European flour treatments

by Dana Holt
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Europe is doubtless coming closer to a uniform definition and regulation of chemical flour treatment. Nevertheless, there is still a wide scope for the use of numerous, generally approved additives for flour treatment.

Examples of stricter provisions are the French regulations on white bread that state "pain de tradition" (traditional bread) may only contain yeast, sour dough, gluten, soy or bean flour, maize flour and fungal amylases, but not ascorbic acid or lecithin. Denmark's stringent enzyme approval regulations also suggest future uniform regulation.

This article aims to provide an overview of the flour improvers most commonly used in Europe. It does not go into details of the differences between specific countries, as these will surely change in upcoming years.

OXIDATION. Due to time constraints, natural "aging" of the flour by exposure to the atmosphere alone is no longer possible and oxidative preparations must be used. Oxidation primarily affects sulfur-containing amino acids within the gluten. The oxidation of two adjacent, hydrogen sulfide groups creates a disulfide bridge between different sections of the gluten molecule or between different gluten molecules, causing a hardening of the protein.

The most important substance for oxidation is ascorbic acid (AA). Using a complex, biochemical method, it is produced in a very pure form from glucose and sold as a fine or crystalline powder in various concentrations used to facilitate dosing. Less often, AA of purely biological origin is used. The most common product is Acerola fruit powder, the dried juice of the Acerola (Barbados) cherry, with 17% to 19% pure AA. Other substances on the market are AA obtained from rose hips and mixed preparations, some of them containing AA of biochemical origin. However, natural variants are much more expensive (up to 50 times more) than the synthetic product.

At the mill, flour is treated with about 0.5 to 3 grams of pure AA per 100 kilograms of flour. Very soft glutens or flours for certain applications (mainly frozen dough) require a larger dose of 6 to 10 g.

AA does not act on the protein directly, but protects against the loss of protein stability by counteracting glutathione, a natural part of flour. This is only possible if AA is oxidized to dehydroascorbic acid at the beginning of the kneading process with the aid of the flour's own enzymes (ascorbic oxidase and glutathione dehydrogenase). In this process, glutathione is oxidized to glutathione disulfide, thus eliminating the gluten-softening effect of glutathione.

Proof of adaquate quantity and homogenous distribution of the product in the flour can easily be obtained with Tauber's reagent in conjunction with a Pekar test. A convenient and storable set with the two solutions required is available on the market. Titration with iodine, which is more accurate but less convenient, is still common practice as well.

One enzyme from soy flour, lipoxy-genase, also has an oxidative effect on the protein of the gluten. During the oxidation of lipids by lipoxygenase, peroxides are formed that have a cross-linking effect on thiol groups. However, the gluten-strengthening effect of soy flour is comparatively slight; its bleaching effect is more important.

The enzyme glucose oxidase (GOD) is usually derived from the mold Aspergillus (in a similar manner to amylase). Honey is also a rich source of GOD, but its taste restricts its suitability. The enzyme enters the honey from the pharyngeal glands of the bees.

With the aid of oxygen, GOD in dough oxidizes glucose into gluconic acid, transforms water into hydrogen peroxide and tightens the thiol groups of the gluten. But because other chemical reactions within the dough consume oxygen, such as yeast in the fermenting process, extra oxygen must be supplied during the dough preparation.

Typical GOD doses range from 10 to 50 g per 100 kg of flour, but this depends on the product and process.

In Europe, the powerful oxidizing agent, potassium bromate, may now only be used in flours for export. Although it has a very long lasting effect, it starts later than AA, allowing better processing of the dough. The result is good fermentation tolerance and high volume yield.

Because of doubts about its effects on health, bromate has gradually been replaced by AA since the 1950s. Also, bromate accelerates fire and explosion and is actually a constituent of fireworks.

Combinations of AA and enzymes offer good, alternative ways to achieve satisfactory dough and baking properties. Because of the low doses required and its lower price, bromate can hardly be replaced without intervention by public authorities. Bromate is easily detected and determined with a kit similar to the AA test.

