18.13 Flour Treatment for Specific Applications

Transcription

1 18.13 for Specific Applications 264 and thus on the wheat, but it may also thrive on flour residues on the walls of the bakery or on the equipment. When it finds its way into the dough it survives baking and destroys the crumb during storage of the bread. Warm, damp conditions promote the development of the micro-organisms, so its appearance is more frequent in summer. The dough shows normal baking properties and the fresh bread has a normal appearance. But within a short time a fruity flavour develops in the bread, turns into sweet smell and finally becomes disgusting. Meanwhile, degradation of the bread crumb takes place, along with a yellowish-brownish discoloration. When the bread is broken, thin slimy strands are formed (Fig. 158). The optimum growth conditions for B. mesentericus are 37 C and ph 6. But it can grow in the range of C and a ph of At 97 C only 90% of the spores are inactivated within 2 h, and this temperature is far higher than that reached in the bread crumb. Thorough cleaning of the wheat reduces the chance of the bacterium to get into the bread, because it only adheres to the surface of the kernels. The baker can reduce its survival by proper cleaning of the bakery and equipment. If ropiness has occurred, the bakery and equipment should be disinfected, e.g. by washing with vinegar solution. Acidification is a means of controlling the growth of Bacillus mesentericus in the dough, for instance with sour dough or edible acids. Antimicrobial substances such as acetic or propionic acid and their salts (acetates and propionates) are also very effective in suppressing the growth of the organisms. Their effect is improved at lower ph values, i.e. in the presence of other acidifying agents. Since they affect taste and yeast growth, their dosage should be limited to a required minimum. The lack of volume yield caused by the antimicrobial agents can be compensated for by increased yeast levels and with flour additives such as enzymes or emulsifiers for Specific Applications Steamed Bread Introduction Although they differ in details, steamed breads from various regions have several properties in common, for instance the lack of stabilization by a firm crust (in contrast to baked bread), a very fine crumb structure, and a mild, almost bland taste. This can be considered an advantage because of the absence of acrylamide and the possibility of combining the steamed bread with various fillings and dishes. Since little or no salt is normally used, the dough is very extensible, but the stability of the finished, steamed product is also reduced. This is a special challenge to additives such as enzymes, ascorbic acid and other flour improvers. In the laboratory, steamed bread can be prepared in the traditional way in baskets placed on woks containing boiling water (Fig. 159), stainless steel pots placed on a fire or electric hotplate, or in stainless steel steam chambers (Fig. 160). For the following investigations a steam chamber was used. Fig. 158: Ropiness in wheat bread (Schünemann and Treu, 2002) Furthermore, flour with normal properties without any obvious quality problems was used. It fell into the flour quality range usual for steamed bread (Tab. 95).

2 18.13 for Specific Applications Fig. 159: Basket for traditional steaming (source: H. Moegenburg, Muehlenchemie Asia Pte. Ltd.) Fig. 160: Stainless steel steaming chamber The course of the core temperature during steaming is significantly lower than during baking (Fig. 161). This has to be taken into account if ingredients coated with fats or emulsifiers or pure fat or emulsifier powders Tab. 95: Flour quality for steamed bread trials Parameter Range Wet gluten % Gluten index Ash % Falling Number s Farinogram are used, and also if enzymes that have a high inactivation temperature, such as bacterial amylase, are included. Whereas the former would not dissolve readily, the latter would survive the curing process and cause damage in the final product. Enzymes Amylases Amylases affect the volume yield and crumb softness of the steamed bread. Fig. 162 shows the effect of adding pure fungal α-amylase with 5,000 SKB/g. The volume yield increased by almost 25%, displaying a maximum at 250 ppm (equal to 1,250 SKB per kg of flour). 265 Water absorption % Dough development min Dough stability min min. 2 Dough softening FU max Extensogram (135 min) Energy cm Steamed bread Baked buns Extensibility mm Dough resistance BU Ratio Baking time (min) Fig. 161: Core temperature of baked buns and steamed bread

3 18.13 for Specific Applications Reference Alphamalt VC 5000, 125 ppm Alphamalt VC 5000, 250 ppm Alphamalt VC 5000, 500 ppm 266 Fig. 162: Effect of α-amylase with 5,000 SKB/g (Alphamalt VC 5000) on the size of steamed bread. The volume yield per 100 g of flour was 300, 325, 369 and 351 ml respectively (from upper left to lower right). Hemicellulases Not unexpectedly, the positive properties of hemicellulases, described in chapter , were also observed in the preparation of steamed bread. For instance, a hemicellulase from Aspergillus niger (Alphamalt HCC) achieved a volume increase similar to that of amylase (Fig. 163). At the same time the pore structure became much finer (not shown). Reference Alphamalt HCC, 5 ppm Alphamalt HCC, 10 ppm Alphamalt HCC, 20 ppm Fig. 163: Effect of hemicellulase on the size of steamed bread. The volume yield per 100 g of flour was 300, 382, 373 and 373 ml respectively (from upper left to lower right)

