red color).
• FIRING OF CERAMICS:  In turning clay into pottery, it is first heated at high temperatures causing the water to evaporate.  Further heat applied is absorbed by atoms in the crystal resulting in more kinetic energy.  Atoms on the surface of crystals with extra nonbonded electrons “jump” back and forth between unoccupied spots in adjacent crystals.  Eventually, they form stable bonds to another atom on the surface of the next crystal, forming bridges between the crystals until the mixture achieves the more cohesive structure of a single material.  For terra cotta, the temperature required are relatively low and can be provided by a wood fire.
• GLAZING:  In the East, glazing was invented to make the outside surface of ceramic pottery more waterproof.   “Ash” is applied on the surface of the ceramic which then turns into a glass coating after firing. Glazing, however, did not eliminate the issue of porosity which weakens the ceramics and makes them vulnerable to cracking when heated.
• THE MAKING OF PORCELAIN:  Experimentations done by the Chinese during the Eastern Han Dynasty led to the discovery of the use of the white mineral kaolin, which when added to clay along with other minerals like feldspar and quartz, led to a type of white ceramic with vastly improved properties.  This white ceramic did not attain its special properties unless fired to a very hot 1300 Celsius.  This white ceramic, now called porcelain, had the following properties:
o A very smooth surface
o Stronger and tougher than any other known ceramic
o It could be made very thin because of its strength
• In the words of the author, “porcelain came to represent the perfect marriage of technical skill and artistic expression”.  The discovery of porcelain brought much pride to the Han Dynasty that royal dynasties throughout Chinese history came to be associated with different types of imperial porcelain.  As he noted, porcelain was a physical manifestation of “how much more technically advanced the Chinese were than anyone else in the world” during this era.
• In 1704, the British “discovered” the process used by the Chinese to create porcelain which had remained a secret, discovering a local source of kaolin and achieving the high temperature (1350 C) needed to fire the correct mixture to produce, 50 years later, their version of “bone china porcelain”.

CHAPTER 10: IMMORTAL
• On artificial implants
• The material used for body casts (for immobilizing broken parts) (called plaster of Paris) is made by adding water to dehydrated gypsum (hydrated calcium sulfate) and letting it dry and harden like cement.
• AMALGMA DENTAL FILLING:  Amalgam, an alloy composed of tin, silver, and mercury used as dental filling, was invented in 1804.  The mercury in the mixture (acts like a solvent for the other metals?) keeps the alloy liquid at room temperature.  Upon reaction with the other components (the author does not mention what they are), a reaction takes place that causes the entire mixture to harden and mechanically bond to the tooth.
• COMPOSITE RESIN DENTAL FILLING:  This resin composite filling is made from a mixture of transparent plastic and silica powder, which, upon exposure to UV light, hardens into wear-resistant filling the color of natural tooth.
• TITANIUM:  This metal is one of the few metals that can be tolerated by the body for use as structural replacement or screws.  It also is notable for its ability to osseointegrate, forming strong bonds with real bone.  It is strong, light, and chemically inert which makes it an ideal material.  The titanium oxide that forms on its layer helps retain the structural health of the entire metal.
• REPLACEMENT JOINTS:  The internal surfaces of joints are very susceptible to wearing because they are dependent on lubricating fluid and cartilage to prevent damaging friction between bone surfaces due to constant motion and weight-bearing.
• Hip joint replacements using ivory was first attempted in 1891.  Presently, ceramic and titanium are used.  High density polyethylene is used as the artificial cartilage to line the newly drilled pelvis socket as a protection against friction from the mobile titanium ball.  The fit can be made quite perfectly in some cases that the artificial cartilage is not needed.
• TISSUE ENGINEERING:  In the 1960’s, Professor Larry Hench discovered the mineral hydroxyapatite that was found to bond to bone strongly.  They used this material to produce a porous, bioactive “glass” with tiny channels in which osteoblasts (bone cells) embed themselves as they grow new bone, breaking down the bioglass in the process.