Azodicarbonamide, a chemical foaming agent used in manufacturing expanded plastics, also has an oxidative effect, decomposes into large-volume gases upwards of 120° C, and has been used as a temporary replacement for bromate. A great disadvantage is its low dosing tolerance; a slight overdose causes the bread to split badly, although the properties of the dough are still good. The dosage is similar to that of AA or bromate. Most often, azodicarbon-amide is mixed with calcium sulfate to reduce its inflammability, usually with 23% of the pure substance.

Cystine is formed when two molecules of the cysteine amino acid are linked by a disulfide bridge to give the molecule an oxidative effect. But at low doses, the gluten may soften as reducing cysteine is released when cystine reacts with thiol groups of the protein.

Although this has yet to be thoroughly investigated, cystine is used in spite of its high price (as compared to ascorbic acid) because it is found to have a positive effect on the dough properties.

Tests have shown it is possible to use dehydroacorbic acid, the oxidized form of AA. But it is rarely used because it is unstable, difficult and expensive to synthesize and was not included in the directives on additives in the European countries.

Except in the United Kingdom and Ireland, chlorine and chlorine dioxide are no longer used as oxidizing agents in Europe because of their possible harmful effects on health and the technical risks they involve. There is no doubt, however, that with certain baked goods, for example, cake with a high proportion of fat and sugar, chlorination of the flour — which can only happen at the mill — produces the best results.

REDUCTION. Gluten that is too short is difficult to process and results in a low volume yield, since the gas formed by the yeast is not enough to expand the dough. One solution is to use substances with reducing properties that break down surplus disulfide bridges, giving the protein molecules more room to move. Short gluten properties may result from the varieties used, but they are sometimes caused during grain processing (overheating) or storage (freezing shortens the gluten).

Cysteine is a simple amino acid that is a constituent of all proteins and produced either by hydrolysis of extremely cysteine-rich proteins, complex purification procedures or synthetic means.

It was thought that as cysteine splits, disulfide bridges counteract the effect of AA, but cysteine and AA actually complement each other. One makes gluten firmer while the other ensures elasticity. This is possible because the two substances act on different constituents of the gluten and attack it at different sites.

The use of these flour improvers in frozen doughs, especially, requires very large doses of both substances for good fermentation stability is required (AA), but the deep-freezing process shortens the gluten, a problem that can be solved at least in part by cysteine. The amount of cysteine added is often two-thirds of the quantitiy of AA. This method is expensive, as cysteine prices fluctuate greatly and have even exceeded 100 deutschmarks (U.S.$52).

Cysteine is usually sold as anhydrous L-cysteine hydrochloride or L-cysteine hyrdochloride monohydrate, as it is more easily synthesized and has better water-solubility in this form. Sodium nitro-cyanoferrate/ammonium hydroxide can be used for detection, but this is an unreliable method as the blue spots are sometimes difficult to see and fade quickly.

Sodium metabisulfate (MBS) and sulfur dioxide are now approved in the U.K. and Ireland only. However, MBS is used occasionally in Spain. These powerful reducing agents are especially good at breaking down the gluten fast and reliably, which greatly simplifies the production of biscuits, cracker and wafers. But as these substances also are known to destroy vitamin B, (thiamin) their use should be avoided; enzyme alternatives achieve the same results.

ENZYMES. Enzymes have been commonly used in the food industry for years. The challenge is that even though they are added in the mill, they don't take effect until the baker adds water.

If enzymes are pure enough, they act on selected targets and only have to be added in small quantities. They are entirely natural and can only be obtained from fermentation of micro-organisms or from vegetable or animal tissue and fluid extractions.

Like all highly-concentrated, natural substances, enzymes have a strong potential for causing allergies. For this reason, care must be taken during processing to prevent enzyme dust.

