What Einstein Kept Under His Hat: Secrets of Science in the Kitchen (26 page)

How does bleached flour differ from unbleached flour? And why does unbleached flour cost more than bleached flour? They’re charging me extra for not bleaching it?

....

W
heat flour is naturally slightly yellowish because it contains carotenoid pigments, natural yellow and orange compounds found in many fruits, vegetables, and grains. (Carrots’ famous orange color, carotene, is the mother of them all.) But most people are less color-tolerant than you and don’t like their flour to be yellow. The major exception is the semolina flour used in making pasta. Although it contains even more carotenoid pigment than other wheat flours, it isn’t usually bleached. Pasta that is slightly yellow, with its implication of eggy richness, is more appealing than if it were dead white.

If given half a chance, though, flour bleaches itself. That is, as it ages in contact with air, the pigments are oxidized and transformed into colorless compounds. But aging requires storage time, and time is money. That’s why “unbleached”—meaning naturally self-bleached during storage—flour costs more.

Flour millers can simulate the effects of aging by adding an oxidizing agent such as potassium bromate (in which case the flour is said to be bromated), or chlorine dioxide, or benzoyl (BEN-zo-eel) peroxide. The bleaching of flour isn’t mere cosmetics. Flour that has been
matured
, either by natural aging or by being treated with oxidizing agents, makes doughs that produce finer-grained, higher-volume bread and a dough that bakers report as being more elastic during kneading. That’s because oxidation not only removes the yellow color of flour but removes certain sulfur-containing chemicals (
thiols
) that interfere with the formation of gluten, the sticky, elastic protein in dough that traps gas bubbles and gives bread its light texture.

Some people are concerned about the intimidating names and properties of the bleaching chemicals. But after doing their jobs they are gone, having been chemically transformed into harmless substances. Chlorine dioxide is a gas that dissipates, so there is none of it left in the flour. And any excess of benzoyl peroxide would decompose in the heat of an oven.

After reacting with the carotenoids and thiols in the flour, the 50 or 75 parts per million of added potassium bromate turn into potassium bromide, a perfectly harmless salt. For most of the eighty-plus years of bakers’ use of potassium bromate, no one was able to detect any residual excess bromate in baked goods. However, chemists today have such sensitive analytical methods—down to billionths of a gram in many cases—that extremely low levels of residual bromate can be detected in baked goods made with bromated flour. Analytical detection instruments are so sensitive these days that they can find traces of almost any given chemical in almost anything, a fact that much of the public doesn’t understand. A finding that a certain food “contains toxic XYZ” often generates unfounded fears. But
everything
is toxic in large enough amounts and harmless in small enough amounts.

Nevertheless, because
high
levels of bromate have been found to cause cancers in rats, many consumers fear it, and the American baking industry, in consultation with the FDA, has voluntarily stopped using it. Canada and the United Kingdom have banned the chemical altogether.

Incidentally, the claim that the bleaching of flour destroys its vitamin E is true but empty, because wheat flour contains negligible amounts of vitamin E to begin with.

I have a recipe that calls for self-rising flour, but I can’t find any where I live. Can I make it myself?

....

S
ure. Self-rising flour is flour that has some baking powder and salt already mixed into it. Most of the bigger supermarkets carry it. But to make it yourself, just add about 1
1
/
2
teaspoons of baking powder and
1
/
2
teaspoon of salt to each cup of all-purpose flour or cake flour and mix well. A gently wielded whisk does the best mixing job.

What kind of wheat is buckwheat? Could I make bread out of buckwheat flour?

....

N
o, for two reasons: buckwheat isn’t wheat at all, and even if it were, its flour couldn’t make bread.

Buckwheat groats, known as
kasha
in eastern Europe and
sayraisin
in France, are the seeds of the plant
Fagopyrum esculentum
, which is not related to wheat or any other grassy cereal plant. The generic word
groats
refers to hulled and cracked grains of any kind, such as wheat, buckwheat, oats, or barley. When the grain happens to be corn,
groats
morphs into
grits
.

The name
buckwheat
comes from the German and Dutch for “beech wheat,” because its edible seeds, shaped like tetrahedra (pyramids with four equal, triangular sides), resemble beechnuts. The seeds can be cracked down into groats or ground to flour and added to wheat flour for making buckwheat pancakes. But buckwheat flour isn’t good for breadmaking because when wet it forms very little gluten, the elastic protein that traps gas bubbles and gives bread its open structure and chewiness. Wet buckwheat flour is just barely sticky enough for the Japanese to make
soba
noodles out of it.

Is there any reason for using one shape of pasta rather than another, such as using flat linguine rather than round spaghetti? I would think that the shape with the greatest surface-to-volume ratio would absorb the most sauce and be most flavorful. So why do people use all of those other shapes?

....

S
urface-to-volume ratio? I’ll bet you’re an engineer.