4 18.13 for Specific Applications Glucose Oxidase The enzyme glucose oxidase (GOD) converts glucose into gluconic acid while oxidizing water into hydrogen peroxide, an oxidizing agent, as described in chapter The reaction requires oxygen, which is readily consumed by yeast and some chemical reactions at the very beginning of the dough preparation process. This means that the effect of GOD is often only perceptible on the surface of the dough or the baked product (dryer dough surface, stabilized structure), while the volume yield is hardly affected. Most probably due to the specific dough development process often used in the preparation of steamed bread, the GOD has a better supply of oxygen. The effect on volume yield is therefore measurable. In our example the improvement was about 10% (Fig. 164). One further effect is always mentioned by the bakers: the doughs have better machinability because of reduced stickiness. Lipase Lipase is yet another miracle enzyme, underestimated for a long time. The enzyme converts lipids into di- and monoglycerides, i.e. emulsifiers (chapter ). Especially after extensive kneading, lamination or long fermentation processes, a dramatic effect on dough stability and volume yield can be noted. In the example shown in Fig. 165, the increase was a net 70%. Since it is highly dependent on processing conditions, this effect cannot be reproduced with all dough preparation methods. Development of the dough by sheeting promotes the beneficial effect of lipase. This is probably due to a more extensive exposure to atmospheric oxygen. Endogenous lipoxygenases prefer to react with free unsaturated fatty acids rather than with unsaturated fatty acids bound to the glycerol backbone. Lipolysis exposes the fatty acids to the action of lipoxygenases which, in the presence of sufficient oxygen, are converted into hydroperoxides; these in turn react with components of the flour. In addition to dough strengthening, a bleaching effect occurs due to the oxidation of flour carotenoids. Since lipases are specific to the type of fatty acid present in the triglyceride, not all lipases are suitable for improving steamed bread. 267 Reference Alphamalt Gloxy, 20 ppm Alphamalt Gloxy, 125 ppm Alphamalt Gloxy, 250 ppm Fig. 164: Effect of glucose oxidase on the size of steamed bread. The volume yield per 100 g of flour was 300, 317, 334 and 321 ml respectively (from upper left to lower right).

5 18.13 for Specific Applications Reference Tigerzym 01, 5 ppm Tigerzym 01, 25 ppm Tigerzym 01, 50 ppm 268 Fig. 165: Effect of a commercial enzyme preparation containing a specific lipase on the size of steamed bread. The volume yield per 100 g of flour was 300, 447, 477 and 512 ml respectively (from upper left to lower right; colour differences were due to a rising thunderstorm). Fig. 166 and Fig. 167 summarize the effects of various enzymes on volume yield. The data are taken from two sets of trials, so there are two different references. Tigerzym 01 and LP signify two different lipases; Gloxy 7082 stands for glucose oxidase from Aspergillus niger; VC 5000 is 5,000 SKB/g α-amylase from A. oryzae; HCC, HCE and HCH are hemicellulases from A. niger, Thermomyces lanoginosus expressed in Volume yield (ml/100 g flour) Reference Tigerzym 01, 5 Tigerzym 01, 25 Tigerzym 01, 50 LP 12066, 20 LP 12066, 50 LP 12066, 100 Gloxy 7082, 20 Gloxy 7082, 125 Gloxy 7082, 250 VC 5000, 125 VC 5000, 250 VC 5000, 500 HCC, 5 HCC, 10 HCC, 20 Dosage (ppm) Fig. 166: Effect of specific lipases (Tigerzym 01, LP 12066), glucose oxidase (Gloxy 7082), α-amylase (VC 5000) and hemicellulase (HCC) on the volume yield of steamed bread

