Effect of fungal α-amylase on the dough properties and bread quality of wheat flour substituted with polished flours

Food Research International 39 (2006) 117–126 www.elsevier.com/locate/foodres

EVect of fungal
-amylase on the dough properties and bread quality of wheat Xour substituted with polished Xours Ji Hyun Kim a, Tomoko Maeda b, Naofumi Morita

a,¤

a

Laboratory of Food Chemistry, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1, Gakuen-cho, Sakai, Osaka 599-8531, Japan b Department of Life and Health Sciences, Hyogo University of Teacher Education, 942-1, Shimokume, Yashiro, Hyogo 673-1494, Japan Received 18 February 2005; accepted 9 June 2005

Abstract Whole grains of a hard-type wheat cultivar ‘1CW’ (No. 1 Canada Western Red Spring) were polished from the outer layer to the inner layer by 10% of the total grain weight using a modiWed rice-polisher. The polished Xours of three fractions; C-1, C-5, and C-8 corresponding to 100–90%, 60–50% and 30–0% layer of the 1CW grain, respectively were used in this study. EVects of fungal
-amylase on polished Xour substitution for the common wheat Xour CW of 1CW on rheological or physicochemical dough properties and bread qualities were studied. When the polished Xours were substituted for CW without fungal
-amylase, the mixing tolerance index of dough in a farinograph and all parameters of viscoelastic properties signiWcantly increased rather than those of CW alone. As a result, baking qualities of breads made from the substituted Xours were signiWcantly inferior. But, the polished Xours increased the total gas generation signiWcantly during fermentation, as compared with CW alone. The addition of fungal
-amylase to polished Xour substituted CW distinctly developed gluten matrix in the SEM images and produced large amounts of the generated gas during fermentation. Therefore, the loaf volume and Wrmness of breads were improved by the combined additions of polished Xours and fungal
-amylase. Especially, the C-8 of the innermost fraction was more susceptible to aVection of fungal
-amylase among all polished Xours, and resulted in improvement of gas cell distribution and softness of breadcrumbs without lowering the loaf volume as compared with CW bread.  2005 Published by Elsevier Ltd. Keywords: Polished wheat Xours; Fungal
-amylase; Dough property; Bread quality

1. Introduction Polished-graded Xours can be obtained from the outer layer to the inner layer of the whole-wheat grain using gradually polishing method, as reported previously (Maeda & Morita, 2000, 2001, 2003; Maeda, Kim, & Morita, 2004). The Xour is absolutely diVerent from the conventionally milled Xour, which mainly consists of only the endosperm after removal of bran and germ from wheat grains. Therefore, the polished Xour contains large amounts of dietary Wbers, vitamins, minerals and *

Corresponding author. Tel.: +81 72 254 9459; fax: +81 72 254 9921. E-mail address: [email protected] (N. Morita).

0963-9969/$ - see front matter  2005 Published by Elsevier Ltd. doi:10.1016/j.foodres.2005.06.008

antioxidant compounds, as compared with commonly milled wheat Xours. However, the presence of bran and dietary Wbers in the grain causes some diYculties for the practical application of polished Xours to processed foods, that is, poor appearance, mouthfeel or texture, presence of a bitter Xavor and a darker color were formed. We have shown that polished Xours could improve the bread qualities with some modiWcations in baking procedure (Maeda et al., 2004) and are potentially suitable for use in composite Xours when combined with enzymes or emulsiWers (Maeda, Maeda, & Morita, 2001). And also, sourdough made from polished Xours improved the dough properties and bread qualities of wheat Xour (Kim, Maeda, & Morita, 2005). And then, additional studies on

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functional properties of polished Xours are needed for the practical application in the baking industry. Recently, consumers do not want artiWcial or synthetic additives to be used for breadmaking. Therefore, the use of enzymes is very important as improvers for breadmaking (Harada, Lysenko, & Preston, 2000; Morita, Arishima, Tanaka, & Shiotsubo, 1997). Actually, various kinds of amylase have been used in the baking industry to improve dough-handling properties and enhance bread quality (Maeda, Hashimoto, Minoda, Tamagawa, & Morita, 2003). The addition of
-amylase which has not only a substantial anti-staling eVect but also improves the elasticity of bread crumb, is quite popular and necessary on breadmaking, because the
-amylase activity is normally very low in the sound wheat Xour (Bowles, 1996; Cauvain & Chamverlain, 1988; Kulp & Ponte, 1981 MartínezAnaya & Jiménez, 1997; Ranum & DeStefanis, 1990; Si, 1997). Moreover, some enzymes and damaged starch with
-amylase have been well known to give synergistic eVects to baking processes (Farrand, 1964; Si, 1997). When some of other enzymes or damaged starch are present with even a very small amount of
-amylase, normally the loaf volume of bread increases and handling properties of dough are still acceptable without the dough stickiness problem. Although the present polished Xours have been focused as the functional materials to improve baking qualities (Maeda & Morita, 2001, 2003; Maeda et al., 2004), the new Xours containing a large amount of damaged starch and high enzyme activity were expected to give additional improvements to breadmaking by combination with
-amylase. Therefore, in this study, the authors would investigate whether the
-amylase of general additive on food industries could eVectively improve the dough and bread properties of polished Xour substitution, and its aim was to clarify the application ability of polished Xours to the combined addition of
-amylase for their development to various processed foods.

