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Storage properties of bread made from hard-type polished-graded wheat flours

T. Maeda1, N. Matsuura2 and N. Morita2

1Department of Life and Health Sciences, Hyogo University of Teacher Education, 942-1, Shimokume, Yashiro, Hyogo 673-1494, Japan.
2
Lab. of Food Chemistry, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1, Gakuen-cho, Sakai, Osaka 599-8531, Japan.

Introduction

Polished-graded wheat flours (PGF) could be obtained by polishing whole-wheat grains from the outer layer with stepwise manner by 10 % unit of total weight of grains using a traditional rice polisher in Japan (Maeda et al, 1999; Maeda et al, 2001; Maeda et al, 2004). Characteristics of thus polished flours such as flour qualities; functionality and processing properties have been studied using soft- and hard-type wheat grains (Maeda et al., 1999; Maeda et al, 2001; Maeda et al, 2004; Kim et al, 2005). Whole-wheat grain flours (WWGF) contain bran and germ with large amounts of nutrients, however the poor flour qualities are considered to be unsuitable for breadmaking. In Japan, the amounts of WWGF produced or consumed are quite low and the milling method is neither common nor uniform. In contrast, PGF are easily and conveniently prepared by only a polishing process of whole wheat grains, and then the PGF had different flour qualities from those of conventionally milled flours (CMF) or WWGF. In this study, to develop the whole grain flours on baking industries, especially the storage properties of breads were compared between the WWGF and PGF.

Materials and methods

Flour and chemicals

The wheat grain used for the preparation of PGF was a hard-type wheat cultivar ‘1CW’ (No. 1 Canada Western Red Spring). The PGF were manufactured by the polished-grading method as reported previously (Maeda et al, 2004; Maeda and Morita, 2001). The flours 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 flour (C-1 corresponds to 100-90 % of the whole grain; C-2, 90-80 %; C-3, 80-70 %, C-4, 70-60 %; C-5, 60-50 %; C-6, 50-40 %; C-7, 40-30 %; and C-8, 30 % to the core of grain) were prepared, as reported previously (Maeda and Morita, 2001). Only three fractions of C-2, C-4 and C-6 were used in the present study. In addition, commercial hard-type wheat flour ‘Hermes’ provided from Okumoto Flour Milling Co., Ltd. (Osaka, Japan) was used as control sample. As to WWGF, a hard-type commercial product (Nisshin Flour Milling Co., Ltd., Tokyo, Japan) was used. As for additives to breadmaking of PGF, sucrose fatty acid ester (SE-S1670) by Mitsubishi Kagaku foods Co. (Tokyo, Japan) and pentosanase (PEN) by Novo Nordisk Inc. (Tokyo, Japan) were used. SE-S1670 (hydrophile lipophile balance (HLB)=16) and PEN (2,500 U /g) were added to the bread ingredients with 0.3 % and 100 ppm on the flour weight basis, respectively.

Breadmaking

The bread making formula and procedures were carried out with a slight modification of AACC Method 10-10B (2000) and Morita et al (2002a). Fifteen grams of yeast, 18 g of sugar and 4.5 g of NaCl were used and 10-30 % of the wheat flour was replaced by PGF, and the same baking procedure was conducted as reported previously (Morita et al, 2002b). The optimal amount of water for the flour was determined from water absorption values by a farinograph mixing (AACC 54-21, 2000).

Bread qualities

Specific volume of bread samples were measured by a rapeseed method and the distribution of gas cells in the breadcrumbs was determined by an image analysis system (Image Hyper Ⅱ, DigiMo Co., Ltd., Osaka, Japan). Namely, after baking and storage for 45 min, the breads were sliced into a piece of 4x4x2cm3 from the central portion by electric cutter, and it was copied by Canon 5020 and scanned using CanoScan 676U/N1240U (Canon Co., Ltd., Tokyo, Japan). The image analysis of crumb grain of scanned areas (160,000 mm2) was conducted according to the manufacturer’s manual (Image Analysis System Operator Manual Ver 4.8, DigiMo) (Kim et al, 2005).

Storage properties of breadcrumbs

Rheological properties. The staleness of breadcrumbs during storage was measured from the values of compression stress or textural parameters using a rheometer (RT-2002D-D, Yamaden Co., Ltd., Tokyo, Japan).

Differential scanning calorimetry (DSC). In general, starch crystallisation is considered to be a major factor contributing to bread staling. When the staled bread was heated in the DSC, a prominent endothermic peak was appeared around 50C, which was absent in the fresh bread, and notably increased with storage time (Biliaderis et al, 1995). This endothermic peak was due to the melting of retrograded amylopectin. Therefore, the staleness of breadcrumbs with PGF and various additives was studied by the determination of melting enthalpies of recrystallised amylopectin during storage at 25C, using the same DSC as described previously (Maeda et al, 2001). The DSC data were obtained using the dried breadcrumbs with ethanol and acetone. The analyses were carried out in triplicate using 8 to 12 mg of sample weight and the twice amount of water. The samples were heated at the rate of 10C/min, and its temperature was scanned in the range of 25~120C.

