Molecular Gastronomy: Exploring the Science of Flavor (27 page)

when it is removed from the water, after cooking. Adding a knob of butter or a

squirt of olive oil to the dish at the table produces the same result.

Finally, the cooking water has its own role to play. Jacques Lefebvre at the

inra station in Nantes has shown that the more proteins the water contains,

the less amylose the starch loses during cooking. Therefore pasta should be

cooked in a rich broth. Moreover, the Montpellier team demonstrated that cook-

ing pasta in mineral water increases the loss of starch content and therefore

stickiness as well, whereas pasta cooked in slightly acidified water (through

the addition of a tablespoon of vinegar or lemon juice, for example) preserves

a satisfactory surface state, even after overcooking. Proteins in water with a pH

of 6 have an electrically neutral form, allowing them to combine more easily

and form a network that efficiently traps the starch.

178 | investigations a nd mod el s

51

Forgotten Vegetables

The introduction of novel vegetables requires extensive research.

a h o s t o f u n f a m i l i a r v e g e t a b l e s — Japanese artichokes, pepinos,

Cape gooseberries, Peruvian parsnips, tuberous chervil, sea kale, skirret—are

now available to enliven the diet of those who are tired of carrots, leeks, and po-

tatoes. Jean-Yves Péron and his colleagues at the École Nationale d’Ingénieurs

des Travaux de l’Horticulture et du Paysage in Angers are studying forgotten

or unknown vegetables with a view to improving their reproduction and cul-

tivation. Not only are food lovers eager to try these novel varieties, but econo-

mists also welcome the interest of the Angevin agronomists in promoting di-

versification because saturation of the market for garden produce diminishes

the profitability of capital investment. And from the point of view of farmers,

cultivating a new or neglected vegetable sometimes is necessary if they are to

increase demand for their products.

In Search of Ancient Agronomists

The introduction of new or forgotten vegetables entails a number of related

studies: Producers need to be persuaded of the viability of new crops in both

horticultural and commercial terms, and consumers have to be convinced of

their gastronomic and nutritional interest. It took decades to bring the first

Japanese artichokes and Peruvian parsnips to markets in France and a few

restaurants. Tuberous chervil and sea kale will not be slow to follow.

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Sometimes the reintroduction of a vegetable is made easier by older agro-

nomic studies of the vegetable itself or, when no study has yet been carried

out, members of the same family (the various cabbages in the case of sea kale;

members of the parsley family, such as celery, in the case of tuberous chervil,

and so on). Tuberous chervil, which grows wild in the east of France, was first

identified by French agronomist Charles de l’Écluse in 1846. Nonetheless, de-

spite the efforts of many gardeners of the period, its cultivation was never very

widespread. When the researchers in Angers began their work, it was limited

to a few truck farms in the Dole and Orléans regions.

Tuberous chervil traditionally is planted in the fall, and its roots, similar

to carrots, are harvested the next July. Seed-bearing specimens are planted

in December. Why is this vegetable largely unknown? No doubt there are a

number of reasons: Germination does not take place without prior stratifica-

tion; the germinating potency of seeds is limited to a year; crop yields are low;

the root becomes edible and gastronomically pleasing only when it reaches a

certain size, at which point it has a delicate taste similar to that of the chestnut;

and the root is very sensitive to the saprophytic mushrooms that develop on

surface lesions.

Seeking to remedy these two last defects, the Angevin researchers studied

the genetic variability of the species by crossing wild plants with greenhouse

specimens and by means of in vitro cultivation, using plant tissues and growth

hormones to develop variants. At the same time they looked for ways to im-

prove cultivation methods. In particular, they wondered how the dormancy

period of tuberous chervil seeds could be eliminated and the plant population

optimized. Because the mechanisms responsible for inhibiting fertilization

in related plants (sometimes associated with the presence in the walls of a

ripened ovary of inhibitory substances that are easily removed) were already

understood, the agronomists were able to test various methods for eliminating

the dormancy period under controlled conditions: variations in temperature,

light cycles, application of growth regulators (gibberellin and cytokinin), con-

servation under oxygen-free conditions, and so on. Finally, they showed that

dormancy is embryonic in nature; that its onset occurs during the last stages of

the seeds’ maturation, once they have lost most of their water; and that it can

be blocked only if the seeds have been exposed to a cool, moist environment

for eight to ten weeks.

180 | investigations a nd mod el s

This research has also led to the creation of new plant lines and the selec-

tion of a number of commercially promising hybrids. By themselves, however,

such studies do not guarantee that the new vegetable will be brought to market.

Growing techniques must be explained to farmers and seed manufacturers,

and promotional efforts aimed at bringing it to the attention of the public must

continue until it reaches buyers’ dinner tables. Nutritional studies therefore

are needed to determine how a new vegetable is best prepared. For example,

tuberous chervil loses starch, gains in various reductive sugars, and develops

its distinctive flavors during storage. Recipes created by renowned chefs on the

basis of these studies can make a great difference in determining whether the

new (or newly reintroduced) vegetable is accepted.

Forgotten Vegetables
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52

Preserving Mushrooms

Modifying the atmospheric pressure under which button mushrooms are

packaged helps retain their freshness for a long time.

m u s h r o o m s a r e f r a g i l e a n d h a r d t o k e e p. Consumers will put

up with wild mushrooms that are a bit bruised, but they want ordinary button

mushrooms to be nice and white, with a short stem, small cap, and gills that

are covered by a continuous veil, for they know that mushrooms can rapidly

change character. A few days is all it takes for mushrooms to darken, for their

stems to lengthen, for their ink-black gills to be exposed, and, worse still, for

their taste and texture to be denatured.