(No. 1 Canada Western Red Spring). The polishedgraded Xours were manufactured by the polishedgrading method as follows: The whole wheat grains without debranning were polished from the outer layer to the inner layer by a unit of 10% of the total wheat grain weight using a modiWed rice-polisher (Itomen Co., Ltd., Hyogo, Japan). The Xours obtained from the outermost layer (10%) of the whole grain were named as C-1. The remaining 90% of whole grain was re-polished by the same method in a stepwise manner as described above. These operations were repeated until the eight fractions of polished Xour (C-1 corresponds to 100–90% of the whole grain; C-2, 90–80%; C-3, 80– 70%, C-5, 60–50%; C-6, 50–40%; C-7, 40–30%; and C8, 30% to the core of grain) were prepared, as reported previously (Maeda & Morita, 2001; Tang, Ando, Watanabe, Takeda, & Mitsunaga, 2000; Tang, Ando, Watanabe, Takeda, & Mitsunaga, 2001). Three fractions of C-1, C-5, and C-8 were only used in the present study. The Xour qualities of these fractions reported previously (Maeda & Morita, 2001) were shown in Table 1. In addition, the conventionally milled wheat Xour of 1CW (CW) was donated by the Miyake Flour Milling Co., Ltd. (Osaka, Japan). The origin and activity of fungal
-amylase were Aspergillus oryzae and 100,000 U/g, respectively (Amano Pharmaceutical Co., Ltd., Nagoya, Japan). Ten percent (w/w) of the CW was substituted with polished Xours (C-1, C-5 and C-8) for the following experiments. Further comparison of dough and bread properties between the CW and substituted Xours was carried out using fungal
-amylase (300 U/100 g Xour) except for viscograph, fermograph and SEM experiments (500 U/100 g Xour). Especially, for test baking, the two levels of 300 and 500 U/100 g Xour were used for the same ingredients to obtain the clear eVects of fungal
-amylase on baking results.

2. Materials and methods

2.2. Rheological properties of dough

2.1. Flours and chemicals

2.2.1. Farinograph Mixing properties of various Xour samples were determined using a 50 g farinograph mixer by AACC method 54-21 (2000).

The wheat grain used for the preparation of polished Xours was a hard-type wheat cultivar ‘1CW’ Table 1 Compositional data of various wheat Xours (Maeda & Morita, 2001) Wheat Xour

Protein (%)

Ash (%)

Dietary Wber (%)

Damaged starch (%)

Diastatic activity mg/10 g of Xour


-Amylase activity (U/g Xour)

-Amylase activity (U/g Xour)

CW C-1 C-5 C-8

12.3 16.1 13.9 8.1

0.2 4.3 1.0 0.5

2.1 32.8 5.7 3.8

15.5 16.5 39.1 28.0

267.0 486.0 618.0 618.0

11.6 11.0 11.1 11.2

2.1 3.2 2.9 1.7

CW, common hard-type wheat Xour of 1CW; C-1, C-5, and C-8 were polished Xours obtained from 100% to 90%, 60% to 50%, and 30% to 0% layers of the 1CW whole grains, respectively. Diastatic activity, amount of maltose formed (mg).