6 18.13 for Specific Applications Volume yield (ml/100 g flour) Reference Tigerzym 01, 25 HCE, 20 HCE, 40 HCE, 60 HCH, 20 HCH, 35 HCH, 50 C 132, 10 Dosage (ppm) C 132, 35 C 132, 50 BG 31, 35 BG 31, 50 Tigerzym 02, 10 Tigerzym 02, 50 Tigerzym 02, 100 Tigerzym 02, 150 Fig. 167: Effect of specific lipases (Tigerzym 01), hemicellulases (HCE, HCH), cellulase (C 132), β-glucanase (BG 31) and an enzyme combination (Tigerzym 02) on the volume yield of steamed bread A. niger and from Bacillus subtilis respectively; C 132 is a cellulase from a Trichoderma species, and BG 31 is a β-glucanase from A. niger. By combining several enzymes, additive effects resulting in even larger volume yield can be achieved (Tigerzym 02). Pure lipase, Tigerzym 01, served as an internal standard for both sets of trials. Oxidation Ascorbic acid is known to improve dough stability, crumb structure and volume yield in baking. Would it have comparable effects in steamed bread? Fig. 168 answers part of this question, showing the volume yield when ascorbic acid is combined with α-amylase in normal and long fermentation (1 h and 2 h respectively). A distinct maximum as a function 269 Volume yield (ml/100 g) Ascorbic acid (g/100 kg) Normal fermentation Normal fermentation with amylase Long fermentation Fig. 168: Effect of ascorbic acid on the volume yield of steamed bread

7 18.13 for Specific Applications 270 of ascorbic acid concentration appeared in all the trials. Amylase caused a shift towards higher concentrations, which is analogous to baking. The exact amount necessary to achieve a maximum depends on various factors such as the recipe, process, and flour quality. Emulsifiers The number of emulsifiers used in baking is still increasing. In our investigations we used the most common ones, i.e. SSL, CSL, DATEM and mono/diglycerides. The dosage was in the typical range for baking applications, i.e. between 0.1 and 0.5% on flour. While DATEM had the best volume yield (Fig. 169), the appearance and pore structure of the buns were not satisfactory. The best overall result was achieved with SSL, which produced good volume, a regular shape, a fine, even and bright pore structure and prolonged crumb softness. Trials with sucrose esters also resulted in improved volume (not shown), but the overall properties were inferior to SSL and the cost was much higher. Volume yield (ml/100 g flour) Reference SSL, 0.1 SSL, 0.3 SSL, 0.5 CSL, 0.1 CSL, Rye and High-Fibre Flour In Northern Europe high-fibre bread has a long tradition. Rye flour contributes a large proportion of the dietary fibre in all countries around the Baltic Sea. Rye per se does not have a higher fibre content than wheat, but the dark flours used for most types of rye or mixed flour bread provide up to 3 times as much fibre as standard wheat flour (Fig. 170). A large variety of breads are made with rye flour (Fig. 171). Due to the lack of a gluten network, the volume yield is comparatively low if a large proportion of rye flour is used. Acceptable processing conditions and sufficient dough stability can only be obtained by acidification, either through sour dough or with acidifiers such as lactic acid, acetic acid or fumaric acid. Ascorbic acid as a maturing agent is only used in mixed flour bread. Sour dough fermentation reduces the amount of available simple sugar, improving the glycemic index further. CSL, 0.5 DATEM, 0.1 Dosage (%) DATEM, 0.3 DATEM, 0.5 Mono/Di, 0.1 Mono/Di, 0.3 Mono/Di, 0.3 Fig. 169: Effect of emulsifiers on the volume yield of steamed bread

8 18.13 for Specific Applications Content (% d.b.) Content (% d.b.) Type: Rye flour Whole Wheat flour Type: Whole Protein (Nx5.8) Fat Available carbohydrates Dietary fibre Minerals Fig. 170: Composition of wheat and rye and some typical flours (data from Souci et al., 2000) Fig. 171: Selection of rye bread

9 18.13 for Specific Applications Fig. 172: Effect of glucanase on the structure of rye kernels. Left: untreated, right: treated with β-glucanase. (Source: K. Autio, VTT, Helsinki, Finland) 272 Enzymes for Wheat and Rye "Volume" Bread Amylases Although bread with a high fibre content already has a lower staling rate due to the higher water absorption, amylolytic enzymes of microbial or cereal origin are able to improve this even further, particularly if grains with low intrinsic enzyme activity (i.e. high Falling Numbers) are used (chapter , page 246). Hemicellulases Pentosanases and glucanases affect the hemicelluloses of wheat and rye (Fig. 172). Pentosans consist of two fractions, one of which is water soluble, while the other is not. Hydrolysis of the water-insoluble fraction results in smaller, water-soluble fragments (solubilized) which absorb more water. When soluble or solubilized pentosan is hydrolyzed, water is released from the gel. Some pentosanases only act on one or the other pentosan fraction, while others are less specific. Non-Specific Pentosanase Secabon, a standard wheat flour treatment pentosanase from a Trichoderma species, acts on both soluble and insoluble pentosans. At a suitable concentration the water absorption will first rise, improving machinability. Later in the process, water will be released from the pentosan gel through the continuing hydrolysis of soluble and solubilized pentosans (Fig. 173). This increases the availability of water and thus softens the dough structure (better volume yield), retarding and reducing starch retrogradation. Dough "Drying" with Specific Pentosanases If the doughs are already quite slack, a very specific xylanase which acts almost solely on the insoluble pentosans may be useful: it increases water absorption and thus results in dryer and more stable dough. Fig. 31 shows the effect of such a xylanase on a wheat flour type 550 in the Farinograph. The effects may be even stronger in rye and dark wheat flour. Viscosity (%) Fermentation time (min) Fig. 173: Effect of Secabon on the viscosity of wheat pentosans