• 3-D PRINTING:  This very new technology has been used to manufacture objects using printer technology with metals, glass, plastic, etc. as the “ink”.  In , Professor Alex Seifalian and his team created a 3-D copy of a patient’s windpipe.  They built a scaffolding in which mesenchymal stem cells taken from the patient are embedded.  This was then placed in a bioreactor to grow an exact replica of the windpipe.  Using the patient’s own stem cells to grow the replica windpipe avoids transplant rejection by the body.   Two issues still need to be resolved for this to be a viable transplant process:  1) developing tissue integration for blood supply to the artificial portion and 2) sterilization method that does involve high temperatures (the scaffolding is a polymer that cannot withstand high temperatures).

CHAPTER 11: SYNTHESIS
• Our material world is composed of “complex expressions of human needs and desires” and materials science is the way by which humans try to understand and “master the complexity of the inner structure” of these materials.  “It is no less significant, no less human, than music, art, film, or literature, or the other sciences, but it less well known.”
• This inner structure is not apparent from the sometimes monolithic, homogeneous appearance of many of these materials.  The most fundamental of these inner structures is, of course, the atom but at the larger scales, materials scientist see “dislocations, crystals, fibers, scaffolds, gels, and foams” despite how shiny or cohesive a material may look.
• Useful note:  94 different types of atoms exist naturally on earth.  8 of these make up 98.8% of the mass of the earth (iron, oxygen, silicon, nickel, magnesium, sulfur, calcium, and aluminum), with carbon only making up a trace. All the gold ever mined would fit inside a large house.
• THE IMPORTANCE OF STRUCTURE OVER ATOMIC COMPOSITION FOR DETERMINING PROPERTIES:  The author makes the point that the rarity of technologically useful elements like neodymium or platinum may not turn out to be a big problem because as we have seen in the case of graphite versus diamond, atomic composition is not the only determinant for a material’s properties; structure plays a very significant, sometimes, overriding role.  In this topic, the author offers a simplified explanation of the basis for understanding structure in material:
o “These structures are not arbitrary – you cannot create any structure – but are governed by the rules of quantum mechanics, which treat atoms not as singular particles but as an expression of many waves of probability.  (This is why it makes sense to refer to the atoms themselves as structures, as well as their formation when they bond with one another.)  Some of these structures create electrons that can move, and this results in a material that can conduct electricity.  Graphite has such a structure, and so conducts electricity.  Exactly the same atoms in a diamond but in a different structure do not allow the electrons to move so easily within the crystal, and so diamonds do not conduct electricity.”
• THE MATERIALS SCIENCE DICTUM:  Plumbing the depths of this structure is the primary work of materials scientists:  “It is hard to overestimate the philosophical as well as the technological importance of this dictum of materials science: that knowing the basic chemical composition is not enough to understand materiality.”
• NANOSCALE LEVEL UNDERSTANDING AND MANIPULATION:  These unique characteristics of materials stemming from the atomic composition and structure first make themselves known at the nanoscale level (a nanostructure consists atoms in the hundreds) and “it is manipulations at this scale that will affect their properties”.
• The author gives the following example illustrating that this level of material manipulation has been going on for hundreds of years (they just were not aware of it back then):  “When a blacksmith hits a piece of metal, he or she is changing the shape of metal crystals within it by “nucleating” nanoscale dislocations – in other words, by causing the transfer of atoms from one side of the crystal to the other at the speed of sound.”
• NANOSCALE:  Nanostructures have been manufactured that can collect light and store it as electricity or create light sources or even sense smells.  They can also self-assemble because of strong electrostatic and surface tension forces at this scale (gravity is a weaker force acting on a car). Nanoscale self assembly is already taking place in the molecular machinery of cells.