J.H. Kim et al. / Food Research International 39 (2006) 117–126

2.2.2. Extensograph The extensibility or resistance of the dough samples was determined after aging for 45, 90 and 135 min according to the AACC method 54-10 (2000). 2.2.3. Viscoelastic properties To measure the viscoelastic properties of doughs, the dough samples were mixed with a 50 g farinograph mixer for 15 min. After mixing, doughs were taken in a plastic vessel of 25 mm of height and diameter, and then placed into the cabinet for 10 min at 30 °C as reported previously (Maeda et al., 2004). Doughs were measured using a Rheometer (Rheotech Co., Ltd., Tokyo, Japan) connected to a data processing computer program, Rheosoft TR-06 (Rheowin 205, Rheotech Co., Ltd.). 2.3. Breadmaking Bread was prepared according to the formula and procedure of a slightly modiWed AACC method 10-10B (2000). The bread formula was consisted of wheat Xour (300 g), salt (4.5 g), sugar (18 g), dry baker’s yeast (6 g) (J. T. Foods Co., Ltd., Shizuoka, Japan), and the optimum amount of water determined from the farinograph mixing. The formula for substituted Xours was changed only for the ratio of Xour (CW; 90%, polished Xour; 10% w/ w). In addition, these breads were also prepared by adding
-amylase (300 U/100 g Xour). All the ingredients were mixed in the bowl of a KN-200 mixer (Taisho Denki Co., Ltd., Tokyo, Japan) designed at the speed of 380 rpm for 15 min. Then the dough was fermented in a cabinet at 30 °C and 85% relative humidity (rh) for 90 min, punching was carried out twice at 30 and 60 min after the start of fermentation. Then the dough was divided into 130 g pieces and rounded. After the doughs were benched for 15 min at room temperature, the pieces were molded using a molder SM-230 (Baker’s Production Co., Ltd., Osaka, Japan). The molded dough pieces were placed in baking pans with internal dimensions of bottom, 90 £ 50 mm2; top, 105 £ 60 mm2; and height, 65 mm. As for another experiment, the fungal
-amylase (500 U/100 g Xour) was added to the same ingredients and accordingly prooWng conditions were also carried out as follows: the prooWng time, 50 min; temperature, 38 °C; and humidity, 90% rh. 2.4. Physicochemical properties of dough 2.4.1. Viscograph The pasting properties of substituted Xours were investigated with a viscograph (Brabender PT 100) according to AACC method 22-12 (2000). Sixty-Wve grams of Xour was completely dispersed with 450 ml of distilled water and then the suspension was heated from 30 to 93 °C at a rate of 1.5 °C/min. After keeping at 93 °C

119

for 15 min, the paste was cooled to 30 °C at the same rate and held for 15 min. 2.4.2. Fermograph To determine the gas production of various doughs, dough samples consisted of 300 g of Xour, optimum amount of water obtained by a farinograph mixing, 4.5 g of salt, 18 g of sugar and 6 g of yeast were mixed in a KN-200 mixer (Taisho Denki Co., Ltd., Tokyo, Japan) for 15 min at room temperature. After mixing, dough was divided into 35 g pieces and then put in a testing glass vessel (225 mL) after rounding. The glass vessel was placed into a water bath, which was maintained at 30 °C and connected with a fermograph (Atto Co., Ltd., Tokyo, Japan). In the present study, two kinds of gas generation, such as total and retained gases were determined. The amount of gas production was measured at intervals of 30 min during incubation for 9 h. The data were calculated as the gas amount for the 10 g dough. 2.4.3. Scanning electron microscopy Scanning electron microscopy (SEM) observation of various doughs with or without fungal
-amylase was carried out by the same methods as reported previously (Maeda & Morita, 2001; Morita et al., 2002; Nihei, Torikata, & Kageyama, 1990). A small portion of dough samples was frozen and lyophilized by the same method as used in the previous report (Maeda & Morita, 2001). The prepared samples were coated with Pt–Pd for 4 min before the observation, and SEM apparatus (Model S-800 Hitachi, Ltd., Tokyo, Japan) was operated at 10 kV according to the same procedure as reported previously (Morita et al., 2002). 2.5. Baking properties 2.5.1. Loaf volume of bread Breads were allowed to cool for 45 min before the measurement of the loaf volume by a rapeseed displacement. 2.5.2. Firmness of bread Firmness of breadcrumbs during storage was determined using the Rheometer (Rheotec Co., Ltd., Tokyo, Japan) as described previously (Maeda & Morita, 2000). 2.5.3. Image analyses of crumb grain An image analysis system (Image Hyper II, DigiMo Co., Ltd., Osaka, Japan) was used to generate data for gas cell distribution of various breads with or without fungal
-amylase. After baking 45 min, the breads were sliced into a piece of 4 £ 4 £ 2 cm3 from the central portion by electric cutter, and it was copied by Canon 5020 and scanned by CanoScan 676U/N1240U (Canon Co., Ltd., Tokyo, Japan). The image analyses of crumb grain of scanned areas (40,000 mm2) were conducted

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according to the manufacturer’s manual (Image Analysis System Operator Manual Ver 4.8, DigiMo). 2.6. Statistical analysis All tests were conducted at least three times for each sample and data were independently analyzed by analysis of variance (ANOVA) and then performed using Duncan’s multiple-range test to compare the means (Steel & Torrie, 1960). SigniWcant diVerences for all results were deWned by SPSS (Version 11.0, SPSS Inc., Chicago, USA) at P < 0.05.

