Additives for flour standardisation - Part II: Additives other than enzymes

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    Digital Re-print -May | June 2013

    Additives or four standardisation- Part II: Additives other than enzymes

    www.gmt.co.uk

    Grain & Feed Milling Technology is published six times a year by Perendale Publishers Ltd of the United Kingdom.All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies,the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis ofinformation published.Copyright 2013 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any formor by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1466-3872

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    The most commonly used material

    to strengthen gluten is ascorbic

    acid, also called vitamin C. The

    material itself is originally a reducing rather

    than an oxidizing agent, but it is convert-

    ed into an oxidative substance, namely

    dehydroxy ascorbic acid (DHAA), through

    the action of flour enzymes during dough

    preparation. DHAA basically inactivatesthe glutathione molecules which break

    down the sulfur bonds between the

    gluten molecules (Grosch and Wieser,

    1999). With this action, dough mixing

    results in sulfur bond protection without

    excessive breakdown, which in turn leads

    to dough with desired structure.

    Pure ascorbic acid is added to the f lour in

    mills at rates of typically 0.5-3 grams per 100

    kg of flour. This dosage may go up to 6-10

    grams per 100 kg in very weak flours or for

    weakening applications like frozen dough.

    Ascorbic acid is mainly produced by com-

    plex biochemical processing of glucose and

    sold as powder with different granule sizes.

    There are also natural sources for ascorbic

    acid, for instance acerola fruit powder, but

    these are too expensive compared to the

    synthetic ones.

    Potassium bromatePotassium bromate as a strong oxi-

    dative is still used as flour improver in

    many countries in the world. The very

    long lasting effect of bromate starts

    later than the effect of ascorbic acid andallows easier processing of the dough.

    Bromate creates new disulfide bonds

    resulting in more resistant doughs but

    it also oxidizes glutathione and hence

    prevents gluten weakening, just like

    ascorbic acid but without the help of

    the flours enzymes.

    Usage of bromate in flour industry

    is prohibited in the EU and many other

    countries because of the health con-

    cerns and its unstable/fire-accelerating

    nature.

    AzodicarbonamideAzodicarbonamide (ADA) is utilized

    in flour industry because of its oxidative

    action. Its dosage is similar to ascorbic

    acid (with a recommended maximum

    of 45 ppm), but the dosage tolerance is low,

    so even a slight over dosage may result in

    bucky doughs and rough bread surfaces. It is

    a flammable material and its usage in food-

    stuff is not permitted in the EU and several

    other countries.

    Others

    Other than the ones stated above, thereare many oxidative materials and oxidation

    processes utilized throughout the world.

    Chlorination, usage of peroxides, iodates,

    persulfates, cystine and oxidative enzymes

    are some of these. All of these methods dif-

    fer by their effects on flour/dough, and their

    pace of action.

    Dough relaxation, softening,reduction

    Dough with short gluten (low extensibil-

    ity) is hard to process. In addition to this, gas

    produced during fermentation will not be able

    to expand the dough sufficiently and hence

    the volume of the end product will be small.

    Furthermore, for products like biscuits, crackers

    and wafers, the optimum processing condi-

    tions can be reached when gluten structure is

    weaker than normal. In these situations, reduc-

    tive materials are used to break the disulfide

    bonds and provide gluten with more flexibility.

    CysteineL-cysteine, a sulfur-containing amino acid

    found in diverse proteins, breaks down the

    disulfide bonds between and within gluten

    molecules and becomes attached to the

    bond forming regions. This prevents gluten

    from getting stiff, and a mobile, flexible but

    still coherent structure is secured. This effect

    seems to be the opposite of ascorbic acids,but actually they seem to complement each

    other in some processes. This synergy is

    especially used in frozen dough processes:

    Ascorbic acid provides the necessary fer-

    mentation stability whereas cysteine gives

    extensibility to gluten strands which have

    shorten because of freezing.