• MICROSCALE
o THE SILICON CHIP:  The silicon chip is an example of a microscopic size object ten to a hundred times bigger than a nanostructure.  Although they have no moving parts, they use electric and magnetic properties to direct the flow of information.
o BIOLOGICAL CELLS:  Cells also exist at the microscopic level but is composed of hundreds of nanostructures.  [Its operation relies on interactions between these nanostructures.]
o SUGAR CRYSTALS AND COCOA GRAINS IN CHOCOLATE:  Manipulating at this scale allows more control over the texture and taste of chocolate.
o INVISIBILITY SHIELDS:  The design is based on manipulating how microstructures within an object (meta-materials) refract light by designing them with variable refraction indices.  When this object is formed like a shield and wrapped around an object, they can bend light in such a way that the object shielded is not visible from whichever direction it is viewed.
• MACROSCALE:  The atomic scale, nanoscale, and microscale then grow into the macroscale structure of a material.  It is at this level, that all the different underlying structures come together to form a cohesive, strong, smooth, and optically dynamic material.  The author used the example of the touch screen of a tablet or smartphone which appears flawlessly smooth but is in fact composed of tiny pixels of liquid crystals whose colors can change so fast that a movie appears smooth and continuous.  Porcelain is another good illustration of this jump to macroscale.
• MINIATURE SCALE:  Combining the atomic, nano, micro, and microstructures to a size just visible to the naked eye:  hair strand, needle, thread, 12-size font etc.  At this level, regular thread and Kevlar would appear the same.  “It is at this scale that our sense of touch engages with materials.”
• HUMAN SCALE:  The scale at which we can hold stuff in our hands.
• THE REAL CHALLENGE:  To connect structures designed starting from the atomic scale in a way that they can intelligently interact with each other to form a macroscopic human-sized object, wired-up internally with nanoscale electronics that can act as its nervous system.  The author imagines such an object being able to produce its own energy, modulate and distribute where it is needed and repair itself, just like “living materials” like us.   The author points out:
• “One of the biggest questions in science is whether communication between the scales combined with active responses is a sufficient explanation of what makes something alive”.  [This segueways well to the next prospective book on my reading list:  Life’s Ratchet].
• RELATIONSHIP BETWEEN THE LIVING AND THE IMMATERIAL AND MATERIA WORLD:  “What makes us human, though, is not just the physical materiality of our bodies, synthetic or not.  We inhabit an immaterial world, too: the world of our minds, our emotions, and our perceptions.  But the material world, although separate, is not entirely divorced from these worlds – it strongly influences them…This is because for humans, materials are not just functional…(Materials) mean something, they embody our ideals, they give us part of our identity.”
• The author ends the chapter as well as the book by condensing the essence of materials science and the two-way relationship between us and our stuff in the following statement:  “…Materials are a reflection of who we are, a multi-scale expression of our human needs and desires” and in the same way, the materials that we choose to grace our bodies and our homes and those that we choose to surround us in the workplace, in the cities, in the world say a lot about who we are as humans and as individuals.

THE END

STUFF MATTERS: Chapter 8

CHAPTER 8: UNBREAKABLE
• On carbon and its many allotropes
• The word diamond is derived from the Greek adamas, meaning “unadulterated” or “unbreakable”.
• BONDING STRUCTURE OF DIAMOND:  Two of the 6 electrons of a carbon atom do not participate in the “atom’s chemical life” as it interacts with other atoms.  The four electrons do “make the difference between the graphite of a pencil and the diamond of an engagement ring”.  In diamond these four electrons are each shared with another one of the 4 electrons of another carbon atom, with the four bonds arranged in a tetrahedral geometry around each carbon atom,
• BIGGEST EXTRATERRESTIAL AND TERRESTIAL DIAMONDS:  The biggest diamond yet discovered has a size five times that of the earth and was detected in the constellation of Serpens Cauda in the Milky Way where it is orbiting a pulsar star called PSR J1719-1438.  On earth, the biggest one was found about a mile down and is about the size of a football and weighs a half kilogram.
• PROEPRTIES OF DIAMOND:  The structure of diamond gives rise to its unique properties:
o Its strength, hardness, and stability are due to the stable configuration of electrons that are essentially “locked in place”.
o It is transparent because the electrons do not absorb in the visible range. It also has a high optical dispersion capability which allows it to split light into its constituent wavelengths.
