Kitchen Mysteries_ Revealing the Science of Cooking Part 9

The body, a very synthetic impression, also corresponds to what certain wine lovers call the const.i.tution. The const.i.tution varies between full-bodied, powerfully built wines, and thin or hollow wines.

If such gustatory a.n.a.lysis allows for correcting the olfactory a.n.a.lysis that precedes it, tasting with the nose, after the first pa.s.s through the mouth, allows for perfecting this gustatory a.n.a.lysis: the scents rise from the throat to the nasal pa.s.sages.

Finally, we must not forget to judge the astringency of the wine, especially at the tip of the tongue, its bitterness, its sweet or possibly salty (this is rare) character, and its finish: that is to say, after swallowing, the time during which the palate remains permeated with the various sensations experienced in the mouth. A good finish is the sign of an interesting wine. It is noted by measuring the number of seconds that the sensations persist. We say, for example, "this wine lasts five caudalies caudalies," if the sensations persist for five seconds. Certain exceptional wines create the impression of the aromas returning after a short time. Then we say that the wine "makes a peac.o.c.k's tail."

Finally, Drinking the Wine In practice, the taster can employ two different methods or employ them one after the other.

According to the first method, one drinks without swallowing a small quant.i.ty of wine. After placing the wine just behind the teeth, the tip of the tongue is immersed in it in order to determine the astringency (an impression of harshness, typical of tannic wines and which one can learn to recognize by chewing a rose petal), a possible sweetness (a sweet wine provides a clear sensation at the tip of the tongue, combined with an impression in the mouth more or less oily or thick), or acidity (impression of coolness on the sides of the tongue). Then, keeping the head back, one slightly parts the lips to breathe in a thin stream of air and aerate the wine. New "retro-olfaction" flavors appear; these are less volatile odorant molecules than those inhaled when projecting one's nose into the wine gla.s.s.

According to the second method, one chews the wine by turning it over in the mouth. In this way, the body and the fat of the wine are perceived.

A final note: when tasting several wines, one after another, it is standard practice to spit out each mouthful into a pail.

To describe the sensations in the mouth, we have the following list of adjectives from which to choose: winey, full, aggressive, harsh (synonymous with hard; the harshness of a wine is due to its bitterness or its tannin), pungent (more pejorative than rough), round, charming, well filled-out, voluminous, ample, supple, drinkable (wine that is easy to drink and refreshing), fleshy (wine that is so fortified and rich that it feels as though you could chew it; wines rich in tannins are often fleshy and are said to have a chew), frank, rich, lively, structured, fruity, flat, alcoholized, heavy, with a strong finish, with balanced aromas, solidly built (well structured in tannins), tannic in the back of the mouth, lingering, fat (for rich wines, full of substance, that fill the mouth well), with a good body, light (low in alcohol), smooth, silky (delighting the palate with a softness, similar to that of silk), heady, young, firm, unctuous, fortified (very rich in alcohol, going to the head), astringent (for wines with abundant tannins, not yet transformed enough, as we shall see, and lacking suppleness, like young Medocs), acid. For faults, we have the following: musty, maderized, oxidized, seche, flat, short (a poor finish, used for wines that provide too fleeting an aromatic sensation, not lingering in the mouth).

A wine taster's overall a.s.sessment is neither truly objective nor completely subjective. It is objective insofar as it cannot be positive if the wine has obvious faults, but it remains partly subjective because a wine may give an all-around good impression and still offer little pleasure.

Improve a Wine?

It is a great temptation, considering the price of wine, to buy cheaper wines and try to improve them.

Your wine is too light? A chemist would add ethylic alcohol to it. It lacks bouquet? Why not try a drop of ca.s.sis or vanilla extract? It lacks body? A little glycerin, for example. Not tannic enough? Add the necessary tannins. You like the taste of old wine? A little vanillin or even Madeira or port. You prefer a flowery wine? A hint of linalool. Drawn to the bordeaux? Try n-octanol and 2-methoxy-3-isobutylpyrazine. You prefer the leathery aromas of the burgundies? A little parethylphenol. And then there are still other compounds that are naturally present in wine but may be insufficiently evident in the bottle you have in your hand: ethyl methylanthranilate, paravinylphenol, wood lactones (compounds extracted by the wine from oak casks), cinnamon, nutmeg, acetaldehyde (the main aldehyde in all wines, found in large proportions in sherry, to which it contributes its characteristic taste). In light wines, a small quant.i.ty of acetaldehyde highlights the bouquet; in excess, it is undesirable, unstable, and causes oxidation.

