The current issue and full text archive of this journal is available at www.emeraldinsight.com/0007-070x.htm BFJ 564 Effect of composition of gluten proteins and dough rheological properties on the cookie-making quality Sheweta Barak, Deepak Mudgil and Bhupendar Singh Khatkar Department of Food Technology, Guru Jambheshwar University of Science and Technology, Haryana, India Abstract Purpose The purpose of the paper is to study the effect of the gliadin and glutenin fractions of gluten on the cookie quality. Design/methodology/approach Ten different wheat varieties were analyzed for the flour physicochemical characteristics, gluten composition and rheological properties. The different flours were baked into cookies. The cookies were analyzed for spread ratio and texture. Relationships of various flour parameters, gluten composition and cookie characteristics were determined. Findings Gluten subfractions, damaged starch, protein, AWRC values were significantly correlated to the cookie spread and texture. Damaged starch ðr ¼ 20:638Þ; protein ðr ¼ 20:508Þ and AWRC (r ¼ 20:844Þ had a negative relationship with the cookie spread. The flours with higher SDS sedimentation value also produced cookies with lower spread ratio and harder texture. The study clearly demonstrated a positive correlation between Gli:Glu ratio ðr ¼ 0:765Þ and spread ratio and a negative correlation ðr ¼ 20:528Þ with hardness of the cookies measured in terms of breaking force. Flours with lower dough development time and dough stability performed better as cookie flours. Originality/value The gliadins and Gli/Glu ratio had a significant effect on the cookie spread and texture and the prediction equation developed during the study could accurately predict the cookie spread from the Gli/Glu ratio and AWRC values. Keywords Wheat, Cookies, Gliadin, Glutenin, Rheology, Cereals Paper type Research paper British Food Journal Vol. 115 No. 4, 2013 pp. 564-574 q Emerald Group Publishing Limited 0007-070X DOI 10.1108/00070701311317847 Introduction The end-use quality of the wheat largely depends on the composition of the grain. Extensible dough that produces larger diameter and lesser height cookies are considered better for cookie quality. Desirable cookie flour generally has lower water holding capacity (Faridi et al., 1994). Flours with low hydration properties produce cookies with greater spread (Yamazaki, 1962). Especially in cookies, higher levels of damaged starch leads to stiffness in dough, and smaller spread (Gaines et al., 1988). Gluten protein quality and quantity determine dough strength; generally, soft wheat with weak gluten and low protein content are preferred for cookie making (Gaines, 1991; Souza et al., 1994). Faridi et al. (1994) reported a negative association between protein content and cookie diameter while Yamamoto et al. (1996) found no relationship between protein content and sugar-snap cookie diameter. Dough rheology characterisation, which relates to dough handling properties, is an important parameter in the evaluation of wheat quality for cookie making. Several methods are used to characterise the rheological properties of cookie dough, including the
Farinograph and Extensograph methods (Bloksma and Bushuk, 1988). Low content of protein (8 10 per cent in the grain), low water absorption (WA), and low resistance to deformation, are the characteristics used to describe the suitability of wheat for cookie production. The SDS sedimentation value depends on the swelling of the glutenin strands and higher values have been associated with superior gluten characteristics and bread quality (Lorenzo and Kronstad, 1987). However, Carter (1999) found negative relationship of SDS value and protein content of the soft wheat. Wieser and Kieffer (2001) found significant high correlation between the quantity of gluten proteins and the bread loaf volume. The effects of gliadins and glutenins composition have been previously studied with respect to the bread quality, but very limited studies have been reported on the role of gluten protein fractions on the quality of cookies. Moreover, test baking has been used for a long time to predict the suitability of the wheat flour for the cookie production. However, the baking test is time consuming, thus there is a thrust to find a method which can test the suitability of flours in terms of cookie quality in relatively short period of time. Thus, the study aims to expand our knowledge on the influence of the flour quality parameters, particularly gluten composition and rheological properties of dough in relation to cookie making potential of the Indian wheat varieties, and to investigate the possibility of predicting the cookie making quality using these parameters. Composition of gluten proteins 565 Material and methods Selection of wheat varieties and flour extraction Samples of ten wheat varieties differing widely in their cookie making quality were selected for the study. These varieties were milled to 65 per cent extraction rate in a Chopin mill. The wheat flours obtained were stored at 48C for further analysis. Chemical analysis of wheat flours The wheat flours were analysed for the protein and alkaline water retention capacity (AWRC) using standard AACC methods (AACC, 2000). SDS Sedimentation volumes of flour were estimated according to the Axford et al. (1978). Damaged starch was evaluated by the Chopin SDmatic. Dough rheological characteristics Dough rheological parameters were evaluated by Chopin Mixolab. The Mixolab Simulator profile, which gives different parameters such as water absorption capacity of the flour (per cent), dough development time (min), stability (min) and softening (FU), respectively was used to study the rheological characteristics of different flours. Gluten isolation and characterization Gluten was isolated from different selected wheat varieties by Glutomatic. Wet gluten, dry gluten and gluten index was evaluated for the different wheat varieties. The extensibility of the gluten was determined by Kieffer dough/gluten extensibility rig with the test speed of 3.3 mm/sec and data acquisition rate of 200pps. The test mode of the instrument used was force in tension.