3. Results and discussion 3.1. Rheological properties of dough 3.1.1. Farinograph results EVects of fungal
-amylase and polished Xours on farinograph mixing are shown in Table 2. The MTI (mixing tolerance index) of polished Xours signiWcantly increased, as compared with that of CW, that is, the substitution of polished Xours for the CW weakened the mixed dough properties. As the polished Xours contained larger amounts of bran and dietary Wber, these materials were considered to disturb the continuous gluten network structure in the wheat dough and also this tendency coincided with previous data (Gan, Galliard, Ellis, Angold, & Vaughan, 1992; Lai, Hoseney, & Davis, 1989; Maeda & Morita, 2001). The addition of fungal
-amylase to substituted Xours did not change their water absorption, whereas fungal
-amylase to CW signiWcantly decreased it, as compared with the CW without enzyme. The addition of fungal
-amylase to Xours signiWcantly decreased arrival, development, stability times and valorimeter value, regardless of kinds of polished Xours. These results were similar to those reported previously (Maeda et al., 2003). This tendency could be

attributed to weakening of mixed doughs caused by the presence of a low molecular weight dextrin, which was produced from damaged starches by amylase hydrolysis. Moreover, the addition of fungal
-amylase to the polished-Xour-substituted CW decreased the stability time and valorimeter value much more than that of CW. These results may be due to the presence of polished Xours containing larger amounts of damaged starch as compared with the CW as shown in Table 1 (Maeda & Morita, 2001). The present results coincided with the reports that damaged starch granules were susceptible to enzymatic hydrolysis and could be hydrated rapidly (Ranhotra, Gelroth, & Eisenbraun, 1993). 3.1.2. Extensograph results In the case of doughs without fungal
-amylase, the ratio (R/E) of resistance (R) and extensibility (E) showed no signiWcant diVerences between the CW and substituted Xours except for C-1 during aging. The addition of fungal
-amylase resulted in a decrease of E and in an increase of R for all samples tested. Therefore, the ratio of R/E for dough samples containing fungal
-amylase signiWcantly increased as compared with those without fungal
-amylase (data was not shown). The following equation was used to investigate the eVects of fungal
-amylase on extensogram: (R/E) of doughs with fungal
-amylase/(R/E) of doughs without fungal
-amylase (Fig. 1). The values of all samples were higher than 1.0; that is, the R/E of dough samples increased by addition of fungal
-amylase. Moreover, the values of substituted Xours gradually increased, whereas that of CW did not change signiWcantly during aging from 45 to 135 min. Especially, the C-8 had the highest value of from 1.56 to 1.71 among all samples during aging. These results suggest that C-8 was the most susceptible to fungal
-amylase among the substituted Xours. Although the addition of fungal
-amylase to the substituted Xours weakened the mixing properties as shown in Table 2, the fungal
-amylase led to a

Table 2 EVect of fungal
-amylase on farinograph data of doughs substituted with various polished Xours Sample

CW CW +
-AM* C-1 C-1 +
-AM* C-5 C-5 +
-AM* C-8 C-8 +
-AM*

Water absorption (%) 67.0b 64.5a 68.0bc 68.0bc 67.0b 67.8bc 69.0c 67.5bc

Time (min) Arrival

Development

Stability

2.5c 0.9a 1.8b 0.9a 2.5c 0.8a 2.8c 0.9a

19.5d 1.8a 18.6c 1.4a 17.5b 1.8a 18.5c 1.6a

26.0d 7.3b 23.3c 1.7a 23.0c 2.5a 26.0d 1.7a

MTI (BU)

Valorimeter Value

5.0a 50.0c 21.7b 65.0d 20.0b 80.0e 16.7ab 75.0de

94.5d 48.0b 94.2cd 42.5a 93.0c 43.0a 94.3cd 42.5a

Abbreviation. CW, common hard-type wheat Xour; C-1, C-5 and C-8 polished Xours of 100–90%, 60–50% and 30–0%, respectively. Amount of the polished Xour substitution, 10%; the rest of the Xour (90%) is CW.
-AM*,
-amylase (300 U/100 g Xour). MTI, mixing tolerance index. a–e Values followed by diVerent letters in the same column are signiWcantly diVerent according to Duncan’s multiple range test (P < 0.05).