In Germany, most enzymes are defined as "technical aids" that have significance in the end products and do not have to be declared on the label. But with the standardizing of European regulations, clearly the time will come when enzymes require declarations.

Fungal amylases are generally approved in all E.U. countries except Denmark. The U.K. does recommend analysis by the Committee of Toxicity, but it has not prohibited the use of untested enzymes. Amylases and proteases are generally approved in the U.K.

Amylases split unbranched sections of the starch molecule into smaller components. Like all enzymes, amylase only acts on dissolved substrates, such as swollen, damaged starch in the dough, which reduces dough viscosity and improves processing characteristics. This chain reaction increases fermenting power and volume yield, enhances flavor and browning and prolongs shelf life.

Like all living material, grain needs enzymes for its vital functions. Germination is the phase when enzymes are produced in large quantities, so bakers and brewers often germinate cereals before processing them further. Enzyme-active malt flour is the dried product made from germinated barley or wheat. Although the functions are largely identical, approvals for use in flour treatment differ from one country to another. France, for example, only permits malt flour made from wheat.

Just as the flour's own amylases, the amylase of the malt flour has a pronounced effect on falling numbers. If the falling numbers are very low, (i.e. the flour's own enzymatic activity is very low) up to 150 g of malt flour may be needed to bring the falling number into the range of 250 to 300. With falling numbers around 300, no more than 50 g should be added to prevent the dough from becoming too sticky.

Fungal amylase is derived from the molds of the genus Aspergillus, whose molds are often used in the production of enzymes for food because of its many numerous, well-defined strains that have no detrimental effect on health. In large fermentation equipment, the molds are made to produce amylase and then release it into the environment. A multi-stage purification process then results in a crude enzyme concentrate that is usually spray-dried to form a powder with good shelf life. Various carriers, such as maltodextrin, starch or flour, are added to make the substance more convenient to use at the mill.

Amyloglucosidase (AMG) is a natural side activity of many amylase preparations, but specialized Aspergillus strains offer a purer form. AMG breaks down starch into its smallest units, glucose. But AMG alone is a slow viscosity reducer, as the enzyme only acts on one end of the starch, splitting off one glucose molecule at a time. Hence, the main significance of AMG is browning and maintaining the fermentation process over an extended period (controlled fermentation). AMG is usually dosed in very small amounts.

Wheat flour contains about 2.5% pentosans, which can bind water up to ten times their weight and belong to the category of hemicellulases, relatives of cellulose. Pentosans are made up of different sugar molecules and hemicellulases break down these substances. Initially this process leads to the formation of soluble molecules and increases the binding of water, and thus viscosity. As the molecules are broken down further, water is released and viscosity reduced.

It is assumed that pentosans form a network with gluten; the more pentosans are involved, the firmer the network. This is why darker flours have a lower volume yield. The volume can be increased considerably by adding hemicellulases.

Most of these enzymes are also derived from Aspergillus strains, but these are strains that have been selected for or specialized in the production of hemicellulases. Hemicellulases have little effect on the falling numbers, are mostly sold in compounds with amylase and have no general dosing requirements because there is no method to measure hemicellulase activity.

Also known as proteinase or peptidase, protease splits the protein strands of the gluten molecule, leading first to a softening and then to a complete collapse of the structure. Unlike amino acids, protease does not stop acting when the addictive is used up. Its effects increase with the fermentation time of the dough — causing a demand for enzyme preparations without protease.

The use of protease is useful in the production of biscuit or wafer flours, where elasticity is an unwanted characteristic. Protease allows use of greatly fluctuating raw materials while ensuring uniform technical characteristics.

EMULSIFIERS. Bakers have long been familiar with lecithin. At first, lecithin in egg yolks was used to distribute large amounts of fat evenly in a product, but now concentrated lecithin from soybeans is available. In its de-oiled form, it is well suited for use in mills.

