The Effects of Protein Content of Flour and Emulsifiers on Tanoor Bread Quality

Journal of Cereal Science 26 (1997) 137–143

The Effects of Protein Content of Flour and Emulsifiers on Tanoor Bread Quality N. Farvili, C. E. Walker∗ and J. Qarooni Department of Grain Science and Industry, Kansas State University, Manhattan, KSU 66506-2201, U.S.A. Received 7 July 1995

ABSTRACT Emulsifiers (SSL, GMS-90, DATEM, S-570, S-1170, S-1670, P-1670) with three concentrations (0·25%, 0·50%, 0·75%) and three flour types (soft red winter wheat flour with 9·7% protein, hard red winter wheat flour with 11·2% protein, and hard red spring wheat flour with 14·2% protein) were used to evaluate their effects on tanoor bread quality. For baking breads, an air impingement oven was used. The low and high protein flours were not suitable for this bread because breads made from high protein flour had significantly lower scores for crust smoothness, uniformity of thickness and crumb appearance, but higher scores for area index, first-day rolling, first- and secondday tearing. The low protein flours produced breads with light crust colour and significantly lower scores for rolling, and first- and second-day tearing quality characteristics. Rolling and tearing qualities were improved when high concentrations of emulsifiers were used with low protein flour. The results of this study indicate that optimum tanoor bread was produced from moderate protein flour (11·2%). Emulsifiers improved first- and second-day tearing, and first-day rolling ability, but reduced the score for crust smoothness. Sucrose esters P-1670, S-1670 and S-1170 gave breads with higher overall scores compared to the other emulsifiers studied, but with darker crust colours. Shelf life stability indicated that P-1670, S-1670 and S-1170 at 0·50% concentration improved tearing but not rolling ability characteristics after five days storage at room temperature.  1997 Academic Press Limited

Keywords: flat bread, tanoor (taftoon) bread, emulsifier, sucrose ester, air impingement oven, shelf life, staling.

INTRODUCTION Tanoor bread (also known as taftoon bread) is single layered, flat and docked. Docking is used for decoration, as well as for preventing pocket formation during baking. Tanoor bread is popular in the south western part of Iran1. Tanoori, tandur, khubz and naan are different names used for the same product in various parts of the Middle East2. The name comes from the type of oven used to bake this product, i.e. tanoor, which means clay

 : SSL=sodium stearoyl-2-lactylate; GMS-90=glycerol mono-stearate; DATEM=di-acetyl tartaric acid esters of monoglycerides. ∗ Corresponding author. 0733–5210/97/040137+07 $25.00/0/jc960112

oven. Tanoor bread requires 100% flour, 1% active dry yeast, 0·75–1·5% salt, and various amounts of water. The processing steps are mixing, dividing, proofing, sheeting, docking, baking and packaging. Crust colour is reddish brown. High quality tanoor bread has a uniform thickness with an even distribution of small blisters on the top crust. A bread that withstands rolling without breaking and is not tough or torn too easily is considered high quality. Qarooni and co-workers3 reported that high quality tanoor bread was produced from 85% extraction flour of 11–13% protein. Faridi et al.4 concluded that soft white wheat was generally the best suited for five Iranian flat breads. Flat breads have short shelf life and stale fast. It has been reported that addition of emulsifiers  1997 Academic Press Limited

N. Farvili et al.

138

improves shelf life5–7. A number of studies have been developed for test baking procedures, scoring systems4,8, and extending the shelf life of flat breads5. Traditional flour tests, suitable for pan bread production, are not as suited for flat bread, due to different processing requirements9. The relationships between flour, emulsifier and flat bread quality have not been clearly demonstrated. Furthermore, little evidence has been presented on protein and emulsifier influence on tanoor bread quality. Emulsifier and protein effects are considered because it has been found that surfactants slow the firming rate of bread crumb during storage6 and gluten is a major fraction10 which can reduce the staling rate due to dilution of starch11. The objectives of this study were: (1) to establish whether there are protein effects that influence tanoor bread quality; (2) to evaluate the effects of various concentrations of sucrose fatty acids and other commercial emulsifiers; and, (3) to evaluate shelf life during storage at room temperature.

