studies on baking of high alpha-amylase flours: effect of ph, salt and l-cysteine . hci in the dough

10
Die Nahrung 32 (1988) 5,481 ~-490 Department of Food Science and Technology, Punjab Agricultural University, Ludhiana, India Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine - HCI in the dough K. I~ARIKDER and G. S. BAINS The erect of varying concentrations of sodium chloride (0 to 2.5 70, pH (5.8 to 4.2) and KBrO, (75 ppm) with and without addition of L-cysteine . HCl(25 to 75 ppm) on the baking of flours with high content ofalpha- amylase (108 to 540 SKBjlOO g) was compared with a normal flour. Decreasing the pH of dough to 4.2 and increasing the salt concentration to 2.5 "0 reduced the loaf volume and gluten recoveries considerably. Decreas- ed pH also reduced the mixing tolerance ofdough, which wascounteracted by increased salt content of normal and high alpha-amylase flours. A combination of low pH, salt and L-cysteine HCI and 75 ppm of KBrO, without sugar in the dough of higher alpha-amylase flour produced a satisfactory loaf by eliminating bulk fermentation. The detrimental effect of sprouting on the baking quality of wheat flour has been known for several years. Biochemical characteristics of rain damaged/sprouted wheats have been studied extensively [ 1-41. Increased alpha-amylase activity due to sprouting adversely affects the functional properties of wheat for baking [5. 61. Lowering the pH to inactivate alpha-amylase was reported by MEREDITH [7) and FULLER et al. [8]. WIEPERT [9] added 2% NaCl and 0.6:; lactic acid for obtaining an acceptable bread loaf. N~RFER et al. [lo] observed that dilute hydrochloric acid inhibited the alpha-amylase activity of rye flour. RANHOTRA et al. [I I] suggested the control of baking variables to obtain an acceptable loaf of bread from laboratory sprouted wheat. Baking of high alpha-amylase flours poses a serious challenge to the industry. The present investigation aimed at developing conditions based on integrating the effects of pH, salt and L-cysteine . HCI for producing an improved loaf of bread from flour having 10.8- and 54.0-fold increased alpha-amylase activity . Experimental Flour of an extensivelycultivated bread wheat cv. WL 1562, was milled on the Biihler Pneumatic Laboratory Mill (MLU 202). The straight grade flour of about 727; extraction was used in various tests. It contained 10.1 s; protein, 2.2 '4 maltose value and 8.3 :<damaged starch content [ 121. Sprouted wheat having an alpha- amylase activity of 108 SKB/g was produced by steeping 10 43 % moisture followed by germination for five days at 20 T. It was dried at 45 "C and roots were removed by rubbing. The sample was milled on Falling Number Kamas AB mill and mixed with the normal flour at the rate of I to 5%. which introduced alpha- amylase activity of 108 to 540 SKB/lOO g flour. the equivalence of a sprouted wheat. The colour grade of the normal and alpha-amylase augmented flours was 1.9 and 4.9, respectively.

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Page 1: Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine . HCI in the dough

Die Nahrung 32 (1988) 5,481 ~-490

Department of Food Science and Technology, Punjab Agricultural University, Ludhiana, India

Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine - HCI in the dough K . I ~ A R I K D E R and G . S. BAINS

The erect of varying concentrations of sodium chloride (0 to 2.5 7 0 , pH (5.8 to 4.2) and KBrO, (75 ppm) with and without addition of L-cysteine . HCl(25 to 75 ppm) on the baking of flours with high content ofalpha- amylase (108 to 5 4 0 SKBjlOO g) was compared with a normal flour. Decreasing the pH of dough to 4.2 and increasing the salt concentration to 2.5 "0 reduced the loaf volume and gluten recoveries considerably. Decreas- ed pH also reduced the mixing tolerance ofdough, which wascounteracted by increased salt content of normal and high alpha-amylase flours. A combination of low pH, salt and L-cysteine HCI and 75 ppm of KBrO, without sugar in the dough of higher alpha-amylase flour produced a satisfactory loaf by eliminating bulk fermentation.

