Enzymes in breadmaking

by Meyer Sosland
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Global population growth is a challenge for the suppliers of staple food. A projection from 2007 into the year 2050 predicts an average population growth rate of 0.8 %, or an increase from 6.7 billion to 9.3 billion people (Table 1, below).

Provided that the per capita consumption of staple crops remains constant, the production of wheat and rice will have to grow from the current 600 million tonnes each to 850 million tonnes, and corn (maize) production has to rise from 850 million tonnes to 1 billion tonnes. These figures do not even take into account the growing demand for biofuels. Achieving this increased output won’t be easy, since the production of wheat in the major wheat growing areas was basically constant during the past decade. One approach could be to improve the wheat’s tolerance towards drought, heat and rain in order to grow wheat in less favorable regions of this planet. In that regard, promising steps have already been taken.

The development of this market affects the whole food production chain, including the suppliers of additives and enzymes. The current market for bakery enzymes is estimated to be about $200 million (Figure 1, page 46). Although the share of bakery enzyme of the total enzyme market (5%) will not increase, their consumption will rise with the increasing demand for enzymes in general, to an estimated volume of almost $300 million through 2011. In the same period, the total market for food enzymes is expected to grow at a rate of almost 6% to about $1.2 billion.

The growth is supported by the perception that enzymes are a natural way to improve efficiency and quality, and that chemicals can be replaced, avoiding labeling or omitting "E-numbers." Declining prices due to competition of supplier and consolidation of the food industry provide an additional impetus.

Most of the new enzymes will be produced with genetically modified (GM) organisms, and some of the enzymes will even be "protein engineered." In other words, their original sequence of amino acids will be modified, although there is some market resistance against enzymes from GM organisms.

The properties of existing enzymes and enzyme combinations are constantly being improved, creating a wider field of use and increasing the demand. The most efficient driving force for growth still will be innovation.

Three markets have been selected to visualize the development of the bakery enzyme segment: the United States (U.S.), the European Union (E.U.) and China. For the U.S., the average annual growth rate is estimated to be 7.2 % through 2010, with revenues of about $70 million at the end of the period. The E.U. starts from a higher level, but due to a smaller estimated growth of 4.5%, the market will have a volume of only $80 million in 2010. The expected growth rate of the Chinese market is stronger, with an average of 9.5% through 2013, but the starting point is also much lower, the revenues being only 13% of those in Europe (2003).

Figure 2 (right) summarizes the world bakery enzyme market in 2006 and projects it through 2011, based on market research and on the author’s data and estimates. The Asia-Pacific area is expected to grow at a similar rate as the U.S., while growth in Africa and Latin America will be closer to the development of the European market.

The general enzyme requirements and trends differ significantly between developed and emerging markets. Developed markets are mainly looking for:

• reduction of prices of classical enzymes;

• new enzymes with new functionalities;

• enzymes for replacement of chemicals;

• enzymes for increasing the shelf-life of baked goods with soft crumb;

• segregation of enzymes from conventional and GM micro-organisms.

As for emerging markets, their concerns are centered on the following factors:

• classical enzymes being used;

• bread prices are regulated in some areas, not allowing for ingredients adding to costs;

• the volume yield;

• coping with varying wheat properties; and

• compensation for performance losses of composite flours.

The enzymes currently being used most widely in the baking industry are (more or less in order of decreasing importance): fungal a-amylase; hemicellulase (comprising pentosanase and xylanase); lipolytic enzymes (lipase, phospholipase, galactolipase etc.); glucose oxidase; protease (endopeptidase); intermediate heat-stable a-amylase; and glucoamylase.

Recent enzyme developments comprise: asparaginase for avoiding acrylamide formation; sulfhydryl oxidase as dough strengthener; feruloyl esterase as a rheological tool for improved flavor formation and possible for improved nutrional value of baked foods; and more specific lipolytic enzymes not acting on triglycerides for bread and cake applications in recipes, including shortening or butter, or as egg replacement.

Acrylamide is a potentially carcinogenic substance found in baked and fried food items. Potato products, wafers, biscuits and crispbread are most affected. It is formed during the Maillard (caramelization) reaction. At present there are no defined limits for acrylamide in food, but national "warning thresholds" exist.