    OthersInactive yeast preparations are rich in

    reducing material, but their dosage (500

    5,000 ppm) and price are relatively high,

    as compared to cysteine. Levels of other

    reducing agents like sodium metabisulfite

    and sulfur dioxide which are used as dough

    softening agents in biscuit and cracker pro-

    duction are limited to 50 ppm. This amount

    is not sufficient to observe a softening effect

    in strong flours. Furthermore, many coun-

    tries require declaration if the concentration

    of residual sulfur dioxide exceeds 10 ppm

    Table 1: Suggested emulsifiers with potential use in baking applications

    EmulsifierCommon

    abbreviationHLB Application and benefit

    Acetyl esters of monoglycerides AMG 2.5-3.5 Whipped cakes, volume

    Calcium stearoyl lactate CSL 7-9 Bread, shelf-life, volume

    Diacetyl tartaric esters of monoglycerides DATEM 9.2 Bread, shelf-life, volume

    Ethoxylated mono- and diglycerides(polyglycerates)

    EMG 12-13High-fibre bread; shelf-life

    (combined with monoglycerides)

    Glycerol monostearate (non self-emulsifying) GMS 3.7 Shelf-life

    Glycerol monostearate (self-emulsifying) GMS 5.5 Shelf-life

    Lecithin LC 3-4 Shelf-life, dough properties

    Lactyl esters of monoglycerides LMG 3-4 Whipped cakes, volume

    Mono- and diglycerides MDG 2.8-3.8 Bread, cakes, cookies, volume

    Polyglycerol ester PGE 12-13 Whipped cakes, volume

    Propylene glycol monostearate PGMS 1.8 Whipped cakes, co-emulsifier

    Polysorbate 60 PS 60 14.4 Whipped cakes, co-emulsifier Succinyl monoglyceride SMG 5-7 Yeast leavened baked goods; volume

    Sorbitane monostearate (e.g. SPAN 60) SMS 4.7-5.9 Whipped cakes, volume

    Sodium stearoyl lactate SSL 18-21 Bread, shelf-life, volume

    Sucrose esters SUE 7-13 Bread, cake, volume

    Additives for flour standardisation -

    Part II:Additives other than enzymesby Lutz Popper, Mhlenchemie GmbH & Co. KG, Germany

    Gri&fd milliG tcholoG12 | may - June 2013

    FEATURE

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    in the final product. Figure 1 compares the

    effect of cysteine and inactive yeast on the

    extensibility and resistance towards exten-

    sion in a standard wheat flour dough.

    EmulsifiersEmulsifiers are polar molecules that can

    interact with many constituents of Emulsifiers

    that interact with gluten during mixing process

    strengthen the bonds between protein chains,but they also provide a lubricating effect that

    allows the chains to slide over each other eas-

    ily. They are involved in the stabilisation of the

    gas bubbles in dough by binding to the bound-

    ary layers. As a result, dough elasticity, oven

    rise and volume increase, and the crumb pore

    size reduces. The bakers will note an increase

    in the practical water absorption, although the

    dough rheological measurements may not

    confirm this percep-

    tion. Other emulsifiers

    strongly interact with

    the starch delaying ret-

    rogradation and staling

    and thus provide bread

    with improved and

    prolonged softness and

    freshness. Some have

    potent foaming ability

    because of their sur-

    face-active nature and

    are used as whipping

    agents for sponge cake

    and the like. They ease the mixing of water

    and fat and hence improve fat dispersion in

    bakery products that contain larger amounts of

    fat, such as biscuits, or in liquid systems such as

    wafer batters. They also decrease the amount

    of necessary fat, contributing to cholesterol,

    calorie and cost reduction.

    Lecithin

    Lecithin is an emulsifier which has beenused in bakery products for a long time. Once

    egg yolk was used as the source of lecithin,

    but nowadays concentrated lecithin obtained

    from soy beans, canola or sunflower seeds

    is used. The most obvious benefit of lecithin

    is to lower the stickiness of the dough and

    improve its machinability. Other than this,

    lecithin softens the crumb due to its interac-

    tion with starch. But its effect on volume is

    less than that of its synthetic counterparts.

    The dosage of lecithin is about 30-150 g per

    100 kg of flour (0.03 0.15 %). Low dosages

    increase the processing quality of the dough,

    whereas high dosages increase dough stability

    and fermentation tolerance, improve crumb

    structure and prolong shelf life.

    Mono- and diglyceridesThese molecules are formed by breaking-

    off fatty acids from edible fats and oils. The

    forms that are preferred as flour improver

    are the ones that prevent staling best. This

    property is found in linear saturated fatty acids

    that interact best with starch, and the most

    effective of them all is glycerol monostearate.

    The dosage starts at 0.05 percent and may

    go up to one percent, especially in high-fat

    products.