The detrimental effect of sprouting on the baking quality of wheat flour has been known for several years. Biochemical characteristics of rain damaged/sprouted wheats have been studied extensively [ 1-41. Increased alpha-amylase activity due to sprouting adversely affects the functional properties of wheat for baking [5. 61.

Lowering the pH to inactivate alpha-amylase was reported by MEREDITH [7) and FULLER et al. [8]. WIEPERT [9] added 2% NaCl and 0.6:; lactic acid for obtaining an acceptable bread loaf. N~RFER et al. [lo] observed that dilute hydrochloric acid inhibited the alpha-amylase activity of rye flour. RANHOTRA et al. [ I I ] suggested the control of baking variables to obtain an acceptable loaf of bread from laboratory sprouted wheat. Baking of high alpha-amylase flours poses a serious challenge to the industry. The present investigation aimed at developing conditions based on integrating the effects of pH, salt and L-cysteine . HCI for producing an improved loaf of bread from flour having 10.8- and 54.0-fold increased alpha-amylase activity .

Experimental

Flour of an extensively cultivated bread wheat cv. WL 1562, was milled on the Biihler Pneumatic Laboratory Mill (MLU 202). The straight grade flour of about 727; extraction was used in various tests. I t contained 10.1 s; protein, 2.2 '4 maltose value and 8.3 :<damaged starch content [ 121. Sprouted wheat having an alpha- amylase activity of 108 SKB/g was produced by steeping 10 43 % moisture followed by germination for five days at 20 T. I t was dried at 45 "C and roots were removed by rubbing. The sample was milled on Falling Number Kamas AB mill and mixed with the normal flour at the rate of I to 5%. which introduced alpha- amylase activity of 108 to 540 SKB/lOO g flour. the equivalence of a sprouted wheat. The colour grade of the normal and alpha-amylase augmented flours was 1.9 and 4.9, respectively.

Page 2: Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine . HCI in the dough

482 Die Nahrung 32 (1988) 5

p H adjilrstmmi

Dilute ( 1 N ) hydrochloric, orthophosphoric. lactic and acetic acids were used for pH adjustment of the doughs to 5.0 and 4.2, as compared to 5.8 of the controls.

Baking

The baking formula consisted of 100 g flour (14;; mb), 2.5 g compressed yeast, 2 g sugar. I g fat, 75 ppm potassium bromate and 0.0, I .5 and 2.5 :G sodium chloride. The level of L-cysteine 'HCI in the pH4.2 doughs was varied from 25 to 75 ppm. The dough was optimally mixed in the Swanson mixer, recovered for 15 min at 30 C and 90% RH. mechanically sheeted, moulded, proofed for 65 min and baked at 232 C for 25 min. After cooling, the loafvolumewas measured by the AACC [I21 rape seed displacement method. The loaves were scored for crust and crumb characteristics.

Crumb anal-vsis

Peripheral portions of sliced bread were removed. and the interior section cut into small cubes, air dried at 15-18 -C before grinding in the Falling Number Kamas AB mill (0.8 mm sieve). The samples were kept in air-tight containers for analysis. Amylose was determined essentially by the colorimetric method of JULIAM) [ 131. Reducing sugar was determined in deproteinized aqueous extracts by NELSON'S method [14]. A portion of bread crumb was used for the determination of the degree of gelatinization by the falling number technique (8 g + 25 ml water). For pH, 10 g of bread crumb were homogenized with 50 ml distilled water. Acidity was determined in an aliquot (5 ml) of the crumb extract (10 g + 50 ml water) by titrating against 0. I N NaOH using phenolphathalein indicator. Moisture, protein. gluten, and damaged starch contents were determined using AACC [ 121 methods. Farinograph curve characteristics of the flours were determined using the 50 g capacity stainless steel mixer and the AACC constant flour method.

