Process optimisation: baking with enzymes
What are enzymes?
Put simply, enzymes are protein molecules produced by cells which work as biological catalysts. They speed up chemical reactions but do not get used up in the process meaning they can be used repeatedly.
Why use enzymes?
Reducing the cost of manufacturing is top of the priority list for all companies producing bakery products. Competition on price is fierce and small savings in cost can help protect or secure the market for a product. One way to achieve cost savings is to optimise processes to make more efficient use of ingredients and resources. Enzymes have the potential to achieve this. This article examines some of the ways that enzymes can help.
Enzymes are natural biological catalysts that speed up and improve the chemical reactions required in the baking process. All enzymes are protein molecules; they are fast and efficient in their action, with just small quantities in the range 10-150 ppm being required. Whether naturally present in raw materials or added by the manufacturer, enzymes play a vital role in the production of many food products. Enzyme manufacture is now big business - multinational companies have even been established to replicate naturally occurring enzymes using modern techniques. This has resulted in enzymes that are highly specific in the way they work and more effective than their natural counterparts.
The bakery sector uses enzymes for numerous applications and it’s worth remembering that they are destroyed by the high temperatures involved in the baking process, helping bakers to maintain the highly desirable clean label image for their product.
One of the historic uses of natural enzymes is in traditional bread manufacture. This uses lengthy fermentation times that allow the natural enzymes present in wheat flour to break down the starch, proteins and lipids so that the baked bread has more flavour and the nutrients are more available. Enzymes are now seen by the industry as vital processing aids, for example, in helping to oxidise gluten during dough mixing, manage water movement during dough processing, and providing crumb softness throughout shelf-life.
There are three essential requirements for enzymes to work effectively:
- the presence of specific substrates, for example starch, protein, lipid
- suitable conditions such as temperature and pH where the reaction happens quickly, and
- time to work.
This is where an understanding of the specific enzyme action is necessary so that processing and ingredient conditions can be adjusted to meet those needs. Unlike a typical chemical reaction, enzymes have an optimal temperature and pH level at which they operate at maximum functionality. Going too far outside these levels, either below or above, will result in poor reaction rates and require higher dose levels. Enzymes can be expensive ingredients so it makes sense to use the minimum quantity and make sure they work effectively.
Process optimisation with dedicated enzymes
One of the first enzymes to be added commercially to a bread recipe was amylase derived from fungal sources, also known as fungal alpha amylase (FAA). This creates sugar molecules from the starch in wheat flour. In bread dough, a gradual formation of fermentable sugars helps the yeast work in a more controlled way. Too much sugar could result in excess carbon dioxide and over-inflation of gas cells, which could rupture. This would create bread with large holes and an undesirable structure. FAA works slowly to maintain the balance of sugars for fermentation until the yeast is killed during baking around 55°C. Enzymic sugar generation continues for a few minutes after this until the FAA is inactivated by the oven heat. This happens when the bread has reached around 70°C. Small quantities of sugar left in the dough contribute to crust browning and provide flavour.
Natural amylases are also present in wheat flour, known as cereal amylases. They work in a similar way to FAA but have a higher level of heat stability, remaining active to around 85°C. The main concerns with cereal amylases are the variable levels in flour. If too high, there will be processing inconsistencies because of excessive sugar generation causing sticky dough. Line stoppages will occur resulting in economic losses. If too low, the yeast will not work effectively. By adding FAA in controlled amounts to wheat flour, the baker retains control of the yeast fermentation process.
Another type of amylase that is added to most sandwich bread recipes is known as maltogenic alpha amylase (MAA). This acts on a specific part of the starch polymer that affects the way that starch recrystallizes over storage. Its name is given because it releases maltose as it works. The shelf-life of packaged bread is around 5-7 days before visible mould growth can be seen by the consumer, however, by this time the bread will be too firm to use. By including MAA in the recipe it is possible to extend the time the bread stays soft so that the bread is still soft enough up to the end of its shelf-life. The enzyme works during the dough processing and early baking stages and is inactivated during later stages of baking.
Enzyme technology moves at a rapid pace and there are new generations of crumb softening enzymes that break the starch polymer chain in different positions. Instead of releasing maltose these release maltotriose or maltotetratriose. They are thought to be even more effective at keeping bread softer for longer.