Table I

Quality characteristics for three flour types Flour 1a

Flour 2b

Flour 3c

Proteind (%) 9·70 Moisture (%) 13·10 Ashd (%) 0·450 Particle sizee (micron) 17·79 Starch damage (%) 2·5 Falling number (Sec.) 387 Stirring number unit 282 Colour grade (L value)f 90·97 Farinograph absorptiond (%) 51·8 Development time (min) 1·3 Valorimeter value 57 Mixograph absorptiond (%) 52·0 Peak time (min) 1·95

11·23 12·70 0·520 27·92 5·6 394 233 88·70 58·5 2·8 69 57·5 3·10

14·15 14·30 0·570 44·95 5·1 270 161 88·80 62·4 9·4 74 62·4 3·50

Parameter

a

Soft red winter wheat flour. Hard red winter wheat flour. c Hard red spring wheat flour. d Corrected to 14% moisture basis. e Measured by Horiba; average of 3 replications. f The higher the number, the lighter the colour. b

Tanoor (taftoon) bread baking process MATERIALS AND METHODS Three flour types (soft, hard red winter, and hard red spring wheat flours) and seven types of emulsifiers (SSL, GMS-90, DATEM, and the sucrose esters: S-570, S-1170, S-1670 and P-1670) (S refers to stearic acid which is derived from hydrogenated edible tallow and P refers to palmitic acid which is derived from vegetable oils, 5, 11 and 16 refer to hydrophilic–lipophilic balance, 70 refers to purity of the sample) were tested for their effects on the quality of tanoor breads. The providers of the samples were the same as for an earlier study on pita bread8. Detailed analytical data12 for the flours are shown in Table I. Tanoor bread baking was carried out in a prototype rotating-shelf, WindShear, air impingement oven. The action of the air jets resulted in rapid heat transfer and fast moisture removal from the product. In the second part of the study, for shelf life determination, the most effective emulsifiers (S1170, S-1670, P-1670) were used at 0·50% concentration with medium protein flour, and 0·25% calcium propionate to retard molding. After packaging, the breads were stored at room temperature for 5 days before being evaluated for their ability to roll and fold, and for tearing quality characteristics.

A number of small-scale baking processes and scoring systems have been developed to assess the suitability of U.S., Australian and Canadian wheat varieties for flat breads13,14. The tanoor bread baking procedure was based on the method reported by Qarooni and co-workers3. This method uses the optimization of product quality as in automated production, aims to produce consistent quality under set conditions, and uses specific quality parameters appropriate for flat bread. This method has an adequate degree of precision and produces bread that meets consumer acceptance in Middle Eastern countries. In this process, flour (100%), salt (1%), instant yeast (0·5%) and different levels of water, depending on the flour type, were used. The processing steps were dough mixing (to optimum development), fermentation (1 h), dividing and rounding (50 g pieces), proofing (15 min), sheeting, docking (Fig. 1), baking (288 °C, 75 s), cooling and packaging. For the sheeting process, the dough pieces were first flattened by hand then passed through the sheeter twice. The dough pieces were passed through the second rolls in the same direction that they went through the first rolls, so the final shape was oval. The gaps between the first and second sets of sheeter rolls were 1·3 and 0·8 mm, respectively, and they re-

Protein and tanoor bread quality

Figure 1

139

Docking of tanoor bread (putting holes in the sheeted dough to prevent the separation of layers during baking).

duced the dough pieces to a thickness of 0·8 mm with a diameter of 13–14 cm. The actual nozzle air velocities from the top and bottom jets were 884 and 610 m/min, respectively. The heat transfer coefficients for the top and bottom jets were 34·0 and 13·1 cal/s/m2/°C, respectively. The large air nozzle plates (10·9 mm diameter) were used on top and bottom.

urements of area index were in the range of 5·8–6·2 cm in diameter. (ii) Crust colour. For colour measurements (L value), a Minolta Chroma Meter (model CR-210, Osaka, Japan) was used. In Qarooni’s score, L values of 65·5–67 (dark colour) and 76–77·5 (light colour) both scored 3·6. One could not differentiate between light or dark colour. In this study for crust colour, the scores given in Table II were used.

Loaf scoring system for tanoor (taftoon) bread In this study, the scoring system of Qarooni and co-workers3 with some modifications was used. The factors which were investigated and scored included area index, crust smoothness, uniformity of thickness, crust colour, uniformity of blisters, first- and second-day rolling and tearing and crumb appearance. The following modifications to Qarooni and coworker’s method3 were used: (i) Area index. In Qarooni’s method the small and large diameter loaves both received the same score. One could not know if the loaf were too small or too large; therefore in this study, area index was not scored but the measurements were reported directly. The acceptable meas-

Table II

a

Scoring system for tanoor bread crust colour L value

Score

Above 73·7a 71·2–73·7a 68·6–71·1a 66·0–68·5a 63·4–65·9b 60·8–63·3b 58·2–60·7c 55·6–58·1c 53·0–55·5c Below 53·0c

22·5 20·0 17·7 15·0 12·5 10·0 8·5 6·5 4·5 2·5

Light colour. Optimum colour. c Dark colour. b

N. Farvili et al.

140

Table III

The acceptance range for sheeting was 13–14 cm. (iv) Overall score. The maximum overall scores were 11 (Table III). Medium to maximum scores were categorized in the range of 75% acceptability (which means an acceptable quality bread). When the product had 75% acceptability, a score of 1 was given. Otherwise, the score was 0.

