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Wednesday October 26, 2005
By CHIA JOO SUAN
Today bread can be made in a shorter time and has a longer shelf-life. What is behind these improvements in bread quality?
The simplest breads are made from flour, water, yeast and salt. Usually there is “mother” yeast dough that keeps the yeast alive. The fresh dough is prepared at night and allowed to “rest” until early next morning. The baker then shapes the dough and bakes them for breakfast. The bread tastes and smells really good when it is fresh from the oven. On keeping, it turns stale and becomes dry and hard.
Texture and aroma
In bread-making, wheat flour is the main ingredient. The wheat grain has three main components: the bran coating, embryo or germ and endosperm.
White bread is made using white flour, which is derived from the endosperm that consists mainly of starch and protein with little fat, sugar and minerals. Wholemeal flour on the other hand includes the bran and germ of the grain, which is more nutritious. Without the fibrous bran, and the oily germ, white flour has fewer nutrients and can be kept longer. It has lighter texture that makes higher rising bread.
The protein in flour is known as gluten that consists of gliaden and the enzyme glutenin. The difference in the amount of protein differentiates the various types of flour available in the market. Flour with higher gluten is used for bread-making. The strength of gluten determines the toughness of the dough. Bread dough requires high gluten strength while cake batter requires low gluten strength.
When water is added to flour and the mixture is kneaded, the gluten binds it into an elastic texture. This gives the dough the ability to capture carbon dioxide produced by yeast during the fermentation process. Other than carbon dioxide yeast also makes alcohol.
The bread then increases in volume and the space is filled with carbon dioxide. It has a lighter texture than the original dough and is set for baking. The warm heat burns off the alcohol and brings forth the appetising lingering aroma of bread.
If you examine a slice of bread closely, you will see that it is full of air holes which were occupied by the carbon dioxide before baking. This makes the bread spongy and soft.
The salt not only adds taste; it slows down the rate of fermentation of the yeast. This gives the baker a certain amount of control over the rising process to ensure that the bread has the desired texture and cooks evenly with a brown crust. Sometimes sugar, or high fructose corn syrup is added as yeast nutrients to make the crust of the bread brown more easily.
Stale and dry bread
On keeping, bread turns stale. It becomes dry and hard which is due to recrystallisation of the starch in the bread. Adding butter, margarine or oil as additional ingredients keeps the starch in a flexible gel form and keeps the bread softer and moist for a longer time.
If it gets too oily, however, it makes the gluten strands shorter and prevents the loaf from getting volume. If you are making bread at home, do not be too generous with the oil.
In commercial products, additives are needed for automated production of bread.
Emulsifiers are commonly used to control staling. Chemically, emulsifiers have a fatty acid at one end that can combine with the starch, and a water-loving end that helps to keep it dispersed in the dough. Emulsifiers aid in distributing fats and oils throughout the dough, so less fat or oil is needed.
Other than lecithin, which is a common emulsifier, sodium stearoyl lactylate, glycerol monostearate or diglycerides are other options. Homemakers can add egg or sugar instead to make softer loaf.
Other additives function to standardise the fermentation characteristic, improve dough strength for machine handling, increase the rate of dough development or give better gas retention. In other words, every batch of bread made has the same appearance, size and quality.
A few of the additives are fungal alpha-amylase, proteolytic enzymes, L-ascorbic acid, azodicarbonamide, potassium bromate and mono-calcium phosphate.
A loaf of commercial bread usually comes with a five-day expiry date. Calcium propionate is a common preservative that ensures its good keeping quality.
The date marking serves as a guide on how long the loaf can be kept at room temperature. A reader, Teh C.P., asked whether it is still safe to eat the slices that are a couple of days beyond the expiry date. If the loaf has been kept refrigerated or frozen, it is safe to eat it.
Baked foods keep well in the freezer in proper packaging or containers. Bread maintains its freshness much longer if kept frozen in a plastic container. Frozen bread defrosted in a microwave oven, toaster or steamer tastes as good as fresh bread.
People with gluten allergy should avoid eating bread made of wheat flour but can opt for gluten-free bread. Gluten sensitivity or Celiac disease is an inflammatory condition of the small intestine due to ingestion of wheat. Individuals with certain genetic make-up are allergic to gluten in wheat.
They may experience severe symptoms such as diarrhoea, weakness, and weight loss, which could be due to marked decrease in intestinal absorptive surface area of the small intestine. Gluten sensitivity can also manifest itself as a blistering, burning, itchy rash on the extensor surfaces of the body.
Potassium bromate was used as early as the pre-war days as a bread-improving salt. It oxidises the gluten in dough, allowing it to retain gas better, which resulted in a taller, larger loaf. But bromate is toxic in high concentration. Home users should not use it generously. Other slightly expensive but safer ingredients like ascorbic acid or vitamin C and azodicarbonamide can be used instead.
During milling of flour, some of the nutrients are lost when the wheat germ and bran are discarded. Most commercial breads are enriched with nutrients. Commonly, the vitamins niacin, thiamine, riboflavin, and folic acid are added, along with the minerals iron and calcium. Others have dehydrated fruits, grains or seeds added to supply extra nutrients.
Bread-making is easy
Nowadays, bread-making is no longer a tedious task at home. The commercially available home bread-maker can make oven-fresh bread at your convenience. Merely by adding flour and yeast as the additional items in your shopping list and acquiring a little knowledge on properties of flour, your family can enjoy hot oven-fresh bread every morning.
Bread can be made plain or enriched with vitamin A from carrot or iron from spinach or nuts. Use rye flour for low gluten or soy flour for a change.
Chia Joo Suan is a food chemist who advocates safe eating habits. She is the author of What’s in your food?(Pelanduk).
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