• RELATIVE STABILITY:  Although diamonds give the impression of stability, it’s the other allotrope of carbon, graphite that is actually more thermodynamically stable although because diamond is kinetically stable, it will take billions of years for the conversion from diamond to graphite can happen.
• STRUCTURE OF GRAPHITE:  The structure of graphite is quite different from that of diamond even though they both consist purely of carbon atoms. In graphite, the carbon atoms are bonded in a planar hexagonal arrangement forming layers that are relatively more weakly held together compared to the bonds between the carbon atoms.  The bond between the carbon atoms within a hexagon of 6 bonded carbon atoms is stronger than the C-C bond in diamond.  The “softness” of graphite derives from the relatively weak attractive forces between layers of hexagonal planes that allow the planes to move relative each other (causing the ease with which one can write with graphite, depositing layers of the hexagon planes stripped from the rest).
• STRONG AND WEAK BONDS IN GRAPHITE:  The author explains that the strength of the C-C bond in graphite derives from the fact that the four electrons of each C atom are shared with only two other C atoms.  However, this leaves no shared electrons between layers, weakening the “bond” between these layers.  These layers are held together by the weaker van der Waal’s forces generated by “fluctuations in the electric field of molecules”.  These are the bonds that are breached when graphite is held firmly down and slid across a piece of paper, stripping layers of the graphite.
o Graphite is an electrical conductor because partial electron density from the outer electrons shared among three carbon atoms forms a “sea of electrons” (delocalized in standard chemical parlance ) between the layers that are mobile and can carry an electric current.  In diamond, all the electrons are “locked-up (localized) between C atoms and not sufficiently mobile to carry an electric current.
o Edison used graphite as a lightbulb filament because of its high melting point, glowing “white hot without melting when a high current passes through it”.
o Graphite has a metallic luster because the “sea of electrons also act as electromagnetic trampoline for light” and this reflected light is what gives shininess to graphite.
• COAL FORMATION:  Unlike soot that is formed by simply burning carbon-based material, coal is produced by millions of years of exposure to extreme heat and pressure and geological processes that give coal its unique structure and properties.  Coal starts off as a form of peat (brown, soil-like material consisting of decayed vegetable organic matter as defined by the Oxford American Dictionary) which turns into lignite (“soft brownish coal showing traces of plant structure, OAD) then becomes bituminous coal (semi-solid, oily mixture) which hardens into anthracite coal (hardened, almost pure carbon, OAD), the final precursor to coal which has the hexagonal planes of graphite.  At each step, the C content is concentrated into a dense structure after volatile compounds containing S, N, and O evaporate.
• BLACK DIAMOND?  “Jet”, the most aesthetically appealing type of coal because of its hardness and black metal-like luster, is a type of coal derived from fossilized monkey puzzle trees.  It has been called “black amber” because of its “similar triboelectric properties”:  the ability to create static electricity and make hair stand on end.
• BURNING DIAMOND?  In 1772, Antoine Lavoisier, investigating the properties of carbon, succeeded in burning a piece of diamond upon heating it until it was red hot.  However, instead of making soot, the diamond just simply became a gas and the diamond disappeared.  Upon heating in a vacuum to eliminate air, the diamond upon heating simply turned into pure graphite.  These experiments, of course, led to speculations and, later, attempts to reverse the process: turn graphite into diamond.
• SYNTHETIC DIAMOND:  In 1953, finally, a process was developed to turn graphite into synthetic diamond.  The much faster transformation from fossil-based graphite to the diamond structure causes impurities and defects that give color to synthetic diamond unlike real diamond formed from millions of years of heat and pressure.  The hardness of synthetic diamond, however, makes it useful for tools for cutting through granite and other hard rocks.
• LONDALEITE, PURE CARBON HARDER THAN DIAMOND:  In 1967, a different allotrope of C found to be 58% harder than diamond was discovered in the Canyon Diablo meteorite.  It was named lonsdaleite with a structure like graphite’s hexagonal layers but arranged in three-dimension.  Very few samples exist as it takes the heat and pressure of a meteorite impact for this allotrope to form.