The effect of acid, pH, salt concentrations and sprouting on the baking quality of flours was evaluated statistically by analysis of variance [IS].

Results and Discussion

Furinoyraph curi'e characterislies

At the initial pH 5.8 of dough of normal flour, the development time increased from 6.0 min to 8.1 min as the salt concentration was increased from nil to 2 .5% (Table I). At pH 5.0, the dough development time was considerably decreased without salt, whereas with salt i t further decreased to 1.6 min. Peak mid-point consistency of dough was nearly the same for the various pH doughs. However, in the presence of salt at different pH of dough, there was a decline in the consistency, which was higher at pH 5.0 and 4.2 as compared to the normal pH dough. This was also observed previously by TANAKA et al. [16]. Mixing tolerance index value for pH 5.8 doughs without salt was 45 B.U., which decreased to 25 and 15 B.U. as the salt level increased to 1.5 and 2.5 %, respectively. Mixing tolerance value increased as the pH decreased.

The dough development time (DDT) of 108 SKBjlOO g flour at pH 5.8 was drastically reduced as compared to that of normal flour. With increased salt content in this dough, DDT was about double that of the control. At p H 5.0 and 4.2, with and without salt, the dough development times were much below that of the control. Dough consistency decreased perceptibly when the same farinograph water absorption was employed in the test. The

Page 3: Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine . HCI in the dough

HARlNDERiBAlNS: High alpha-amylase flours 483

Table 1 Effect of pH*, salt and alpha-amylase (AA) on the farinograms of flour

Flour pH 5.8 pH 5.0 pH 4.2

Salt DDT' PCb MTI' DDT' PC" MTI' DDT' PCh MTI' [";I [min] [B.U.] [B.U.] [min] (B.U.] [B.U.] [min] [B.U.] [B.U.]

Normal 0.0 6.0 500 45 4.8 510 55 3.5 SIP 75 (IOSKB, AA) 1.5 7.0 465 25 1.6 465 35 1.5 460 75

2.5 8.1 465 15 1.6 460 30 1.5 440 35

108 SKB, AA 0.0 1.5 495 65 1.2 460 I0 1.2 490 110 1.5 3.0 410 25 1.2 425 80 1.2 415 90 2.5 2.0 425 15 1.4 400 50 1.2 405 60

540 SKB, AA 0.0 1.3 470 110 1.2 425 110 1.1 450 I40 1.5 1.5 435 70 1.4 405 95 1 . 1 405 110 2.5 1.5 415 60 1.3 485 60 1.3 385 115

* Adjusted with lactic acid a Dough development time

Peak consistency Mixing tolerance index

mixing tolerance index values of pH 5.8 and 5.0 doughs without salt were in the range of 60-70 B.U., as compared to 90- 110 B.U. of pH 4.2 doughs. On increasing the alpha- amylase level to 540 SKB/100 g flour, a gross reduction in the DDT was observed. pH and salt had no improving effect on the mixing times of the doughs, which were drastically reduced to 1.1 and 1.4min with a concomitant decrease in the peak consistencies of the doughs. A further decrease in the peak consistencies due to salt in the dough was observed. Tolerance to mixing was improved by salt in the dough. The beneficial effect of salt on the mixing properties of dough, in contrast to that of decreased pH, was observed. The decreased activity of amylolytic and proteolytic enzymes was attributed to the strong ionic strength

Table 2 Effect of pH, salt and alpha-amylase (AA) on the recovery of gluten from flour

Flour Salt Dry gluten [%]

[ 901 pH 5.8 pH 5.0 pH4.2

Normal 0.0 (10 SKB, AA) 1.5

2.5

108 SKB. AA 0.0 I .5 2.5

540 SKB. AA 0.0 1.5 2.5

12.6 12.5 12.0

12.7 12.0 12.0

10.8 12.9 12.4

10.3 10.8 10.3

10.8 11.7 10.8

10.7 12.0 11.8

9.4 9.1 9.3

9.7 9.6 9.1

9.7 8.7 8.6

Page 4: Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine . HCI in the dough

484 Die Nahrung 32 (1988) 5

of salt in the solution in dough [17]. Salt is also a factor in lipid hinding with proteins, as reported by MECHAM et al. 1181, resulting in increased tolerance to dough during mixing.