J.H. Kim et al. / Food Research International 39 (2006) 117–126

The ratio of viscoelasticity values for flour samples with vs. without α-amylase

The ratio of R/E values for doughs with vs. without α-amylase

1.8

1.6

1.4

1.2

121

1.5

1.3

1.1

0.9

0.7 CW

1.0 45

90

Fig. 1. EVect of fungal
-amylase on the extensogram of various dough samples. 䉬, CW; 䊏, C-1; 䉱, C-5; 䊉, C-8. Amount of the polished Xour substitution, 10%; the rest of the Xour (90%) is CW. CW, common hard-type wheat Xour; C-1, polished Xours obtained from 100–90%; C-5, 60–50%; C-8, 30–0% of whole-wheat grains. Amount added of fungal
-amylase: 300 U/100 g Xour.

perceptible change of maturity of the dough during aging with the increasing R and R/E values for substituted Xours, as compared with CW. It was expected to improve the dough properties during fermentation by the addition of fungal
-amylase to the substituted Xours. 3.1.3. Viscoelastic property results When the polished Xours were substituted for CW, the compression stress (g), modulus of elasticity (
) and viscosity coeYcient () of the doughs signiWcantly increased as compared with those of CW except for C-8 substitution (data not shown). Fig. 2 shows the eVect of
-amylase on visoelasticity of various Xour doughs: the values for each parameter were calculated by the same equation as used in Fig. 1 between the dough samples with or without fungal
-amylase. Addition of fungal
amylase to Xours showed a slight decrease in the compression stress and modulus of elasticity of the dough, whereas slightly increased in viscosity coeYcient and relaxation time of all dough samples. C-5 showed the lowest values of compression stress and modulus of elasticity among all samples. In addition, C-8 signiWcantly changed viscosity coeYcient and relaxation time when fungal
-amylase was added. Therefore, the viscoelastic properties of polished Xour substituted doughs were aVected by the addition of fungal
-amylase. Especially, dough properties with C-8 substitution might be distinctly aVected by fungal
-amylase as shown in extensograph results of Fig. 1.

C-5

C-8

Samples

135

Maturity time (min)

C- 1

Fig. 2. EVect of fungal
-amylase on the viscoelastic properties of various dough samples. 䉫, g; 䊐,
; 䉭, ; 䊊, ; g, compression stress (102 N m¡2);
, modulus of elasticity (104 N m¡2); , viscosity coeYcient (104 N m¡2); , relaxation time (s). Abbreviations and amount added of enzyme is the same as in Fig. 1.

3.2. Baking results Table 3 shows the baking results of substituted Xours with or without fungal
-amylase (300 U/100 g Xour). Substitution of polished Xours signiWcantly decreased the speciWc volume by 11.4–26.3% as compared with the CW alone, but the addition of fungal
-amylase to the substitution increased rather than samples without fungal
-amylase. In contrast, the speciWc volume of CW inversely was decreased by addition of fungal
-amylase. The speciWc volume values of C-5 and C-8 containing fungal
-amylase did not show the signiWcant diVerences as compared with that of CW with fungal
-amylase. During the storage for 3 days, the crumb Wrmness of all samples was signiWcantly lowered by the addition of Table 3 Baking results of polished Xour substitution with or without fungal
amylase Sample

CW CW +
-AM* C-1 C-1 +
-AM* C-5 C-5 +
-AM* C-8 C-8 +
-AM*

SpeciWc volume (cm3/g) 4.03d 3.77cd 2.97a 3.20ab 3.57bc 3.73cd 3.57bc 3.70cd

Firmness (102 N/m2) 0 day

1 days

2 days

3 days

62.7b 28.4a 76.4c 69.6b 67.2b 33.3a 63.3b 26.5a

79.4b 59.8a 140.1d 113.7c 85.3b 66.6ab 82.3b 55.9a

101.9bc 66.6a 170.5e 136.2d 111.7c 83.3ab 108.8c 63.7a

117.6b 81.3a 188.2d 149.0c 134.3bc 93.1a 126.4bc 75.5a

Abbreviations and added amount of fungal
-amylase are the same as in Table 2. a–e Values followed by diVerent letters in the same column are signiWcantly diVerent according to Duncan’s multiple range test (P < 0.05).