BFJ 566 Gluten fractionation into gliadins and glutenins Wheat flours were defatted by successive extraction with chloroform according to MacRitchie (1987). Flour (100 g) was extracted with 200 ml of chloroform at room temperature and then filtered through filter paper. The extraction was repeated two more times for a total of three extractions. The defatted flour was left to stand at room temperature until dry. Gluten was extracted from defatted flour samples by glutomatic and freeze-dried. The freeze-dried gluten samples were ground in a pestle mortar. The resulting freeze-dried gluten powder from each wheat variety was dissolved in 200 ml of 70 per cent ethanol. The mixture was stirred on a magnetic stirrer for 3 h at 258C. It was then centrifuged for 30 min at 1000 g at 48C. Supernatant was collected and the pellet was again extracted with 70 per cent ethanol. The supernatants were pooled and ethanol was removed from the gliadin extracts using rotary evaporator at 308C. The gliadin and glutenin fractions, thus, obtained were freeze-dried and powdered in pestle and mortar. Cookie preparation Cookies were prepared according to AACC Approved method 10-50D (American Association of Cereal Chemists, 2000) with slight modifications. The ingredients used were flour (225 g), sugar (130 g), shortening (64 g), dextrose solution (33 ml), sodium bicarbonate (1.6 g), ammonium bicarbonate (0.9 g), sodium chloride (2.1 g) and distilled water (16 ml). The dough was sheeted to 10 mm thickness on a dough sheeter and cut into round shape with cutter of 60 mm diameter. Baking was performed in baking oven at 2058C for 15 min. The diameter and thickness of six cookies was measured and the average was calculated. The spread ratio was calculated by dividing diameter (mm) with thickness (mm). Cookie preparation was done in triplicate. Textural analysis of cookies The texture of cookies was determined by Texture Analyser (TA-XT 2i) in terms of the breaking force required to fracture the cookies. The probe used was Warner Bratzler blade using 50 kg load cell. The test mode used was force in compression with pre test speed, test speed and post-test speed of 1.5, 2.0 and 10.0 mm/sec, respectively. Statistical analyses The experimental data collected was analysed for significant differences with the help of analysis of variance (ANOVA) conducted using SPSS 16.0 software. The correlation matrix was obtained using SPSS 16.0. The regression equation was evaluated by using multiple-linear regression in SPSS 16.0. Multiple-linear regression was conducted with cookie-spread ratio as the dependent variable. Best-fit linear regression model was determined using stepwise variable elimination. Results and discussion Physicochemical analyses of the wheat flours The results of the flour quality analysis of wheat varieties are presented in Table I. All the flour quality parameters such as protein, SDS sedimentation volume, damaged starch content and alkaline water retention capacity (AWRC) varied significantly. Protein content ranged from 10.06 per cent to 14.17 per cent. The highest protein content was observed in wheat variety HW 2004 while PBW 590 showed the lowest values, respectively. SDS sedimentation volume ranged from 29 ml in variety WH 1025