10 18.13 for Specific Applications Proteases Some baking properties of rye flour and dark wheat flours, for instance the volume yield, can be improved by adding vital wheat gluten. It does not have exactly the same functionality as native gluten (chapter 18.9). Some of its natural behaviour can be recovered by protease. It can be used to improve the structure of the protein if the bread-making process is well controlled, taking into account the time-dependent action of the enzyme. Purified fungal proteases will be preferable due to their comparatively mild (specific) action at acidic ph. High-Extraction Wheat Flour In addition to rye, bread from dark wheat flour (high extraction) or whole wheat meal is also fairly common, especially in Germany but also in some other northern European countries. Its specific volume is superior to that of rye bread. Sour dough or acidification is not necessary but sometimes used, in particular for dark varieties of bread. Flour treatment is not unlike that for white wheat flour, i.e. oxidation or ascorbic acid and enzymes (amylases, hemicellulases). Crispbread Crispbread (Fig. 174) is a speciality from Scandinavia. Most types are made from a rather liquid yeast sponge dough (dough yield about 190%) which is sheeted, or rather spread, after 2 h fermentation into a layer 2.5 mm thick. This is followed by another fermentation of min. Major challenges are the sticky dough and the instability of the sensitive sheeted foam, as well as sufficient energy supply to the yeast without impairing the taste and colour of the final bread. The energy necessary for dehydration is a further important factor, as the dough moisture has to be reduced from about 50% to below 6%. The flour treatment for crispbread can be summarized as follows: Ascorbic acid: little or none Amylase: for browning and fermentation Hemicellulases and cellulases: to decrease water addition and avoid checking (hairline cracks) Protease to avoid checking. Amylases are able to provide a constant supply of energy to the yeast. While a given sugar addition can result in vigorous fermentation at the beginning followed by a sudden stopping of yeast activity once the sugar resources are finished, the amylases continue to produce fermentable sugar in the same measure as the yeast continues its fermentation. Instead 273 Fig. 174: Examples of crispbread

11 18.13 for Specific Applications of collapsing dough due to over-fermentation, a constant volume increase can be achieved, with its maximum at the beginning of the baking process. Some pentosanases are able to increase the amount of bound water at the beginning of their action, while in the long run water will be released again. This is a property that can be exploited particularly for the crispbread process. During pre-fermentation and dough processing, good stability with dry surfaces is required, whereas after a further fermentation time the water retention should be low to improve the drying behaviour. Biscuits and Crackers Biscuits and crackers offer yet another possibility of incorporating high-fibre flour. Whereas rye is not very common for crackers or biscuits, wholemeal is. In this case, distribution is not limited to Northern Europe. Typical examples are biscotti integrale (biscuits) or crackers integrale from Italy and granola biscuits from England (Fig. 175). Here again, Secabon, a hemicellulase with broad activity on pentosans, is very useful. It improves the chewing properties, making the bite shorter, but it also improves the properties of the return dough, since it counteracts the drying out of the dough during processing. 274 Oxidases mainly affect the surface of the dough. Only in a small mixer such as the Farinograph mixer do they have a visible effect on the dough rheology (Fig. 138, page 248), because the surface to volume ratio is large enough to permit the access of sufficient oxygen to the system. In crispbread production they reduce the stickiness of the dough sheet, improving its processing behaviour Noodles and Pasta Flour Improvers for noodle flour include: vital wheat gluten; emulsifiers; bleaching agents; colorants, in particular ß-carotene; ascorbic acid; hemicellulase and lipases Fig. 175: Wholemeal and high-fibre biscuits (and crackers)