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J.H. Kim et al. / Food Research International 39 (2006) 117–126

fungal
-amylase, and did not show signiWcant diVerence between the CW and substituted Xour breads, except for C-1. As a result, utilization of fungal
-amylase for C-5 and C-8 polished Xours improved the bread qualities such as loaf volume and storage properties, as compared with CW breads with or without fungal
-amylase. The
-amylase generally provided large speciWc loaf volume, which was due to the hydrolyzed starch or oligosaccharide molecules that are fermentable by yeast (Gujral, Guardiola, Carbonell, & Rosell, 2003). However, the speciWc volume of bread made from CW decreased by the addition of fungal
-amylase in this study. This was attributed to shortage of proof time and unsuitable level of fungal
-amylase for CW. Therefore, the proof time (from 33 to 50 min) and quantity of fungal
-amylase (from 300 U/100 g Xour to 500 U/100 g Xour) were redesigned by experimental conditions of Si (1997) who found that synergistic eVects of enzymes for breadmaking. 3.3. Physicochemical properties of Xours 3.3.1. Pasting results Viscograph data of substituted Xours with fungal
-amylase are summarized in Table 4. The addition of polished Xours to CW signiWcantly decreased the peak viscosity of wheat Xour suspension, but increased the break down value. In particular, the addition of C-1 showed extremely a low peak viscosity, setback and total setback, as compared with CW. Sandstedt and Abbott (1964) reported the eVects of wheat starch concentration on amylograms, and obtained lower peak viscosity in lower concentration of wheat starch. Because C-1 was the outermost layer of wheat grain, it included large amount of bran. The general compositions of bran have been reported to be 11.5% water, 16.0% protein, 4.6% fat, 61.9% total carbohydrate, and 6.0% ash. The amounts of carbohydrates in bran were 8.0–10.7% (db) dietary Wber, 21.6–26.5% pentosans, 21.4% cellulose, 7.5–9.0% starch and 4.6–5.6% total sugar (Atwell, 2002; Pormeranz, 1988). The C-1 substituted Xours thereby had relatively

low starch content as compared with the CW Xour. Furthermore, Johnson, Shellenberger, and Swanson (1946) investigated the relationship between the diastatic activity and peak viscosity of the amylograph of 130 commercial Xour samples. They reported the peak viscosity of amylograph was negatively correlated with diastatic activity, that is, the Xours with high diastatic activity had low peak viscosity on the amylograph. Since the polished Xours have been reported to contain 1.8–2.3 times higher diastatic activity than CW (Maeda & Morita, 2001) as shown in Table 1, the present data agreed with previous results. The decrease in the peak viscosity was observed from CW and substituted Xours, when fungal
-amylase was added to them (Table 4). Farrand (1964) reported that the peak consistency obtained from amylograph mixing was reduced by increasing amounts of damaged starch and small addition of
-amylase. The CW used for the control Xour in the present study remarkably showed high peak viscosity, followed by a close aYnity to its processing ability, as compared with other Xours. In contrast, peak viscosity values of Cameria and Hermes, common commercial hard-type wheat Xours in Japan, were 580 § 12 and 420 § 20 BU, respectively (Park & Morita, 2004). The values were similar to those of substituted Xours with added fungal
-amylase (500 U/100 g Xour) in the present study. Therefore, the
-amylase could improve the pasting properties of polished-Xour-substituted CW, resulting in making the similar peak viscosity to commercial Xours as described above. 3.3.2. Fermograph results When the polished Xours were added to the CW, the generation of total gas produced by yeast signiWcantly increased, whereas the amount of retained gas that exists only inside of dough signiWcantly decreased (data was not shown). This might be attributed to the weakened gluten matrix of the substituted-Xour doughs. The polished Xours included lower gluten content and larger amount of bran than CW. Therefore, the substituted

Table 4 Pasting properties of polished Xour substituted samples with or without fungal
-amylase Samples

Pasting temperature (°C)

Peak temperature (°C)

Peak viscosity

Break-down (BU)

Setback (BU)

Total setback (BU)

CW CW +
-AM* C-1 C-1 +
-AM* C-5 C-5 +
-AM* C-8 C-8 +
-AM*

65.0a 66.1a 69.9b 74.3c 64.8a 66.7a 65.5a 66.0a

91.9b 93.2c 91.1a 91.7ab 91.8ab 92.0b 92.1b 92.0b

762.5g 647.0ef 532.0b 420.0a 616.0de 557.5bc 657.5f 592.5cd

156.0abc 137.0a 195.5d 176.5cd 172.5c 148.0ab 175.0cd 163.5bc

1883.5d 2323.0e 304.5a 313.0a 1183.5b 1442.5c 1890.0d 2132.0d

2039.5c 2460.0d 481.0a 508.5a 1356.0b 1591.0b 2068.0c 2295.5cd

Abbreviations are the same as in Table 2, except for the amount of enzyme (500 U/100 g Xour). The Xour sample (wheat Xour: distilled water D 65 g:450 ml) was heated at a rate of 1.5 °C/min from 30 to 93 °C, holding the temperature (93 °C) for 15 min, cooled at the same rate until 30 °C, and then holding for 15 min at 30 °C. a–g Values followed by diVerent letters in the same column are signiWcantly diVerent according to Duncan’s multiple range test (P < 0.05).

