Effect of Processing Methods on Quality Characteristics of Maize Flour ^†

Abstract

Maize flour (MF) is a cheap and common cereal product that can be used in various foods. However, different processing methods can affect its quality and suitability for different purposes. This study compares the effects of three processing methods (grain non-soaking (GNSM), grain soaking (GSM), and nixtamalization (NIX)) on the nutritional, pasting, and functional properties of MF. MF samples (GNSM-MF, GSM-MF, and NIX-MF) were analyzed using standard laboratory techniques. Protein and moisture contents ranged from 9.34 to 10.12% and 5.35 to 7.05%, respectively, with NIX-MF having significantly (p < 0.05) higher protein content. Calcium, iron, and zinc contents ranged from 3.64 to 10.91 mg/g, 3.69 to 7.64 mg/g, and 1.45 to 1.92 mg/g, respectively. GNSM-MF had the lowest calcium content. Peak, breakdown, final, and setback viscosities were 980.25–2904.15 RVU, 91–1147 RVU, 778–1210 RVU, and 331.5–919 RVU, respectively. GSM significantly (p < 0.05) increased peak, breakdown, final, and setback viscosities. Water-holding capacity (WHC), emulsifying capacity (EC), and oil absorption capacity (OAC) values of MF ranged from 78.93 to 111.95%, 4.97 to 42.18%, and 160.27 to 186.13%, respectively. High protein and calcium contents in NIX-MF make it a nutritious option for pregnant women and children. GSM-MF might be incorporated into snacks, complementary foods, and puddings. This study provides insights into appropriate selection of maize flour processing methods based on food application.

1. Introduction

Maize, a staple cereal, is cultivated and processed for food primarily in developing countries across Africa. With the global population projected to exceed 9 billion by 2050 [1], there is an urgent need to address the growing pressure on agriculture and food processing sectors to develop affordable, accessible, and nutritious food products. Processing techniques such as soaking and nixtamalization have been established to enhance the nutritional quality of cereals by reducing antinutrient content and improving the bioavailability of key nutrients [2,3].

Soaking has been reported to significantly decrease the antinutrient content of cereals (polyphenols, phytate); it also increases protein digestibility in vitro and improves the bioavailability of zinc and iron [4]. Nixtamalization, an alkaline processing technique, holds particular promise for improving maize-based food products. By removing the pericarp through hemicellulose disruption, this method enhances nutrient bioavailability, especially that of calcium and niacin, while also improving protein quality [5]. These attributes make it especially beneficial for vulnerable populations like children and pregnant women, who require higher calcium intake. Low processing costs coupled with simplicity of technology and product diversity from the same unit operations have recently drawn the interest of researchers to alkaline cooked maize.

Despite its potential, the adoption of nixtamalization and other processing techniques in developing countries often prioritizes end-use over nutritional outcomes. This has limited the ability to fully harness their benefits. A more systematic comparison of maize flour quality derived from different processing methods is needed to guide the choice of techniques that balance simplicity and nutritional delivery. This study aims to compare three maize flour processing methods and evaluate their effects on the quality characteristics of maize flour, thereby providing insights into optimizing processing techniques for improved nutritional and functional outcomes.

2. Materials and Methods

2.1. Material

White maize grains were procured from a local market in Ibadan, Oyo State, Nigeria. Damaged grains and foreign materials were manually sorted out to ensure purity. The cleaned grains were stored in airtight containers to maintain freshness and prevent contamination before milling.

2.2. Maize Flour Processing Methods

2.2.1. Grain Non-Soaking Method (GNSM)

Cleaned whole maize grains (10 kg) were milled using a locally fabricated disc attrition mill [6], which is widely utilized in small-scale grain processing. The resulting maize flour was stored in airtight polythene bags to preserve its quality before analysis.

2.2.2. Grain Soaking Method (GSM)

A similar quantity of whole maize grains as that used for GNSM (grain non-soaking method) was soaked in water at room temperature for 3 h and then drained. The soaked grains were dried in an oven (Eurosonic, SW-XY, China) at 55 °C for 16 h. Milling was performed using the same method as GNSM, and the resulting flour was stored in airtight polythene bags to maintain quality [6].

2.2.3. Nixtamalization (NIX)

The nixtamalization process was performed following the method described in [7] (2007). Ten kilograms of maize grains were submerged in water at a 1:6 ratio, and 2% lime [Ca(OH)₂] was added. The mixture was cooked for 80 min and then allowed to stand for 14 h to complete the process. The nixtamalized grains were washed thoroughly under running water, with four rinses performed to ensure complete removal of residual lime. Drained grains were dried in a hot air oven at 55 °C for 12 h to reduce moisture content. The dried grains were then ground into flour.