Variety TKW(g) HLW (kg/hl) SDSV(ml) DS (%) AWRC (%) Protein(%) D G(%) GI(%) R/E Composition of gluten proteins NIAW 917 39.36f 78.66b 53 h 8.85 h 89.40 g 13.03 g 9.89e 68.13f 1.27i HI 977 40.85 g 82.36 g 52 g,h 8.80 g 89.96 h 12.25e 9.72d 96.33i 0.74e CBW 38 36.02c 75.30a 51 g 8.44e 90.23i 11.81d 8.43b 97.52j 0.92f HW 2004 48.67j 87.86j 47f 8.55f 84.62e 10.06a 7.92a 56.80e 0.53d MACS 1967 45.30i 80.66c 39e 8.94i 79.57b 12.34f 10.64i 48.12c 0.26a PBW 590 37.82e 85.66i 37d 6.02c 83.10d 14.17i 10.03f 78.90 h 1.02 g PBW 550 36.91d 82.63 h 34c 5.82b 82.35c 13.56 h 10.07 g 71.85 g 1.45j DBW 16 34.23b 82.23f 31b 8.79 g 90.22i 12.25e 10.29 h 42.61b 1.04 h C 306 42.56 h 81.46e 30a,b 6.14d 88.45f 10.85c 9.20c 49.10d 0.43c WH 1025 34.12a 81.07d 29a 4.68a 73.39a 10.62b 10.72j 40.22a 0.33b Notes: TKW ¼ Thousand kernel weight; HLW ¼ Hectoliterweight; SDSV ¼ SDS sedimentation volume; DS ¼ Damaged starch; AWRC ¼ Alkaline water retention capacity; DG ¼ Dry gluten; GI ¼ Gluten index; R=E ¼ Resistibility/ extensibility of gluten. Values followed by different letters are significantly different at p, 0.05 567 Table I. Grain and flour quality characteristics to 53 ml in NIAW 917. The lowest damaged starch content of 4.68 per cent was reported in variety WH 1025 while variety MACS 1967 had the highest damaged starch content of 8.94 per cent. AWRC values for the different flour samples ranged from 73.39 per cent in variety WH 1025 to 90.23 per cent in variety CBW 38. SDS sedimentation volume (0.503) and damaged starch (0.618) were found to be strongly positively associated with the AWRC of the wheat varieties indicating that varieties with higher SDS sedimentation volume and damaged starch content result in poor quality cookies (Table II). Wheat variety HW 2004 reported the lowest dry gluten content among all the wheat varieties studied. Gluten index ranged between 40.23 per cent and 97.52 per cent. The R/E ratio of gluten also varied significantly among the different varieties. Highest values were found in variety PBW 550(1.45) while the variety MACS 1967(0.26) had the lowest ratio. Spread ratio Breaking force SDS sedimentation volume 20.541 0.636 * Damaged starch 20.638 * 0.709 * AWRC 20.844 ** 0.568 Protein 20.508 0.315 Gluten Index 20.531 0.313 R/E ratio 20.587 0.396 Dough development time 20.328 20.187 Dough stability 20.644 * 0.193 Degree of softening 0.423 20.007 Gliadins 0.207 20.183 Glutenins 20.590 0.528 GLI/GLU ratio 0.765 ** 20.528 Notes: * Correlation is significant at 0.05 level; ** correlation is significant at 0.01 level Table II. Relationship of cookie characteristics with the flour quality parameters and gluten composition
BFJ 568 Rheological characteristics The data on the rheological characteristics of the wheat varieties studied has been presented in Table I. Strong dough characteristics were shown by varieties HI 977 and PBW 590. The highest DDT was observed for variety HI 977(4.5 min) followed by the variety PBW 590 (4.0 min) while the variety CBW 38 showed the lowest. The water absorption capacity was highest for the variety HW 2004 (60.2 per cent) while the variety DBW 16 (51.7 per cent) had the lowest. The stability of the dough ranged between 1.5 min and 8.5 min while the degree of softening recorded the highest value of 140 FU for variety MACS 1967 while variety HI 977 (23 FU) reported the lowest indicating that it is a strong flour. DDT correlated positively with dough stability ðr ¼ 0:822Þ and negatively with DOS ðr ¼ 20:806Þ: The flour s protein content was positively correlated with DDT ðr ¼ 0:547Þ and dough stability ðr ¼ 0:586Þ: It was observed that the varieties with higher glutenin content required longer time for dough development. Such dough also reported a relatively longer dough stability time and low values of degree of softening. Similar results between the glutenin content and the dough strength has been reported previously by Primo-Martin (2003). It is well established that overall gliadins decrease the dough mixing time. Results of correlation analysis revealed negative correlations between the Gli:Glu ratio and DDT ðr ¼ 20:400Þ; dough stability ðr ¼ 20:670Þ and positive correlation with the degree of softening ðr ¼ 0:434Þ; thus strengthening