Range of overall scoresa acceptability for tanoor (taftoon) bread

Parameter Area indexb Crust smoothness Uniformity of thickness Crust colourc Uniformity of blisters Rolling ability Quality of tearing Crumb appearance Rolling ability Quality of tearing Sheetingd

Range of 75% acceptability

Score

5·8–6·2 7·5–10·0 12·0–15·0 7·5–10·0 7·5–10·0 15·0–20·0 15·0–20·0 7·5–10·0 22·5–30·0 15·0–20·0 13·0–14·2

1·0 1·0 1·0 1·0 1·0 1·0 1·0 1·0 1·0 1·0 1·0

a

The maximum overall score is 11·0. Measured on bread produced from dough cut to 6·0 cm diameter; the diameter itself was recorded. c The new proposed scoring was reported. d The dough diameter before baking. b

(iii) Sheeting score. Sheeting score was added to the quality characteristics. This sheeting score referred to the size of the dough right after sheeting. The importance of this quality parameter was that it determined the shape and diameter of the final product.

Table IV Parameter

Experimental design In order to investigate the relative contributions of emulsifiers to bread quality and to determine their optimum levels, an experiment involving three flour types and seven emulsifiers with three replications were used. Each emulsifier was used at three concentrations (0·25%, 0·50% and 0·75% flour weight basis) for each type of flour. The data for flour and bread quality were subjected to statistical analysis15 and on separate days, four batches of each flour by emulsifier combination were used, including the control (no emulsifier added). The selection of emulsifier and flour combination for each day was completely randomized.

Individual loaf quality parameters for tanoor (taftoon) bread Low proteina (control)

Medium proteina (control)

High proteina (control)

Area index Crust smoothness Uniformity of thickness Crust colour Uniformity of blisters Rolling ability Quality of tearing Crumb appearance Sheeting

First day 5·56±0·09 a 8·17±0·73 a 12·40±0·76 a 14·29±2·87 ab 7·42±0·38 a 12·89±2·87 a 13·20±1·19 a 6·04±0·37 a 14·47±0·49 a

5·73±0·09 b 8·48±0·42 a 12·51±1·17 a 10·90±2·56 bc 7·53±0·18 a 15·94±1·81 b 14·42±1·63 b 6·07±0·32 a 14·40±0·52 b

5·89±0·17 c 6·86±0·58 b 10·19±1·09 b 8·69±1·74 cd 7·78±0·87 a 16·49±0·82 b 15·42±1·19 c 5·59±0·52 b 12·50±0·48 c

Rolling ability Quality of tearing

Second day 19·26±3·97 a 13·00±1·66 a

21·80±2·58 b 14·00±1·24 b

20·46±2·02 a 14·66±1·40 b

131·8 5·10±0·69 b

124·5 3·10±0·63 a

Sum of overall Overall score a

126·7 3·29±0·62 a

Average of 21 bakes±standard deviation. Light colour. c Optimum colour. d Dark colour. Where non-superscript letters in a row are different, mean values differ significantly (P<0·05). b

Protein and tanoor bread quality

141

Figure 2 Tanoor bread from three flour types (controls have no emulsifier added). (F1=low protein, light crust colour, long oval shape) (F2=medium protein, optimum colour and length) (F3=high protein, dark crust colour, reduced length.)

RESULTS AND DISCUSSION Effect of flour types on tanoor bread quality Flour type had a significant effect on all quality attributes except for uniformity of blisters and second-day rolling ability (data not shown). Breads made from high protein flour had a high score for area index (Table IV), probably because of the flour’s higher elasticity. Rolling ability improved with high protein compared with low protein flour. This was due to higher water absorption which made a softer bread. On the other hand, the scores for crust smoothness, uniformity of thickness and crumb appearance were reduced significantly with high protein flour. These were due to uneven surfaces and an undesirable coarse/open grain. Overall scores (Table IV) indicate that the high protein flour is not suitable for tanoor bread unless one can overcome the dark crust colour and small diameter oval shaped doughs. With low protein flour, first- and second-day scores for rolling and tearing were reduced significantly (Table IV). Bread made with this flour had a light crust colour. The dough sheeted thinly, had a long oval shape, and produced dry bread. The amount of water absorbed by low protein flour was lower than that absorbed by medium and high protein flours, which also made the bread dry and hard to tear. The overall score (Table IV)