I do not want to suggest that such manipulations are panaceas. First, only individuals who drink wine for pleasure can play such games, as it would be adulteration, that is, fraud, for wine merchants to do so. For trade purposes, wine is wine, not a mixture of chemicals. Second, some wines are works of art, gourmand Mona Lisas that chance attempts have little possibility of reproducing, and the bouquets of many products offered by true winegrowers are not reducible to simplistic formulas. The chemist must also consider his health and only use compounds uncontaminated by dangerous substances, and he must not abuse these trials; drunkenness waits to catch him unawares.

Your Own Fruit Wine To understand why wine is such a complex crowning jewel, let us examine the preparation of an original wine made from raspberries, strawberries, black currants, potatoes.... One can, in fact, make wine beginning with almost any fruit at all.

Wine is produced through the fermentation of the sugar in grapes. One recipe consists of placing the grapes (or other fruit, or potatoes boiled with sugar and lemon juice, for example) in the presence of baking yeast in an open jar. As soon as fermentation has taken place, the liquid is poured into a container through a filter. Then it is tightly corked. Of course, the grape is the fruit that best lends itself to wine making.

Winegrowers carefully choose the yeast cultures they use. To make a burgundy or a Cotes du Rhone, they often use Saccharomyces cerevisiae Saccharomyces cerevisiae yeasts, from the Montrachet culture, which ferment at between 18 and 25C (64 and 77F) in a few days. They make white wines at lower temperatures, because the yield in fruity esters is higher that way. To produce a sparkling wine, they resort to cultures that undergo a secondary fermentation, like yeasts, from the Montrachet culture, which ferment at between 18 and 25C (64 and 77F) in a few days. They make white wines at lower temperatures, because the yield in fruity esters is higher that way. To produce a sparkling wine, they resort to cultures that undergo a secondary fermentation, like Saccharomyces baya.n.u.s Saccharomyces baya.n.u.s.

Similarly, the type and quant.i.ty of the sugar contained in the fruit's juice is fundamental. A must containing 20 percent sugar produces a wine containing 12 percent alcohol. From this perspective, the grape is ideal. Other fruits generally contain too little sugar, and it must be added before the fermentation.

Acidity, as well, plays a role in the development of the yeasts. The ideal fermentation takes place when the juice is acid (the pH between 3.2 and 3.6). At the end of fermentation, it is preferable to have a little acidity, because alkalinity dulls the wine. On the other hand, when the juice is too basic, there is the risk of undesirable substances being produced. That explains the importance of adding lemon juice at the beginning of fermentation in your attempts at fruit wines.

During fermentation, the higher the temperature, the more significant the extraction of tannins and color will be if the juice is in the presence of the pulp and stems. Nevertheless, at too high a temperature, the yeasts produce substances (decanoic and octanoic acids, and corresponding esters) that neutralize their properties, feed on them, and kill them off. The fullest, darkest, most tannic red wines, which have the longest possible lives, remain in contact with the skins for ten to thirty days (the skins contain both the pigments called anthocyanins and the tannins). On the other hand, the lighter red wines are separated from the skins at the end of just a few days. White wines are obtained by fermenting the juice alone.

When the fermentation has ended, that is, when bubbles have ceased to form (strictly speaking, fermentation takes place in a closed but not air-tight vessel, in a cool, well-ventilated place), siphon off the juice and place it in a sterilized container. Then add a small quant.i.ty of a solution of 10 percent sodium metabisulfite, which will protect against oxidation and clarify the product. In the winegrowing industry, sodium metabisulfite is replaced by sulfurous anhydride or as...o...b..c acid, which are aseptic. Some winegrowers also perform a "flash pasteurization" at this point. In order to kill the yeasts, they bring the wine to 80C (176F) for about thirty seconds. The yeasts are inactive above 36C (96F), and the enzymes are destroyed at temperatures above 65C (149F).