Gluten rcwwerj,

The low pH 4.2 dough glutens showed a definite change of physical behaviour and quanti- tative recovery (Table 2). The gluten turned extremely short and incoherent in the case of pH 4.2 doughs. This effect was further aggravated by salt in those doughs. Disruption of gluten structure was probably caused by the cleavage of salt linkages by the higher hydrogen ion concentration in dough [19]. The glutens of high alpha-amylase (108, 540 SKB, 100 g flour) flours were elastic and more extensible up to pH 5.0.

Baking

Douyh handling

The doughs without salt were extensible and became more e.Jstic as the sa in the dough of normal flour was increased. The pH 4.2 doughs became highly elastic with salt. Addi- tional water was required to prepare dough of desired consistency for baking with increased salt up to 2.5%. The pH 4.2 dough containing 2.5:{ salt had a curdled appearance unlike the smooth finish of pH 5.8 and 5.0 doughs. The handling of pH 5.0 dough of 108 SKB/lOO g flour without salt was satisfactory, and it further improved with the addition of 1.5 7 , salt. The same pH dough adjusted with lactic acid but without salt was sticky and extensible as compared to doughs containing salt, which were elastic. The doughs of 540 SKBilOO g flour were sticky and necessitated total elimination of sugar and reduction in floor time to 10 min. Such doughs without salt were unmanageable and their handling was ameliorated with the use of salt in the dough.

Loaf characteristics

The loaf volume of the normal flour generally decreased as the pH was reduced to 4.2 and salt content increased from 1.5 to 2.57; (Table 3). With 1 .S”,d salt in normal flour dough the loaf volume increased to 645 from 600 ml without salt. Adjusting the pH to 5.0 with either of the acids gave a loaf volume of 620 ml (lactic acid) and 640 ml (HCI) without salt in the dough, as compared to 605 and 625 ml of dough having I .So/, salt.

The initial pH 5.8 dough of higher alpha-amylase, i.e. 108 SKBjlOO g flour, gave a loaf volume of 620 ml without salt and 630 ml with 1 .5 salt. which decreased to 560 ml with the addition of 2.5% salt (Table 4). At pH 5.0 of dough, irrespective of the acid used. the loaf volume without salt varied from 655 to 665 ml. The loaf volume of lactic acid dough of this pH decreased to 560 and 440 ml on the addition of 1.5 and 2.5 yd salt respectively. In the case of similar dough where HCI was used, the loaf volume decreased from 610 to 500 ml. The loaf volume of lactic acid pH 4.2 dough was 640 ml, as compared to 605 ml of the corresponding hydrochloric acid pH adjusted dough. As the level of salt in the dough was increased to 1.5 and 2.57;. thcre was a drastic reduction in the loaf volumes which were 485 and 415; 560 and 455 ml respectively. I t is inferred that the higher salt content of 2.5g; was highly deleterious to loaf volume, more particularly if the pH was adjusted with lactic acid as compared to hydrochloric acid. Overall. pH and salt had a highly significant effect

Page 5: Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine . HCI in the dough

~iAWrN1~ER~BAlss: High alpha-amylase flours 485

Table 3 Effect of pH, salt and acid on the baking quality of a normal (10 SKB) flour

Acid pH Salt Baking Mixing Loaf Crumb characteristics ab- time volume sorption pH TA'as 0.1 RSh as Arnylose FN'

N NaOH dextrose 1x1 1x1 [min] [rnl] ImIi100 sl [%I I %I 14

~

Nil 5.8 0.0 59.1 3.5 600 5.75 14.1 4.7 17.0 484 (control) 5.8 1.5 60.6 3.5 645 5.79 14.3 4.7 16.6 507