Water activity (aw). Water activity of breadcrumbs was measured with Novasina IC-500 AW-LAB (Axair Ltd., Switzerland). About 2.0 g crumbs cut into about 64 cubic millimeters was used. Water activities of fresh (day-0, aw0) and stale (day-3, aw3) crumbs were measured. The changing of water activity (ΔaW) during storage for 3 days was calculated as follows: ΔaW = (aw3 - aw0) / aw0 x100.

Results and discussion

Bread qualities

Additions of PGF and WWGF to Hermes (CMF) increased the water absorption, but increasing amounts were quite larger for PGF addition than that with WWGF addition. Substitution of PGF decreased the specific volume as compared with WWGF substitution (Table 1). SE and PEN additions to these substituted flours distinctly increased the specific volume rather than Hermes; this positive effect was obtained for WWGF substitution. However, partial substitution of PGF improved the gas cell distribution with smaller size and larger numbers than that of WWGF.

Table 1. Effects of various additives on the specific volume of bread.

Sample

Specific volume (cm3/g)

Control

3.308

PGF30

3.088

PGF30+SE+PEN

4.011

WWGF30

3.507

WWGF30+SE+PEN

4.275

Control, Hermes (CMF) 100 %; PGF30, Hermes 70 %+C-4 30 %; WWGF30, Hermes 70 %+WWGF 30 %. SE, sucrose fatty acid ester; PEN, pentosanase.

Table 2. Effects of various additives on storage properties of breadcrumbs.

   

Firmness (g)

   

Storage days

Sample

0

1

3

Control

65.38

187.80

257.86

PGF30

114.38

190.57

351.43

PGF30+SE

85.75

189.33

253.25

PGF30+PEN

83.71

227.00

285.60

PGF30+SE+PEN

73.63

119.50

206.29

WWGF30

59.63

158.29

258.33

WWGF30+SE

53.13

111.00

213.83

WWGF30+PEN

69.63

153.88

225.17

WWGF30+SE+PEN

50.88

103.13

155.25

Abbreviations are the same as in Table 1.

Storage properties of breadcrumbs

Firmness of breadcrumbs during storage was compared between the breads including PGF and WWGF. The 30% substitution of WWGF for CMF did not harden the firmness of breadcrumbs, whereas that of PGF increased the hardness (Table 2). Combined additions of PEN and SE improved the softness, but its improvement was also sufficient for WWGF. The changing ratio of cohesiveness of breadcrumbs during storage was also smaller for WWGF, and there were different effects on the storage properties from the rheological values between the PGF and WWGF substitutions for breadmaking. For the case of DSC analyses, PGF substitution suppressed the recrystallised amylopectin during storage rather than WWGF (Figure 1). The value of aw0 of breadcrumbs increased by substitutions of PGF or WWGF, especially for PGF substitution. These results were considered to relate to the higher water absorption of these flours than CMF. The changing value of ΔaW described above was larger for breadcrumbs with PGF, however the PEN and SE additions decreased the dryness of breadcrumbs with low value of ΔaW, as compared with the CMF bread.

Figure 1. Effects of various additives on staleness of breadcrumbs after storage for 3 days by DSC analysis. Abbreviations are the same as in Table 2.

Conclusion

Partial substitution of WWGF or PGF for CMF decreased the storage properties as compared with those of CMF bread. But, the PGF improved the gas cell distribution of breadcrumbs with smaller size and larger numbers than WWGF, without depending on the additions of enzyme and emulsifier. The additions of enzyme and emulsifier with WWGF or PGF decreased the retrogradation of amylopectin during storage, but the values could not arrive at that of CMF. As for the firmness of breadcrumbs during storage, these additives could retard the staleness of bread samples including WWGF or PGF, resulting in the similar values to that of CMF bread. Combinations of additives with WWGF or PGF improved the bread qualities, such as loaf volume, cohesiveness and a water holding ability, as compared with CMF bread.

Acknowledgements

The authors wish to thank Okumoto Flour Milling Co., Ltd. (Osaka, Japan) for supplying wheat flour; Asahi Yeast Co., Ltd., (Nagano, Japan) for providing yeast and Mitsubishi-Kagaku Foods Co., Ltd. (Tokyo, Japan) for providing emulsifiers.

References

American Association of Cereal Chemists, Approved Methods, 10th Edition. (2000). Approved Method 10-10B; 54-21.

Biliaderis C. G., Izydorczyk M. S., and Rattan O. (1995). Food Chemistry 53:165-171.

Kim, J. H., Maeda, T., and Morita, N. (2005). Cereal Chemistry 82: 144-151.

Maeda, T., Kim, J. H., and Morita, N. (2004). Cereal Chemistry 81: 660-665.

Maeda T., Maeda N., and Morita N. (2001). Journal of Applied Glycoscience 48: 27-36.

Maeda, T., and Morita, N. (2001). Journal of Applied Glycoscience 48: 63-70.

Maeda T., Ohkura M., and Morita, N. (1999). Journal of Applied Glycoscience 46: 413-422.

Morita, N., Maeda, T., Miyazaki, M., Yamamori, M., Miura, H., and Ohtsuka, I. (2002a). Cereal Chemistry 79: 491-495.

Morita, N., Maeda, T., Miyazaki, M., Yamamori, M., Miura, H., and Ohtsuka, I. (2002b). Food Science and Technology Research 8: 119-124.

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