Part 9 (2/2)

Once the alcohol is made, its taste can then be improved by letting it age in bottles in which sticks of dry wood have been placed (in eastern France, hazel wood is often used). (Better still, the wood in question can be heated briefly over a fire before being placed in the bottles. This operation, also carried out by barrel makers who heat their staves, causes other interesting compounds to appear.) The acids in the brandy gradually break down the lignin in the wood into phenol aldehydes, which are then oxidized into phenol acids. The brandy becomes less acidic while at the same time aromatic compounds, such as synapic, syringic, vanilic, and ferulic acids, appear.

Why dry wood and not green wood? Because green wood contains aesculin (bitter), which is gradually transformed into aescutin (sweeter) when the wood dries.

Since compounds like vanilla are present in aged alcohols in contact with wood, why not speed up the aging process by adding these compounds directly to young alcohols? Adding a few drops of vanilla extract to whisky, for example, will make it more full-bodied-but stop before the whisky smells like vanilla. Similarly, you can add a very small amount of cinnamon, since cinnamic aldehyde is formed in the same process as vanillin as alcohols age.

Cold Distillation Another distillation method, less well known but perhaps even simpler than the one I've described, consists of placing the mixture to be distilled in a freezer. When it freezes, the water forms into a block of ice, separating itself from the alcohol and the other compounds that remain in the liquid phase.

Alas, it is also against the law to proceed in this fas.h.i.+on ...

Why Does Alcohol Make You Drunk?

The compound commonly referred to as alcohol, which chemists call ethylic alcohol, or ethanol, is only one member of a huge chemical cla.s.s of alcohols. In its pure form, it is a colorless, odorless compound that burns the tongue.

From its chemical formula, CH3CH2OH, we can locate its alcohol function in the OH group, which replaces a hydrogen atom in ethane (a compound with the formula CH3CH3).

Why the name ”alcohol”? Because the Arab word, al Kohl al Kohl, means ”fine powder.” Actually, the Egyptians tinted their eyelids with an inorganic compound, sulfur of antimony, which they ground in order to apply it. Then, the name was given to the essence of anything at all, notably liquids obtained by distilling wines, when this operation was invented by Avicenna in the tenth century.

Why does alcohol make you drunk? Because it stimulates the brain, which frees the cortex of inhibitory controls; that explains the excitement of drinkers, at least in the first stages of what health workers call ”alcoholic intoxication.” More precisely, alcohol works by interacting during neurotransmission. The brain cells called neurons function by receiving information from other neurons, by calculating the sum of activations and inhibitions, and by stimulating neurons further along in the system according to that calculated sum. A neuron activates other neurons by releasing neuromediating molecules that attach themselves to the receptor molecules of neurons further along.

The neuromediator with which alcohol interacts is gamma-amin.o.butyric acid, or GABA, which acts as an inhibitor. By attaching itself to its receptors, GABA deforms them and facilitates the entry of chloride ions into the neuron, which becomes less excitable.

On the other hand, when it attaches itself to the GABA receptors, alcohol facilitates the fixation of the neuromediator, so that the neurons further along in the system are less inhibited.

Now knowing the dangers that lurk for us in alcoholic beverages, let us remain temperate....

Jams Why Does Lemon Juice Make Jams Set?

Jam? Preparing it is so simple that we could leave it to children if they did not run the risk of getting burned: heat a mixture of sugar, a trace of water, fruit, and seal it in a canning jar. And there you have it!

You may encounter a few difficulties in the details, however, not from the point of view of conservation but regarding consistency. How to obtain jam that holds together? Why do some fruits make better jam than others?

The key to jam is a long molecule called pectin, present in the walls of vegetable cells in varying proportions. This is the jelling molecule. Composed of a chain of groups of hexagonal rings with five carbon atoms and one oxygen atom bound by short segments, pectins, like proteins, are kinds of long threads that bear COOH acid groups capable of ionizing, that is, the hydrogen atom can lose an electron.

This ionization is important for making jam because, when it takes place, the pectin molecules all have the same electrical charge and repel one another.

To form the gel that jam becomes through linking the pectin molecules, this repulsion must be avoided. The pectin molecules, separated from the fruit by heating it, must be allowed to rea.s.sociate into a three-dimensional network that fills the whole container.

