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Bread and bakery products represent an important sector of the food industry. They are known and consumed throughout the world for thousands of years. However, we can say that their production is relatively new only thinking of how fast the technology evolves from year to year. Bread with composite flour may be made from other types of flour than wheat flour or may be made from flours derived from pseudo – cereals mixed with wheat flour. In recent years the demand for gluten – free products has been on the rise and so interest in gluten-free biscuit production is growing. The gluten free bakery products have become available in market and it was prepared out of non – wheat flour such as rice, maize, soya and quinoa. Therefore, the aim of the current study was to produce pan bread and functional bakery products (biscuit) using whole meal quinoa flour (QF). QF was used for substitution of wheat flour by 5, 10, 15, 20 and 25% levels to study the rheological properties of dough, and substitution levels of 5, 10 and 15% to study their effect on pan bread properties. Also, wheat flour was substituted with 20 and 25% QF to produce biscuit. The effect of using composite flour (quinoa, corn and rice), as well as the acceptability of the produced gluten – free biscuit was also studied.
The obtained results can be summarized as follows
5.1. Chemical composition of raw materials
The obtained results refer to the moisture, protein, lipids, crude fiber, ash and nitrogen free extract, which were 12.60, 12.25, 0.70, 0.64, 0.63 and 85.78%, respectively for strong wheat flour (SWF), but which were 11.73, 8.92, 0.68, 0.61, 0.51 and 77.55%, respectively for weak wheat flour (WWF). On the other hand whole meal quinoa flour (QF) had the highest amounts of protein, lipids, crude fiber, and ash compared to another samples under investigation, which were 15.10, 6.33, 3.80 and 3.72% respectively.
5.2. Amino acids content
The obtained results indicated that, the total essential amino acids contents of QF, corn flour (CF) and rice flour (RF) were relatively high compared to SWF (72% ext.), which were 38.48, 43.85 and 43.39 g/ 100g protein for QF, CF and RF, respectively and it was 34.29 g/100g protein of strong wheat flour. On the other hand, threonine, methionine and lysine in QF were higher than those in SWF. Also, the essential amino acids for CF and RF were higher than those in SWF. The total amino acids were 91.27, 89.60, 97.98 and 97.26% for SWF, QF, CF and RF, respectively. Also, from the obtained results, it could be concluded that the quality of protein parameters (CS, C.PER, EAAI and BV) indicated that QF can be utilized as a good protein sources were computed with the reference to the FAO / WHO.
5.3. Physicochemical characteristics
Physicochemical characteristics of SWF (72% ext.), i.e., wet gluten, dry gluten, gluten index and falling number values were 34.52%, 11.3%, 96.33% and 351.33 sec., respectively. the substitution of SWF with different levels from QF ( (5, 10, 15, 20 and 25%), these parameters were gradually decreased by increasing the levels of substitution with QF . The reduction percentage of wet gluten, dry gluten, gluten index and falling number were 16.57, 15.93, 8.81 and 19.64 for wheat flour sample containing 15% QF, respectively compared to control sample (100% SWF) due to increasing of QF addition, the gluten network become weak recorded negative relation to gluten network strength and the spread of dough. On the other hand, falling number decrease by adding QF to SWF, because the QF had more activity of α- amylase (low falling No.) than SWF.
5.4. Rheological study
5.4.1. Farinograph parameters
Results revealed that the water absorption was significant differences (p ≤ 0.05) and increased gradually with increasing the level of substitution of SWF by QF. The water absorption decreased from 60.4% for control flour sample to 64.70% for SWF contained 25% QF. The stability time of wheat flour dough was gradually decreased with increasing the level of substitution with quinoa flour, stability decreased from 12.0 min for control sample to 5.5 mine for wheat flour sample contained 15 % QF. On the contrary, degree of softening was increased.
5.4.2. Extensograph parameters:
Resistance to extension value of the dough was gradually decreased as a result of substitution of wheat flour by 5, 10, 15, 20 and 25% of quinoa flour. The resistance to extension decreased from 960 B.U for control sample to 250 B.U for sample contained 25% QF.
Extensibility of the dough was increased from 145 min for control wheat sample to 155 and 165 min for wheat flour sample contained 5 and 10 % QF, respectively and the extensibility was decreased gradually by increasing of QF (from 15 to 25%). Concerning to the energy, all treatments were lower in comparison to control.