    Diacetyl tartaric esters of mono-and diglycerides (DATEM)

    DATEMs currently are the most effective

    emulsifiers for bread volume. They are variousmolecules formed by esterification of mono-

    and diglycerides (obtained from edible oils)

    with mono- and diacetyl tartaric acid. Some

    of these molecules are more active than the

    others (Khler, 1999), but the effect of the

    mixture is better than any single type of pure

    emulsifier.

    DATEM is rather used in bread improvers.

    The optimum dosage is about 400 g per 100 kg,

    Figure 1: Effect of reducing agents on the dough consistency

    Gri&fd milliG tcholoG may - June 2013 | 13

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    but much lower dosages are used actually because

    of the high prices. We mentioned that the effect

    of lipolytic enzymes is comparable to emulsifiers.

    Recent studies are focused on producing carboxyl

    esteerases that may reduce DATEM usage, or

    replace it completely.

    Sodium and calcium stearoyllactylate (SSL and CSL)

    These emulsifiers are formed by the

    esterification of stearic acid with lactic acid.

    They act like DATEM, with a slightly weaker

    effect on dough stability and baking vol-

    ume. On the other hand, they are more

    effective in preserving the crumb softness.

    Furthermore, they are more suitable for

    bakery products that require a softer crust.

    Other emulsifiersOther than the ones stated above, there

    are many more to be used in high-fiber prod-

    ucts, cake bases etc. The distinctive property

    among them is the HLB value (Hydophilic-

    Lipohilic Balance). This value shows if theemulsifier displays a more hydrophilic or

    lipophilic character. Emulsifiers for high bread

    volume yield rather have an HLB of 7 or

    higher, while emulsifiers that improve the shelf

    life of the crumb softness exert a lower HLB,

    probably because they have to be able to

    interfere with the non-polar interior of starch

    helices. Table 1 provides a list of common

    emulsifiers used in baking applications.

    Acidifiers and acidity regulatorsWith germination, high amounts of amy-

    lase are formed in grain. This enzyme works

    like amylase added to the flour, but has

    a stronger impact on lowering the Falling

    Number (FN). If there is too much cereal

    amylase, the baking properties are negatively

    affected and the FN is too low. To restore

    good baking properties, the dough may be

    acidified by natural lactic acid fermentation,

    resulting in a sour dough. This prevents the

    cereal enzymes from finding the optimum

    conditions and hence their activity decreases.

    But the taste and aroma developed during

    acidification of the dough may not be well

    received by everyone. Moreover, this proc-

    ess takes a long time. Other than naturalacidification, agents that are allowed in

    foodstuff, like fruit acids, salts of these acids,

    carbonates and phosphates may be used. By

    careful adjustment of these, the pH range

    (acidity) of the dough may be altered to a

    level where the enzymes cannot work opti-

    mally. Most preferred of these additives are

    the ones that keep the pH value at a desired

    level regardless of the chemical changes in

    the dough, called buffering agents. A typical

    dosage is 50-200 grams per 100 kg of flour.

    It should be kept in mind that phosphates

    and carbonates add to the ash content of

    flour. For sprout-damaged wheat, it is advisable

    to lower the extraction of enzyme-rich outer

    layers of the kernels (that is, to decrease the

    milling yield) and produce a whiter flour that

    allows addition of ash-increasing improvers.

    BleachersEven though customers are getting more

    and more aware of the fact that darker milled

    flours are richer in vitamin and mineral content,

    bread with a crumb as white as possible is pre-

    ferred in many regions. Bleaching of the carote-

    noids which give the flour a dark colour, namely

    lutein, can be achieved with oxidative materials.

    Soy FlourThe best-known legal material for this applica-

    tion is enzyme-active soy flour. A clearly visible

    effect can be achieved at dosages around 0.5

    percent. There are two types of enzyme-active

    soy flour in the market: deoiled and untreated.

    The bleaching effect is related to the lipoxygenase

    enzyme in soybeans. Deoiled soy flour may have

    lost some or all enzyme activity during the proc-

    ess and hence may not be suitable for this pur-

    pose, but nevertheless there are enzyme-active,

    deoiled soy flours available. On the other hand,

    untreated soy flour may cause an unwanted bitter

    taste because of the enzyme urease.

    Because the soy flours bleaching effect isdue to an enzymatic reaction, the bleaching

    only starts after contact with water, that is,

    during dough mixing.