12 18.13 for Specific Applications Enzymes with xylanolytic, glucanolytic and particularly lipolytic activities have proved extremely useful in the production of noodles and instant noodles from soft and hard wheat. They offer many advantages, for instance: reduced tendency to bend; increased firmness of the cooked noodles; enhanced overcooking tolerance; reduced oil uptake of fried instant noodles; reduced drying time; improved surface appearance and mechanical stability of dried noodles, reduction of raw material costs. The addition of a lipolytic and xylanolytic enzyme compound (Pastazym) improves the tolerance of noodles made from soft and hard wheat flour to overcooking, as shown in Fig With 10 g of the compound per 100 kg flour, the resistance to compression increases by almost 30% for over-cooking conditions (10 min). The uncooked noodles already show improved stability (Fig. 177). This results in improved handling properties such as better resistance to mechanical stress (e.g. packaging) and reduced stickiness. To create the optimum texture of instant noodles is a major challenge: On the one hand dry noodles have to rehydrate as quickly as possible, and on the other they must have a homogenous texture without overcooked outer layers and hard cores. Furthermore, they should not become soggy through extended exposure to hot water. As Fig. 178 shows, Pastazym improves the firmness of cooked instant noodles while the rehydration properties remain constant. The result is a firm bite without a hard, dry core texture. The colour of raw noodles tends to deteriorate rather quickly. With the enzyme compound the darkening is reduced, and the noodles show improved whiteness even after 24 h (Fig. 179). The difference in L* between the reference and the noodles with 10 g Pastazym is about 3. The human eye can detect differences Force (N) Cooking time (min) Dosage (g/100 kg flour) Fig. 176: Improvement of overcooking tolerance Firmness (%) Dosage (g/100 kg flour) Fig. 177: Firmness of fresh, uncooked noodles with the addition of a lipolytic and xylanolytic enzyme compound Firmness (%) Dosage (g/100 kg flour) Fig. 178: Firmness of cooked instant noodles made from soft wheat with the addition of a lipolytic and xylanolytic enzyme compound Color (L*) Hours after extrusion Dosage (g/100 kg flour) Fig. 179: Colour of fresh, uncooked noodles with the addition of a lipolytic and xylanolytic enzyme compound 275

13 18.13 for Specific Applications A B Fig. 180: Effect of Pastazym on the colour of dry and rehydrated noodles made from wheat flour. A: Dry noodles, reference; B: with Pastazym; C: Cooked noodles, reference; D: with Pastazym 276 exceeding L* = 1. The colour difference persists after cooking (Fig. 180). Other additives Tab. 96 is a summary of noodle extrusion trials with soft wheat flour using various additives. Although hemicellulases have the potential to reduce the viscosity of the extruded noodle or pasta dough or to reduce the water addition if added in very large amounts, this did not show at the chosen dosage. Surprisingly, they did not modify the appearance or texture of the finished products even at very high dosages. In sheeted noodle production, hemicellulases improve sheetability because they soften the dough without weakening the protein. Transglutaminase strengthens the protein, which should improve the cooking tolerance Tab. 96: Soft wheat noodle extrusion trials (double spiral noodles) with various additives Product Reference EMCEvit Plus Dry gluten Transglutaminase Dosage g/100 kg Water addition % Dough moisture content % Extrusion pressure bar Vacuum cm Hg Sensory evaluation Cooking water milky milky milky milky Appearance, raw bright beige brownish bright beige bright beige Appearance, cooked a bit slimy, a little slimy, slimy, brownish-grey slime, instable white brownish-grey brownish-grey shape, white Eating properties tough, tough, tough, irregular bite, a little sticky elastic elastic tougher

14 18.13 for Specific Applications C D of noodles. The bite was indeed firmer, but the appearance of the cooked noodle did not improve as compared to the reference. The addition of vital wheat gluten achieved the expected improvement in texture. A phospholipid-protected gluten resulted in better visual ratings. An emulsifier compound of mono- and diglycerides and lecithin sprayed onto a carrier (Mulgaprot S1) was rated best. For many years Mulgaprot has been used successfully as a flour improver in Central European countries. Its use in tropical and subtropical areas is limited by the negative effects of elevated temperatures on particle size distribution. Oxidizing agents and ascorbic acid also strengthen the protein, but they impair the processing properties of the dough. This may result in an irregular noodle structure with an increased tendency to checking. Furthermore, this strengthening cannot be detected in the finished product in the form of improved cooking tolerance. 277 Hemicellulase Guar gum Guar gum Mulgaprot S1 Mulgaprot S milky milky less milky less milky less milky bright beige bright beige bright beige smoother surface, smoother surface, darker darker irregular, porous surface, a little slimy, white a little slimy, white not slimy, white not slimy, white slimy, white irregular bite, tougher, irregular bite, slimy tough, regular, tough, regular, slimy regular bite surface, off-taste pleasant pleasant

