The central concepts of chemistry – which, for our purposes, may be taken as facts – are to do with what matter is made of and how the basic parts combine to make different sorts of matter. Everyone knows about atoms: how they were thought to be the fundamental particles until it was found that they could be broken up to release huge amounts of energy. For our purposes, we can take atoms as fundamental, with the reservation that each atom is made up of a central nucleus round which whizz one or more electrons. The nucleus has a positive electrical charge and the electrons a negative charge. Atoms vary in how they are made up:hydrogen has only one electron, carbon has six, nitrogen seven and oxygen eight. Depending on how they are constituted, atoms have different characteristics. There are just over a hundred types of atom, each type being known as an element. All matter is made up of atoms of those hundred elements, usually in combination with other atoms of the same or other elements. Combinations of atoms are called molecules, and it is as molecules that we mostly experience atoms. Just about everything is made up of molecules. Atoms differ in their propensity to combine with each other. This difference is expressed numerically as the valency of the atom. Hydrogen has a valency of one, oxygen of two and carbon of four, which means that one carbon atom can combine with four hydrogen atoms and two oxygen, yielding methane, CH4 and carbon dioxide, CO2, respectively. One oxygen can combine with two hydrogen, to produce a compound commonly known as water, or H2O.In conventional depictions, each atom is represented by a letter. Thus carbon is C, oxygen O, hydrogen H and nitrogen N. Some elements have two letters such as lead, Pb (from the Latin plumbum, meaning lead). The number of atoms of a given element in any molecule is shown by a numeral at the bottom right of the relevant letter, as methane CH4, in which one carbon atom has combined with four hydrogen atoms. Similarly, water is H2O, meaning two hydrogen atoms attached to one oxygen. This notation is known as the molecular formula.Carbon atoms have very peculiar properties and are quite unlike any other kinds of atom. Organic chemistry is the chemistry of the carbon atom in all its compound forms, of which there are millions. There are so many of these and they play such an important part in our lives, that they warrant special attention. The chemistry of living things is organic chemistry: for all living things are made up of organic molecules. We are made of organic compounds and so are most of the things we taste and smell, so the chemistry of taste is organic chemistry. That is, it is about one lot of organic compounds reacting with another lot. The difference is that the first lot – us – is alive and the other, by and large, isn’t. There are exceptions: we eat oysters which are alive as we eat them, which some vegetarians find disgusting. So are most fruits, though nobody seems to be disgusted by the idea of eating apples.Alcohols
Methyl alcohol is the simplest in a series which contains a truly enormous number of compounds. Ethyl alcohol – the next one up the chain – is not so volatile as methyl: by the time we get to amyl and hexyl alcohols, the fluids are beginning to look like oils. Indeed, in the whisky industry, they, along with other even higher alcohols, are known as fusel oils. Being heavier and less volatile, they evaporate later in the
distillation process and are sent to the feints receiver. The middle cut, which is what becomes whisky, contains only traces of the higher
alcohols. Though present in infinitesimally small quantities, they nevertheless make a significant contribution to the flavour of the finished whisky.Methyl alcohol is also present in most wines, but in concentrations so low that it does no harm. In whisky, it is present in the wash, but being very volatile, is normally lost in the foreshots. That is not to say it isn’t dangerous, though, and it should on no account be consumed in any appreciable concentration. A single measure of the pure stuff will kill you and much smaller doses will attack your optic nerve and blind you. All of the alcohols are characterized by the possession of the -OH group. Also known as ethanol, this is the substance which we usually refer to as alcohol, since it is the alcohol which we normally encounter in our drinks. The term comes from the Arabic al kuhl. This phrase
originally meant the fine powder, antimony sulphide, which is used to darken the eyelids to make the wearer more alluring to the members of the opposite (or in some cases, the same) sex - I bet you thought there would be no sex in a chapter on chemistry. Anyway, these Arabs – chaps, mostly – thought pretty highly of the stuff they put on their eyes. It seems they thought it the very essence of sexuality: so much so that the phrase came to be used to refer to the essence of just about anything. It is a short step to the application of the term to distillate, given that the Arabs invented perfume as we know it and they used distillation to extract essential oils from flowers.The Arabs are commonly credited with having invented distillation. This is probably not true. There is evidence that Gnostic Christians used distilled wine in their religious ceremonies, long before anyone had heard of the Arabs. The Gnostics were an early Christian sect, deeply influenced by Neoplatonism, who were heavily into spirituality. This got them into trouble with the Church, which even then was overly bureaucratic and kept its spirituality at a comfortable distance. The Gnostics thought that the soul was akin to the volatile component of distilled wine and that when people died they more or less evaporated. Heaven was a kind of celestial condenser in which the purer part of us would be reconstituted. Anyway, it’s pretty clear that the Chinese knew about alcohol long before the Gnostics. Being Chinese they did things differently from the rest of the world and though they knew how to make hard liquor, they didn’t drink it – much as they knew how to make gunpowder and used it in warfare to make firecrackers to frighten their enemies, rather than bombs to kill them. Making whisky