Now, "collez" (glue) your wine in order to clarify it. After fermentation, wine contains matter in suspension, which can cause cloudiness in the bottle. The collage collage (gluing) clarifies the wine and eliminates some of its undesirable characteristics. The most common clarifiers are egg white, gelatin, bentonite, fish glue, and casein. Egg white, with its positive charge, eliminates negatively charged matter (for example, undesirable tannins or anthocyanins), whereas bentonite, negatively charged, eliminates positively charged matter (proteins and other organic materials). (gluing) clarifies the wine and eliminates some of its undesirable characteristics. The most common clarifiers are egg white, gelatin, bentonite, fish glue, and casein. Egg white, with its positive charge, eliminates negatively charged matter (for example, undesirable tannins or anthocyanins), whereas bentonite, negatively charged, eliminates positively charged matter (proteins and other organic materials).

Finally, sometimes wine is put in wooden casks (generally oak) to age, where the alcohol extracts tannins from the wood and gradually react with them, producing various aldehydes and then odorant molecules like vanillin (which is why I encourage you to put vanillin in certain slightly weak wines; also see the chapter on alcohols).

Why Does Red Wine Darken as It Ages?

Red wine owes its color to vegetable pigments called anthocyanins. When red wine ages, the anthocyanins react in a variety of ways. Some react with other colorless but bitter compounds, which are also present and collectively designated by the name of tannins. This reaction does away with the bitterness and astringency of the tannins, which precipitate (thus forming the deposit in certain old wines), and improves the taste of the wine.50 A wine that is too green and astringent becomes smoother and more supple. As the wine continues to age, this reaction makes the red of the anthocyanins disappear and lets the dark tannins become visible. A wine that is too green and astringent becomes smoother and more supple. As the wine continues to age, this reaction makes the red of the anthocyanins disappear and lets the dark tannins become visible.

Why Does White Wine Lose Its Green Highlights as It Ages?

The color of white wines is especially due to the presence of quercitin, a molecule that becomes brown as it is gradually oxidized. Initially, young white wines have a green tint because of the chlorophylls that are extracted during fermentation, but gradually the quercitin dominates the robe and enriches it. Chlorophylls also generate odorant molecules as the wine ages.

How Should We Keep Wine?

The answer to this question is based only on experience; science, alas, has not studied it. Common wisdom says that the temperature of the wine cellar should remain constant, between 8 and 15C (46 and 59F) all year round. Wine bottles should be kept in the dark, resting on their sides, and should not be moved, and the air of the cellar must be good.

All these recommendations warrant verification, because they contradict other stories, such as the one about those bordeaux wines that were improved, it is said, by a round-trip to the Indies. So much for rest and cool air!

The fact remains that the ultraviolet rays of sunlight should be avoided, because they stimulate chemical reactions that alter the wine. Brown wine bottles offer better protection than green ones. Some of the photochemical effects from ultraviolet light may be reversed, it is claimed, by keeping the wine in total darkness for a few months.

Why Does Wine Weep?

The tears of wine, which make wine lovers say with a knowing air, "Ah, this wine has legs,"51 are due to the presence of alcohol in the water, but their movement also depends on the presence of glycerol (the chemical name for glycerin). The tears are more evident to the degree that the alcohol level is raised. Often the legs that descend when the gla.s.s is inclined are confused with the real tears, which form spontaneously at the ambient temperature when the gla.s.s remains immobile. are due to the presence of alcohol in the water, but their movement also depends on the presence of glycerol (the chemical name for glycerin). The tears are more evident to the degree that the alcohol level is raised. Often the legs that descend when the gla.s.s is inclined are confused with the real tears, which form spontaneously at the ambient temperature when the gla.s.s remains immobile.

In 1855 the British physician James Thomson proposed that the tears of wine resulted from the differences in wettability between the wine in the gla.s.s and the wine that was lower in alcohol content because of the alcohol evaporating.

The phenomenon works as follows: in a still gla.s.s, the liquid rises spontaneously along the walls, forms a thin crown a few millimeters above the wine's surface, and then descends again in the form of tears that remix with the wine. Since the crown is replenished by a rising tide of liquid, the tears remain for several minutes after wine has been poured into the gla.s.s.