5.5. Baking quality of pan bread
5.5.1. Chemical composition
The results revealed that, crude protein, lipids, ash and crude fiber contents of prepared pan bread had gradually increased with increasing the substitution level with quinoa flour in comparison to control pan bread samples but nitrogen free extract was decreased. Crude protein, lipids, ash and crude fiber increased from 12.35 to 12.78%, 1.40 to 2.20%, 1.14 to 1.62 % and from 1.02 to 1.49%, respectively.
5.5.2. Physical properties
The weight of pan bread was increased gradually as substitution level by quinoa flour increased. The weight was increased from (1.2 to 1.4%) compared to control sample. Gradually decrease in pan bread volume and specific volume were noticed for bread samples prepared by substitution of wheat flour with quinoa flour at different levels. Specific volume was decreased from 8.5 to 20.0% for pan bread containing 5 to 15 % quinoa flour, compared to control sample (100% strong wheat flour).
Results of color determination showed that, control pan bread was characterized by higher L* and b* values (60.81 and 32.91), respectively. These parameters were decreased gradually by increasing the substitution level by quinoa flour, but redness (a * value) of pan bread was increased. Subjective evaluations confirmed that the quinoa pan bread samples were darker, more red (a* value) than control.
For the effect of storage of pan bread at room temperature (25̊c ±2), the results showed that the lightness (L*) of crumb pan bread was slightly decreased during storage (from 0 to 72 h). On the other hand , yellowness (b*) and redness (a*) values of pan bread crump containing quinoa flour at different levels were significantly increased compared to control at zero time or during storage up to 72 h. Generally, the rate of changes of redness and yellowness which observed for control pan bread sample were more than pan bread samples containing quinoa flour.
5.5.3. Organoleptic characteristics
from the obtained results, it could be concluded that, pan bread made from strong wheat flour substituted with 5, 10 and 15% quinoa flour had the highest overall acceptability scores compared to control pan bread (100% wheat flour). Bread containing 5 and 10 % QF had acceptable sensory qualities similar or slightly higher to those obtained from control, except crumb color. Generally, the quinoa flour successfully replaces wheat flour in production of pan bread up to 10% without any unfavorable change in the sensory characteristics of prepared bread.
5.5.4. Texture profile analysis
Texture of pan bread texture was determined as hardness, springiness, cohesiveness, chewiness and gumminess by using texture profile analyzer (TPA). Hardness (g) was gradually increased by increasing the substitution level by quinoa flour. On the other hand, hardness of pan bread was also gradually increased during storage of pan bread at room temperature (25̊c ±2). The relative increasing of hardness of pan bread made from wheat flour containing quinoa flour lower than of pan bread made by 100% wheat flour (control sample). Springiness, cohesiveness, chewiness and gumminess of pan bread were also gradually increased by increasing the substitution levels by QF. For the effect of storage of pan bread on these parameters, the results showed that, hardness, chewiness and gumminess increased gradually by increasing the storage period of pan bread (0 to 72h), but springiness and cohesiveness were decreased. The relative increasing or decreasing of these parameters of pan bread containing quinoa flour was lower than that of control pan bread.
5.5.5. Stalling characteristics
Sensory properties of pan bread (crumb softness, crumb folding and mouth feeling) were determined after cooling and storage for (24, 48 and 72 h) at (25̊c ±2). from the results, it could be observed that, the staling rate of pan bread increased gradually (low freshness) during storage. The lower reduction in staling value (high freshness) was noticed in bread sample which prepared by partial substituted with 5% QF compared to pan bread containing 10 or 15% QF.
5.6. Baking quality of biscuit
5.6.1. Chemical composition
The results revealed that , crude protein , lipids , ash and crude fiber contents of biscuit samples had gradually increased with increasing the substitution level with QF (from 20 to 25%) compared to biscuit control sample, but NFE was decreased.
5.6.2. Physical properties
The weight, diameter and spread ratio of biscuit samples were gradually increased as substitution level by QF increased. Spread ratio was increased from 5.59 for control biscuit sample to 6.90 and 7.19 for biscuit samples made from weak wheat flour containing 20 and 25% QF, respectively. Also, gradually decrease was noticed in both biscuit volume, specific volume and thickness for biscuit samples which prepared by substitution of WF with QF.
