Physico-chemical characteristics
The fibre enrichment in the form of amaranth flour produced significant differences in the pH of dough and breads (Table 2). The pH of dough increased with amaranth fortification but statistically the mean values differed significantly (P<0.05) only at 15% level. The pH of breads increased with baking. The amaranth flour incorporated breads had significantly (P<0.05) higher pH than control which might be due to higher pH of amaranthus flour than that of wheat flour which was replaced
(Tamsen et al., 2018).
Incorporation of amaranth flour produced an increase in water activity values which might be due to the higher water absorption capacity of fibres as well as due to the smaller particle size of amaranth flour and as the size decreases the surface area increases which tends to absorb more water. The amount of fiber can play an important role in binding water and increasing the moisture content of final products. Higher water binding capacity is associated with the fibre and protein content as water percolates inside fibre pores and binds through hydrogen bonds
(Liu et al., 2019). The bread with highest level of amaranth (T3) showed the highest water activity that differed significantly (P<0.05) from rest.
The baking yield was positively affected by amaranth incorporation as the yield increased with the level of incorporation (Fig 1). The increased yield might be attributed to the higher fibre content of amaranth flour especially IDF and various studies indicate that IDF such as lignin, cellulose and hemicelluloses usually have high water-holding capacity.
The baking loss of the treatments decreased significantly (P<0.05) with the increase in level of replacement Fig 1. The lower baking losses might be due to higher moisture content as well as because of lower fermentation due to higher replacement of whole wheat flour which is the major source of starch. Similarly, lower moisture loss was observed in amaranth breads in comparison to whole wheat breads
(Liu et al., 2019).
Amaranth flour incorporation increased the moisture protein ratio of bread Fig 1. The 15% amaranth containing bread showed the highest ratio while control the lowest. A low moisture protein ratio is desirable for stability of a product. Moisture retention values influences the product eating quality thus higher moisture retention is related to a better product. The moisture retention increased significantly (P<0.05) with each level of substitution Fig 1. This increase in moisture retention might be due to higher amaranth flour level which provided higher insoluble fibres than wheat flour
San-Penella et al. (2013).
Proximate and physicochemical attributes
The moisture values increased with the level of incorporation and 15% (T3) amaranth containing bread evinced the highest moisture content (Table 2). The moisture increase might be due to the inclusion of a greater amount of insoluble dietary fibre with the amaranth flour. The higher fibre content of amaranth might be implicated for the increase in moisture content of treatments as the amount of fibre can play important role in water binding and thus increasing the moisture content of breads
(Pourafshar et al., 2015).
The protein content of samples did not show significant (P>0.05) differences. Results were similar to
Pourafshar et al., (2015) reporting that amaranth incorporation at 20% in traditional Iranian breads did not much affect their protein content. But amaranth incorporation at higher levels
i.e. more than 20 per cent have been reported to increase the protein content in breads (
Bodroza-Solaroza et al. (2008);
Tosi et al., 2002). The fat content increased with replacement but the differences were more prominent (P<0.05) in 10% and 15% level. The results were in agreement with the findings of
Nasir et al., (2020). The ash content of breads was not much affected by incorporation until the level of incorporation was high enough
i.e. at 15% level.
Dyner et al., (2007) observed significant increase in mineral and dietary fibre contents in bread and pasta by amaranth flour substitution at levels up to 20 g/100 g.
Liu et al., (2019) studied the feasibility of amaranth as an alternative gluten-free ingredient to improve the nutritional quality of gluten-free breads and reported that acceptable breads were produced which were also characterized by having significantly higher levels of minerals.
The carbohydrate values decreased significantly (P<0.05) with each level of replacement. This decrease in carbohydrate values might be attributed to the proportionate decrease of whole wheat flour from the formulation resulting into lower starch level. The carbohydrate content of amaranth is lower than that of whole wheat
(Liu et al., 2019). The energy values showed significant (P<0.05) decrease with the increase in amaranth flour level. There was significant (P<0.05) decrease at each level of replacement of whole wheat flour with amaranth flour.
The dietary fibre contents increased significantly (P<0.05) with amaranth flour incorporation in breads. Similar results were also reported by
San-Penella et al. (2013);
Tosi et al., (2002) and
Bodroza-Solaroza et al. (2008) in amaranth incorporated breads.
Gambus, et al., (2002) also observed higher fibre content in amaranth incorporated breads as compared to their gluten free counterparts. Among fibre components the insoluble fraction evinced similar significant (P<0.05) increase in values with amaranth inclusion. The soluble fraction showed significant (P<0.05) increase in values from control but among treatments the 5% and 10% amaranth containing breads differed non-significantly (P>0.05) in soluble fibre content; while 15% amaranth containing bread contained significantly (P<0.05) highest soluble fibre fraction.
Total phenolics
The total phenolic content decreased with whole wheat flour replacement by amaranth flour (Table 2). The decrease was statistically significant (P<0.05) at higher levels of amaranth incorporation. The lower total phenolic content in treatments might be due to lower phenolic content in amaranth flour than whole wheat flour. Thus, higher level of replacement significantly affected the total phenolic content.