15 18.13 for Specific Applications Composite Flour In most cases the use of non-wheat flours in 158 mixtures with wheat flour results in a noticeable loss of volume and changed appearance (Fig. 181); the sensory attributes are also different. If the overall quality of goods baked from composite flour (taste and smell, chewing properties, appearance, shelf-life) is to approach that of pure wheat products, the wheat flour component of the composite flour must first be treated although even then the amount of other flours that can be added is very limited. The well-known flour improvers potassium bromate and ascorbic acid have proved useful for this purpose. The dosage has to be adjusted to the particular wheat flour quality. As a rule it is between 20 and 50 ppm. To take the other flours into account seems to make little difference. If lipases are used in conjunction with soy flour, for example, there is no noticeable improvement in volume (Fig. 182), although this would be the case with wheat flour alone. Modern enzyme preparations also help to compensate for the loss of volume caused by using composite flour instead of wheat flour alone. Besides amylases, hemicellulases and also lipases can be used. Fig. 183 shows the effect of treatment with ascorbic acid and a baking enzyme on the structure of bread made from wheat flour with Fig. 181: Structure of bread made from untreated wheat flour, alone or mixed with tapioca starch, rye flour or soybean flour (70 / 30%; upper left to lower right)

16 18.13 for Specific Applications Fig. 182: Bread made from composite flour (90/10) with defatted soybean flour (upper row) and toasted, full-fat soybean flour (lower row), using a lipolytic enzyme (from left to right 0, 60 and 180 ppm Alphamalt LP 12066) 279 Fig. 183: Effect of flour treatment on bread made from composite flour with defatted soybean flour, (70:30). 60 ppm ascorbic acid plus Powerzym 6000 (hemicellulase/amylase compound), 0, 75, 100 and 150 ppm on wheat flour (upper left to lower right)

17 18.13 for Specific Applications 280 the addition of soy flour (70:30). Other additives commonly used in baking improvers, such as emulsifiers, improve the results still further. Fig. 184 shows the effects of various flour improvers on the volume of pan bread made from a composite flour consisting of CWRS and cassava flour in comparison with CWRS flour alone. In this case a combination of ascorbic acid, enzymes and emulsifiers made it possible to restore the volume of the loaves almost completely up to a wheat/cassava ratio of 85:15. If the wheat flour used is less strong it will be necessary to add wheat gluten or reduce the proportion of non-wheat flour. The nature of the foreign cereal may also play an important role. The effect of the emulsifiers GMS, CSL and lecithin, and also of pre-gelatinized starch, has already been described in chapter 16. There are no rules for such flour treatment. It has to be optimized in each case, depending on the composition of the flour and the baking properties of the wheat flour used. Relative volume yield (%) WF+AA+FAA WF untreated CF untreated Reference has also been made to the use of potassium bromate and ascorbic acid as flour improvers in chapter 16. The wheat flour used should have optimum baking properties, and these can be achieved by suitable treatment with enzymes and oxidizing agents along with emulsifiers and waterbinding substances Flours for Biscuits, Crackers and Wafers Whereas a high protein content and strong gluten are desirable properties in many bread processes, flours with little and weak gluten are preferable for durable baked goods. The tendency of dough to spring back after rolling and the undesirable formation of gluten lumps in wafer batters are the reasons for this requirement. Whether a flour with low and weak protein is available or not, the use of elasticityreducing agents (proteases, L-cysteine, glutathione, inactivated yeast, sodium metabisulphite) will have benefits at all stages of the process: the lamination will be more uniform; CF+AA CF+AA+ENZ CF+AA+ENZ+EMUL WF+bread improver Fig. 184: Effect of flour treatment on pan loaves made from composite flour (CWRS flour/cassava flour 85:15) in comparison with wheat flour alone (WF = wheat flour, CF = composite flour, AA = ascorbic acid, FAA = fungal α-amylase, ENZ = enzyme compound, EMUL = emulsifier, DATEM)