    Powerful oxidativesBenzoyl peroxide, potassium bromate and

    their derivatives cause bleaching because of their

    powerful oxidative effects. Added at dosages of

    5-10 g per 100 kg, the effect of benzoyl perox-

    ide starts during storage of flour and the process

    is completed in about 1-3 days. These chemicals

    pose health risks by undesired residues and

    reaction products remaining in the final food or

    at least because of their inflammable, fire-accel-

    erating or even explosive nature. Furthermore,

    their usage in food is not permitted in the EU

    and in several other countries.

    Other agentsThe colour lightening effect on crumb experi-

    enced with the usage of ascorbic acid, emulsifiers

    and some enzymes is mostly a physical illusion.

    Using these improvers, one can have smaller and

    more evenly distributed pores which cast less

    shadow and therefore the crumb seems whiter.

    Using lipases also may contribute to a bleaching

    effect provided that there is enough of oxygen inthe dough. The unsaturated fatty acids produced

    by lipase are converted to hydroperoxides by the

    flours own lipoxygenase, and these molecules in

    turn bleach carotenoids.

    Vital wheat glutenVital wheat gluten is produced by separating

    the water-insoluble proteins of wheat flour from

    the starch and soluble materials by a thorough

    washing process with water and drying of the

    resulting wet gluten. The material obtained via

    this process consists of around 80 percent glu-

    ten plus some remaining starch, lipids and non-

    starch carbohydrates (Pomeranz, 1988). When

    added to the flour, vital wheat gluten increases

    the protein strength. This effect is easily detected

    with the help of flour analysis equipment like the

    Alveograph or the Extensograph.

    The properties of gluten added from outside

    are different from those of native gluten. The

    difference that can be observed by determining

    the water absorption and rheological properties,

    resulting from partial denaturation of the protein

    during the drying process. Because of this, a

    proper drying practice is the most important

    factor in preserving the function of vital gluten.

    Some manufacturers do not worry about keep-

    ing the quality of the protein, because vital gluten

    is sometimes still considered as a byproduct of

    starch production. Using this low quality vital

    gluten increases the protein content of the flour,

    but does not improve the gluten properties.

    The water absorption capacity of added vital

    gluten is lower than that of native gluten. A ratio

    of 1.3-1.5 parts of water per one part of vital glu-

    ten can often be observed, while this ratio goes

    up to 2.5-3 parts of water per one part of native

    gluten in flour. Also the structure of vital gluten

    becomes shorter because of the drying process.

    Because of this, softer wheat varieties are more

    suitable for producing valuable vital gluten.

    The colour of gluten is also an importantcriterion in the market. Vital gluten mostly has a

    grayish tone that will also contribute to colour of

    flour. This is not a desired quality though; bright

    white or yellowish tones are preferred in flour

    industry. The colour is affected by the wheat

    variety, extraction and drying methods.

    ServicesMhlenchemies mission and practical knowl-

    edge lie in selecting and combining the individual

    raw materials described. The optimum composi-

    tion brings about synergistic effects. Since wheat

    qualities fluctuate, Mhlenchemie helps mills to

    produce flours with consistent baking qualities.

    The samples of flour sent in by the mills are

    subjected to a rheological analysis in the compa-

    ny, and the results are used to develop specific

    compounds for each customer. Baking trials are

    then carried out to test the flour improvers for

    functionality before they are offered to the mill

    asAlphamalt.

    Besides customized products, Mhlenchemie

    offers whole systems. The EMCEbest WA series

    increases the water absorption capacity of

    doughs, and thus the yield, and results in a more

    succulent crumb and a longer shelf life. The

    EMCEgluten Enhancers can save on vital wheatgluten at 1/10 of its usage level, strengthen weak

    flours and make it possible to use composite

    flours.

    Mhlenchemie offers mills further support in

    their daily work in the form of seminars, labora-

    tory equipment and technical training courses

    and helps with the quality control and improve-

    ment of flours on the spot.

    More inforMation:

    Website: www.muehlenchemie.deThe first part of this article, which dis-

    cusses enzymes and flour standardisa-

    tion, is in t he March/April 2013 issue

    of Grain and Feed Milling Technology.

    It is also online at www.gfmt.co.uk

    Gri&fd milliG tcholoG14 | may - June 2013

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