J.H. Kim et al. / Food Research International 39 (2006) 117–126

Xours diluted the gluten concentration in the dough, because the bran materials with the large size were distributed in the gluten matrix. However, the damaged starch and high enzyme activity of polished Xours as shown in Table 1 (Maeda & Morita, 2001) resulted in increase of total gas by the supplement of polished Xours Fig. 3 shows amount of gas generated in the doughs made from substituted Xours with or without fungal
-amylase during fermentation. Amounts generated for total and retained gases signiWcantly increased depending on the present of fungal
-amylase in all samples. In particular, the aYnity of fungal
-amylase on polishedXour-substituted doughs was suYciently observed, because the amounts of gas generated from polished Xours distinctly became larger by addition of fungal
-amylase. Damaged starch in polished Xours was easily hydrolyzed by
-amylase, and then some dextrin and maltose were considered to be produced. Probably, thus formed dextrin and maltose would be used by yeast as the ferment-

able sugar, generating larger amounts of gas during fermentation. From the present study, we obtained similar results to those reported by Johnson et al. (1946) regarding the relationship between gassing power, diastatic activity and peak viscosity of the amylograph. They found that peak viscosity of amylograph was negatively correlated with diastatic activity (¡0.693) and gassing power (¡0.833). In the present data, the high maltose values (diastatic activity) of polished Xours decreased the peak viscosity and increase the gassing power when the CW was substituted with polished Xours. 3.3.3. SEM results The CW dough without fungal
-amylase addition showed large and small sizes of starch granules coated by gluten network to form a continuous Wlm (Fig. 4A and B). Smaller starch granules surrounded and Wlled by large starch granules were observed in wheat Xour

20

20

CW

C-1

Total gas Each CO2 gas (ml/10g dough)

123

Total gas

15

15

10

10

Retained gas

Retained gas

5

5

0 0

2

4

6

8

10

0 0

2

4

6

8

20

20

C-5 Each CO2 gas (ml/10g dough)

10

Fermentation time (hr)

Fermentation time (hr)

C-8

Total gas

Total gas

15

15

10

10

Retained gas Retained gas

5

5

0

0 0

2

4

6

8

Fermentation time (hr)

10

0

2

4

6

8

10

Fermentation time (hr)

Fig. 3. EVect of fungal
-amylase on gas generation of various dough samples during fermentation. 䉱 and 䉭, amount of total gas; 䉬 and 䉫, amount of retained gas. Black and white color symbols mean dough samples with and without
-amylase, respectively. Abbreviations and experimental conditions are the same as in Fig. 1, except for the amount of fungal
-amylase (500 U/100 g Xour).

124

J.H. Kim et al. / Food Research International 39 (2006) 117–126

Fig. 4. SEM images of various dough samples with or without fungal
-amylase. A and B, CW without
-amylase; C and D, CW with
-amylase; E and F, C-8 without
-amylase; G and H, C-8 with fungal
-amylase. Abbreviations and amount added of enzyme are the same as in Fig. 3.

doughs added with fungal
-amylase (Fig. 4C and D). C-8 without fungal
-amylase had starch granules whose size was very small and sharp or not round, and the starch granules were united each other. Furthermore, a continuous gluten Wlm was not observed in C-8 dough without fungal
-amylase (Fig. 4E and F). However, the gluten network in C-8 dough with
-amylase was more developed and covered the increased amounts of smallsized starch granules (Fig. 4G and H). Thus swollen or pasted starches that were produced by hydrolysis of damaged starch might accelerate developed gluten network structure. Tang et al. (2000) prepared polished barley Xours using the same apparatus as used in the present study, and reported that the ratio of large granules decreased in the order from the surface to the central core, and those of medium- and small-sized granules increased. In addition, they found that the physicochemical properties of granules diVered relating to the granular size and each fraction. The SEM images showed large amounts of small starch granules in the dough substituted with C-8, which was the innermost layer of wheat grain. Therefore, it is expected that polished Xours included diVerent sizes of starch granules for diVerent fractions, like those of barley Xours. In this study, the physicochemical properties of doughs were changed by additions of polished Xours and fungal
-amylase. These results might be due to the diVerence in size of starch granules for each fraction of polished Xours. However, more study is needed to declare the relationship between the fractions and size of starch granule of the polished Xour.