• CARBON FIBER COMPOSITE, ANOTHER SYNTHETIC CARBON:  Carbon fiber is manufactured by “spinning graphite” to arrange the hexagonal layers lengthwise into fibers.  The fibers are arranged into sheets and rolled up retaining the material strength within the sheets.  The fibers are then epoxy sealed to replace the weaker can der Waals force between the fibers. The resulting composite benefits from the strength within the hexagonal layer leading to a material that is strong and light (high strength-to-weight ratio) and can be made stiff.
• LIGHT BUT STRONG:  Using a bicycle made from carbon fiber in 1996, Chris Boardman demonstrated the record for the fastest human speed achieved under his own power, reaching a speed of 56.375 km/hr.
• OTHER USES OF CARBON FIBER:  Carbon fiber composite has also been used to provide structure for artificial limbs.
• BUCKYBALLS, A FOURTH TYPE OF CARBON: In 1985, Harry Kroto and others discovered a fourth carbon allotrope formed in the flame of a candle.  This allotrope contains 60 carbon atoms, with the hexagonal sheet arranged in a spherical shape.  The name buckminsterfullerene was given to this fourth type after Buckminster Fuller , the architect who designed geodesic domes with the same hexagonal sections.
• CARBON NANOTUBES, THE FIFTH TYPE:  The name carbon nanotubes derived from this group of C atoms to self-assemble into nanometer-sized tubes.  The hexagons of C atoms are arranged in such a way that there are no van der Waal’s forces present and that the entire network of hexagons are held together by the same strong bond between C atoms within the hexagon.  (They are just like the carbon fibers but, in this case, the fibers are held together by this stronger C-C bond rather than the epoxy).  As a result, these carbon nanotubes have been found to have the highest strength-to-weight ratio of any known material on earth.
• 2-DIMENSIONAL GRAPHENE, THE PROSPECTIVE WONDER MATERIAL:  Graphene was first identified as a distinct material with potentially special properties by Andre Geim’s group at the University of Manchester.  Graphene is a single-atom hexagonal sheet of C atoms which can be derived by using tape to separate sheets of hexagonal structures from a thin sample of graphite until only one layer is left.  Some of these record-breaking distinctions of graphene include
o being the thinnest but strongest and stiffest known material on earth
o fastest thermal conductor
o ability to conduct more electricity, faster and with less resistance
o ability to allow Klein tunneling, “an exotic quantum effect in which electrons within the material can tunnel through barriers as if they were not there”
o it only retains these properties as long as it remains a 2-dimensional material (while it cannot be made thinner, add another layer on top and it just becomes graphite again)

STUFF MATTERS: Chapter 7

CHAPTER 7: INVISIBLE
• On glass
• Sand is a heterogenous mixture of different substances, a large proportion of which are quartz made from silicon dioxide crystals.  When this quartz crystal is heated to its melting point, the silicon dioxide molecules break apart and dissociate.  Unlike water, however, as it starts to cool down, the silicon dioxide molecules do not rearrange themselves in the same crystalline pattern but rather in an amorphous solid material that has the “molecular structure of a chaotic liquid, a glass”.
• The Romans developed much of the process for the practical, cheaper production of glass.  They invented the use of flux, a substance mixed with a solid to lower its melting point, in the form of natron or naturally occurring sodium carbonate.  Although not a new process (the Egyptians and the Greeks have developed it before the Romans), the Romans found a way to make it cheaper to be accessible by the masses.  The Romans invented the use of glass for:
o windows
o mirrors by layering a thinner mass of metal over transparent glass
o thin-walled wine glasses developing the technique of glass blowing (blowing air into glass while red hot)
• In discussing why some materials are transparent while some are not, the author first starts off with a good analogy of the structure of the atom and its sub-atomic particles:
o “Inside an atomic stadium, to continue the analogy, the electrons are only allowed to inhabit certain parts of the stands. It is as if most of the seats have been removed and there are only certain rows of seats left, with each electron restricted to its allotted row. If an electron wants to upgrade to a better row, it has to pay more—the currency being energy. When light passes through an atom it provides a burst of energy, and if the amount of energy provided is enough, an electron will use that energy to move into a better seat. In doing so, it absorbs the light, preventing it from passing through the material.”