Thus we can understand what conditions jam needs to jell successfully. The fruits must provide a sufficient quant.i.ty of pectin, the sugar content must be high, so that pectin a.s.sociation is promoted (see later), and the environment must be acid enough for the acid groups in the pectin not to disa.s.sociate and for the electrostatic repulsion between molecules to be kept to a minimum.52 Let us draw some conclusions from this a.n.a.lysis. First of all, the mixture of sugar and fruit must cook enough for the pectin to be extracted from the cell walls. The sugar, which must be well heated, pulls the water out of the cells into the surrounding syrup (through osmosis). It thus damages the cells, which further releases the pectin molecules. Since the sugar increases the boiling temperature for the mixture (pure water boils at the temperature of 100C [212F] but a mixture of one liter [33.8 ounces] of water and 900 grams [31.75 ounces] of sugar does not boil until it reaches 130C [266F]), it promotes the extraction of pectins as well.

The quant.i.ty of sugar must be significant because, even in an acid solution, pectins do not jell easily; they bind to water rather than among themselves. If sugar is added, it attracts the water molecules and leaves the pectin molecules unattached. Thus they partic.i.p.ate in a group marriage, and gel appears. Some fruits do not contain enough pectin to form a good gel on their own (blackberries, apricots, peaches, strawberries) and must be supplemented with fruits in which pectin is abundant (grapes, apples, most berries). Finally, fruits that are not naturally acid must be supplemented with lemon juice, which deters the ionization of the acid groups of molecules in the pectin and thus their repulsion.

How Much Pectin?

Jam lovers are well aware of the fact: jams that are too firm are rarely good. Why add pectin to jam? Although it helps to preserve it, can it nevertheless do harm? In exploring the relations.h.i.+ps between consistency and taste in jams, physical chemists at the INRA taste research laboratories in Dijon determined a few methodological ingredients for a good strawberry jam. The results can easily be applied to other fruits.

Traditionally, as we have seen, strawberry jam is made by heating the fruit in a mixture of sugar and water. After boiling it for a few minutes to let the excess water evaporate and to kill the microorganisms that are present, the preparation is poured into sterile jars. Should the pot be covered? Should the mixture be heated slowly or at a rapid boil? Will poor-quality strawberries make a good jam nevertheless? What is the actual effect of adding a jelling agent? These important questions motivated the studies of the physical chemists in Dijon. If the consistency of commercial jams seems right, commercial products are well-known-and perhaps inaccurately-for lacking the flavorful characteristics of our grandmothers' jams. Where might the commercial jam industry's error lie?

Knowing that certain products called hydrocolloids, used to increase the viscosity of foods, reduce their taste and odor, the physical chemists in Dijon studied first the relations.h.i.+p between the gel in jams and the odorant compounds present. Many types of pectin are used by the farm-produce industry. Generally, highly methoxylated pectins with many lateral groups-called methoxyl-serve as gels for foods high in sugar, and pectins low in methoxyl are used instead in foods low in sugar. The INRA researchers thus compared five samples of jam containing very methoxylated pectin, at different concentrations; five samples with unmethoxylated pectin, at various concentrations; and a control sample in which the pectin came only from the strawberries.

Done under standardized conditions, the jam evaluation consisted of two parts: a chemical a.n.a.lysis of the volatile compounds and a sensory a.n.a.lysis, during which selected tasters described the products given to them with the help of twenty-five terms, defined preliminarily, including ten attributes for aroma and three attributes for taste. For each sample, the tasters also noted their a.s.sessment of the jam's consistency in the mouth. The tasting took place in a room lit with red lights, so that the color of the different samples (varying accord to the type of preparation) could not influence the gustatory a.s.sessment. The tasters were only given unlabeled samples, and each jam was presented twice and in random order.

The preliminary chemical a.n.a.lyses, in which thirty-one volatile compounds capable of contributing to the flavor were identified, showed that the concentration of these products differed greatly from jam to jam according to the fruit lots. The quality of the jam depended heavily on the quality of the fruit used in it.

In addition, during a preliminary evaluation of the jam's consistency by the tasters, it was verified that the tasters' responses were consistent, and two unexpected phenomena became apparent. All the tasters preferred the jams that did not contain highly methoxylated pectins, and the ideal concentration was in the neighborhood of the concentration generally used by the jam-making industry.

The next step involved determining the relations.h.i.+p between sensory perception and the presence of pectin. Thus it was discovered that increasing the concentration of highly methoxylated pectins enhanced the consistency and viscosity but diminished the notes of sweetness, acid, and caramel. The chemical a.n.a.lyses showed that only seven volatile compounds a.n.a.lyzed had notably diminished in concentration (the compound called mesifurane, which contributes a note of caramel, and various flowery or fruity esters).