If the gla.s.s only contained pure water, in a moist atmosphere, these tears would not exist. With wine, the crown is regularly replenished. The water-alcohol mix wets the gla.s.s, forming a meniscus at the extremities of which the alcohol evaporates more rapidly than the water. The impoverishment at the extremities prompts an aspiration of the wine, from the bottom of the gla.s.s to the top of the meniscus. Simultaneously, the solution weaker in alcohol redescends in the gla.s.s.

When the tears redescend, the nearly pure water that they contain comes into contact with the wine that remains in the gla.s.s, and sometimes the difference in wettability makes it so these two liquids do not mix. It is the same effect as when a sink is drained after doing the dishes. The detergent sometimes remains clinging to the enamel, so that if drops of water are applied to it, they do not wet the sink. Here it is the alcohol that plays the role of the detergent (or the surfactant, to borrow the term used with regard to emulsions: mayonnaise, bearnaise sauce, etc.) with its CH3CH2 group, insoluble in water, on one side, and its hydrophilic group OH on the other. group, insoluble in water, on one side, and its hydrophilic group OH on the other.

Currently, the physical chemists who have studied the tears in wine have concluded that the alcohol and water in wine do not entirely explain the phenomenon. Glycerol, especially, noticeably alters their dynamic. We have already seen that the sweetness and slippery texture (the viscosity) of glycerol make it an interesting compound in wine. What we have not yet seen is that this compound is produced by the n.o.ble rot (the fungus Botrytis cinerea Botrytis cinerea) that, under certain conditions, attacks grapes, damaging their skins and thus causing the water they contain to evaporate. Enriched in glycerol, such grapes produce sweet, smooth wines.

Is It Necessary to Let Wine Breathe Before Drinking It?

The authors of wine books are divided on this important question, and, once again, science offers little help in resolving it. The best rule seems to be to open the bottle a bit in advance and taste it. If the wine is a little rough, then aerate it by decanting it into a carafe. If not, leave it in its bottle to keep oxidation from deteriorating it.

This method has the advantage of revealing if the ideal temperature for consuming the wine has been attained (red wines with strong aromas are served warm, so that the volatile aromas are more easily released; nevertheless, excessive heat should be avoided, as the alcohol will volatilize in the air, and the wine will become sweet). Be careful in handling light wines; they deteriorate more easily than aged, heavy wines.

And now let us raise our gla.s.ses with Rabelais, and, "Drink!"

The Alcohols How Can We Distill Alcohol?

In the past, distillers set up shop on the outskirts of villages with their carts and their copper stills to distill cider, wine, and the fermented juice of various fruits: pears, apples, plums. The principle behind distillation is simple. Since ethylic alcohol boils at 78C (172F) and water boils at 100C (212F), alcohol is separated from water by heating a mixture of the two substances; the alcohol, which evaporates first, is condensed in a coil, while the water remains in the vat.

In practice, the operation is a bit more complex, because the aim is to recuperate not pure alcohol but flavored alcohol. In addition, the methanol, or methylic alcohol, must be eliminated by eliminating the first distilled fractions; this alcohol is toxic and, most important, causes blindness (nevertheless, it contributes to the bouquet when it is present in weak concentrations in certain white alcohols).

It is especially important to know that a high-quality brandy can only be obtained beginning with white wines that are quite acid, have a very light bouquet, and are low in alcohol content, because distilling strongly flavored wines produces too heavy a brandy.

In addition, it is important that the distilling vat be copper. Copper atoms fix the fatty acids in the wine and also capture the sulfur of the sulfur dioxide often present in white wines.

If distillation were not forbidden, anyone could easily practice it at home. All you have to do is put the mixture to be distilled in a pressure cooker, connect a length of pipe over the safety valve, and make cold water run over the pipe to condense the distilled vapors. One or two runs in succession, eliminating the first and second fractions in which various toxic products are concentrated, will procure an alcohol of the desired degree.

Improved Whisky?

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 fashion ...

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 relationships 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 relationship 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 relationship 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?