Generally, the weight and thickness values for biscuit prepared from WWF substituted with QF were higher than those for biscuit prepared from SWF at the same substitution level but the diameter and spread ratio values of WWF biscuit, were lower than biscuit made from SWF.
Results showed that, the crust color of biscuit samples partially substituted with QF had significantly lower lightness (L*) value compared to control sample. Redness (a*) value of crust biscuit samples were significantly different between all treatment. Addition of QF at 20 or 25% significantly increased (a*) value compared to control sample. On the other hand, the crust of biscuit samples prepared from weak wheat flour containing 20 %QF showed higher (b*) values compared to other samples.
5.6.3. Sensory evaluation
from the obtained results, it could be concluded that, there were non-significant differences in texture, taste and mouth feel between control biscuit sample and biscuit samples prepared from weak wheat flour substituted with 20 or 25 %QF. Concerning overall acceptability, there were non-significant differences between control sample made from weak wheat flour and biscuit samples containing 20 or 25% quinoa flour. Control sample had a slightly higher score (8), but the score of biscuit containing 20 and 25% QF were 7.5 and 7.0, respectively. Generally, from the sensory acceptability rating, it was observed that quinoa flour could be incorporation up to 25% level in the formulation of biscuit made from weak wheat flour without affecting their sensory quality.
5.6.4. Texture profile analysis
Hardness of biscuit samples containing QF were significantly different from control samples, higher values of hardness were recorded to biscuit sample prepared from wheat flour containing 25% QF. The height (mm) of biscuit samples were slightly decreased by increasing the level of QF addition. On the other hand, the higher values of distance (mm) and peak time (s) were recoded to biscuit containing 25%QF. Also, non-significant differences could be observed between the control sample and biscuit samples containing QF for stickiness.
5.7. Baking quality of gluten-free biscuit
5.7.1. Chemical composition
from the obtained results, it could be observed that, there were significant differences between gluten-free biscuit samples prepared from 100%QF (T1)and biscuit samples made from composite flour (70% QF+15% CF+15% RF), (T2) and (40% QF+30% CF+ 30% RF), (T3). Biscuit made from 100% QF (T1) had the highest content of moisture, crude protein, lipids, ash and crude fiber compared to other treatments (T2 and T3). These contents mentioned above were gradually decreased by increasing the substitution level by corn and rice flour (T2 and T3) compared to (T1).
5.7.2. Physical properties
The weight of biscuit samples were gradually decreased as substitution level by corn and rice flour increased. On the other hand, volume, (cm3), specific volume, thickness (mm) and spread ratio of biscuit (T1) were 19.80, 1.49, 5.00 and 12.00, respectively. The above mentioned values was increased to 20.70, 1.65 and 5.50 respectively for biscuit samples (T3).
The lowest value of lightness (L*) was recorded to the crust of biscuit (T2) compared to biscuit (T1 and T3). On the other hand, the high (a*) value was recorded for biscuit contained QF (T1 and T2) compared to (T3). Also, the results it could be noticed that the minimum value of (b*) was found for biscuit containing 100% QF (T1) compared to (T2 and T3). Generally, with increasing the percentage of added corn and rice flour to QF, the values of whiteness (L*) and yellowness (b*) increased, but (a*) value decreased. It could be concluded that, the gluten-free biscuit contained QF (70%) was darker compared to other samples contained QF (40 and 100%).
5.7.3. Sensory evaluation
The results showed that, there were non- significant differences in crust and crumb color of biscuit samples between all treatments. Also, the results showed that non-significant differences recorded between all treatments for taste, mouth feel and total acceptability of biscuit samples, but there were slightly differences between biscuit samples (T1, T2 and T3) for surface characteristics and texture. Generally, it could be concluded that the gluten-free biscuit produced by 100% QF or mixed with different levels from corn and rice flour gave sensory acceptable for human celiac disease.
5.7.4. Texture profile analysis
from the obtained results, it could be observed that, there were significant differences could be recorded between all treatments (T1, T2 and T3) for the hardness (g), height (mm) and stickiness (g) of biscuit samples. The highest value of hardness and lowest value of height were recorded for biscuit (T1), but the highest value of stickiness was noticed in (T3). Also, there were non-significant differences could be observed between all treatments of biscuit (T1, T2 and T3) for distance (mm), and peak time (s).