Gelinas and McKinnon (2006) found that breads baked from wholegrain flours contain much higher amount of phenolic compounds compared with those baked from refined flours or white breads.
Ragaee et al., (2011) reported that inclusion of 30 g/ 100 g of wholegrain flours into the bread formula resulted in an increase in the content of both phenolic fractions, free and bound, as compared to the control bread.
Instrumental texture profile analysis
The hardness values of amaranth incorporated meat breads increased with the level of incorporation (Table 3). The T3 and T2 samples required significantly (P<0.05) higher force of compression than control. The effect might be due to the dilution of gluten content.
Springiness values indicate the rapidity and degree of recovering after a deforming force.
Pourafshar et al., (2015) reported that firmness of barbari bread increased by replacing 20% of wheat flour with amaranth flour. Whereas contrary to our results
San-Penella et al. (2013) observed amaranth substitution did not produce significant changes in crumb hardness until 40 g/100 g substitution. The springiness values increased with amaranth incorporation which differed significantly (P<0.05) from control. This increased springiness of treatment might be attributed to the six times higher lipid content of amaranth flour than wheat flour, which act as a surface-active agent
San-Penella et al. (2013). The higher lipid content of amaranth improves elasticity in breads by stabilising entrapped gases
Alvarez-Jubete et al. (2010). Similar studies indicating higher elasticity in amaranth incorporated bread with increasing level of incorporation have been reported earlier
(Nasir et al., 2020).
The cohesiveness and gumminess values decreased non-significantly (P>0.05) with the amaranth replacement. The decrease in values might be attributed to the poorer matrices of bread due to higher gluten reduction. The chewiness value increased with the increase in amaranth flour level in breads. Resilience is breads is a combined function of proteins, fibres and carbohydrates
(Liu et al., 2019). Amaranth replacement did not significantly affect the resilience of breads which might be due the fact that the increase in fibre content was counteracted by the decrease in carbohydarate while, change in protein content was insignificant (P>0.05).
Instrumental colour analysis
Colour is a perceived quality that influences consumer purchasing behavior (
Umaraw and Verma, 2016). The result revealed that redness values increased from 2.68 in control to 3.94 in T3 (Fig 2). A proportionate significant (P<0.05) increase was observed with level of incorporation which might be attributed to the inherent dark colour of amaranthus. The yellowness values increased non-significantly (P>0.05) with the level of amaranth addition in breads. The mean values for chroma also increased non-significantly (P>0.05) from 16.05 in control to 17.60 in T3. Amaranth addition to developed breads brought about significant effects at higher level of incorporation. The mean values differed significantly (P<0.05) at 10 % and 15% replacement from control and T1 (5%).
Sensory evaluation
Colour and appearance of crust and crumb of developed amaranth incorporated breads was rated higher than that of control by the sensory panelists (Table 4). Amaranth incorporation produced darker crusts which was preferred over lighter colour of control. Increased darkness might be attributed to the inherent colour of the amaranth flour. Amaranth flour contains betacyanin pigment which imparts darker colour to the final product in comparison to wheat which lacks this pigment
(Tamsen et al., 2018). Similarly,
Rosell et al., (2009) observed that replacement of wheat flour by up to 50% of amaranth led to darker breads with good sensory perception.
The mean porosity values did not differ significantly (P>0.05) among all the samples. This could be due to higher stabilization of gases by high polar lipids present in amaranth during bread making improving its elasticity
Alvarez-Jubete et al. (2010) that counteracted the gluten dilution effect of amaranth. The flavour of bread crumbs is largely affected by enzymatic fermentation while that of crust is affected by heating during baking. Sensory panelists rated T3 significantly (P<0.05) higher than the control for flavour.
Rosell et al., (2009) observed that sensory analysts preferred nutty flavour of amaranth breads over white breads. The texture of breads evinced non-significant (P>0.05) differences in scores. The lower scores of treatments could be due to the more closed structure. Similar to texture meat flavour intensity did not differ significantly (P>0.05) in all samples but panelists scores decreased with the increase in amaranth flour content. The lower scores could be attributed to the stronger masking effect of amaranth over meat.
The aftertaste of bread samples as perceived by panelists increased with the level of amaranth that was highest at 15% replacement. This might be due to the higher fat content of the sample as amaranth flour contains approximately six times higher fat content than wheat flour
Alvarez-Jubete et al. (2010). The overall acceptability scores of sensory panelists rated T2 highest which differed non-significantly (P>0.05) with T1 and T2 but significantly (P<0.05) from control. This might be attributed to the texture, porosity and meat flavour intensity which was perceived strongly in T2 without affecting the bread qualities. The flavour attribute, the freshness, colour, texture and biting properties dramatically influence the overall perception of bread. Similarly,
Tosi et al., (2002) reported that upto 8% substitution of wheat flour with hyperproteic whole amaranth flour produced breads with greater quality and acceptability.