3.1. Comparison of Nutritional and Functional Properties of ALP and RWF
Table 2 shows the comparative study between ALP and RWF for their nutritional composition and functional properties. It is noticeable that ALP is a good source of protein and ash. Moisture, fat, and total carbohydrate content were significantly (
p < 0.05) higher in RWF. Moisture, ash, protein, fat, and total carbohydrate of ALP were almost similar to that reported by Hamman [
35]. In the case of RWF, the results were in agreement with [
36,
37,
38].
Different functional properties of ALP was compared with RWF and shown in
Table 2. Functional properties of powder/flour reflect endogenous physical and chemical properties that influence food properties during handling, storage, processing, and analysis, among other things [
39]. The bulk density of RWF (0.65 ± 0.05 g/mL) was significantly (
p < 0.05) higher than ALP (0.48 ± 0.04 g/mL).
Table 2 suggested that WAC (g water/g sample) were significantly (
p < 0.05) higher in ALP than RWF. WAC plays a very important role in the textural quality of food products such as soups, ground meat, dressing, sauces, and bakery products. High WAC leads to swelling properties which provide consistency, thickening, viscosity, adherence properties, increasing weight and decreasing of height, specific volume, and volume of the cakes [
40,
41]. Therefore, higher WAC of ALP/RWF might cause an increase in weight, height, and volume of the cakes. The study also suggested that OAC (g/g) and swelling power (%) was significantly (
p < 0.05) higher in ALP than RWF. Comparative analysis for mineral content shows that ALP contains significantly higher amount of iron (Fe) than RWF; whereas RWF contains higher amount of calcium (Ca) and potassium (K). Total polyphenols and total flavonoids content of ALP were found to be 75.01 ± 3.22 mg of GAE/100 g and 6.87 ± 0.18 mg of CE/100 g, respectively. However, antioxidant capacity of ALP (measured as ORAC hydrophilic and total) was found to be 49.55 ± 1.2 µmol of TE/g. Plain (loaf) cakes fortified with ALP are high in antioxidants and a viable option for making healthy baked goods.
3.2. Particle Size Analysis of Mix Flour (ALP and RWF) and RWF
Figure 1 illustrates the particle size distribution of mixed flour (4, 6, and 8% ALP mixed with RWF) and control flour (RWF). Bimodal particle size distribution was observed for all flours, with two distinct peaks for mixed flour and no distinct peak for RWF. The results are in agreement with [
11,
21,
42].
Figure 1 also indicated that most of the flour tested had particle sizes ~100 µm, indicating a higher volume of flour. Particle size distribution of mixed flour and RWF was ranged from 0.1–100 µm. However, volume of particles for all mixed flour was at ~140 µm and for control (RWF) at 88 µm. This result suggested that RWF has lower protein and fiber content as smaller particle size (SPZ) flour suggests low protein and fiber content [
43]. SPZ flour gave hard dough with higher density results in less development of biscuits, cake, and bread [
11,
44]. Hence, coarser particle size flour from composite or mixed flour is the most desirable for cake preparation. Mean volume diameter (MVD) (d4,3: 68.85 µm) and surface mean diameter (SMD) of RWF (d3,2: 25.75 µm) were less than (
p < 0.5) all mixed flour (d4,3: 78.15 µm; d3,2: 30.55 µm, respectively). There was no significant difference (
p > 0.5) among 4, 6, and 8% mixed flour. The particle size of flour often affects the water absorption capacity, swelling power, and density of cakes. Flour with fine particle size has a higher density and less effective baking properties [
11]. Therefore, coarser composite flour is desired for the preparation of cake.