Benefits include a drier dough surface, better machinability, greater smoothness, longer shelf-life, and larger volume yield. Lecithin fractions are available offering natural emulsifiers that are specially adjusted to specific applications. The dosage of lecithin for flour treatment is in the range of 30 to 150 g per 100 kg of flour.

Mono- and diglycerides are produced by splitting off one or two fatty acids from edible fats and oils. By selecting the fatty acids left on the glycerol backbone, it is possible to produce emulsifiers with greatly differing properties.

In flour treatment, mono- and diglycerides with good anti-staling properties are in demand. These are most often found with linear, saturated fatty acids that interact well with starch and thus slow down the staling process. These emulsifiers also have similar effects to lecithin, namely greater volume yield and a finer crumb. With fat-rich products, the dose required may be up to 1% of the flour.

In many cases, creating emulsifier complexes by combining two emulsifiers enhances the two agents' properties. For example, the mono- and diglycerides only achieve optimum suitability when combined with lecithin, which improves their flowability, solubility, dispersion and interaction with other constituents of the flour.

Well-known and widely used "organic" flour improvers fall into this category. The combination makes it possible to reduce the dose necessary for optimum effect to 100 to 300 g with 50% emulsifier in the complex. Interestingly, the combinations are only effective if the emulsifiers are mixed before converted into their powdered form.

One very effective group of emulsifiers in respect to volume yield, diacetyl tartaric esters of mono- and diglycerides (DATEM), is one of the main constituents of most baking improvers, especially when the aim is to produce voluminous baked goods with a crisp crust. In Europe, DATEM esters are not often used in flour treatment. The optimum dose is about 300 to 400 g per 100 kg of flour.

Under the new "miscellaneous" directive, sodium stearoyllactylate (SSL) and calcium stearoyllactylate (CSL) emulsifiers have been approved for food additives throughout Europe. The remarks concerning DATEM also apply to these, but SSL and CSL are especially suitable for baked goods with a soft crust.

ACIDULANTS AND ACIDITY REGULATORS. Sprouting in rye and wheat causes a high level of amylase activity. Generally, even flours with very low falling numbers produce good baking results if well acidified. But not everyone likes acidity in bread.

By adding fruit acids, salts, carbonates and phosphates, it is possible to adjust the pH of the dough slightly to reduce the enzymes' effect. This influences the swelling of the flour constituents, helping to counteract the negative effects of excessive enzyme activity. The best preparations stabilize the pH at the level that it was adjusted. In most cases, the dosage is typically low, about 50 g to a maximum of 200 g per 100 kg of flour.

BLEACHING AGENTS. Although the industry is aware of the importance of roughage, minerals and vitamins, there is still a demand for a very light-colored crumb in many wheat products. Even the German language bears witness to the low opinion traveling neighbors once had of the dark, rye-flour bread popular in Germany, "pumpernickel." The word is derived from pain pour Nickel (bread for Nickel) – Nickel apparently being the name of the horse ridden by Napoleon I.

Benzoyl peroxide is used in flours for export. It has a slight influence on the structure of the gluten, but this is not apparent when other flour improvers such as AA are used. The dosage is about 5 to 10 g per 100 kg of flour. It is usually sold as a 30% product, and the dose is then correspondingly higher. Bleaching effects on the flour are visible after 24 to 72 hours of storage.

Only enzyme-active bean and soy flour, made from soy or faba beans, may now be used throughout Europe to achieve a light-colored crumb. The quantity that can be used is very much limited by another enzyme, urease, a side activity that causes an undesirable, bitter taste. For this reason, the maximum quantities used are usually 0.5% for soy flour and 2.0% for faba bean flour. Baguettes are the classic application for soy flour, which is increasingly replacing the less effective bean flour.

The brightening effect noticed when ascorbic acid or emulsifiers are used has a physical cause — the finer texture changes the reflecting properties of the crumb and the color appears lighter. Strong oxidizing agents such as bromate or chlorine actually remove the color from the dark pigments.