o But there is a catch. The energy of the light has to match exactly that required for the electron to move from its seat to a seat in the available row. If it’s too small, or to put it another way, if there are no seats available in the row above (i.e., the energy required to get to them is too large), then the electron cannot upgrade and the light will not be absorbed. This idea of electrons not being able to move between rows (or energy states, as they are called) unless the energy exactly matches is the theory that governs the atomic world, called quantum mechanics. The gaps between rows correspond to specific quantities of energy, or quanta. The way these quanta are arranged in glass is such that moving to a free row requires much more energy than is available in visible light. Consequently, visible light does not have enough energy to allow the electrons to upgrade their seats and has no choice but to pass straight through the atoms. This is why glass is transparent.  Higher-energy light, on the other hand, such as UV light, can upgrade the electrons in glass to the better seats, and so glass is opaque to UV light. This is why you can’t get a suntan through glass, since the UV light never reaches you. Opaque materials like wood and stone effectively have lots of cheap seats available and so visible light and UV are easily absorbed by them.”
• “Chemistry was transformed by glass perhaps more than any other discipline.”  Glassware allowed them to run reactions in sturdy but inert vessels that also allowed them to see the material inside for mixing and monitoring.  The use of pyrex glass was a further improvement as it introduced a higher degree of thermal tolerance.
• Addition of boron oxide to regular glass as an additive reduces the tendency of glass to expand and contract under temperature changes allowing pyrex glass (borosilicate glass) to maintain structural integrity and strength even after a series of thermal changes.
• Toughened glass, the kind used in cars, was designed to fracture into smaller pieces upon impact.  It is made by cooling the outside of the glass fast enough to allow a compression state to develop.
• Laminated glass shatters but remains in one piece because of a layer of plastic in the middle acting as glue to keep the shards together.
• Bulletproof glass uses the same technology as laminated glass, just many more layers of plastic alternatively imbedded in the glass. Hitting and breaking an outer layer of glass absorbs some of the energy of the bullet and “blunts” its yip.  The plastic layers act as a damper that absorbs and redistributes the force over a larger surface area.  The higher the number of laminate layers, the more energy can be absorbed upon bullet impact:  one laminate layer will stop a 9mm pistol bullet, 3 a 0.44 magnum pistol bullet, and 8 layers can stop AK-47 bullets.  Plastic used must have the same refractive index as the glass so that transparency is maintained uniformly as the glass gets thicker.
• Cultural significance:
• The use of glass, Pyrex in particular, allowed the field of chemistry to progress much faster as an experimental science; it is the “workhorse” in the chemists’ lab.
• The author suggests that because the Chinese and the Japanese ignored the use of glass for a thousand years, this may have caused them to miss out on valuable technological innovations and contributions while glass “revolutionized one of Europe’s most treasured customs”.
• Use of glass in lenses has allowed us to explore the microworld and the astronomical world, allowing humans “to transcend scale”.
• It has allowed us to live inside and be protected from the elements but still be able to see outside.
• “Perhaps it is because we look through it rather than at it that glass has not become part of the treasured fabric of our lives”: it is INVISIBLE, “not just optically, but culturally”.

STUFF MATTERS: Chapters 4-6

CHAPTER 4: DELICIOUS
• On chocolate
• Chocolate is a food concoction designed to be ingested solid and to slowly melt in the mouth.
