Fungus formula: Yeast essential ingredient

[Guest guest]

Fungus formula: Yeast essential ingredient in making bread, beer and

wine

By Hudson Sangree

Scripps News Service

Complete Living Index

http://www.seacoastonline.com/news/exeter/03102006/currents/91960.htm

Exeter News-Letter - Exeter,NH

With hopes for a bountiful new year, this is a good time to say a

word of thanks to Saccharomyces cerevisiae - the common yeast - and

the many gifts it bestows on us.

Invisible yet indispensable, the one-celled fungus is the key agent

of bread, beer and wine.

There's no doubt that without it we'd be drinking grape juice.

Yeast, it seems, might even have prompted the beginnings of modern

civilization. According to some historians, humans gave up their

nomadic ways and settled in villages to grow grain for baking and

brewing after they discovered the benefits of yeast, namely

fermentation and leavening.

Writing, science and culture followed.

There are scholars who say the Egyptians who built the pyramids were

paid with bread and beer.

" Without yeast, where would the human race be? " asks

, head winemaker at Bogle Vineyards in sburg, Calif.

Calling yeast an " unsung hero, " suggests that a bit of

gratitude might be in order. Billions upon billions of yeast cells

must die in their own alcoholic excretions to make a bottle of

petite sirah, he notes.

" It's a great sacrifice they make for us, " says .

Not all yeast are so unlucky.

At the University of California-, millions of the microbes are

living to old age in a room resembling a walk-in cooler.

The university's Department of Food Science and Technology houses

one of the world's largest collections of yeast, with more than 500

species and 6,000 strains, including heirloom wine yeast from

California and Europe.

Much of the collection was gathered by professor Herman J. Phaff,

who has been called the Indiana of yeast.

On expeditions to Japan, Argentina, the Caribbean and Mexico, Phaff

gently scraped samples of yeast from tree branches and fruit,

cactuses, flowers and rotting stumps. He brought the prizes back to

UC-, where he worked for decades.

" He really laid the foundations for our understanding of yeast, "

says Kyria Boundy-Mills, Phaff's successor as curator of the

collection.

Though Phaff died in 2001 at age 88, much of his yeast lives on in

thousands of test tubes arrayed on wooden shelves.

Stepping into Phaff's storeroom is like entering a strange n

museum, except the natural specimens aren't dead and stuffed but

resting quietly, giving off their distinctive yeasty scent.

The oldest of the yeast is from 1893, according to Boundy-Mills.

There are about 20,000 test tubes filled with small samples of yeast

and fluid and corked with cotton wool. The yeasts are dormant but

can be revived easily.

For efficiency's sake, the collection gradually is being transferred

to a freezer and stored at a temperature of minus 100 degrees

Fahrenheit. That's cold enough to freeze human skin on contact, but

the hardy yeast can survive. Warm it up, give it food and water, and

the yeast will grow again.

The yeast in the Phaff collection is identified, studied and shared

with other universities.

Boundy-Mills also assists biotechnology companies that use yeast in

genetic research and as living factories for organic chemicals,

including pigments, proteins and enzymes.

Much of this work ultimately benefits humans, with whom yeasts have

more in common than they do with plants or bacteria.

" They are the simplest form of higher life, " says Boundy-Mills.

Yeasts must eat; unlike plants, they can't produce their own food

through photosynthesis. And unlike bacteria, yeast cells have a

nucleus and genetic structure like ours.

Still, they are very basic organisms. They are also tiny. One gram

of yeast contains some 20 billion cells.

Yeast feeds on sugars and excretes carbon dioxide and alcohol. As a

kind of fungus, yeast grows naturally on high-sugar fruits such as

grapes. It even floats through the air.

At her lab, Boundy-Mills is experimenting with different strains of

yeast meant to attract flies that are destroying California's olive

crop.

One of Phaff's discoveries, gathered from a tree in Japan, is a type

of yeast that contains a rosy pigment. The substance is fed to

farmed salmon to give their flesh - naturally white - its pink

color.

In bread-making, yeast colonies can thrive for decades, producing

flavorful sourdoughs and crusty baguettes. Some dough starters in

France are more than 100 years old.

At the Village Bakery in , Aziz Fattahi has been feeding and

growing his yeast strain for a dozen years. On a recent Friday, a 5-

gallon bucket of yeast, flour and water sat bubbling by a sunny

window.

Yeast thrives on warmth and food.

" If you add a couple of grams of yeast to water and flour, within 24

hours you'll have a few gallons of poolish, " he says, using the

French term for the baking mixture.

That, in turn, will produce dozens of airy, golden loaves - the

leavened bread that first persuaded nomads to take up farming.

Even good yeast can go bad, however.

The microorganisms are always present in large numbers in our

bodies. In their natural balance, they are beneficial, but an

imbalance can cause infections.

Jungle rot, which has plagued soldiers by eating up their canvas

tents and leather boots, is the result of yeast at work.

In beer-making, bad or weak yeast can impart a " funky, moldy, cheesy

taste, " says Costello, owner of Brew It Up in Sacramento,

Calif.

The right yeast, however, can impart pleasant flavors such as cloves

or banana to wheat beer, and will create a clean-tasting lager or

ale under proper conditions, he said.

At the Anheuser-Busch plant in Fairfield, Calif., brewmaster

Poley says he works hard to keep his yeast happy, making sure it is

well-fed and has ideal conditions in which to grow.

The brewery can produce 136 million gallons of beer each year. But

all that Budweiser depends on the well-being of the yeast, a secret

strain used by Anheuser-Busch since 1876.

" I think of the yeast as almost having a personality, " Poley

says. " You have to have a lot of respect for the yeast. If you don't

treat it right, it will not produce the beer you are trying to

produce.

" It's like your companion in the brewing business, " he says. " If

it's not happy with you, then you're not happy. "

Distributed by Scripps News Service, www.shns.com.