5.8 2.5 62.1 3.5 545 5.85 12.5 4.8 15.6 494

Lactic 5.0 0.0 61.2 3.0 620 5.08 19.3 4.9 16.1 260 5.0 1.5 61.7 3.2 605 5.11 19.3 4.6 17.7 5 70 5.0 2.5 62.4 3.2 510 5.15 21.0 5.0 16.5 564

4.2 0.0 59.7 3.0 560 4.27 33.4 4.0 16.5 705 4.2 1.5 59.7 4.0 520 4.31 31.3 4.1 17.1 699 4.2 2.5 61.1 4.0 390 4.33 29.6 4. I 16.9 635

Hydro- 5.0 0.0 61.3 3.5 640 5.20 17.1 4.3 15.3 660 chloric 5.0 1.5 61.9 3.5 625 5.21 18.6 4.3 15.0 617

5.0 2.5 62.1 3.5 505 5.23 20.6 4.3 14.0 667

4.2 0.0 60.6 3.0 595 4.54 21.0 4. I 16.0 78 I 4.2 1.5 60.7 3.5 480 4.63 21.3 4.0 14.6 79 I 4.2 2.5 61.3 3.5 360 4.68 20.9 4.3 14.5 630

a Titrable acidity Reducing sugar

' Falling number

(P < 0.01) on the loaf volumes of 108 SKBjlOO g flour. The crust of pH 5.8 loaves was dark brown irrespective of salt concentration. A similar crust colour was observed for pH 5.0 and 4.2 doughs without salt. The pH 5.0 loaves, where hydrochloric acid was used. appeared dark brown at 1.5 % salt. Increasing the salt to 2.5 7; in the dough produced a distinguishably harder crumb texture. The pH 5.0 and 4.2 loaves where hydrochloric acid was used had softer texture, despite reduced loaf volume where 2.5 % salt was used.

The dough of several-fold increased alpha-amylase, i.e. 540 SKB/100 g flour at pH 5.0 with I .5 ' ,I( , salt, produced higher loaf volume (Table 5). There was shredding and the crumb was softer with fine grain. By increasing the salt content to 2.5% but keeping the dough pH at 5.0, the loaf volume decreased and the crumb possessed a very fine grain. The crust of loaf of pH 4.2 dough having 1.5 o,', salt was less brown. The loaf was uniformly symmetri- cal, however, with medium fine grain indicative of less enzyme activity in the dough system. Increasing the salt content to 2.5% in pH 4.2 dough reduced the loaf volume, which had an anaemic crust and compact texture but finer grain. The dough pH and salt had significant (P < 0.01) effect on loaf volumes. The results were promising in as much as 5 :; of flour was replaced by a highly enzymatic sprouted wheat flour. The slicing of pH 4.2 loaves with salt in the dough system was excellent.

Crumb characteristics

The results of crumb characteristics of normal and high alpha-amylase flour loaves as influenced by pH and salt are given in Tables 3, 4 and 5. The average amylose content of

Page 6: Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine . HCI in the dough

486 Die Nahrung 32 (1988) 5

Table 4 Effect of pH, acid and salt on the baking quality of 108 SKB flour

Acid pH Salt Ab- Mixing Loaf Crumb characteristics sorption time volume

pH TA"as KShas Amylose FN' 0 1 N NaOH dextrose

[?"I ["/,I b n l Lmll [m1/100 gl "4 [""I [sl

Nil 5.8 0.0 58.6 3 .O 620 5.81 12.5 6.0 14.7 62 (control) 5.8 1.5 60.1 3 .O 630 5.86 14.2 6.2 15.1 62

5.8 2.5 61.6 3.0 560 5.90 14.2 6.3 14.7 6.1

Lactic 5.0 0.0 60.2 3.0 655 5.15 21.2 6.3 14.5 64 5.0 1.5 60.7 3 .O 560 5.19 21.9 6.5 14.9 68 5.0 2.5 61.3 3 .O 440 5.26 22.2 6.4 13.7 6 7

