Q: I live alone and am rarely able to use an entire loaf of bread before it turns stale. I have tried storing bread in the refrigerator but find that once I do that it never tastes the same. What is it about refrigeration that ruins bread?
A: Bread turns stale as its starch undergoes a change in structure. Although stale bread has a dried-out appearance, a loss of moisture is not the complete explanation -- a loaf will even turn stale in a well-sealed, never-opened package. Temperature, it turns out, is the key.
There are two main types of starch, or carbohydrate, in bread. Over time, each will change from a random to a more rigid arrangement. The first of the two starches changes as freshly baked bread cools to room temperature. The settling of the second starch takes about a week. As the second starch changes, though, the texture of the bread shifts from soft to hard, or as we call it, stale.
While refrigeration extends the shelf life of many foods, the starch in refrigerated bread tends to settle faster. Your bread will be stale in about a day. This is the reason that refrigeration is not recommended for the storage of any raised bread product.
Freezing may provide a solution. Freezer temperatures keep the starch from settling. If you are unable to get through a loaf before it goes stale, consider splitting your loaf and storing half in the freezer.
Another possible solution is to look for breads that use preservatives, called emulsifiers. They can slow down the settling of starch and effectively extend shelf life. The most common emulsifiers in bread, the mono- and di-glycerides, are effective, yet harmless additives.
But however you decide to store your bread, make sure the package is always well sealed.
Q: Carrots in the refrigerator get soft and flexible after a few days and eventually they shrivel. When are they no longer safe to eat?
A: Carrots are a root crop. This means they are the route by which the water from the soil is taken up and transported to the rest of the plant. The fibrous part of the carrot contains flexible little compartments that hold water until needed by the rest of the plant above.
When the carrot sits, exposed to the air, the water evaporates. Over a matter of days, this will result in the more flexible vegetable you described. Eventually the carrot will wilt and rot. To retain moisture and firmness, carrots should first be washed, the excess water shaken off, and then placed in a plastic bag in the refrigerator crisper.
If you buy carrots with greens attached, remove them after purchase as they tend to draw the water out of the carrot. Carrots can be considered safe as long as they're not discolored, overly shriveled or slimy in feel. If a carrot has only begun to lose its firmness, it can often be brought back by soaking carrots in cold water.
Q: I recently saw a brand of eggs from vegetarian hens. Will this make a difference in the nutritional value of the egg?
Q: What are the nutritional differences between fertile and non-fertile eggs?
A: Laying hens are normally fed a meal that contains meat scraps as a source of protein. Vegetarian-diet hens rely on vegetable protein sources, such as soy. The vegetarian diet is more costly; this is usually reflected in the price of the eggs.
Fertile eggs come from hens having had sexual contact with roosters. Incubated properly, the eggs could develop into new chickens. Eggs found in most stores are infertile.
There are no nutritional differences among any of these eggs.
Edward Blonz is a nutrition scientist based in Berkeley, Calif.