The amino acid aspargine is the key factor in acrylamide formation. In a Swedish study (Holmgren, 2007), adding aspargine increased acrylamide from 80 parts per billion (ppb) to as much as 6,000 ppb. It forms mostly in the crust (99%), which indicates an influence of temperature and/or humidity. Darker products have higher acrylamide values. The addition of sugars or their enzymatic removal has no effect on acrylamide. Temperatures above 200 degrees C (392 degrees F), lower final product humidity and baking powder, in particular, with ammonium bicarbonate, increase acrylamide values, whereas yeast fermentation reduces them.

The decomposition of the precursor asparagine by asparaginase, Innovase ASP, is an effective means to reduce the acrylamide formation. The enzyme is active in a pH range of 5 to 8.5 and at 30 to 65 degrees C, hence in an optimum range for most baking applications. In crisp bread trials Innovase ASP reduced acrylamide to less than 25%, and in wafers Innovase ASP reduced it to about 10% of the original level.

Several oxidases have been proposed and are being used for improving the baking properties of flour, in particular dough stability and mechanical tolerance. The common principle of most oxidases applied in baking is their action on monoor oligosaccharides or other glycosides, creating a carboxyl group and hydrogen peroxides. The hydrogen peroxide then acts as a non-specific oxidant, oxidizing available electron donors in dough, including sulfhydryl groups. This results in the creation or protection of dough-strengthening disulfide bridges. In addition, oxidation gelation of pentosans via feruloyl residues may occur, increasing the water absorption.

An undesirable side-effect of the above oxidases is their action on unsaturated lipids, which creates an unpleasant offflavor. In particular, bakery items from frozen and sheeted dough, such as croissants, may be severely affected. Therefore, the use of glyco-oxidases as a general flour-improving enzyme is not recommended.

Sulfhydryl oxidase (SOX, EC specifically oxidizes sulfhydryl groups in protein and peptides. Hydrogen peroxide is also formed in this reaction. But in relation to the number of oxidized sulfhydryl groups, much less hydrogen peroxide is formed by SOX than by glycoside oxidases.

In baking trials, SOX from S. cerevisiae showed good potential, in particular in applications involving lamination steps and prolonged fermentation. Figure 3, (page 47) shows a comparison of glucose oxidase and SOX in steamed bread baking trials. Furthermore, a partial replacement of ascorbic acid used as a dough stabilizer was possible. Steamed bread with reduced ascorbic acid had a brigher crumb color. The reason for this effect is not yet known. In butter croissants made from frozen dough, no formation of off-flavor was noted, while GOX-treated samples developed a strange smell.

In wheat or rye flour dough, ferulic acid contributes to the mechanical stability by absorption of water and the stabilization of gluten. An excess of stability can result in a limited volume yield during the bread-making process. As in other hemicellulases, ferulic acid esterase is able to soften the xylan/gluten complex by the release of water from the gel and by the breakdown of covalent linkages. Unlike the most often used hemicellulases exerting an endo-1,4-ß-xylanolytic action on the xylan polymer, ferulic acid esterase cleaves the side-chains between the galactose residue and the ferulic acid. Both activities improve the expandability of the dough and hence can be used to increase the volume yield.

The enzyme has a significant effect on the dough rheology. When applied in the Alveograph, it was possible to achieve a significant reduction of the powder/liquid (P/L) ratio while the energy remained constant over a wide dosage range. At prolonged resting times (120 minutes), the energy was close to that of untreated flour even when the P/L was diminished to 0.46 instead of the initial ratio of 0.66.

The extensibility of the dough could be increased by about 30%. Obviously, the enzyme is capable of partially hydrolyzing the linkages between gluten and arabinoxylan) and/or to break down the pentosan gel, resulting in the release of water from the gel, which is then available for gluten hydration and softening. The enzyme also reduces the viscosity of flour suspensions, such as wafer batters.

The potential reasons for future growth of the bakery enzyme market are summarized in Figure 4 (above). One of the factors mentioned is the replacement of gluten. The rising global wheat price increases the tendency to replace expansive wheat with high gluten content and good baking properties by cheaper wheat. The lack of gluten content and baking performance can at least partially be replaced by adding functional ingredients such as enzymes.

The second position in Figure 4 is taken by the term "shelf life," in this case comprising microbial stability as well as crumb softness. Both are increasingly required due to the continuing trends of bakeries merging to larger units with centralized production, which means longer distances from factory to shop. WG

Dr. Lutz Popper is director of research and development, Mühlenchemie GmbH & Co. KG, Ahrensburg, Germany. For further information, he may be contacted at lpopper@muehlenchemie.com.