Q: What are pregelatinized flours, and what is their functionality?
B.T., Miami

A: Pregelatinized flours, also called stabilizers, are substances with high water absorption ability. Guar flour and carob gum are two of the best known pregelatinized flours. Pregelatinized flours are essentially used in improvers for interrupted fermentation. In this case, the part of free water in the dough is reduced, which means when the product is frozen, fewer crystals form. These crystals lead to a deterioration of the gluten membranes and thereby to a deterioration of the product. Carob gum is extracted from the seeds of the carob tree that is found in Mediterranean countries. Guar gum is extracted from a type of bean that grows in India. The kernels of these beans are ground into flour.

Q: Recently we came across a formula that called for curled wheat. Can you tell us what this is?
Chris, via e-mail

A: Curled wheat is ground whole wheat containing about 11 percent protein that has been mixed with liquid and an edible acid to produce dough. The heated dough is then extruded through a die under particular conditions — from high to low pressure zones — to provide a high protein expanded curled wheat product that can be used as an ingredient.

Q: Lately we have seen violet discolorations in the crumb of our sourdough breads. What causes this?
Madlyn, via e-mail

A: The discoloration is caused by flied cow wheat (Melampyrum arvense), a weed that grows in wheat fields. The seeds are similar to wheat grains and are difficult to remove in the mill. Remains and pieces of cow wheat in the flour cause violet discolorations in the crumb of sour breads.

Q: Is there an economical substitute for marzipan?
Gary, via e-mail

A: Persipan is an economical substitute for marzipan. Raw persipan paste is manufactured through the same process as marzipan and consists of debittered apricot kernels and sugar. The moisture content does not exceed 20 percent, and a maximum of 35 percent sugar is added. Apart from this, the paste contains 0.5 percent potato starch, which is added to comply with food regulations. Persipan for forming is made by blending raw persipan with sugar. Up to one-and-one-half parts sugar may be added to one part raw persipan. It is recommended to add up to 5 percent glucose syrup and 5 percent sorbitol syrup, but these additions must be deducted from the sugar amount. Labeling is required.

Q: What makes San Francisco sourdough bread special, and can it be duplicated anywhere in the country?
D.C., Mora, N.M.

A: What makes the San Francisco sourdough bread special is the bacterium Lactobacillus sanfrancisco, which was found in starter doughs from San Francisco bakeries. An unusually acid-tolerant yeast, Saccharomyces exiquus, worked with the bacterium in a symbiotic relationship to produce the bread's unusual flavor, crust and texture. Pure cultures now are grown commercially and are commonly used to control the quality of the sourdough bread, which can be produced anywhere in the world.

Q: What kind of walnut is best suited for baking?
Edwin, via e-mail

A: There are three basic varieties of walnuts:

English walnuts: Also called Persian walnuts, these are the most familiar type. Although native to Asia and Europe, California is now the major world producer. The shells of English walnuts are relatively easy to crack with a nutcracker, and the halves of the nut kernel can usually be removed in one piece.

Black walnuts: These walnuts have a very tough, dark outer hull, and the inner shells are also thicker than those of English walnuts. The shells have to be broken under so much pressure that the nut meats are usually crushed as well. These have a very distinctive, “cheesy” flavor. They are not to everyone's taste, but aficionados of these walnuts will go to great lengths to get their hands on them.

Butternuts: Also called “white walnuts,” these are native to the United States, but are rarely harvested for the marketplace. They are oilier and sweeter tasting than the other two walnut varieties.

As the English walnuts are easily available I use these for all my application in the bakery.

Q: I have two questions. Can the roots and leaves of rhubarb be consumed, and what can be used to sweeten the rhubarb stalks?
David, via e-mail

A: Rhubarb, which looks like a pink celery stalk, is botanically a vegetable, but it is used as a fruit, largely in pies and sauces. The roots and leaves aren't edible; indeed, the leaves are highly poisonous. Rhubarb stalks are extremely tart, and they require sweetening to make them appetizing. This can increase their calorie content considerably. For example, a typical home recipe for rhubarb pie calls for 4 cups of diced rhubarb to which 1 ¼ cups of sugar are added. This converts 104 calories' worth of rhubarb to more than 1,000 calories. An alternative to this is to sweeten rhubarb with other sweet fruits, such as apples.

Q: Our supplier offers us various kinds of cinnamon. Which one do you recommend using?
R.B., Davis, Calif.

A: Cinnamon is the dried inner bark of a tropical evergreen tree with about 100 different species, all with similar aromatic properties. The two most commonly available varieties are Ceylonese cinnamon and Chinese cinnamon. Chinese cinnamon, which is actually from the bark of the cassia tree, is not considered a true cinnamon. Grown in southern China, and other parts of eastern Asia, cassia is a dark reddish color and stronger in flavor than its Ceylonese cousin. Cassia is less expensive to process than true cinnamons and is the type of “cinnamon” most commonly sold and used in bakeries — though it is sometimes blended with Ceylonese cinnamon. Most cinnamon is sold in powdered form; however, it also is available in the form of sticks (scrolled portions of bark) and essential oil. Cinnamon sticks are sold in various lengths, though the most common cinnamon stick is about 3 ins. long. My preference changes with my supplier or even the price, as the differences in outcome is very minimal and it has no impact on the application of use.