3.3. Physical Properties, Proximate Composition, and Mineral Content of Control Cake and Cake-fortified with ALP
Table 3 shows different physical properties of the developed cakes. Weight of the ALP-fortified cakes (225.5–250.8 g) was higher than control cake (216.6 g) due to the higher water absorption capacity of ALP (4.76 ± 0.06) than RWF (4.15 ± 0.05) [
36]. As a result, ALP supplementation increased the weight of the cakes. It was also noticeable that weight of cakes (from S
3 to S
1) gradually increased with the increasing percentage of ALP due to the lower baking loss and higher WAC of ALP [
12]. Cakes with varying percentages of ALP had lower volumes (300–310 cm
3) than the control cake (327 cm
3). This might be due to a reduction in gluten content due to supplementation. Research also revealed that substituting nonglutinous flour for wheat flour resulted in lower product volumes [
45]. It was also observed that the volume of the cakes decreased with an increasing percentage of ALP (from S
3 to S
1) due to the absorption of air, oil, and fiber components [
46]. Specific volume of the cakes (from S
3 to S
1) gradually decreased with an increasing level of ALP in the formulation. This could be due to a reduction in gluten content due to supplementation. Previous research also revealed that the specific volume of the developed cakes gradually decreased with increasing levels of nonglutinous flour substitution [
47]. The height of the control cake (6.70 cm) was found to be higher than that of the cakes containing ALP (6.50–5.65 cm). The decrease in height from 6.70 to 5.65 cm of the cake could be the result of reduction in gluten content of the blends due to supplementation with ALP [
38]. When the ALP in the dough was increased, the cake weight increased while the weight loss decreased. Baking loss (%) of the ALP supplemented cakes (S
3 = 47.03%, S
2 = 45.92% and S
1 = 42.66%) were lower than control cakes (50.52%). ALP supplementation of RWF reduced weight loss due to ALP’s higher protein and fiber content than RWF [
12].
Table 3 shows that L* of crumb decreased with increasing ALP percentage (from 67.90 to 53.28). S
2 (6%) and S
1 (8%) did not show any significant difference (
p > 0.05) for L*-values. a*-value of cake crumb increased with ALP supplementation in dough. However, as ALP concentration was increased, the b*-values of cake crumb decreased. ALP used for cake processing was less light, less yellow, and more reddish in color (
Table 2) than RWF, resulting in lower L*, b*, and higher a*-values.
The ALP supplemented cakes were analyzed for their nutritional composition (
Table 3). Moisture content analysis showed that replacing RWF with ALP results in a gradual increase in moisture content in cakes. This might be due to low water-binding capacity of ALP protein, high fiber content of ALP, and lower baking loss of supplemented cakes. However, research revealed that non-wheat proteins increased the water absorption of dough due to high water-binding capacity [
48]. This could be due to ALP’s higher fiber content than RWF, which helps to retain moisture and contributes to the higher moisture content of composite loaf cakes [
49]. Lower baking loss, on the other hand, is responsible for the higher moisture content of the ALP-supplemented plain cakes. Furthermore, higher initial moisture content may result in an increase in the moisture content of the final products. Protein content of all samples was higher than the control sample, as ALP is a rich source of protein. For instance, dietary protein is required for functional needs such as improving health, muscle, and growth [
44]. Consumption of cakes enriched with 8% ALP can easily supplied recommended dietary allowance (RDA) of protein for healthy people. Fat content of S
4 was the maximum (22.24%) among all samples though it is not significantly different (
p > 0.05) from S
3. Sample S
2 and S
1 were not significantly different (
p > 0.05) with each other. It was observed that ash content cake increased gradually with the addition of ALP. 8% ALP (S
1) cake had the highest ash content (2.95%) and revealed a significant amount of minerals present in the ALP.
For an adult aged 19–50 years, 100 g plain cake enriched with 8% ALP contribute more than 15% RDA for iron, compared to 8% iron contribution from control cakes. The result suggested that 100 g plain cake enriched with 8% ALP contributes more than 6% RDA for calcium, compared to 8% iron contribution from control cake for an adult aged 19–50 years based on Institution of Medicine, Food, and Nutrition Board [
50]. The results suggested that ALP could be used as an alternative protein source in bakery products. Total carbohydrate content decreased in ALP-enriched cake (from S
3 to S
1) with increasing amount of ALP in dough. This may be due to the lower percentage of carbohydrate present in ALP determined in the present study (49.37%) than that of wheat flour (72.46%) [
36]. Total polyphenols and antioxidant activity (measured as ORAC) increased in ALP enriched cake (from S
3 to S
1) with increasing amount of ALP in dough, as ALP is a rich source of polyphenols and flavonoids.