3.4. Bread qualities To demonstrate the eVect of
-amylase on polished Xour bread qualities, the additional baking test was conducted using increased amount of fungal
-amylase and proof time according to the previous report (Si, 1997). Results of baking tests using 10% substitution of polished Xours with or without fungal
-amylase (500 U/ 100 g Xour) and proof time for 50 min are shown in Table 5. The substitution of polished Xours signiWcantly

Table 5 EVect of fungal
-amylase on baking properties of wheat Xour substituted with various polished Xours Sample

SpeciWc volume (cm3/g)

Gas cell size (mm)

Firmness (102 N/m2)

CW CW +
-AM* C-1 C-1 +
-AM* C-5 C-5 +
-AM* C-8 C-8 +
-AM*

5.39b 6.63c 4.35a 5.52b 4.41a 6.79c 5.35b 6.43c

1.32c 1.32c 1.37c 1.17b 1.18b 1.00a 0.99a 0.95a

20.45b 17.83ab 40.64e 31.94d 28.24c 15.28a 17.12ab 13.98a

Abbreviations and experimental conditions are the same as in Table 3, except for the amount of enzyme (500 U/100 g Xour) and proof time (50 min). a–e Values followed by diVerent letters in the same column are signiWcantly diVerent according to Duncan’s multiple range test (P < 0.05).

J.H. Kim et al. / Food Research International 39 (2006) 117–126

decreased the speciWc volume and increased the Wrmness of wheat Xour bread. However, the speciWc loaf volume and Wrmness of the bread substituted with C-8 did not show signiWcant diVerences, as compared with those of CW. The addition of fungal
-amylase increased the speciWc loaf volume and decreased the crumb Wrmness of breadcrumbs in all samples tested. Addition of fungal
-amylase to substituted Xours improved the speciWc volume with the higher ratio than that of CW (C-1, 26.9%; C-5, 54%; C-8, 20.2%; CW, 18.7%), and the Wrmness of substituted Xour breads was not signiWcantly diVerent from that of CW, and also these values were lower than CW bread, except for C-1. As to the gas cell distribution of breadcrumbs, the decrease of gas cell size with increasing numbers of gas cells was generally reported to improve both volume and crumb grain (Vadlamani & Seib, 1999). The gas cell size of CW bread (1.32 mm) did not diVer signiWcantly by addition of fungal
-amylase, regardless of the increase of speciWc volume (Table 5). However, the gas cell size of CW bread signiWcantly decreased by combined additions of polished Xours and fungal
-amylase. Especially, C-5 and C-8 substituted Xours with
-amylase decreased the size by the 24% and 28%, while they increased the speciWc volume by the 26% and 19.3%, respectively, as compared with CW bread. Therefore, the appearances of breads made from C-5 and C-8 substituted Xours with
-amylase could be improved more than that of CW bread. In general,
-amylase is one of major hydrolytic enzymes used for breadmaking and has been reported to improve loaf volume, bread score and crumb Wrmness signiWcantly (Cauvain & Chamverlain, 1988; MartínezAnaya & Jiménez, 1997; Ranum & DeStefanis, 1990; Si, 1997). Several reports suggested that the enhancement of bread quality by addition of
-amylase was associated with improvement of gas retention during fermentation and retardation of bread staling caused by low molecular weight dextrins that were produced during baking (Cauvain & Chamverlain, 1988; León, Durán, & Benedito de Barber, 2002). The
-amylase could hydrolyze damaged starch and gelatinized starch, resulting in formation of low molecular weight dextrins as fermentable sugar for gas production (Poutanen, 1997). These general improving eVects of
-amylase more suYciently or eVectively aVected to the dough and bread qualities containing polished Xours in this study. Especially, C-8 was susceptible to aVection of fungal
-amylase among polished Xours tested and strengthened gas production during fermentation, making soft breadcrumbs with many Wne gas cells, even through the bread volume was similar to the CW bread. Therefore, the improvement of polished Xour breads and the development of polished Xour applications to other various processed foods could be proved by combined additions with fungal
amylase.

125

4. Conclusions Substitution of polished Xours (10%) for the common hard-type wheat Xour, CW signiWcantly weakened the doughs mixed in a farinograph and increased vicoelasitic properties. The lowering peak viscosity of substituted Xours in a viscograph was observed according to the low concentration of starch and high enzyme activity. As a result, the substitution of polished Xours signiWcantly decreased the speciWc volume by 11.4–26.3% as compared with the CW alone. However, polished Xours signiWcantly increased fermentation ability rather than the CW Xour. When the addition of fungal
-amylase to the substituted Xours, the rheological and physicochemical properties were signiWcantly changed, making the good dough structure and generated large amounts of gas during fermentation. Therefore, the loaf volume and softness of breads were improved by combined additions of polished Xours and fungal
-amylase. Especially, C-8 was susceptible to improving eVects of fungal
-amylase among all polished Xours, resulted in making soft breadcrumbs with favorable gas cells keeping similar loaf volume to the CW bread.

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