4.2 0.0 59.0 2.7 640 4.27 33.0 6.1 15.1 207 4.2 1.5 59.7 3.3 485 4.38 31.1 5.9 14.6 5 M 4.2 2.5 68.6 6.3 415 4.40 28.3 6.0 14.3 50 I

Hydro- 5.0 0.0 58.8 2.1 665 5.21 20.9 6.4 14.3 64 chloric 5.0 1.5 59.4 3.0 610 5.26 20.4 6.3 14.5 67

5.0 2.5 60.2 3.3 500 5.31 19.2 6.2 14.3 67

4.2 0.0 56.2 4.5 605 4.63 24.0 6.0 13.4 99 4.2 1.5 57.3 5.0 560 4.68 22.7 5.7 14.0 395 4.2 2.5 63.7 5.2 455 4.73 21.9 6.0 14.1 346

" Titrahle acidity I, Reducing sugar ' Falling number

Table 5 Effect of pH, acid and salt on the baking quality of 540 SKB flour

Acid ~ 1 1 Salt Ab- Mixing Loaf Crumb characteristics ~

-

sorption time volume pH TA'as RSbas Amylose FN'

0.1 N NaOH dextrose [%I 1761 [min] [ml] [mli100 gl ["/I I >"I [SI

Nil 5.8 1.5 62.3 3 .O (control) 5.8 2.5 61.4 3.2

Lactic 5.0 1.5 60.9 3 .0 5.0 2.5 60.6 3.0

4.2 1.5 58.6 3.2 4.2 2.5 60.6 3.2

Hydro- 5.0 1.5 59.3 3.0 chloric 5.0 2.5 58.9 3.0

4.2 1.5 54.5 4.0 4.2 2.5 56.5 4.5

Titrable acidity Reducing sugar

' Falling number

505 495

575 440

425 325

590 460

520 315

5.89 17.7 5.4 5.92 19.4 5.6

5.24 22.7 5.2 5.26 23.1 5.3

4.39 30.6 4.2 4.39 28.3 4.0

5.29 23.5 5.4 5.34 21.6 5.4

4.74 28.8 4.8 4.78 27.3 4.9

9. I 60 I I .4 60

11.9 60 1 I .9 X 3

13.2 63 13.1 60

11.9 60 12.3 60

14.3 h7 13.7 63

Page 7: Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine . HCI in the dough

HARINDER/BAINS: High alpha-amylase flours 487

the crumb where lactic acid was used to adjust the pH was 16.7% as compared to 15.4% of hydrochloric acid pH adjusted dough loaves of normal flour. The effect of pH on the crumb falling numbers (FN) was highly significant (P < 0.01). The lower the pH, the higher was the FN. The overall effect of salt on the FN of the crumb was non-significant. The effect of acid, pH and salt on the reducing sugars in the crumb was also non-significant.

The pH of the dough showed a highly significant (P < 0.01) effect on the average values for reducing sugars, amylose content and FN of 108 SKB alpha-amylase flour.Salt also show- ed a significant effect on the amylose content of the crumb. The reducing sugars in the crumb weredistinctly higher than those ofnormal flour bread. A distinguishing feature of thecrumbs of the alpha-amylase flour loaves was the steep fall in the FN values of pH 5.8 and 5.0 loaves with and without salt. However, the crumb of pH 4.2 dough adjusted with lactic acid but without salt had a FN of 207 s, as compared to the notably increased values of 506 and 501 s with 1.5 and 2.5 % salt in the loaves. The alpha-amylase activity of the flour was thus considerably circumvented in the pH 4.2 doughs and more so in the presence of salt.

The titrable acidity in the crumb of lactic acid adjusted pH 4.2 dough loaf was higher than that of the loafwhere hydrochloric acid was used. Organoleptically, pH 4.2 hydrochloric acid bread was less sour. Apparently, a greater binding of hydrochloric acid with bread constituents, especially proteins, occurred as shown by an increased pH of 4.7 of bread as compared to the initially adjusted pH 4.2 of the dough.

In the 540 SKB alpha-amylase flour bread, the effects of pH on the reducing sugars and amylose content of the crumbs were highly significant (P c 0.01). The FN of the crumb, irrespective of variation of pH, acid and salt, were uniformly at rock bottom, which was as- cribed to the higher alpha-amylase activity in the dough system and changes which accompa- nied baking as the temperature in the interior of the loaf increased. The mean reducing sugar content of pH 4.2 bread crumb was decreased to the extent of 18.2 %as compared to the value of pH 5.8 crumb. There was a negligible effect of salt on the reducing sugars and amylose content of bread crumb. It seems that the doughs of pH 5.0 and 5.8 during fermentation and baking suffered greater hydrolysis of the amylose fraction in the 540 SKB flour loaf, which by the normal straight dough or sponge methods of breadmaking would be extremely difficult to bake. pH 5.0 dough containing 1.5 % salt showed elastic behaviour and satisfac- tory handling irrespective of the acid used. However, the amount of orthophosphoric acid and acetic acid required to adjust the pH was greater, which imparted a sour taste to the loa- ves. The taste of lactic and hydrochloric acid pH 5.0 adjusted dough loaves was rated satis- factory.

L-cysteine ’ HCI, low p H and salt interactions

The pH 4.2 dough of normal and high alEha-amylase flours (108 to 540 SKB/IOO g) having 25 ppm of L-cysteine . HCI, 1.5% salt and 75 ppm of KBrO,, showed elastic behaviour as compared to the control without L-cysteine . HCI. The level of Lcysteine . HCl made no difference to loaf volume (Table 6).

Increasing the salt content to 2.5%, Lcysteine . HCl from 25 to 75 ppm, with the oxidant, also resulted in satisfactory doughs which could be managed during baking. The loaf volume showed an increase as the L-cysteine . HCl content was increased in the 2.5 % salt and pH 4.2 dough. A combination of 25 ppm of L-cysteine . HCl, 1.5% salt, 75 ppm of KBrO,, in a pH 4.2 dough of high alphy-amylase flours contributed to a resilient and silky bread crumb with fine grain and satisfactory loaf volume.

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488 Die Nahrung 32 (1988) 5

Table 6 Effect of L-cysteine . HCl, low pH*, KBrO, (75 ppm) and salt on the baking of normal and high alpha-amylase (AA) flours

Flour L-cysteine Sdh Sugdr Ab- Mixing Loaf Crumb characteristics HCI mrp- time volume

tian pH TA’asO I R S h d s Amy- bN’ N NdOH dex- 10%

[rose I P P ~ I I”,] IX [’4 lmlnl lmll Im1’lWgl 1”.1 1”J 14

Normal 25 (I0 SKB, AA) 50

25 50 75

I0RSKB.AA 25 50

25 50 15

540SKB. AA 25 50

25 50 75

* pH 4.2 dough a Tirrable acidity I, Reducing sugar ‘ Falling number

1.5 2.0 1.5 2.0

2.5 2.0 2.5 2.0 2.5 2.0

1.5 2.0 1.5 2.0

2.5 ’ 2.0 2.5 2.0 2.5 2.0

1.5 0.0 1 5 0.0

2.5 0.0 2.5 0.0 2.5 0.0

60.2 5.0 60.1 4.5

62.3 5.0 62.1 5.0 62.1 4.5

60.7 4.5 59.1 4.0

66.1 4.0 66 I 4.0 64.1 3.5

60.4 4.0 59.4 3.5

61.9 4.2 61.9 4.2 58.4 4.0

545 540

445 505 520

645 685

485 560 560

610 615

490 515 520

4.32 35 3 4.32 34.1

4.32 36.4 4.33 36.6 4.34 34.1

4.30 34.7 4.29 35.9

4.33 34.1 4.33 32.3 4.26 35.4

4.39 33.5 4.39 31.7

4.43 30.3 4.40 36.0 4.38 33.5

4.0 14.6 6x7 4.2 13.8 620

4.2 14.3 625 4.2 14.2 656 4.0 14.4 640

4.5 12.R 522 4.1 12.6 51Y

4.9 12.2 475 5.3 12.5 522 5.2 13.8 .%3

3.6 12.7 X8 4.0 12.8 103

3.9 12.6 343 3.8 12.9 .M4 4.0 13.6 97

The crumb of 540 SKBjlW g flour loaf without sugar contained minimal amounts of the reducingsugar, i.e. 3.6 to4.495, ascompared to normal and 108 SKB/100gflour loaves made from dough containing 27” sugar (Tables 3,4). A distinct reduction in the arnylose content of the crumb of 540 SKB flour loaf was observed. The FN values of the crumbs of normal flour bread with L-cysteine . HCI and salt were higher than those of the high alpha-amylase flour loaves. The FN of the crumb of 540 SKB flour loaf using 25 and 50 ppm of L-cysteine ’ HCI and 2.5 salt in the‘dough were 343 and 344 s, as compared to 88 to I03 s in the case of 1.5 ”/, salt in the dough. This indicated the beneficial effect of increased salt level on the physical characteristics of the starch in the crumb.

From the farinograph, gluten recovery and baking tests data, it was concluded that a judicious selection of pH, reducing and oxidizing agents with an appropriate level of salt would go a long way to produce a loaf of acceptable quality even from 10.8- to 54.0-fold higher alpha amylase in the flour than that of a normal flour. The baker sometimes has to contend with flours of varying characteristics. especially as a result of indifferent harvest conditions and annual variations. The flours of such wheats are considered with indifference for baking [5, 20-231. Eliminating or minimizing the deleterious effect of enzyme activity affecting starch and protein components which are responsible for bread architecture are

possible technological options, as discussed [24].

Page 9: Studies on baking of high alpha-amylase flours: effect of pH, salt and L-cysteine . HCI in the dough

HARINDER/BAINS: High alpha-amylase flours 489

Zusammenfassung

K. HARINDER und G. S. BAINS: Untersuchungen uber Backeigenschaften von Mehlcn mit hohem Alpha- Amylase-Gehalt : EinfluD von pH-Wert, Kochsalz und L-Cystein . HCI im Teig

Es wird der EinfluD verschiedener Konzentrationen von Natriumchlorid (0 bis 2.5 %). pH-Wert (5.8 bis 4.2) und KBr03 (75 ppm) mit und ohne Zusatz von L-Cystein . HCI auf Backeigenschaften von Mehlen init hohem Gehalt an Alpha-Amylase (108 bis 540 SKB/100 g) im Vergleich zu normalem Mehl untersucht. Erniedrigung des pH-Wertes des Teiges auf 4.2 und Erhohung der Sdlzkonzentration auf 2,5"," verringern das Laibvolumen und die Glutenausbeute betrachtlich. Ein erniedrigter pH-Wert reduziert die Mischtoleranz des Teiges: durch erhohten Salzgehalt normaler Alpha-Amylase-reicher Mehle kann dem entgegengewirkt werden. Eine Kombination von niedrigen pH-. Salz- und L-Cystein . HCI-Werten und 75 ppm KBrO, ohnc Zucker in Teigen aus Mehlen mit hohem Gehalt an Alpha-Amylase erzeugt Brotlaibc mit befriedigender Qualitit unter Eliminierung der Hauptfermentation.

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K. HARINDW and Prof. emer. G. S. BAINS, Department of Food Science and Technology, h n j a b Agricul- tural University, Ludhiana-141004, India.

Received May 28, 1986

and S. SEBTI, Baker's Dig. 54, 22 (1980).