Effect of independent variables on overall acceptability
The pizza base’s overall acceptability was evaluated by considering sensory attributes such as color, taste, aroma, flavor and texture. Ratings on a 9-point hedonic scale ranged from 6.2 to 8.7 as depicted in Fig 1 and these variations were influenced by changes in the independent variables (Table 1). The quadratic model was found to be highly significant, as evidenced by an F-value of 19.57 (p< .0001) as shown in Table 2 and there was no significant lack of fit. The model is deemed appropriate due to its high coefficient of determination (0.9073). The quadratic model that describes the relationship between the significant variables and overall acceptability in terms of coded values is expressed in the following equation:
Overall acceptability = 10.4515 * A + 10.2033 * B + 2.73613 * C - 8.11191 * AB + 7.73057 * AC - 0.736872 * BC
In the depicted figure, it’s evident that RWF is the primary influencing factor on overall acceptability, with LMF and PMF flours following in importance. The data illustrates that as the quantity of refined wheat flour increases and millet flours decrease, the overall acceptability of the pizza base increases, reaching a maximum limit. This observation is consistent with findings from prior research
(Biradar et al., 2021). Conversely, the decline in overall acceptability with a higher proportion of millets can be attributed to an increase in the hardness of the base and the emergence of a bitter sensation associated with millets.
Effect of independent variables on antioxidant
The capacity to scavange DPPH in the pizza base ranged from 91.48% to 95.88% and these variances were impacted by alterations in the independent variables, as detailed in Table 1. The quadratic model was determined to be remarkably significant, possessing an F-value of 44.42 (p<.0001), with a lack of fit that was not considered significant as shown in Table 2. The model is deemed appropriate due to its elevated coefficient of determination (0.9073). The quadratic model, delineating the relationship between the pivotal variables and antioxidants in terms of coded values, is articulated in the subsequent equation:
Antioxidant = 87.6341 * A + 94.1213 * B + 102.776 * C + 3.37244 * AB + 2.57498 * AC - 14.8314 * BC
The F-value analysis suggests that PMF is the predominant factor influencing the antioxidant property, while RWF shows no significant impact as shown in the Fig 2. Previous research has consistently demonstrated that polyphenols exhibit remarkable biological activity and antioxidant capabilities. Nevertheless, the typical decline in bioactivity observed in the baking of fortified foods primarily results from the thermal degradation of these functional components
(Li et al., 2022). Antioxidant reduces with decrease in quantity of PMF and a increase in the ratio of LMF. This suggests that augmenting PMF can enhance the pizza’s antioxidant capacity. Similar results was reported by
(Xiao et al., 2023) in which cake prepared using proso millet flour fermented with dietary fiber had increased antioxidant activity followed by cake made using proso millet flour. These results showed PF-based cakes had improved the antioxidant activity of the cakes. These findings imply that including PMF in pizza may contribute to the protection against oxidative stress and may play a preventive role in chronic diseases.
Effect of independent variables on hardness
The pizzabase hardness exhibited a range of fluctuations, ranging from 2344.27 g to 4987.21 g and these fluctuations were influenced by variations in the independent variables as presented in Table 1. The quadratic model was determined to be highly significant, with an F-value of 60.17 (p<.0001) and the lack of fit was deemed not significant. The model is considered appropriate due to its substantial coefficient of determination (0.9678) as shown in Table 2. The quadratic model, which describes the connection between the significant variables and antioxidants in coded values, is expressed by the following equation:
Texture = -2158.51 * A + 3789.78 * B + 6662.27 * C + 6796.42 * AB + 446.896 * AC -1358.66 * BC
RMF emerges as the primary factor influencing the firmness of the pizza base, with LMF and PMF following in significance as shown in Fig 3. Firmness is chiefly associated with density and chewiness reflects the internal resistance of the food structure, both of which are notably essential indicators for assessing the quality of flour-based products, as highlighted in the study by
(Li et al., 2020) As the proportion of RMF increases, there is a reduction in the pizza base’s firmness. Conversely, an increase in the presence of millet results in heightened firmness of the pizza base. The correlation between increased firmness and elevated chewiness in the product is primarily due to the positive relationship between firmness and chewiness, as noted by
(Xiao et al., 2023). The increase in firmness can be attributed to millet’s lack of gluten, which leads to reduced elasticity and structural formation, in accordance with the findings of
(Upadhyaya et al., 2016). When mixing dough, gluten plays a crucial role in creating a structure that traps carbon dioxide produced during fermentation. When gluten-free flours replace wheat flour, the reduced gluten content results in a weaker dough network, leading to denser and harder pizzabase compared to pizzabase made with gluten-containing flour, as shown in a study by
(Mannuramath et al., 2015). Further more, the fiber content in LMF and PMF can interact with starch through its water-binding and embedding capacity. This interaction may delay the aging process of starch and assist in preserving the textural characteristics of flour-based products. The composition involving a 40% replacement exhibited favorable texture, aligning with the conclusions of
(Mastrascusa et al., 2021).
Effect of independent variables on protein
The protein content in the pizza base exhibited a range of fluctuations, ranging from 9.56% to 13.71% and these changes were impacted by alterations in the independent variables (as outlined in Table 1). The quadratic model was determined to be remarkably significant, boasting an F-value of 39.87 (p<.0001) and there was no notable lack of fit as shown in Table 2. This model is deemed appropriate due to its elevated coefficient of determination (0.9522). The quadratic model that delineates the association between the significant variables and antioxidant content in terms of coded values is expressed in the following equation:
Protein= 7.76469 * A + 13.3239 * B + 18.2907 * C + -4.04048 * AB + 2.09445 * AC + -10.0821 * BC
The analysis of the F value indicates that protein content is predominantly influenced by PMF, followed by LMF and RWF as shown in Fig 4. A reduction in the millet content of PMF corresponds to a noticeable decrease in protein levels. Notably, LMF exhibited significantly lower protein content when compared to PMF. (
Mannuramath, Yenagi et al., 2015). The increased contribution of PMF can be attributed to variations in nitrogen content and Proso millet proteins are characterized by their high amino acid content, which makes them valuable resources for the food industry in the development of emerging gluten-free protein sources
(Kumar et al., 2020; Wang et al., 2021).
Optimized composition
Using the design expert software, the desirabilty of 0.911 was obtained. The preferred ration were the desrability was maximum was RWF: 40 g, LMF: 33.3334 g, PMF: 26.6666 g which is being depicted in Fig 5. The optimized composition was subjected to further physio-chemical analysis whose results were shown in Table 3.