How can mushroom producers keep their products fresh for longer peri-

ods of time? The success of various kinds of ready-to-eat salad greens, washed

and packaged under controlled atmospheric pressure, has encouraged food

processing firms to take an interest in the problems associated with bringing

mushrooms to market. Having shown that the shelf life of baskets of mush-

rooms could be extended by altering the preservation atmosphere, a team of

researchers from the Institut National de la Recherche Agronomique (inra)

station at Montfavet working with food technologists from the Association

de Développement et de la Recherche dans les Industries Agro-Alimentaires

et d’Emballage-Conditionnement studied various plastic films to determine

which one does the best job of sealing in freshness.

182 |

Living, Breathing Mushrooms

The researchers began by analyzing button mushrooms kept at room tem-

perature and were able to confirm that cold temperatures reduce microbial

and physiological degradation. The usual form of commercial display calls for

mushrooms to be stored for a day or two at 2°c (36°f) and then put out for sale

at room temperature for a day. This means they will be fresh for only a brief

period after purchase: At 11°c (52°f), in 90% relative humidity, mushrooms re-

main presentable for three to five days, but at 13°c (55°f) this period is reduced

to three days.

The development of a system of refrigerated storage and transportation

links (“cold chains”) for delivering fresh prewashed salad greens to the con-

sumer has made it possible to offer button mushrooms in plastic wrapping

that significantly extends their sell-by date. But in order to know what kind of

atmosphere is optimal for such packaging, it is necessary to understand how

mushrooms change under different conditions.

In the complete absence of oxygen, mushrooms are colonized by potentially

dangerous microorganisms such as
Clostridium botulinum
. In the presence of

oxygen, on the other hand, mushrooms continue to breathe and change. Since

1975 it has been known that the color and texture of mushrooms depend on

the atmosphere is which they develop. In particular, increasing carbon dioxide

concentration while reducing oxygen concentration lowers the respiration of

fungal cells and, for this reason, retards degradation.

To determine under which atmosphere mushrooms are best preserved, G.

Lopez Briones and his colleagues at the Montfavet inra station measured the

effect of various concentrations of oxygen and carbon dioxide on mushrooms

stored at a temperature of 10°c (50°f). They observed a correspondence be-

tween carbon dioxide concentration and the phytotoxic effect of this gas (de-

tected by the increased respiratory intensity of the mushrooms on being put

back into contact with air), which damages the cell membranes and thus favors

their exposure to darkening enzymes and their substrates. From the point of

view of color, the best atmospheres are those in which the carbon dioxide and

oxygen concentrations are lower than 10%.

By contrast, texture is best preserved when the carbon dioxide concentra-

tion is higher than 10%, for mushrooms have a superstructure that resists

Preserving Mushrooms
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modification. In specimens preserved for a week at 10°c (50°f), in an atmo-

sphere containing 15% carbon dioxide, the veils are not ruptured, preserving

the button form preferred by French consumers; the higher the carbon dioxide

content, the longer the cap remains closed. Finally, excessive humidity causes

rapid degradation, so if you put button mushrooms in the refrigerator, don’t

close the bag.

Slowing Maturation

A compromise must be found: The carbon dioxide concentration should

be not too high, or the mushrooms will not remain white, nor should it be too

low, or they will develop too rapidly. Carbon dioxide concentrations between

2.5% and 5% and oxygen concentrations between 5% and 10% appear to be

optimal.

How can such atmospheres be created? The Montfavet team compared

new microperforated polypropylene films and stretchable polyvinyl chloride

films. Mushrooms were placed in baskets, some wrapped and some not, and

stored at temperatures between 4°c (39°f) (the legally mandated temperature

for cold storage of ready-to-eat salad greens) and 10°c (50°f) for eight days.

After eight days of storage at the high end of this range the veils on 85% of

the unwrapped mushrooms had opened, whereas maturation was slowed at

all temperatures in those that were covered with both types of film. But the

old polyvinyl chloride type, being less permeable to humidity, was more suc-

cessful at retarding development. The challenge now facing researchers is to

maximize this impermeability.

184 | investigations a nd mod el s

53

Trufes

European black trufes are all of the same species, but genetic analysis

shows that Chinese trufes are something quite di‡erent.

t h e b l a c k d i a m o n d ! An immense amount of ink has been spilled in

singing its praises. No food writer fails to mention its appearance on a menu,

and no chef neglects to feature it when he aims for stars. For centuries the

merits of the various black truffles that grow in Western Europe have been

debated. The black truffle of Périgord is recognized have a quite different taste

from the one found in Burgundy, and naturally the truffles found in France are

claimed by the French to be far superior to those of Spain and Italy. Can science

provide an objective basis for these opinions?

In Europe there are ten sorts of truffles, which is to say mushrooms of the

Tuber
genus. The black truffle, also called a Périgord truffle (
Tuber melanospo-

rum
), is harvested principally in Spain, France, and Italy, but its gastronomic

qualities vary from region to region. Michel Raymond and his colleagues at the

Centre National de la Recherche Scientifique, the Institut National de la Re-

cherche Agronomique (inra), and the Institut pour la Recherche et le Dével-

oppement in Montpellier sought to determine whether these differences have