the previous studies. It was found that the Gli:Glu ratio was strongly negatively correlated with the R/E ratio of gluten ðr ¼ 20:592Þ and dough stability ðr ¼ 20:670Þ: It is widely accepted that gliadins confer viscous properties and extensibility while glutenin imparts elasticity. Therefore, as the glutenin percentage in the wheat varieties increased, its elastic properties also increased. As a result the extensibility of the gluten decreased and its resistance to extension increased. Similar results were also observed by Khatkar et al. (1995) who found a strong inverse relationship between gliadin/glutenin ratio and elasticity of gluten. These results were also in agreement with the results reported by Weiser and Kiefer (2001) who found the maximum resistance of gluten to be highly positively correlated with the quantity of glutenin. Glutenins, the important indicators of dough strength and dough s tolerance to mixing, showed positive association with the DDT and dough stability as compared to gliadin. Variation in gluten protein composition The proportions of gluten subfractions from different wheat varieties are presented in Table III. Gliadin fraction ranged from 4.16 per cent to 5.60 per cent, the highest for variety MACS 1967 and lowest for variety CBW 38. Glutenin proportion varied significantly among the varieties with HI 977 (6.00 per cent) showing the highest content while the variety HW 2004 (3.99 per cent) showing the lowest value of this subfraction. The gliadin to glutenin ratio (Gli:Glu) ranged from 0.77 to 1.17, respectively. The variety C 306 had the highest Gli:Glu ratio of 1.17, followed by the variety HW 2004(1.05) while the variety NIAW 917 (0.78) showed the least ratio. Significant differences in the gluten protein subfractions in the different wheat varieties could be attributed to varietal differences. The gluten protein subfractions increased with the protein content of the flour, though the increase was less pronounced for gliadin as evident from the strong and significant correlation between glutenin and protein ðr ¼ 0:698Þ indicating that with the increase in protein content of the wheat variety, the percentage of glutenins also increase.
Variety Gli(%) Glu(%) Gli/Glu WAC (%) DDT(min) STA(min) DOS(FU) NIAW 917 5.10f 6.55i 0.77a 55.9d 2.0b 3.5b 119f HI 977 4.98e 6.00 h 0.82b 57.1 g 4.5e 8.5f 23a CBW 38 4.16a 4.78c 0.86c 52.1b 1.5a 5.5d 51c HW 2004 4.20b 3.99a 1.05f 60.2i 2.0b 1.5a 116e MACS 1967 5.60 h 5.84 g 0.96d 56.8f 1.5a 1.5a 140j PBW 590 4.57c 5.53f 0.82b 56.8f 4.0d 6.5e 45b PBW 550 5.09f 5.29e 0.96d 57.9 h 3.0c 4.5c 71d DBW 16 4.57c 5.54f 0.82b 51.7a 1.5a 3.5b 126 h C 306 5.49 g 4.66b 1.17 g 56.5e 1.5a 1.5a 122 g WH 1025 4.87d 4.88d 0.99e 54.2c 1.5a 1.5a 129i Notes: Gli ¼ Gliadins; Glu ¼ Glutenins; Gli=Glu ¼ Gliadin to glutenin ratio; WAC ¼ Water absorption capacity; DDT ¼ Dough development time; STA ¼ Dough stability; DOS ¼ Degree of softening. Values followed by different letters are significantly different at p, 0.05 Composition of gluten proteins 569 Table III. Gluten composition and rheological characteristics Quality parameters of cookies Figure 1 represents the cookies prepared from different varieties. Higher cookie diameter and higher spread ratio are considered as the desirable quality attributes (Yamamoto et al., 1996; Table IV). The cookie spread ratio and breaking force showed significant differences for different wheat varieties. The cookie spread ratio ranged between 5.55 and 10.31. The highest spread ratio was observed for variety WH 1025(10.31) while NIAW 917(5.55) showed the lowest which also reported the lowest Gli:Glu ratio among all the wheat varieties. The spread of the cookies decreased with the increase in the protein content