18 18.13 for Specific Applications reduction of the thickness of the dough sheet can be performed faster and more reproducibly; relaxing periods for the dough sheet can be shortened or even omitted; the dough pieces will keep the shape given by cutting; shrinkage and bending in the oven and also the formation of hairline cracks (checking) are avoided. With suitable amylases, expensive recipe components such as milk solids otherwise necessary for sufficient browning can be omitted. Furthermore, the whole process will be less dependent on flour quality. Emulsifiers, particularly lecithin (Fig. 185), but also mono- and diglycerides or DATEM, improve the spread of cookies and the regularity of biscuits and crackers. They can also be used to reduce fat in a recipe. Emulsifiers are usually applied at the bakery itself. Biscuit and Cracker Applications Tab. 97 shows the recipes for simple hard biscuits made without and with bacterial protease. The last row compares the dimensions of the biscuits. As the length/width ratio shows (average of 25 biscuits), there is almost Tab. 97: Biscuits baked with and without bacterial protease Component (kg) Reference With enzyme Flour Fat Sugar Salt Water Protease Length/width (mm) 62.3 / / 63.3 no difference between the length and width of biscuits with enzyme addition, whereas those without enzyme show shrinkage in one direction. Since the protease takes away most of the internal tension, the products are less inclined to bend during baking: the first row of Fig. 186 shows the underside of biscuits without protease; colouring occurred mainly at the margins, which were still touching the oven stone when the cookies became convex due to 281 Fig. 185: Effect of lecithin on the spread of cookies. left: reference; right: 1% liquid lecithin on flour (Courtesy of J. v. Wakeren, Caracas)

19 18.13 for Specific Applications 282 Fig. 186: Underside of hard biscuits baked without (top) and with bacterial protease (bottom) asymmetric protein shrinkage upon thermal denaturation. Biscuits made with protease remained flat and showed uniform browning (bottom row). This, too, is a common problem that can be observed with many commercially produced hard biscuits. Wafer Applications Batters for wafer production contain a large amount of water. A low viscosity and a uniform dispersion of all the ingredients is essential for even wafers with a homogeneous structure. Since the formation of gluten lumps during mixing can result in standstill of the machinery due to blocked tubes and sieves, or in uneven browning and reduced stability of the baked goods, the use of low protein flour is desirable, but may not be sufficient. Liquefying hydrolytic enzyme complexes are able to decompose any gluten present in a liquid batter, resulting in a uniform mixture with optimum flow properties. The viscosity reduction enables less water to be used in the recipe, and this in turn results in lower energy consumption for baking and a higher oven throughput. Such enzymes are most suitable for semi-continuous processes with batch times of at least 10 min, because the enzyme reaction needs some minutes to take effect. We used the Amylograph at a constant temperature for a simple test to demonstrate the effect of a "wafer enzyme" (bacterial protease, hemicellulase) on the rheological properties of a liquid dough system (Fig. 187). Standard wheat flour for bread making was used in all the tests; 250 g flour was premixed with 330 ml of water in a Braun mixer for 1 min 45 s and then put into the reaction jar of the Amylograph, which was adjusted to a constant 30 C. The wafer enzyme was added to one sample at 20 g per 100 kg flour before the start of mixing. Whereas the reference sample remained at almost the same viscosity for about 40 min, the enzyme caused an immediate viscosity drop. Furthermore, all the gluten strands were destroyed, which is evident from the definite shape of the curve. By contrast, the reference

20 18.13 for Specific Applications no enzyme Alphamalt LQ 4020 Fig. 187: Effect of a "wafer enzyme" on the viscometric behaviour of wheat flour batter (Amylograph, 30 C) curve shows large fluctuations due to gluten lumps or strands adhering to the mixing tool of the Amylograph. Similar results can be obtained with other viscometric devices, e.g. the Brookfield viscometer (Fig. 188), although only the rotating rods of the Amylograph seem to be able to show the development and disappearance of gluten lumps. In baking trials with a pilot-scale plant it was possible to control the water addition and thus the weight and density of the wafers with the help of the enzyme compound. This offers great economic advantages (reduced energy demand, higher throughput) and more freedom for product development (Fig. 189). Wafers of higher density are crisper and remain crisp longer because of reduced water absorption. 283 Viscosity (cps) Time (min) No enzyme Enzyme A, 15 g Enzyme A, 40 g Enzyme B, 15 g Enzyme B, 40 g Energy costs (EUR/100 kg flour) Initial water content (kg/100 kg flour) Density (g/wafer, 29x46 cm) Fig. 188: Viscogram of wafer batter with different proteolytic enzyme compounds and dosages (Brookfield Rotovisco, 25 C) Fig. 189: Effect of water addition on evaporation costs and wafer density (energy costs: 0.15 e/kwh) ➀ with wafer enzyme 2 no enzyme

21 18.13 for Specific Applications Reference SMB 50 g/100 kg Enzyme A, 50 g/100 kg Enzyme B, 50 g/100 kg Enzyme C, 50 g/100 kg Fig. 190: Farinographs with sodium metabisulphite (SMB) or enzymes. A: proteolytic enzyme for liquid wafer batters; B: proteolytic biscuit and cracker enzyme; C: proteolytic, amylolytic and hemicellulolytic enzyme complex. Replacement of Sodium Metabisulphite (SMB) in Cracker and Wafer Production This powerful reducing agent (chapter ) splits the inter-chain and intra-chain disulphide bonds of the gluten, causing an immediate fall in dough resistance (Fig. 115, page 228) or batter viscosity. SMB is very cheap and easy to use.