indicates that low protein flour is not suitable for tanoor bread, unless one can overcome the light crust colour and dryness which caused cracks during rolling. The overall results for medium protein flour were significantly better than those for low and high protein flours (Table IV). Medium protein flour produced doughs with fine sheeting characteristics and breads with optimum quality and colour. The second-day rolling score was also significantly higher. Figure 2 shows tanoor bread baked with the three flour types. This figure indicates that the low protein flour had the longest oval shape (which was not desirable) and lightest crust colour. High protein flour had the least length with the darkest colour, but medium protein flour had optimum quality, colour, length and other characteristics mentioned in Table IV.

Effect of emulsifiers on tanoor (taftoon) bread quality The statistical results (calculations not shown) indicate a significant effect of flour and emulsifier concentration on overall score (Table V). Medium protein flour, at all emulsifier concentrations, had a significantly higher overall score. There were no significant differences between 0·50% and 0·75%

N. Farvili et al.

142

Table V

Least significant difference for flour by emulsifier concentration effects on overall score

Flour

0·25% emulsifier

0·50% emulsifier

0·75% emulsifier

LSD

Low protein Medium protein High protein

4·429 5·619 4·429

5·33 6·00 3·905

5·286 6·524 3·762

0·788 0·788 0·788

LSD

0·635

0·635

0·635

Table VI

Effect of medium protein flour with all emulsifier types on overall scores of tanoor bread

Quality characteristics First day Second day Sheeting

Control

S-570 0·50%

P-1670 0·50%

S-1670 0·50%

S-1170 0·50%

SSL 0·50%

DATEM 0·50%

GMS-90 0·50%

81·58 35·80 14·21

85·00 38·03 14·07

80·16 36·97 14·40

83·02 39·27 14·03

80·94 40·30 14·00

83·60 37·53 14·30

84·80 37·06 13·97

82·27 40·40 14·00

Table VII

Effect of emulsifiers on shelf life stability of tanoor bread after 5 days

Quality characteristics Rolling ability Quality of tearing Total

Control

S-1670 (0·50%)

P-1670 (0·50%)

S-1170 (0·50%)

13·4±0·14 15·1±0·35

14·0a±0·25 17·7a±0·67

13·9a±0·40 17·7a±0·32

13·5b±0·46 16·5a±0·82

28·5

31·7a

31·6a

30a

The same superscripts in a row indicate no significant differences. (Maximum score is 30 and 20 for rolling and tearing, respectively.)

emulsifier, when low and medium protein flours were used. The three-way interactions (data not shown) showed significant effects for crust colour and sheeting score. With the addition of some emulsifiers, crust colour became lighter. In the case of the sucrose esters P-1670, S-1670 and S1170, the crust colour became darker (because of a blistering effect) when compared to the control (appearance of blister on crust is a good quality characteristic). Emulsifier concentrations showed a significant effect on area index, crust smoothness, crumb appearance, first- and second-day tearing quality. Even though the one-way interaction of emulsifiers did not have a significant effect on overall score, they improved first- and second-day tearing and first-day rolling ability. On the other hand, emulsifiers reduced crust smoothness score because the top surfaces did not have the same smoothness as that of the control. Breads baked with high protein flour and added

emulsifiers had a large area index with an undesirable open grain structure. There was no evidence of the emulsifier’s concentration effect on area index. These breads received low scores for crust smoothness, uniformity of thickness, and crumb appearance. Low emulsifier concentration had a better result on crumb appearance and a significantly better effect on crust smoothness. Breads containing emulsifiers but baked with low protein flour received low grades for rolling and tearing because those breads were thin and had long oval shapes, thus they cracked when rolled. A medium concentration level (0·50%) helped to reduce the tearing problem due to their softening effect. A summary of the effects of emulsifiers on first and second day with medium protein flour, at 0·50% emulsifier, is shown in Table VI. When the overall scores for emulsifiers were compared, it was concluded that P-1670, S-1670 and S-1170 had the higher scores.

Protein and tanoor bread quality

143

Effects of emulsifiers on shelf life of tanoor bread

REFERENCES

In this study, rolling ability and tearing quality were the two characteristics used for evaluating shelf life stability. Based on overall least significant means, the sucrose esters S-1670, S-1170 and P-1670 gave breads with higher overall scores compared to the other emulsifiers. For rolling, S1170 gave a significantly lower score than P-1670 and S-1670 (Table VII). However, no significant differences occurred among emulsifiers for tearing, and scores were higher than for the control. This indicates that all emulsifiers had a positive effect on tearing quality after 5 days. The dark crust colour was due to blisters on the top surface of the bread. In summary, S-1670, P-1670 and S1170 at 0·50% concentration, with medium protein flour, helped maintain tearing but not rolling quality characteristics after 5 days of storage at room temperature.