2.3. Proximate Analysis

The proximate properties of maize flour, including ash, crude protein (determined by the Kjeldahl method), moisture, crude fibre, and crude fat (determined by solvent extraction), were analyzed following standard procedures of the Association of Official Analytical Chemists [8,9]. Carbohydrate content was calculated by difference using the formula:

Carbohydrates = (100 − (% Crude Proteins + % Lipids + % Ash + % Crude fibre + % Moisture))

2.4. Colour Properties Determination

Colour measurements of maize flours, including L* (lightness), a* (redness), and b* (yellowness), were obtained using a Hunter Lab colorimeter (Chroma meter CR-10, Osaka, Japan). The instrument was calibrated with the following standard values: L* = 96.9, a* = −0.04, and b* = 1.84. From these measurements, flour colour index, yellow index, browning index, degree of whiteness (%W), colour intensity (ΔE), hue angle (h°), and delta chroma (ΔC) were calculated using standard equations [10,11].

$$\Delta \mathrm{C}=\left(a^2+b^2\right){\displaystyle \raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$$

(1)

$$h^o={\tan }^{-1}\left({\displaystyle \raisebox{1ex}{$b$}\!\left/ \!\raisebox{-1ex}{$a$}\right.}\right)$$

(2)

2.5. Mineral Determination

The mineral assay of processed maize flour was conducted using an Atomic Absorption Spectrometer to determine calcium, iron, and zinc levels, following the method described by [9] (2005). This technique was selected for its accuracy and reliability in quantifying essential minerals important for nutrition.

2.6. Pasting Parameters Determination

Pasting parameters of maize flour samples were analyzed using a Rapid Visco Analyzer (RVA) (TECMASTER, Perten Instruments, Hägersten, Sweden) as described by [6] (2020). For each sample, 4 g of flour was weighed into an RVA container and mixed with 25 mL of distilled water to form a slurry. The slurry was heated and continuously stirred at 50 °C and 160 rpm for 10 s to ensure proper dispersibility. It was then held at 50 °C for 1 min before being heated to 95 °C over 8 min and held at 95 °C for an additional 5 min. The parameters measured included peak viscosity, pasting temperature, time to peak, breakdown, trough, final viscosity, and setback.

2.7. Functional Properties Analysis

The water-holding capacity (WHC), emulsion capacity (EC), and the oil absorption capacity (OAC) of maize flour were analyzed to evaluate its functional properties. For WHC, a modified centrifugation method, described in [12] (1996), was employed. Two hundred milligrams of maize flour sample were placed in a specialized tube, and 20 mL of water was added. The mixture was incubated at 25 °C with continuous agitation for 24 h. After incubation, the supernatant was discarded, and the sediment was weighed. The sediment was then oven-dried at 120 °C for up to 2 h, and its moisture content was measured. WHC was calculated as the amount of water retained per gram of the corresponding sample. The emulsion capacity (EC) and oil absorption capacity (OAC) of the maize flour samples were determined using a centrifugation method described in [9].

2.8. Statistical Analysis

Sample preparation and analyses were performed in triplicates to ensure precision and reliability of the results. The data obtained were subjected to analysis of variance (ANOVA), and mean values were separated using Duncan’s Multiple Range Test at a significance level of p < 0.05. The independent variables consisted of the processed maize flour samples: GNSM-MF (Grain Non-Soaking Method Maize Flour), GSM-MF (Grain Soaking Method Maize Flour), and NIX-MF (Nixtamalized Maize Flour). The dependent variables included measured values for proximate composition, mineral composition, colour properties, pasting parameters and functional properties.

3. Results

3.1. Proximate Composition

The proximate composition of maize flour produced by different processing methods is summarized in

Table 1. Proximate composition (%) of processed maize flour.

Sample	Ash	Crude Protein	Moisture	Crude Fibre	Crude Fat	Carbohydrate
GNSM-MF	1.12 a ± 0.13	9.15 b ± 0.18	7.05 a ± 0.07	2.41 a ± 0.06	3.60 a ± 0.27	76.64 a ± 0.60
GSM-MF	1.18 a ± 0.13	9.34 b ± 0.18	5.35 c ± 0.07	2.89 a ± 0.35	3.85 a ± 0.04	77.41 a ± 0.50
NIX-MF	1.37 a ± 0.08	10.12 a ± 0.16	6.30 b ± 0.14	1.05 b ± 0.03	3.25 a ± 0.29	77.92 a ± 0.35

Values are means of three replicates ± standard deviation. Values in columns with the same alphabet in superscript are not significantly different from each other (p < 0.05). GNSM-MF grain non-soaking method processed maize flour; GSM-MF: grain soaking method processed maize flour; NIX-MF: nixtamalized maize flour.