Bread is a key part of our nutritional diet, particularly when it comes to the amount of fibre it contains. Fibre materials are beneficial to our gut health and efforts are made to include them in bakery products where possible. White bread in particular is a target for fibre inclusion. However, fibres such as wheat bran absorb a lot of water and at a slower rate than other components in dough. This causes processing issues as dough tightens in response to the fibre materials absorbing water slowly. Tight dough does not mould well and also resists expansion by yeast action, resulting in poor quality bread. An enzymic solution to this problem is available using xylanase enzymes and these are now used in most sandwich bread manufacture. Xylanases cut some of the linkages of large fibre polymers to reduce the molecular size and release low molecular weight sugars and water. This helps soften dough slowly so it can be processed with fewer issues.
Amylases and xylanases will find their way into almost all improver systems used by bakeries. In addition, there are several other enzymes used in bakery products that confer specific benefits. Glucose oxidases and lipoxygenases both help with oxidation of gluten proteins, which leads to improvements in the way gluten develops. Lipoxygenase has a secondary benefit in that it also makes bread crumb whiter.
Soya flour is a natural source of lipoxygenase and is often a major component in the improvers used by bread bakeries. The move to replace soya because of its allergenic properties has caused some issues with less optimal dough development during mixing. Addition of glucose oxidase or a similar oxidising enzyme has some potential in recovering the dough quality.
Proteases are another category of enzyme. As the name suggests, these act on proteins to break the molecules down into peptides and amino acids. Biscuit dough can be softened using proteases, reducing the elastic properties and helping it flow better, which is useful when the dough must fill a mould or flatten out as with cookies. However, a protease, like any enzyme, will carry on working until it runs out of substrate or the external conditions become unfavorable. This can cause manufacturing problems if line stoppages occur. Proteases should be used with caution.
Lipases are sometimes added to bread and cake recipes. They can change natural lipids in the ingredients such as wheat flour, egg yolk and oil into materials that have foaming and emulsification properties. These help to stabilize the gas bubbles in bread dough and cake batter, giving a better rise of the product.
Acrylamide is formed during all baking processes that involve cereal ingredients. There are various reaction pathways to acrylamide formation but most involve a reducing sugar and an amino acid. By reducing the concentration of one of these reactants it is possible to reduce the amount of acrylamide formed. One of the more recent additions to the list of commercially available enzymes is one that reduces the formation of acrylamide during baking. It acts on the amino acid asparagine, which takes part in the reaction pathway to generate acrylamide -hence it is known as asparaginase. Commercial forms of asparaginase are added to many biscuit recipes and some bread recipes.
Looking to the near future, however, there are significant changes ahead in terms of the use of enzymes in food due to the changing legislative landscape. For the first time, there may be specific EU legislation on the use of enzymes in food. The EU is in the process of compiling a long list of permitted enzymes that can be placed on the market and used in food. While it remains to be seen what the outcome of European Union Regulation 1332/2008 will be, it is safe to say that it will have far-reaching implications for the baking industry.
Regardless of changing regulatory requirements, enzymes for optimising processing in the baking industry are here to stay. Their functional capabilities, clean label properties, ability to create more efficient processes, and reduce costs mean that they are a must have in a competitive marketplace.
We have been active in the application of enzymes for baking for many years. We have the expertise and facilities to investigate and analyse enzyme blends and conduct research into their effects on dough and batter during processing, as well as testing finished baked goods to assess product quality. We can help manufacturers get the most out of enzyme systems by understanding the needs of the enzymes so that processing conditions can be optimised. Get in touch to find out how our experts can help you.
We’re continually examining innovative technologies. How can fat, sugar and calories be reduced in bakery products? What are the novel technologies that can reduce waste during processing? We’re running a Bakery Conference from 19 to 20 May 2020 to help participants cover the most recent developments and challenges of the bakery sector.
This article was first published in the July/August edition of European Baker and Biscuit.
Gary Tucker is a Fellow at Campden BRI and has worked for the company since 1989. He studied Chemical Engineering at Loughborough University and is a chartered chemical engineer. Read more...