Evenness and edges are symmetrical parameters. Evenness is classified as even, medium even, or uneven. According to subjective analysis, the crust color of the control cake was brown, whereas the crust color of the 8% ALP enriched cake was brownish dark and the consistency changed from tender to medium tender. Crum color of the cakes was brownish yellow, less brownish yellow, less darkish brown, and darkish for control, 4, 6 and 8% ALP supplemented cakes, respectively (
Table 4). Control sample (S
4) and 4% ALP (S
3) showed appetizing flavor though 6 and 8% ALP-enriched cake shows slight bitter flavor. Subjective analysis also suggested that closely bounded grain was noticed for control (S
4) and 4% ALP (S
3), whereas less airy for both S
2 (6% ALP) and S
1 (8% ALP). Because of the increase in ALP, the size and shape of the grain of the crumb lost their uniformity (
Table 4).
3.4. Effect of ALP on the Textural Properties of Cakes
Textural profile of plain cake samples is shown in
Table 5. It can be observed that the hardness of the plain cake samples increased with the increasing percentage of ALP from 0 to 8%. Hardness of ALP-enriched cakes was directly correlated to the volume of the testing materials. This was due to higher protein content and a better water absorption capacity in the mixed flour [
11]. Decreasing the volume increased the hardness due to lack of gluten in the mix. Elasticity represents the springiness which determines the extent of recovery between the first and second compression. Springiness value of plain cake was in the range 0.79–0.92. 8% ALP-fortified cake (S
1) had significantly lower springiness than the other cake samples. There was no significant difference among the three samples (S
2, S
3, and S
4). Again, cohesiveness, gumminess, chewiness, and resilience of plain cake samples are 0.68–0.77, 4.87–5.12, 4.09–4.48, and 0.37–0.38, respectively. Lower cohesiveness and springiness found in this study are related to the water absorption capacity, low gluten, and higher fat content of the dough. However, the result indicated that that only sample S
1 (8% ALP) was significantly different with other plain (loaf) cake samples in cake resilience values. These findings were not surprising given that the lack of gluten structure results in a crumbly, brittle crumb texture [
51]. It was noticeable that all textural parameters decreased due to addition of ALP and differed significantly (
p < 0.05) from the control cake. This reduction in loaf textural parameters could be attributed to the higher fat content in the formulations, which disrupts the gluten network development while lubricating and hydrating the entire mix [
52,
53].
3.5. Organoleptic Parameters of ALP Supplemented Cakes
One-way analysis of variance (ANOVA) suggested that there was a significant (
p < 0.05) difference in color acceptability among the plain (loaf) cakes. Sample S
3 was most acceptable by the panelist than other cakes. In case of flavor preferences, one-way ANOVA showed that there was significant (
p < 0.05) difference in flavor acceptability. Sample S
1 was most preferred, and S
3 was least preferred relative to other sample at 5% level of significance. ANOVA analysis suggested that there was significant texture difference (
p < 0.05) between control loaf cake and loaf cakes containing ALP. Control cake (S
4) was more acceptable and significantly different from the other cake samples. For overall acceptability, ANOVA analysis suggested that Sample S
3 (4% ALP) was the most preferable relative to others (
Table 6). The sample with 4% ALP showed the finest sensory characteristics in terms of color, texture, flavor, and overall acceptability. However, the other samples were also found acceptable. A DMRT analysis revealed that 4% ALP loaf cakes were significantly better in color, texture, flavor, and overall acceptability than other plain (loaf) containing 0, 4, 6, and 8% ALP. However, increasing the amount of ALP decreased the level of overall acceptability.