• One of its main ingredients is cocoa butter whose properties contribute to the overall sensation, flavor, and texture of chocolate:
o Its melting point is close to body temperature.
o It contains antioxidants that help reduce oxidation of the fats resulting in rancidity prolonging the shelf-life (“can be stored for years” according to the author).
o It forms crystals which give chocolate its mechanical strength.  The different ways that the triglycerides pack result in different types of crystals.  Types I and II are mechanically soft and quite unstable with a low melting point of 16 C making them easy to mold, harden, and remelt (like ice scream coating).  Types III and IV are denser but also soft and crumbly and do not snap upon breaking.  Type V is an extremely dense fat crystal which has  a glossy, hard surface and snaps when broken.  Its melting point is 34 C which keeps them hard and solid until they are eaten and start to melt in the mouth.
• Dark chocolate is usually % cocoa fat, 20% cocoa powder, and 30% sugar.  Many of the components of cocoa powder are alkaloids and phenolics, like caffeine and theobromine, that are bitter and astringent, activating the “bitter and sour taste receptors and complement the sweetness of the sugar”.
• Chocolate can have up to 600 different molecules.  The fruity ones are likely esters.  As mentioned above, the alkaloids and phenolics like theobromine and caffeine are bitter tasting.
• After harvesting the cocoa beans, they are left out in the heat to decompose and ferment.  The esters are produced during the fermentation process as enzymes catalyze the reaction between acids and alcohols.
• During roasting, several chemical reactions further turn the chemicals into chocolate ingredients.  The roasting process caramelizes the carbohydrates in the bean.  A second reaction at high temperature (160 C or above) is the Maillard reaction wherein sugar, esters, and alcohols react with proteins producing a variety of flavor molecules.   The Maillard reaction causes the “nutty, meaty flavors of chocolate while also reducing some of the astringency and bitterness”.  (The same reaction is responsible for the flavor of bread crust, roasted vegetables, and many other roasted savory flavors.)
• In the further development of chocolate as a solid gustatory treat, milk was added to further remove the bitterness.  Chocolates from different countries differ in flavor and texture mostly because of the type of milk added:  In the US, they use reduced fat milk (removed by enzymes) which gives it a “cheesy, almost rancid flavor”.  In the UK, they use a concentrate of milk to which sugar has been added giving chocolate a “milder caramel flavor”.  In Europe, powdered milk is used giving the chocolate “a fresh dairy flavor with a powdery texture”.
• Cultural significance:  The author has the following to say: “…I truly appreciate that chocolate is one of our greatest engineering creations. It is certainly no less remarkable and technically sophisticated than concrete or steel. Through sheer ingenuity, we have found a way to turn an unpromising tropical rainforest nut that tastes revolting into a cold, dark, brittle solid designed for one purpose only: to melt in your mouth, flood your senses with warm, fragrant, bittersweet flavors, and ignite the pleasure centers of the brain. Despite our scientific understanding, words or formulae are not enough to describe it. It is as close as we get, I would say, to a material poem, as complex and beautiful as a sonnet. Which is why the Linnaean name for the stuff, theobroma, is so appropriate. It means “the food of the gods.”

CHAPTER 5: MARVELOUS
• On Aerogel (a type of foam)
• Samuel Kistler, an American farmer turned chemist, was the first to create and characterize aerogels stimulated by his initial curiosity about jelly, a mostly liquid substance held within a thin mesh of a solid substance.  In gelatin, the thin mesh is made up of polymeric protein (collagen) which, when added to water, the “gelatin molecules unravel and connect with one another to form a mesh that traps the liquid within it” by surface tension.  This surface tension is strong enough to keep the liquid trapped inside the protein mesh but weak enough to move around which gives gelatin the “wobble”.
• In a letter entitled, “Coherent Expanded Aerogels and Jellies” published in the journal Nature in 1931, Kistler wrote: “…The continuity of the liquid permeating jellies is demonstrated by diffusion, syneresis, and ultra-filtration, and the fact that the liquid may be replaced by other liquids of very diverse character indicates clearly that the gel structure may be independent of the liquid in which it is bathed.”  [Syneresis is the contraction of a gel as a result of separating out the liquid.]
• Gel became the general term for mixtures of similar composition (e.g. hair gel, chicken stock, foam, even concrete).