With the pectins low in methoxyl, on the other hand, the oral consistency also improved with their concentration, but three times more pectin had to be used than with the high methoxyl pectins to obtain the same consistency. The jury did not note sensory variations in comparison with the control jam, even though chemical a.n.a.lysis registered an increase in the concentration of many fruity esters.

What to conclude from these studies? That the addition of pectins makes jam more firm but reduces its gustatory qualities. How? We know that a substance is only sapid or odorant if it circulates very well around the taste buds or the receptors in the nose. If aromatic compounds are bound to pectin molecules, thus blocking that circulation, the olfactory qualities are reduced. This explanation has been corroborated by experiments in which the volatile compounds were extracted by stirring the jam over the course of its preparation. Chemical a.n.a.lysis detected, in the vapors, many more compounds and in much higher quant.i.ties that when the jam was slowly simmered, which confirms that the bonds between the pectin and the volatile compounds are weak.

Finally, since the gustatory quality of jam depends greatly on the presence of weakly bound volatile compounds, the researchers wanted to study the influence of preparation conditions on the products' qualities. In the end, they observed a considerable loss of aromatic compounds through evaporation.

In other words, you will make good strawberry jam if you take the following advice: (1) choose good-quality strawberries; (2) add pectin only when the pectin in the fruit is insufficient (with cherries, for example); (3) do not stir the preparation too much while it is cooking; (4) heat gently in order to extract the natural pectins from the fruit and to avoid eliminating volatile compounds through either too strenuous stirring or extraction by the water vapor; (5) if possible, recuperate the vapors, and condense them, eliminating the water and returning the treated condensates, rich in aromatic compounds, to the jam before pouring it into jars.

Tea How Long Should Tea Steep?

In Southeast Asia, tea leaves were chewed or infused in prehistoric times. Tea has been cultivated in China since the fourth century before our era, and its use was transported to j.a.pan in about the sixth century. But if the practice of infusion is universal, all herbs and plants are not endowed with the same capacity for releasing scents and flavors.

Orientalism and, it must be confessed, a certain perfectionism about tea and its preparation, established its use in our countries, where we have not entirely forgotten that country people have made infusions from plants since time immemorial: mint, linden ...

Let us give in to the tea craze. How long should it steep? Some tea drinkers recommend letting it steep longer than is necessary for extracting all the color, because certain flavors are released from the vegetable substances more slowly than the colorants. No doubt that is true, but only up to a certain limit, in particular the one that corresponds to the extraction of the tannins, substances that are bitter and astringent.

If this limit is pa.s.sed, the solution of putting milk in the tea remains, but...

Tea in Milk or Milk in Tea?

When preparing tea with milk, should you pour the tea into the milk or the milk into the tea? Naturally, this is only a problem for those who, like the English, mix tea and milk together, but its answer may explain why our friends across the Channel are such tea enthusiasts. Prepared according to their method, tea loses its natural bitterness.

Even without having a taste for tea, we must recognize its great delicacy. Its light bitterness allows its delicate flavor and subtle scents to come through. How to retain those latter characteristics without the former? That is the milk's role, no doubt added originally for its natural sweetness, then embraced for the antibitter properties it possesses.

Tea is bitter because it contains tannins, those same compounds that give certain wines their astringency or even a marked bitterness, those same molecules that make a rose petal seem bitter if you put it in your mouth. Milk, on the other hand, contains many proteins, long chains folded back on themselves, that sequester the tannins. They bind themselves to them, destroying the bitterness.

An easy test of this is to add cold, raw milk to cold tea infused for a long time: the bitterness disappears. This same experiment, however, fails ”hot,” because the heat denatures the proteins, that is, it unravels them and deprives them of their sequestering properties. If tea that has steeped too long is added to milk that has boiled, the bitterness remains. Still worse, the taste of cooked milk masks the tea's flavors!

We now have all the elements we need to answer the initial question. If you add milk to very hot tea, its proteins will be denatured, and the tea's bitterness will remain. On the other hand, hot tea added to cold milk will lose its bitterness because the final temperature of the mixture will not be higher, at least at first, than the temperature at which proteins are denatured, and the proteins will sequester the tannins.

Change Tea's Color?

As long as we are adulterating tea, let us mention lemon. Why does its juice make tea lighter in color?

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