22 18.14 References In many countries, therefore, SMB is still used in wafer and cracker production although it causes a sulphurous off-taste. Enzymes as an alternative to SMB improve the taste and have definite technical advantages, namely constant dough properties once the reaction is accomplished, including similar texture of return dough and fresh dough, the reduction of water addition to wafer batters and control of wafer density and stability (Fig. 189). When tested in the Farinograph, both SMB and enzymes show a decline in kneading resistance (Fig. 190). The reaction of SMB occurs much faster, but probably due to the presence of atmospheric oxygen, some of the resistance is restored upon continued mixing, when disulphide bonds broken by SMB recover (upper right). The slower but persistent reaction of the enzymes results in minimum resistance, when all the substrate of the enzymes has been degraded References Ahrenholz SH and Neumeister CE, Development and use of a sampling and analytical method for azodicarbonamide. Am Ind Hyg. Assoc. J. 48: Bauer N, Koehler P, Wieser H and Schieberle P, Studies on the effects of microbial transglutaminase on gluten proteins of wheat. In: Recent Advances in Enzymes in Grain Processing. Courtin CM, Veraverbeke WS and Delcour J, (eds.), Laboratory of Food Chemistry Katholieke Universiteit Leuven, Leuven, Belgium, p Bechtel WG, Meisner DF and Bradley WB, The effect of the crust on the staling of bread. Cereal Chem. 30: Chung OK and Pomeranz Y, Wheat flour lipids, shortening and surfactants. Baker's Dig. 5:32-44; 153. Diderichsen BK and Christiansen L, Preparation of a maltogenic amylase enzyme. US Patent Application 4,598,048. Dirndorfer M, Personal communication. Freund W, Bäckerei Konditorei Management 5 Verfahrenstechnik Brot & Kleingebäck. Gildebuchverlag GmbH & Co. KG, Alfeld, Germany. Frisbæk J, Novel tailor-made xylanases: Their characteristics, performance in cereal processing and use as a tool to understand xylanase functionality in baking. In: Recent advances in enzymes in grain processing. Courtin CM, Veraverbeke WS, Delcour JA (eds.), Lab. of Food Chem., Katholieke Univ. Leuven, Belgium Gebruers K, Courti, CM, Goesaert H, Van Campenhout S and Delcour JA, Endoxylanase inhibition activity in different European wheat cultivars and milling fractions. Cereal Chem. 79(5): Geissmann T and Neukom H, On the composition of the water soluble wheat flour pentosans and their oxidative gelation. Lebensm.-Wiss. Technol. 6(2): Gonzalez P, Sunn Pest Unlocking the Mysteries of an Ancient Problem. Int. Center for Agric. Res. Gray JA and Bemiller JN, Bread staling: molecular basis and control. Compreh. Rev. Food Sci. Food Safety 2:1-21. Grosch W and Wieser H., Redox reactions in wheat dough as affected by ascorbic acid. J. Cereal. Sci. 29:1-16. Hedwig A, Personal communication. Höfer M, Ghyczy M and Popper L, Yeast interaction with lecithin fractions. Food Technol. Int Hoseney RC and Faubion JM, A mechanism for the oxidative gelation of wheat flour watersoluble pentosans. Cereal Chem. 58(5): Jörgensen H, Ein Beitrag zur Beleuchtung der hemmenden Wirkung von Oxidationsmitteln auf proteolytische Enzymaktivität: Über die Natur der Einwirkung von Kaliumbromat und analogen Stoffen auf die Backfähigkeit der Weizenmehle. Biochem. Z. 280:1-37; 283: Kieffer R, Die Elastizität von Weizenteig ein häufig überschätztes Qualitätsmerkmal. Getreide Mehl Brot 57(6): Kieffer R, Kim JJ, Walther C, Laskawy G and Grosch W, Influence of glutathione and cysteine on the improver effect of ascorbic acid stereoisomers J. Cereal Sci. 11: Köhler P, Untersuchungen zur Backwirksamkeit von DATEM und seinen Komponenten. Getreide Mehl Brot 53(4): Kragh KM, Larsen B, Rasmussen P, Duedahl- Olesen L and Zimmermann W, Non-maltogenic exoamylase and their use in retarding retrogradation of starch. WO 99/ Krog N, Amylose complexing effects of food-grade emulsifiers. Staerke. 23: