Effect of Antioxidants on Farinograph and Amylograph Characteristics of Wheat Flour

Abstract

Functionality of synthetic and natural antioxidants on dough rheology for preparation of bread and cookies was studied. Four antioxidants viz. butylated hydroxytoluene, dl-alpha-tocopherolacetate, malic acid and soy lecithin were added on shortening weight basis, with BHT and dl-alpha-tocopherolacetate added at levels of 200, 400, 600, and 800 ppm and malic acid and soy lecithin added at levels of 0.25, 0.50, 0.75, and 1.00 kg/100 kg shortening. Significant variations were recorded in Farinograph and Amylograph characteristics upon addition of antioxidants. These antioxidants even at the minimum concentrations improved dough handling and machinability. In comparison with control, BHT at 200 ppm, dl-alpha-tocopherolacetate at 800 ppm, malic acid at 1.00 kg/100 kg shortening and soy lecithin at 0.75 and 1.00 kg/100 kg shortening level modified the rheological properties and visco-elastic behavior of dough.

Introduction

Processing of wheat flour into dough is an important step in bakery industry as final product quality to great extent depends upon rheological behavior of wheat flour dough. Wheat flour dough is a complex multiphase system in which continuous physical, chemical, and biological modifications take place at molecular and micro structural levels.1 Forces responsible for these changes are generated due to presence of vast number of ingredients present in the formula. Thus, it is highly important to investigate the influence of added ingredients, in this case antioxidants, on rheological behavior of wheat flour.

Various methods have been developed for evaluation of rheological properties of wheat flour dough.2 3 Farinograph is most widely used to understand rheological behavior during dough mixing.4 5 Farinograph is a recording dough mixer that measures torque needed for mixing dough at a constant speed and temperature. The resistance offered is integrated with time and traced on kymograph chart in form of curve. This curve is used to evaluate various rheological parameters such as dough development time, dough strength, dough stability, etc. Amylograph measures important aspects of starch rheology during pasting,4 5 such as gelatinization temperature and changes in viscosity with temperature and time. These pasting properties of starch help to evaluate crumb characteristics and loaf volume.6

Automation of modern baking units and bakery process designing require prior knowledge of changes occurring during dough development and processing due to addition of antioxidants. It has been reported that reductants decrease the apparent viscosity and shear modulus at low temperature of 30 and 60°C, however at higher temperature their effect is diminished.7 During bread dough development, proteins and peptides undergo oxidation-reduction process that leads to rearrangement and reformation of disulphide linkages.8 Addition of ascorbic acid at levels of 200 ppm increases the tolerance of dough to over mixing.9 Use of acids (as chelating agents or improvers) cause depolymerization of starch, thus decreasing viscosity and increasing its water solubility.10 Among various sources of lecithin, soy lecithin due to high concentration of phospholipids (70 kg phospholipids/100 kg soy lecithin) is most widely used as natural antioxidant source.11 Addition of lecithin to wheat flour dough causes increase in its rheological parameters.12 Soy lecithin improves the extensibility, elasticity, and dough handling properties.13 It has also been revealed that lecithin has dough strengthening properties, which benefit yeast-raised baked goods; help to control batter viscosity and produced pleasantly crumbly cookies.14 Safety of synthetic antioxidants is under question and food manufacturers are considering the possibility to achieve antioxidative effect from natural sources.15 16 Objective of this study was to investigate effect of natural and synthetic antioxidants on rheology of what flour and to find most suitable natural alternative for the use in bakery industry.

Materials

Commercial wheat flour was procured from local market. Flour was analyzed for chemical composition (Table 1), according to AACC procedures.4 Four antioxidants i.e., butylated hydroxytoluene (BHT), dl-alpha-tocopherolacetate, freeze-dried soy lecithin (moisture content—0.70 kg/kg soy lecithin and ground to particle size of 18 mesh), and malic acid (white triclinic crystals) were used for study. These antioxidants viz. butylated hydroxytoluene, dl-alpha-tocopherolacetate, malic acid, and soy lecithin were added on shortening weight basis, with BHT and dl-alpha-tocopherolacetate added at levels 200, 400, 600, and 800 ppm and malic acid and soy lecithin added at levels of 0.25, 0.50, 0.75, and 1.00 kg/100 kg shortening. For sake of brevity, the term “tocopherol” will be used to denote the dl-alpha-tocopherolacetate throughout this study.

Table 1 Chemical composition of wheat flour

Characteristics	Values
Protein (% N × 5.7)	9.89
Fat (kg/100 kg wheat flour)	0.82
Ash (kg/100 kg wheat flour)	0.52
Free fatty acids (kg/100 kg oleic acid)	0.03
Wet gluten (kg/100 kg wheat flour)	24.41
Dry gluten (kg/100 kg wheat flour)	8.90
Damaged starch (kg/100 kg starch)	6.89
Diastatic activity (mg maltose/10 g at 30°C)	255.50
Total sugars (mg maltose/10 g)	184.50
Reducing sugars (mg maltose/10 g)	44.75
Sedimentation value (mL)	28.00

Methods

Farinograph Characteristics

Farinograph characteristics of the flour were investigated with and without addition of shortening, according to AACC method given under 54-21.4 From the farinogram, the following parameters were studied: (i) Water absorption (mL): amount of water (mL) necessary to center the farinograph curve on 500 BU (Brabender Units) line; (ii) Dough development time (min): time to nearest half minute from the first addition of water to the development of maximum consistency of the dough; (iii) Mixing tolerance index (BU): difference in BU from the top of the curve at the peak to the top of the curve measured at 5 min after the peak is reached; (iv) Stability (min): Difference in time to the nearest half minute, between the time where the top of the curve first intercepts 500 BU line and the point where the top of the curve leaves 500 BU line; (v) Softening (BU): difference between the center of the curve obtained at 12 min after the peak and reported to the nearest 5 BU.

Amylograph Characteristics

Amylograph characteristics of flour were investigated with and without addition of shortening, according to AACC method given under 61-01.4 From amylogram following parameters were studied: (i) Gelatinization temperature (°C): temperature at which starch starts gelatinizing; (ii) Peak viscosity (BU): viscosity in BU at first peak of curve; (iii) Temperature at peak (°C): temperature at which peak viscosity is obtained; (iv) Viscosity at 95°C (BU): viscosity on attaining 95°C temperature, the relation of this value to peak viscosity reflects the ease of cooking the starch.

Statistical Analysis of Data

The data collected on different characteristics were analyzed with the help of factorial design in CRD.17 All results have been reported at moisture level of 14 kg/100 kg of dry solids, unless otherwise stated. Each value is mean of three observations.

Results and Discussion

Farinograph Characteristics Without Addition of Shortening

Farinograph characteristics of flour after addition of four antioxidants at different levels, without addition of shortening are presented in Table 2. At fixed water absorption (WA), the maximum consistency of flour in most of cases with addition of four antioxidants at different levels was more than 500 BU. So, the amount of water had to be increased to center curves on 500 BU line. Where as, some antioxidants at certain levels, at fixed WA, showed maximum consistency below the 500 BU line and thus in such cases water had to be decreased to center curve on 500 BU line. To center curves on 500 BU line, statistically significant variations were observed in WA of flour at different levels of four antioxidants. Comparing four antioxidants, maximum WA was noticed in case of soy lecithin, followed by malic acid and BHT in the order, where as tocopherol showed decrease in WA as compared to control. Flour with BHT showed almost constant WA at different levels, where as in case of tocopherol and soy lecithin the WA decreased with increase in levels. As shown in Table 2 the dough development time (DDT) did not varied significantly with addition of antioxidants. Similarly, no significant variations were recorded at different levels of each antioxidant.

Table 2 Effect of antioxidants on Farinograph characteristics of wheat flour (without addition of shortening)

Antioxidant	Level	Water absorption (mL)	Dough development time (min)	Stability (min)	Mixing tolerance index (BU)C	Softening (BU)C
Control	—	61.3a	1.25a	2.25a	110a	130a
BHTA	200	61.8b	1.50a	2.50a b	70b	130a
	400	61.8b	1.25b	2.25b	110b	145b
	600	62.0c	1.00a	1.75a	110a	130a
	800	61.8b	1.25a	2.25a	100c	135c
TocopherolA	200	61.4a d	1.25a	1.75a	110a	145b
	400	61.2a c	1.50a	2.00a	100c	140d
	600	61.0f	1.25a	2.00a	110a	150e
	800	61.0f	1.25a	2.25a	80d	120f
Malic acidB	0.25	61.6g	1.50a	2.50a b	90e	130a
	0.50	61.7b g	1.25a	1.75a	105f	150e
	0.75	62.3h	1.00a	1.50a c	110a	155g
	1.00	62.3h	1.00a	2.50a b	90e	130a
Soy lecithinB	0.25	63.1i	0.75a	0.75d	120g	160h
	0.50	62.0c	1.25a	1.75a	80d	135c
	0.75	61.2a	1.25a	3.50e	90e	140d
	1.00	61.2a	1.25a	2.50a b	95h	140d

^a–iMeans superscripted with different letters in column vary significantly (P < 0.05).

^ALevels in ppm of shortening.

^BLevels in kg/100 kg of shortening.

^CBU—Brabender units.

Stability however differed significantly with addition of four antioxidants at different levels. Though most of the levels showed similar or decreased stability as compared to control, but few cases showed improvement in stability over control. Soy lecithin at level of 0.75 kg/100 kg shortening resulted in maximum stability (3.50 min). In case of tocopherol though stability was lower than control except for 800 ppm where it was equal to that of control, but it increased with increasing levels. BHT and malic acid at minimum level of 200 ppm also had appreciable stability.

Mixing tolerance for control flour was 110 BU. With addition of BHT at level of 200, 400, 600, and 800 ppm values were 70, 110, 110, and 100 BU respectively, showing that BHT reduced breakdown of flour at minimum level. Tocopherol at 800 ppm level was most effective in reducing tolerance to mixing. However, malic acid did not showed ordered change in mixing tolerance index, where it improved at extreme levels i.e., at 0.25 and 1.00 kg/100 kg shortening, but breakdown was higher at middle levels. Overall trends for softening value were very similar to trends followed in mixing tolerance index.

These changes in farinograph characteristics with addition of most antioxidants might be attributed to fact that antioxidants prevent oxidation of dough system, which causes improperly oxidized dough, thus hindering oxidative polymerization of gluten proteins,18 which lead to low cross linking and thus stress decays to lower levels during the specified time, which in turn decreases resistance of dough and results in low elasticity and also early break down of dough.19

Slight increase in water absorption (WA) on addition of antioxidants could have been due to the fact that added ingredients compete with gluten proteins for water absorption. In case of tocopherol higher WA at lower levels indicated towards action of tocopherol as oxidizing agent in dough environment i.e., it is not showing any action as thiol blocker or replacing amide groups of gluten proteins with ester groups like other reducing agents, thus there is no decrease in possibility of hydrogen bonding. However, decrease in WA at higher levels indicated the possibility of reducing action of tocopherol. Similarly, effect of different levels of tocopherol on stability and tolerance to mixing could be attributed to oxidizing and reducing action of tocopherol in dough system. BHT at lowest level showed improved stability and tolerance to mixing which could be due to prevention of oxidation of dough system and with increasing level this effect as reducing agent becomes more pronounced, thus resulting in effective thiol blocking and reduced hydrogen bonding due to which stability and tolerance to mixing was either similar to control or even lower. Increase in WA with increasing levels of malic acid might have been due to lowering of pH upon addition of malic acid. Tanaka et al.20 have reported similar observations. Similarly shorter mixing time and reduction in stability and tolerance to mixing with increasing levels of malic acid might have been due to decreasing pH of dough system and the fact that malic acid reacts with free radicals created in gluten during dough mixing, and thiol blocking might not be taking place. Hoseney et al.21 reported similar observations. Increase in WA at lowest level (0.25 kg/100 kg shortening) of soy lecithin might have been due to the fact that water preferably tends to bind hydrophilic sites of emulsifier, which reduces availability of water for flour proteins to bind to, thus lowering of flexibility and tightening of protein structure, and increasing the requirement of water to center curve at 500 BU. Thus, at lower levels increase in WA might have been cause of reduced stability and tolerance to mixing. However, with increasing levels WA was reduced, stability, and tolerance to mixing improved which could be due to the fact that increased amount of emulsifier resulted in better water–protein interactions making dough more flexible.22

Farinograph Characteristics with Addition of Shortening

Farinograph characteristics of flour after addition of four antioxidants at different levels along with addition of shortening are presented in Table 3. At fixed water absorption (WA), the maximum consistency of flour in most of the cases with addition of four antioxidants at different levels with shortening was less than 500 BU. Except in case of soy lecithin where it was more than 500 BU. Thus, the amount of water in all cases except soy lecithin had to be decreased to center the curve at 500 BU line but in case of soy lecithin it was opposite. The variations in WA at all levels of four antioxidants were significant. Soy lecithin, which showed slight increase in WA, had maximum WA (61.4 mL) at the lowest level, while WA was constant at 61.2 mL at all other levels. BHT and malic acid though showed overall decrease in WA at all levels but within levels WA increased. In case of tocopherol WA decreased with increasing levels. Dough development time (DDT) did not vary significantly on addition of antioxidants at different levels. DDT with in levels nearly remained same with nonsignificant variations.

Table 3 Effect of antioxidants on Farinograph characteristics of wheat flour (without addition of shortening)

Antioxidant	Level	Water absorption (mL)	Dough development time (min)	Stability (min)	Mixing tolerance index (BU)C	Softening (BU)C
Control	—	61.0a	1.25a	2.00a	110a	140a
BHTA	200	61.4b	1.25a	1.50a b	100b	140a
	400	60.8c	1.25a	1.50a c	80c	140a
	600	60.2d	1.25a	2.00a	115^d	160b
	800	60.6e	1.25a	1.75a	100b	115^c
TocopherolA	200	61.0a	1.25a	2.50a c	105c	150d
	400	61.0a	1.25a	1.50a b	125f	155e
	600	60.4b	1.25a	1.50a b	90g	120f
	800	60.3b d	1.25a	1.50a b	95h	125g
Malic acidB	0.25	60.2d	1.25a	1.50a b	105e	145h
	0.50	60.4b	1.25a	1.50a b	105e	150d
	0.75	60.5b e	1.25a	1.50a b	100b	145h
	1.00	60.4b	1.25a	1.50a b	90g	140a
Soy lecithinB	0.25	61.4f	1.00a	1.75a	120i	155e
	0.50	61.2g	1.25a	1.50a	80c	130i
	0.75	61.2g	1.25a	2.50a c	95h	130i
	1.00	61.2g	1.50a	2.25a	95g	120f

^a–iMeans superscripted with different letters in column vary significantly (P < 0.05).

^ALevels in ppm of shortening.

^BLevels in kg/100 kg of shortening.

^CBU—Brabender units.

Statistically significant variations in stability of flour treated with four antioxidants at different levels were noticed from that of control. In general stability decreased with addition of antioxidants. BHT, tocopherol, and malic acid showed almost similar timings for stability, except 600 ppm level of BHT and 200 ppm level of tocopherol showing improvement in stability. Malic acid showed constant stability at all levels. Soy lecithin showed decrease in stability at initial levels but improved the stability with increasing levels i.e., 0.75 and 1.00 kg/100 kg shortening. Significant variations were displayed in mixing tolerance index. Soy lecithin showed improved tolerance to mixing at levels above 0.25 kg/100 kg shortening, this improvement in tolerance was also displayed by higher levels of tocopherol and BHT. No define trend could be observed in mixing tolerance index within levels of any particular antioxidant except malic acid showing improvement with increasing levels.

Reduction in WA could be due to emulsifying and lubricating properties of shortening, which acts as plasticizer and thus reducing requirement for water and also improving machinability of dough by reducing friction. Antioxidants like BHT and tocopherol could be evenly suspended in dough with shortening because of their solubility in fat, thus their effectiveness in dough system increased with addition of fat. In case of soy lecithin along with shortening the effects shown could be due to emulsion forming capabilities of soy lecithin, which lead to even dispersion of fat in system and hydrability of soy lecithin's nonpolar fatty acids. Szuhaj23 reported some similar properties of lecithin. The changes in farinograph characteristics with shortening and upon addition with four antioxidants at different levels could be attributed to similar conclusions as for the case of farinograph characteristics without shortening.

Amylograph Characteristics Without Addition of Shortening

Results of pasting characteristics of flour without shortening as influenced by addition of antioxidants at different levels are presented in Table 4. In case of gelatinization temperature (GT), significant variations were noticed. It was observed that GT in case of tocopherol, malic acid, and soy lecithin was lower than control but was higher in case of BHT. However, within the levels of four antioxidants variations in GT were not much appreciable. Though no definite trend was followed, but GT decreased with increasing levels of BHT and tocopherol, whereas GT increased with increasing levels of malic acid and soy lecithin.

Table 4 Effect of antioxidants on Amylograph characteristics of wheat flour (without addition of shortening)

Antioxidant	Level	Gelatinization temperature (°C)	Peak viscosity (BU)C	Peak viscosity temperature (°C)	Viscosity at 95°C (BU)C
Control	—	66.50a	590a	86.00a	510a
BHTA	200	69.50b	600b	86.00a	520b
	400	68.00c	680c	87.50b	560c
	600	71.00d	650d	89.00c	540d
	800	68.00c	670e	87.00d	560c
TocopherolA	200	63.50e	670e	89.75e	540d
	400	62.00f	680c	89.00c	540d
	600	62.00f	690f	89.75e	570e
	800	63.50e	690f	90.50f	570e
Malic acidB	0.25	63.50e	670e	89.75e	560c
	0.50	64.25g	630g	89.75e	530f
	0.75	65.00h	680c	89.75e	560c
	1.00	62.00f	630g	89.75e	520b
Soy lecithinB	0.25	61.25i	670e	79.25g	560c
	0.50	62.00f	680c	86.75d	570e
	0.75	62.00f	680c	84.50h	580g
	1.00	63.50e	670e	86.00a	580g

^a–iMeans superscripted with different letters in column vary significantly (P < 0.05).

^ALevels in ppm of shortening.

^BLevels in kg/100 kg of shortening.

^CBU—Brabender units.

Significant variations were noticed in case of peak viscosity (PV) of flour upon addition of four antioxidants at the different levels, as compared to control. In all the cases PV was significantly higher than control. Tocopherol exhibited maximum increase in PV followed by soy lecithin, malic acid, and BHT in the order. Appreciable variations were observed within the levels of BHT and malic acid, but these variations followed to definite trend. In case of BHT maximum PV (680 BU) was obtained at 400 ppm level, while malic acid at level of 0.75 kg/100 kg shortening gave maximum PV of 680 BU. PV increased with increasing level of tocopherol and soy lecithin, but not much appreciable variation within their (tocopherol and soy lecithin) levels were observed.

Cooking must proceed through peak viscosity temperature (PVT) to obtain usable pastes. Statistically, PVT differences were significant among antioxidant at their different levels. Addition of tocopherol showed maximum PVT followed by malic acid and BHT in the order. No definite trend could be noticed within levels of soy lecithin, which exhibited decrease at levels of 0.25 and 0.75 kg/100 kg shortening and nearly similar PVT to that of control at the other levels. In case of BHT and tocopherol, PVT increased with increasing levels. However, for malic acid PVT remained constant (89.75°C) at all the levels. Statistically significant variations were observed in viscosity at 95°C. For all the treatments these variations followed nearly similar trends as that for respective peak viscosities. Addition of antioxidants caused greater decrease in viscosity at 95°C as compared to control i.e., fall in curve from PV to viscosity at 95°C was larger in terms of BU for flour with antioxidants. This all, among antioxidants was largest (140 BU) at 400 ppm level of tocopherol and lowest (90 BU) at 1.00 kg/100 kg shortening level of soy lecithin.

Increase in gelatinization temperature (GT) on addition of BHT might be due to prevention of breaking down of crystallites, which resulted in requirement of higher energy for gelatinization to occur.24 The decrease in GT in case of tocopherol, malic acid, and soy lecithin could be associated with increase in WA with additives. Rogers and Hoseney25 reported decrease in GT due to increased WA capacity of flour. Increase in GT with increasing levels of soy lecithin might have been due to binding of water by hydrophilic moieties of soy lecithin, thus decelerating penetration of water into starch granule.

Increase in peak viscosity (PV) on addition of antioxidants as compared to control could be explained by the fact that antioxidants prevent oxidative polymerization of wheat flour slurry and this lack of polymer cross linkages lead to higher viscosity of wheat flour slurry.26 But, variations in PV among four antioxidants and within their levels might have been due to their ability to bind free radicals i.e., free hydroxyl groups of starch granule, prevent intermolecular hydrogen bonding between adjacent starch granules, thus reducing intergranular tension and viscosity.24 Dougherty27 reported similar results about effectiveness of tocopherols. Appreciable decrease in PV at highest level of malic acid might have been due to weakening effect of malic acid on starch granule,24 28 Drop in PV at highest level of malic acid can also be attributed to depolymerization of starch due to combined effect of reduced pH and heat.10 Increase in PV with addition of soy lecithin might have been due to hydrophilic and lypophilic moieties of soy lecithin, which formed better complexes with amylose and also resulted in higher intergranular adhesion. Sidhu et al.29 reported similar results.

Peak viscosity temperature of wheat flour slurry depends on hydrogen bonds through which the starch molecules are associated with each other. If these hydrogen bonds are disrupted or hindered, than reduction in PVT occurs. This could be reason for increase in PVT with increasing levels of tocopherol, as effectiveness of tocopherol as antioxidant decreases at levels higher than 600 ppm.27 Also lower PVT for various levels of BHT as compared to tocopherol showed that BHT was more effective in binding free hydroxyl radicals on starch granule as compared to tocopherol. Variations in viscosity at 95°C showed that ease of cooking was faster with addition of antioxidants. This viscosity upon addition of antioxidants might have been due to greater release or amylose from starch granule due to blocking of free hydroxyl radicals. Sidhu et al.29 reported similar results showing decrease in viscosity at 95°C due to high exudated amylose.

Amylograph Characteristics with Addition of Shortening

Results of pasting characteristics of flour with shortening as influenced by addition of antioxidants at different levels are presented in Table 5. Gelatinization temperature (GT) of flour with shortening was reduced, as compared to flour without shortening but there were more significant variations in GT on addition of antioxidants at different levels. GT was on higher side than control in case of BHT, tocopherol, and malic acid, but for soy lecithin it was lower than control. However, no specific trends were observed in GT within the levels of individual antioxidant.

Table 5 Effect of antioxidants on Amylograph characteristics of wheat flour (without addition of shortening)

Antioxidant	Level	Gelatinization temperature (°C)	Peak viscosity (BU)^C	Peak viscosity temperature (°C)	Viscosity at 95°C (BU)C
Control	—	62.00a	610a	86.75a	500a
BHTA	200	65.00b	640b	88.25b	500a
	400	63.50c	670c	86.75a	510b
	600	65.00b	660d	87.50c	510b
	800	63.50c	690e	86.00d	520c
TocopherolA	200	63.50c	680f	89.75e	530d
	400	62.00a	650g	89.00f	510b
	600	63.50c	670c	88.25b	520c
	800	63.50c	670c	88.25b	520c
Malic acidB	0.25	63.50c	680f	90.50g	510b
	0.50	64.25d	630h	89.00f	510b
	0.75	63.50c	700i	90.50g	530d
	1.00	66.50e	690e	89.00f	530d
Soy lecithinB	0.25	60.50f	660d	83.00h	550e
	0.50	59.00g	700i	80.00i	590f
	0.75	64.25d	710j	89.00f	540g
	1.00	61.25h	670c	82.25j	550e

^a–jMeans superscripted with different letters in column vary significantly (P < 0.05).

^ALevels in ppm of shortening.

^BLevels in kg/100 kg of shortening.

^CBU—Brabender units.

Peak viscosity (PV) of flour slurry with shortening was higher in all treatments as compared to flour without shortening. Significant variations were noticed in case of PV of flour slurry with shortening for all treatments. However, trends for all the treatments were nearly similar as that for flour slurry without shortening. In case of control and soy lecithin peak viscosity temperature (PVT) of flour slurry without shortening. PVT was nearly similar for malic acid, but decreased with increasing levels of BHT and tocopherol. Significant variations were noticed in viscosity at 95°C for all the treatments. Decrease in values of viscosity at 95°C upon addition of shortening was of greater magnitude as compared to those with shortening, but trends followed were nearly similar.

Lowering of GT upon addition of shortening could be attributed to the fact that shortening upon melting make forces in the shear field much larger than those encountered in wheat flour slurry without shortening, which causes rise in curve. Increase in PV and PVT with addition of shortening might have been due to the fact that fat maintained intact shape of starch granule and also prevented release of solubles due to formation of fat-amylose complex. This caused granules to swell more, thus increasing PV and PVT. Ghiasi et al.,30 31 reported similar observations. Decrease of larger magnitude in viscosity at 95°C could be attributed to the breaking up of fat-amylose complex at 95°C, which caused release of solubles, deformation, and collapsing of starch granules. Ghiasi et al.31 and Sidhu et al.29 reported similar observations. Other changes in amylograph characteristics with shortening and upon addition of four antioxidants at different levels could be attributed to similar conclusions as for the case of amylograph characteristics without shortening.

Conclusion

Based on the result it is concluded that addition of natural and synthetic antioxidants modified the rheological properties of dough. Even at minimum concentrations there is improvement in dough handling and machinability. It was found that tocopherols at 600 ppm, malic acid at level of 1.00 kg/100 kg shortening and soy lecithin at level of 1.00 kg/100 kg shortening (with addition of shortening) significanlty modified the farinograph characteristics of dough. In comparison with control, BHT at 200 ppm tocopherol at 600 ppm, malic acid at level of 1.00 kg/100 kg shortening and soy lecithin at level of 0.75 and 1.00 kg/100 kg shortening, modified the rheological properties and visco-elastic behavior of dough. Use of freeze dried soy lecithin may not be suitable for cookie and biscuit baking due to its tendency to absorb moisture, because low final moisture (nearly 1.5–2.0 kg/100 kg dry solids) is required in these products.