Bread is one of the most common, relatively low cost, traditional foods around the world. Yet bread actually has close links with biotechnology, the common denominator being enzymes.
For decades enzymes such as malt and fungal alpha-amylase have been used in bread making. Due to the changes in the baking industry and the ever increasing demand for more natural products, enzymes have gained real importance in bread formulations. And new and rapid advances in biotechnology have made a number of exciting new enzymes available to the baking industry.
The dough for white bread, rolls, buns and similar products consists of flour, water, yeast, salt and possibly other ingredients such as sugar and fat. Flour consists of gluten, starch, non-starch polysaccharides, lipids and trace amounts of minerals. As soon as the dough is made, the yeast starts to work on the fermentable sugars, transforming them into alcohol and carbon dioxide, which makes the dough rise.
Starch is the largest component of wheat flour. Amylases can degrade starch and produce small dextrins for the yeast to act upon. A special type of amylase which modifies starch during baking even has a substantial anti-staling effect.
Gluten is a combination of proteins which form a large network during dough formation. It is this network that holds the gas in during dough proofing and baking. The strength of this gluten network is therefore very important for the quality of all bread raised using yeast. Enzymes such as hemicellulases or xylanases, lipases and oxidases can directly or indirectly improve the strength of the gluten network and so improve the quality of the finished bread.
Malt flour and malt extract can be used as enzyme supplements because malt is rich in alpha-amylases. However, it is even better to use a fungal alpha-amylase. Commercial malt preparations can differ widely in their enzyme activity, whereas an industrial enzyme is supplied with a standardized activity.
The alpha-amylases degrade the damaged starch in wheat flour into small dextrins, thus allowing yeast to work continuously during dough fermentation, proofing and the early stage of baking. The result is improved bread volume and crumb texture. In addition, the small oligosaccharides and sugars such as glucose and maltose produced by these enzymes enhance the Maillard reactions responsible for the browning of the crust and the development of an attractive “baked” flavour.
Retarding the staling process
Bread staling is responsible for significant financial losses for both consumers and bread producers. For instance, bread worth more than US$ 1 billion is discarded annually in the USA. Staling is associated with the loss of freshness in terms of increased crumb firmness and decreased crumb elasticity. Staling is believed to be due to changes in starch structure during storage. When the starch granules revert from a soluble to an insoluble form, they lose their flexibility: the crumb becomes hard and brittle. For decades emulsifiers have been used as anti-staling agents but, besides coming under special labelling rules, they actually have a limited anti-staling effect.
Novozymes’s bacterial maltogenic alpha-amylase Novamyl® has been found to have a substantial anti-staling effect. It modifies the starch during baking at the temperature when most of the starch starts to gelatinize. The resulting modified starch granules remain more flexible during storage. Bread produced with Novamyl has a far softer and more elastic crumb than bread produced with distilled monoglycerides as emulsifiers.
As the graphs below show, the addition of Novamyl at 45 ppm results in a much softer and more elastic crumb than the addition of high-quality distilled monoglycerides at 5000 ppm.
Softness and elasticity of American type (sponge & dough) pan bread with Novamyl compared to distilled monoglycerides.
Flour contains 2.5-3.5% non-starch polysaccharides which are large polymers (mainly pentosans) that play an important role in bread quality due to their water absorption capability and interactions with gluten. Although the true mechanism of hemicellulase, pentosanase or xylanase in bread making has not been clearly demonstrated, it is well known that the addition of certain types of pentosanase or xylanase at the correct dosage can improve dough machinability, yielding a more flexible, easier-to-handle dough. Consequently, the dough is more stable and gives better ovenspring during baking, resulting in a larger volume and improved crumb texture.
Normal wheat flour contains 1-1.5% lipids, both polar and non-polar. Some of these lipids, especially the non-polar lipids such as triglycerides, are bound with gluten, impeding its functionality. The addition of a functional lipase modifies the triglycerides, thereby modifying their interaction with gluten. A gluten network with improved strength is achieved. This stronger gluten ensures a more stable dough upon over-fermentation, a larger loaf volume and significantly improved crumb structure. Because of the more uniform, smaller crumb cells, the crumb texture is silkier and the crumb colour appears whiter.
Chemical oxidants such as bromates, azodicarbonamide and ascorbic acid have been widely used to strengthen the gluten for bread making. Oxidative enzymes (e.g. glucose oxidase) can partially replace the use of these chemical oxidants and achieve better bread quality.
As shown in the photo below, glucose oxidase and fungal alpha-amylase cannot only replace bromate but also result in much better bread.
The synergistic effects of enzymes
Each of the enzymes mentioned above has its own specific substrate in the wheat flour dough. For example, lipase has the lipids, xylanase has the pentosans and amylases have the starch. Because the interaction of these substrates in dough and bread is rather complex, the use of enzyme combinations can have synergistic effects that are not seen if only one enzyme is used – not even at high dosages. Quite often an overdose of one enzyme will have a detrimental effect on either the dough or the bread. For instance, an overdose of fungal alpha-amylase or hemicellulase/xylanase may result in a dough that is too sticky to be handled by the baker or the machinery. It is therefore a benefit for some types of bread formulation to use a combination of lower dosages of alpha-amylase and xylanase with lower dosages of lipase or glucose oxidase to achieve optimum dough consistency, stability and bread quality. Another example is to use maltogenic alpha-amylase in combination with fungal alpha-amylase and xylanase or lipase to secure optimum crumb softness together with optimum bread quality in terms of crumb structure, bread volume, etc.
For more information, please order articles A-6513 and A-6565.
The standard Product Range for the Baking industry looks as follows. Most products are available in liquid as well as solid form, and in different concentrations. Please contact your local sales office for further details as well as with inquiries about special products not listed here.
Please note that all products listed are not necessarily available in all countries. Contact your local sales office for details.
An amylogluosidase to increase the formation of glucose, which is advantageous for doughs that will be chilled or frozen, or for improvement of crust colour.
A fungal alpha-amylase for improving the raising ability of wheat flour used in bread production.
Fungamyl Super MA or 500
Blends of fungal amylase and pentosanase activities.
A glucose oxidase for improvement of dough stability.
A protease to degrade proteins in flour for biscuits, crackers and cookies.
A unique bacterial maltogenic amylase used for antistaling.
A purified 1,3-specific lipase for baking.
A xylanase/hemicellulase for general improvement of dough handling and bread quality without fungal alpha-amylase activity.