For one thing, the almost limitless variety of pasta shapes provides both fun for the eye and differing sensations in the mouth. But there are also real differences in their compatibility with different sauces.

It’s not a matter of the pasta absorbing sauce through its surface; pasta isn’t that absorbent and sauces aren’t that liquid. But some sauces adhere better than others and will stick to the pasta surface no matter what its shape. And, of course, the more surface area there is, the more sauce can stick.

Ultimately, however, it’s a matter of how well the heap of pasta on the plate envelops and incorporates the sauce and how well the pasta will retain the sauce when it’s twirled on a fork or, in the case of a small, compact shape, when it’s picked up on a spoon. The overall result is dictated by both stickiness and mechanics.

Most sauces are chunky to some degree, and the spaces that the chunks must nestle into—the empty spaces within the pasta tangle—are very different for long pasta such as spaghetti and linguine, for tube pasta such as penne and rigatoni, and for special shapes such as
conchiglie
(seashells) and
farfalle
(bow ties). Obviously, a pile of fat spaghetti will have more empty spaces than a pile of thin spaghetti, which can nestle together more compactly.

One should therefore try to match the sauce to the pasta shape.

Fusilli
(springs), for example, hold on to chunky sauces well; the larger tubes, such as rigatoni, are good with meat sauces; fettuccine goes well with sticky sauces that coat its flat, ribbon-like surface, such as in fettuccine Alfredo. Spaghetti is probably the most versatile shape, but when it is extra-thin, as in angel hair or
capellini
, it’s best with thin, liquidy sauces that distribute themselves throughout the heap by capillary action.
Capellini
Alfredo would sit in the plate like a ball of mud.

Table 5 on the following page lists the pasta-and-sauce pairings recommended by the Barilla Alimentare S.p.A. pasta company of Parma, Italy, for a few of the shapes it distributes in the United States. For pictures of these shapes, along with everything else you could possibly want to know about pasta manufacture and technology, the website
www.professionalpasta.it
lists 822 shapes from
abissini
to
zituane
. Many of these, however, are aliases used in different parts of Italy.

But hey, the pasta police are greatly understaffed and underfunded, so you can probably get away with any cockamamie combination of shape and sauce that you enjoy.

Mangia!

If I make a smoothie by blending fruit with milk, yogurt, or whatever, are the positive effects of the fiber eliminated by processing the fruit in a blender?

....

N
o. No matter how thoroughly pureed it is, the fiber is still effective.

In the dietary context, the word
fiber
is misleading because it conjures up images of eating coconut husks and mattress stuffing. But
dietary fiber
doesn’t refer to a physical texture. It’s a catchall term for the components of vegetable foods that humans don’t have the enzymes for digesting, and that therefore have no energy value and pass through our digestive tracts unchanged (which is their major virtue). We used to call it bulk or roughage. Although it has no chemical or nutritive value, it is essential for physically moving everything we eat through the processing plant we call the alimentary canal.

Dietary fiber, found in fruits, vegetables, and grains but not in animal products, has been found to decrease the risk of certain disorders such as colon cancer, although that finding has been challenged. Nevertheless, fiber is one of the main reasons that eating fruits and vegetables is so important to health.

There are both water-soluble and water-insoluble fiber substances, and nutritionists recommend eating lots of both kinds. The soluble ones are mostly pectins and gums, found in fruits; they’re what cause fruit jellies to gel. Tart apples, crab apples, sour plums, Concord grapes, quinces, gooseberries, red currants, and cranberries are especially high in pectin. The most common insoluble fibers are cellulose and lignin, the binder between the cellulose fibers that make up the structural framework of plants’ cell walls.

Some termites can digest and utilize the energy inherent in cellulose and lignin, but we humans can’t. On the other hand, termites are lousy at Scrabble.

I was reading the Nutrition Facts chart on my box of cereal. I thought that, by definition, fiber is indigestible and therefore has no calories. But this box shows fiber as carbohydrates. Can you sort this out?

....

D
ietary fiber is indeed completely or almost completely indigestible. In fact, as you point out, that’s how it is defined: those parts of our foods that provide us with no vitamins, minerals, or even calories.

Chemically, the fiber compounds in plants are complex carbohydrates. They are therefore included in the total amounts of carbohydrates listed on the labels. Sometimes the chart will break the dietary fiber down into soluble and insoluble fiber, but they’re both noncaloric anyway. The “other carbohydrates” listed are sugars, sugar alcohols (see p. 233), and—well, other carbohydrates, mostly starches. All the numbers should add up to the number of grams of “Total Carbohydrates.”

The number of carbohydrate
calories
, however, comes only from the digestible carbohydrates: from the starches and sugars that you would expect. If you subtract the number of grams of fiber from the number of grams of total carbohydrates, you’ll have the approximate number of grams of nutritional carbohydrates, which, at 4 calories per gram, should equal the number of carbohydrate calories in the chart.