The business of whisky making begins with starches and ends with alcohols. We take a grain of barley, which consists of two things: a barley plant embryo and a store of energy in the form of starch. We convert the starch into sugar. We then ferment the sugar to produce weak alcohol: we distil to concentrate the alcohol.The barley plant needs to be able to access its energy store to provide for the growing plant. This it does by using enzymes which split the long-chain starch molecules into shorter sugar molecules. Enzymes are organic catalysts which, though they enable a process to take place, are not themselves used up in the process. Your car probably has a catalytic converter in its silencer: it works by converting poisonous compounds in the exhaust gases into harmless ones. The whisky maker exploits both parts of the barley grain – the enzymes and the starch. The process of malting barley consists of dampening the grains, so that they begin to grow. In growing, the barley grain produces the enzyme, maltase. The maltase acts on the stored starch, and converts it into maltose, a disaccharide sugar. You can taste the difference between malted and unmalted barley: the latter tastes dry and mealy, the former tastes distinctly sweet. As soon as the malting is complete, the process is halted, otherwise the plant would grow and use up the sugar. At this stage, the barley is still alive. The kiln which dries the malt, kills it. This is what prompted Burns to say: “And they hae sworn a solemn oath John Barleycorn should die.”Starch is not soluble in water, but sugar is. The next stage in whisky making is the grinding of the dried, malted barley in a mill until it is a flour. That flour is dissolved in water in the process known as mashing. Once the solid, insoluble part of the malt is removed (the draff), we are left with a sweet liquid: water containing dissolved sugars, which is known as worts.Fermentation is the process which converts sugars into alcohols, mainly ethyl alcohol. It is called brewing. It has been known about for a very long time: almost every culture has its own way of brewing alcoholic liquor. The Scots, in common with most other people who live in cold temperate climates, have traditionally used grains as the source of sugars. Barley is easy to use for this purpose, since it produces relatively large amounts of the desired enzyme. Other grains can for the most part be malted, but not as easily. Rice and millet are both used: one to make rice wine, the other for mealie beer.In warmer climates, fruits are used: grapes for wine, apples for cider, cherries, pears, plums, any fruit with sugar in it. There are other sources:
the heart of the agave cactus contains highconcentrations of sugars which, when fermented, yield pulque which is distilled into tequila. The sap of some palm trees gives us palm wine - distilled it becomes arrack.In most cases, the fermenting agent is a yeast (rice wine is different: the agent is an organism called Aspergillus oryzae which grows on the rice). Yeasts, of which there are a great many different varieties, are relatives of fungi. They thrive on sugars and, as a by-product of their metabolic activity, produce alcohol. The kinds of alcohol – and the amounts of compounds other than alcohol – which result from fermentation, depend on the species of yeast employed. For control of flavour, brewers generally prefer to use only pure strains of certain yeasts. Unless they do so, they are unable to predict the outcome of individual brewing processes. Wild yeasts abound in the air, and tend to contaminate batches of malt. When they do, the fermentation which takes place is significantly different from that which is desired. Historically, all wines, beers, etcetera, were fermented by wild yeasts - the quality of a brew depending on which wild yeasts happened to float by at the time. The resulting potations were mostly pretty vile, but they did have two important attributes: they got you drunk and they were sterile. Even at the low concentrations produced by fermentation (up to about five per cent by volume), alcohol is toxic to most organisms. In the absence of a pure water supply, beer or wine was the only stuff safe to drink. Excessive alcohol in society had become recognised as a social evil in most Western societies by the nineteenth century, round about the first time since the Romans that most cities had achieved a decent municipal water supply. Because everyone then took the water supply for granted, the public health virtues of alcohol disappeared from view.The emergence of whisky as a potation for polite persons happened toward the end of the eighteenth century. Its quality had improved, partly through better distilling and maturation processes, partly because of developments in the understanding of the place of yeasts in brewing and control of flavour resulting therefrom. Today, the brewer is one of the most important people in a distillery and the contribution of fermentation to the flavour of the mature whisky is not in doubt.