of the wheat varieties (Table II). The protein content exhibited a significantly negatively correlation ðr ¼ 20:508Þ with the spread ratio of the cookies. This was in agreement with earlier studies by McWatters (1978), Singh et al. (1993) and Guttieri et al. (2004) who also reported a decrease in spread ratio of cookies with increase in protein. It was also observed that as the SDS sedimentation volume increased, the cookie spread decreased. SDS sedimentation volume indicates higher proportion of glutenin in the flour, which in turn makes the dough more elastic, Figure 1. Cookies prepared from different wheat varieties
BFJ 570 Table IV. Quality parameters of cookies Variety Diameter Thickness Compression force Spread ratio NIAW 917 58.24a 10.48 h 17485.86j 5.55a HI 977 67.18d 11.44j 8646.96e 5.87c CBW 38 65.42c 10.06f 14574.56i 6.50d HW 2004 76.47 h 8.88c 7784.40d 8.61i MACS 1967 78.22i 9.26e 10772.45 g 8.44 h PBW 590 70.18e 10.34 g 8945.78f 6.79e PBW 550 72.19f 8.65b 6006.01b 8.34 g DBW 16 62.84b 11.08i 11940.24 h 5.67b C 306 75.63 g 9.13d 6028.60c 8.28f WH 1025 81.97j 7.99a 4870.30a 10.31j Note: Values followed by different letters are significantly different at p, 0.05 as a result of which the cookie spreads decreases. Damaged starch is another important parameter that determines the cookie making potential of the wheat varieties. In previous studies by Moiraghi et al. (2011), greater damaged starch content was associated with lower cookie factor. In this study a similar trend was observed, the damaged starch was found to be negatively correlated ðr ¼ 20:536Þ with the cookie spread. This was probably due to the fact that increase in the damaged starch content increased the water absorption capacity of the flour, which results in stiffness of the cookie dough, decreased cookie diameter and lower spread. Moreover, a higher per cent of damaged starch makes the starch more susceptible to enzyme attack that results in smaller cookies. Also hardness of the cookies measured in terms of breaking force increased as the damaged starch content increased. AWRC is regarded as an important test to judge the suitability of the wheat flour for utilisation in cookie making. Normally good cookie flours have low AWRC values and produce cookies with large diameters. The cookie-spread ratio had a highly significant negative correlation with the AWRC ðr ¼ 20:844Þ in agreement with several authors who found a negative correlation between AWRC and cookie quality (Kisell and Lorenz, 1976; Abboud et al., 1985; Leon et al., 1996; Roccia et al., 2006). The cookie diameter followed an increasing trend with the increase in the Gli:Glu ratio. The correlation analysis indicated significant positive correlation ðr ¼ 0:765Þ of spread ratio with Gli:Glu ratio. This could be attributed to the fact that cookie making requires highly extensible wheat dough and gliadins provide extensibility to wheat dough. This was a key finding of the study, as very little literature is available on the influence of gliadins and Gli/Glu ratio on the cookie spread and texture. According to the previous studies by Kuragano et al. (1991), cookies prepared by addition of gliadins to the base wheat flour result in cookies with greater spread and softer texture. Also, Uthayakumaran et al. (2001) reported that the g-fraction of gliadins increases the extensibility of the wheat dough to the most and thus wheat flours with higher content of this gliadin subfraction improve the cookie making quality of the wheat cultivar. The present study confirmed that hardness indicated by the breaking force was strongly negatively correlated with the Gli:Glu ratio ðr ¼ 20:528Þ indicating that higher fraction of gliadins in flour results in tender cookies.