1. Faridi, H.A. and Finney, P.L. Technical and nutritional aspects of Iranian breads. Baker’s Digest 54 (1980) 14, 19–20, 22. 2. Qarooni, J. Historic and present state of wheat production, milling and baking industries in the countries of the Middle East and North Africa. Department of Grain Science, Kansas State University, Manhattan, KS 665062201, USA (1994) pp. 1–87. 3. Qarooni, J., Posner, E.S. and Ponte, J.G., Jr. Production of tanoor bread with hard white and other U.S. wheats. Lebensmittel-Wissenschaft-Und-Techologie 26 (1993) 100–106. 4. Faridi, H.A., Finney, P.L. and Rubenthaler, G.L. Microbaking evaluation of some U.S. wheat classes for suitability in Iranian breads. Cereal Chemistry 58 (1982) 471–474. 5. Maleki, M., Vetter, J.L. and Hoover, W.J. The effect of emulsifiers, sugar, shortening and soya flour on the staling of barbari flat bread. Journal of the Science of Food and Agriculture 32 (1981) 1209–1212. 6. Pisesookbunterng, W. and D’Appolonia, B.L. Bread staling studies. I. Effect of surfactants on moisture migration from crumb to crust and firmness values of bread crumb. Cereal Chemistry 60 (1983) 298–300. 7. Twillman, T.J. and White, P.J. Influence of monoglycerides on the textural shelf life and dough rheology of corn tortillas. Cereal Chemistry 65 (1988) 253–257. 8. Farvili, N., Walker, C.E. and Qarooni, J. Effects of emulsifiers on pita bread quality. Journal of Cereal Science 21 (1995) 301–307. 9. Quail, K.J. and McMaster, G.J. Flour quality tests for selected wheat cultivars and their relationship to arabic bread quality. Journal of the Science of Food and Agriculture 54 (1991) 99–110. 10. Maleki, M., Hoseney, R.C. and Mattern, P.J. Effects of loaf volume, moisture content, and protein quality on the softness and staling rate of bread. Cereal Chemistry 57 (1980) 138–140. 11. Kim, S.K. and D’Appolonia, B.L. Effects of protein content on staling rate and bread crumb pasting properties. Cereal Chemistry 54 (1977) 207–215. 12. American Association of Cereal Chemists. Approved methods of the AACC, 8th edition. For Ash, method 0801, approved April 1961, revised October 1981; for moisture, method 44-15A, approved October 1975, revised October 1981; for protein, method 46-16, approved October 1988; for mixograph, method 54-40A, approved April 1961, revised October 1988; for farinograph, method 54-21, approved April 1961, reviewed October 1982; for falling number, method 56-81b, approved November 1972, revised October 1982, 1988, and September 1992. 13. Faridi, H.A. and Rubenthaler, G.L. Experimental baking technique for evaluating Pacific Northwest wheats in North African bread. Cereal Chemistry 60 (1983) 74–79. 14. Williams, P.C., El-Haramein, F.J., Nelson, W. and Srivastava, J.P. Evaluation of wheat quality for the baking of Syrian-type two-layered flat breads. Journal of Cereal Science 7 (1988) 195–207. 15. SAS. The SAS Softward Systems. SAS User’s Guide: Statistics, Versions 5, SAS Institutes, Inc., Cary, NC (1985).

SUMMARY AND CONCLUSIONS Emulsifiers improved first- and second-day tearing quality and first-day rolling ability, but reduced crust smoothness score. The medium concentration (0·50%) of emulsifiers gave better overall scores. The medium protein flour (11·2%) produced significantly better quality tanoor bread than the low (9·7%) and high (14·2%) protein flours. Sucrose esters P-1670, S-1670 and S-1170 had better effects on the quality and gave breads with higher overall scores compared to the other emulsifiers studied, but darker crust colours because of blistering effects. Shelf life stability indicated that 0·50% concentration of P-1670, S1670 and S-1170 improved tearing quality but not rolling ability after 5 days storage at room temperature.

Acknowledgement Contribution No. 94-603-J, Kansas Agricultural Experiment Station, Manhattan, KS. The authors wish to express their appreciation to Dr D. E. Johnson from the K.S.U. Department of Statistics for his assistance with the statistical analysis in this project.