• The biggest challenge in making of an aerogel is the removal of the liquid from the gel’s internal skeleton without causing the gel to simply collapse and shrink.  Kistler and collaborators got around this by raising the temperature and pressure of the liquid to its critical point at which the liquid and its gas state have the same density and structure.  At this point, the whole liquid becomes a gas even though the “jelly has had no way of ‘knowing’ that the liquid within its meshes has become a gas”.  The gas is allowed to escape slowly leaving an intact silica aerogel with a silicon dioxide (essentially glass) skeleton.
• Silica aerogel has the following properties:
• It is the least dense solid known (with a density three times that of air) composed of 99.8% air.
• It looks transparent like glass when light goes through it as the very small amount of material causes so little distortion.  When against a black background, it looks blue as it scatters light (just like our atmosphere which makes our sky look blue due to Rayleigh scattering).
• It has extremely effective thermal insulating capacity protecting a flower sitting on its surface from the heat of a bunsen burner flame less than half a centimeter away.
• Despite the wonder properties of aerogel, it has seen only esoteric uses due to its high manufacturing cost.  It is used in some specialized cases.  It has also been used to capture stardust, its highly durable structure being able to withstand the impact of particles travelling at 50 km/s (or 18,000 km/hr) without breaking apart.
• The author offers the following tribute to aerogel and its wonder: “Aerogels were created out of pure curiosity, ingenuity, and wonder. In a world where we say we value such creativity, and give out medals to reward its success, it’s odd that we still use gold, silver, and bronze to do so. For if ever there was a material that represented mankind’s ability to look up to the sky and wonder who we are, if ever there was a material that represented our ability to turn a rocky planet into a bountiful and marvelous place, if ever there was a material that represented our ability to explore the vastness of the solar system while at the same time speaking of the fragility of human existence, if ever there was a blue-sky material—it is aerogel.”

CHAPTER 6: IMAGINATIVE
• On plastic
• When billiard known as pool in the US started to become popular, there was a concern about depleting source of ivory, the substance of which the balls are composed.  Ivory has properties well suited for the game of billiard or pools:
o Hardness that can withstand denting or chipping upon collision
o Overall internal structural integrity to preventing cracking
o Ability to be machined into a sphere
o Ability to absorb dye for coloring
• Nitroglycerin is produced by nitrating glycerol which occurs when it is mixed with nitric acid.
• Nitrocellulose is a cellulose molecule where the hydroxyl groups have been nitrated.  John Wesley Hyatt made nitrocellulose by mixing wood pulp with nitric acid.  Adding naphtha [which contained the camphor?], derived from crude oil, turns the nitrocellulose in a moldable mixture that hardens into a solid.  He referred to this process as plasticization.
• The author later defines the term plastic “which refers to a huge variety of materials, all of which are organic… solid, and moldable.
• A similar product called xylonite was produced in the same way with the exception that camphor was used instead of naphtha.  This resulted in a patent case as related in a play format by the author.
• Celluloid is known as the first commercial moldable plastic.  It later on was used as a substrate for photographic film for taking still and eventually moving pictures.
• Other plastics that followed include Bakelite, nylon, vinyl, and silicone.
• Cultural significance: the invention of this material which allowed the reproduction of normally expensive material at much lower costs allowed the growing middle class the opportunity to acquire similar materials as the wealthy but affordable.
• In the author’s words at the end of the chapter, the cultural contribution of plastics are immense:  “The plastics that followed celluloid, such as Bakelite, nylon, vinyl, and silicone, built on its creative power and have also had an important impact on our cultural psyche. Bakelite became a moldable replacement for wood at a time when the telephone, radio, and television were being invented and needed a new material to embody their modernity. Nylon’s sleekness took on the fashion industry, replaced silk as the material for women’s stockings, and then spawned a new family of fabrics, such as Lycra and PVC, as well as a group of materials called elastomers, without which all our clothes would be baggy and our pants would fall down. Vinyl changed music, how we recorded it and how we listened to it, and along the way it created rock stars. And silicone—well, silicone turned imagination into reality by creating a plastic form of surgery.”