SDSV DS AWRC PRO DG GI R/E GLI GLU GLI/GLU DDT STA DOS SDSV 1 DS 0.686 * 1 AWRC 0.503 0.618 1 PRO 0.077 20.004 0.131 1 DG 20.496 20.294 20.477 0.447 1 GI 0.704 * 0.236 0.472 0.414 20.371 1 R/E 0.214 0.055 0.424 0.713 * 0.021 0.446 1 GLI 20.303 20.142 20.212 0.149 0.573 20.339 20.235 1 GLU 0.270 0.323 0.195 0.698 * 0.625 0.204 0.395 0.445 1 GLI/GLU 20.481 20.420 20.333 20.654 * 20.267 20.495 20.592 0.293 20.720 * 1 DDT 0.276 20.068 0.124 0.547 20.076 0.634 * 0.350 20.051 0.338 20.400 1 STA 0.453 0.156 0.438 0.586 20.020 0.863 ** 0.507 20.267 0.411 20.670 * 0.822 ** 1 DOS 20.427 0.010 20.332 20.454 0.223 20.918 ** 20.419 0.347 20.127 0.434 0.806 ** 20.937 ** 1 Notes: PRO ¼ Protein; SDSV ¼ SDS sedimentation volume; DS ¼ Damaged starch; DDT ¼ Dough development time; DG ¼ Dry gluten; GLI ¼ Gliadins; GLU ¼ Glutenins; GLI=GLU ¼ Gliadin to glutenin ratio; DDT ¼ Dough development time; STA ¼ Dough stability; DOS ¼ Degree of softening. * Correlation is significant at 0.05 level; ** correlation is significant at 0.01 level Composition of gluten proteins 571 Table V. Correlation among flour quality parameters and gluten composition
BFJ 572 Prediction of the cookie making potential of the wheat varieties To assess the influence of the factors affecting the cookie spread ratio, multiple regression was used to find equation that could predict the relationship between the various quality parameters and the cookie quality characteristics. It has been well established from the correlation analysis that cookie spread ratio is negatively correlated with protein, damaged starch, AWRC, R/E ratio, dough stability, glutenins and gliadins. Therefore, an equation to predict cookie spread ratio was developed based on multiple regression analysis of these flour quality parameters and gluten protein fractions (Table V). The best-fit linear regression model was determined using stepwise variable elimination. The strong dependence of spread ratio on the AWRC and Gli/Glu ratio can be described by the equation: Spread ratio ¼ 16:993 þ 6:828 ðgli=gluþ 2 0:186 ðawrcþ The above equation had a multiple correlation coefficient of 0.968, which was high enough to predict the spread ratio of the cookies. The graph between the actual and predicted cookie spread ratio (Figure 2) had the correlation coefficient of 0.976 indicating that the cookie making potential of the wheat variety can be accurately predicted from its Gli/Glu ratio and AWRC values. Conclusion The experimental results suggested that the cookie quality is affected by different factors such as protein, damaged starch, AWRC and gluten protein fractions. It was found that flours with higher protein content adversely affected the cookie quality. The hardness of the cookies showed a negative association with the Gli:Glu ratio indicating that higher gliadin content makes the cookies tender. It can also be stated that flours with higher dough development time and stability proved to be poor cookie flours. The prediction equation developed by multiple-linear regression could help in predicting the cookie spread ratio. Gliadin, glutenin and AWRC were found to be the most important parameters to predict the quality of cookies based on the spread ratio. Figure 2. Actual vs predicted cookie spread ratio
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BFJ 574 Roccia, P., Moiraghi, M., Ribotta, P.D., Perez, G.T., Rubiolo, O.J. and Leon, A.E. (2006), Use of solvent retention capacity profile to predict the quality of triticale flours, Cereal Chemistry, Vol. 83, pp. 243-9. Singh, B., Bajaj, M., Sharma, S. and Sidhu, J.S. (1993), Studies on the development of high-protein biscuits from composite flours, Plant Foods for Human Nutrition, Vol. 43, pp. 181-9. Souza, E., Kruk, M. and Sunderman, D. (1994), Association of sugar-snap cookie quality with high molecular weight glutenin alleles in soft white spring wheats, Cereal Chemistry, Vol. 71, pp. 601-5. Uthayakumaran, S., Tomoskozi, S., Tatham, A.S., Savage, A.W.J., Gianibelli, M.C., Stoddard, F.L. and Bekes, F. (2001), Effects of gliadin fractions on functional properties of wheat dough depending on molecular size and hydrophobicity, Cereal Chemistry, Vol. 78, pp. 138-41. Wieser, H. and Kieffer, R. (2001), Correlations of the amount of gluten protein types to the technological properties of wheat flours determined on a micro-scale, Journal of Cereal Science, Vol. 34, pp. 19-27. Yamamoto, H., Worthington, S.T., Hou, G. and Ng, P. (1996), Rheological properties and baking qualities of selected soft wheats in the United States, Cereal Chemistry, Vol. 73, pp. 215-21. Yamazaki, W.T. (1962), Laboratory testing of flours and cookie quality research, Cereal Science Today, Vol. 7, pp. 98-104. Further reading Khatkar, B.S. and Schofield, J.D. (1997), Molecular and physicochemical basis of breadmaking properties of wheat gluten proteins: a critical appraisal, Journal of Food Science and Technology, Vol. 34, pp. 85-102. Corresponding author Bhupendar Singh Khatkar can be contacted at: bhup2009@hotmail.com To purchase reprints of this article please e-mail: reprints@emeraldinsight.com Or visit our web site for further details: www.emeraldinsight.com/reprints