. The ash content ranged from 1.12% to 1.37%, with NIX-MF exhibiting the highest value and GNSM-MF the lowest. However, there were no statistically significant differences (p > 0.05) among the samples. Protein content varied between 9.34% and 10.12%, with NIX-MF having the highest value, significantly higher (p < 0.05) than those of GSM-MF and GNSM-MF. Moisture content ranged from 5.35% to 7.05%, and significant differences (p < 0.05) were observed across all samples. GNSM-MF had the highest moisture content, while GSM-MF exhibited the lowest. The crude fibre content of NIX-MF was significantly lower (p < 0.05) compared to GSM-MF, which showed the highest fibre content. No significant differences (p > 0.05) were found in the crude lipid content among the samples, though GSM-MF had the highest value at 3.85%.

3.2. Colour Properties

The colour properties of processed maize flour samples are presented in

Table 2. Colour characteristics of processed maize flour.

Samples	L*	a*	b*	Deltachroma ∆C	Colour Intensity ∆E	Hue Angle ho	Whiteness (%)	FCI	Yellowness Index	Browning Index
GNSM-MF	87.93 a ± 0.02	0.07 a ± 0.01	14.59 a ± 0.01	13.62 a ± 0.02	89.13 a ± 0.04	89.73 b ± 0.02	81.06 a ± 0.01	73.34 a ± 0.01	5.92 c ± 0.01	23.70 d ± 0.01
GSM-MF	88.83 a ± 0.01	0.09 a ± 0.01	14.68 a ± 0.01	13.71 a ± 0.01	90.04 a ± 0.01	89.64 b ± 0.01	81.61 a ± 0.01	74.15 a ± 0.03	5.90 c ± 0.02	23.61 d ± 0.02
NIX-MF	90.06 a ± 0.03	0.05 a ± 0.01	25.00 b ± 0.11	24.03 b ± 0.05	93.47 b ± 0.02	89.89 b ± 0.01	73.1 b ± 0.16	65.06 b ± 0.04	9.58 b ± 0.01	39.66 e ± 0.10

Values are means of three replicates ± standard deviation. Values in columns with the same alphabet in superscript are not significantly different from each other (p < 0.05). GNSM-MF: grain non-soaking method processed maize flour; GSM-MF: grain soaking method processed maize flour; NIX-MF: nixtamalized maize flour; FCI: flour colour index.

. The lightness (L*), redness (a*), and yellowness (b*) values ranged from 87.93 to 90.06, −0.05 to −0.09, and 14.59 to 25.00, respectively. Among the samples, GNSM-MF exhibited the lowest lightness, while NIX-MF showed the highest. No significant differences (p > 0.05) were observed in the lightness and redness values across the samples. However, NIX-MF was significantly different (p < 0.05) in yellowness, with nixtamalization notably increasing the yellowness of the maize flour sample. Hue values for all processed samples were below 90°, with NIX-MF having the highest hue angle (89.89°).

3.3. Mineral Composition

The effect of processing methods on the mineral content of maize flour samples is summarized in

Table 3. Mineral content of processed maize flour.

Sample	Calcium (mg/g)	Iron (mg/g)	Zinc (mg/g)
GNSM-MF	3.64 c ± 0.09	7.64 a ± 0.04	1.45 c ± 0.02
GSM-MF	5.85 b ± b0.11	3.92 b ± 0.01	1.92 a ± 0.01
NIX-MF	10.91 a ± 0.01	3.69 c ± 0.01	1.70 b ± 0.01

Values are means of three replicates ± standard deviation. Values in columns with the same alphabet in superscript are not significantly different from each other (p < 0.05). GNSM-MF: grain non-soaking method processed maize flour; GSM-MF: grain soaking method processed maize flour; NIX-MF: nixtamalized maize flour.

. Calcium levels ranged from 3.64 to 10.91 mg/g, with NIX-MF having the highest value and GNSM-MF the lowest. Significant differences (p < 0.05) were observed across all processing methods for calcium content. Iron content varied between 3.69 and 7.64 mg/g, with GNSM-MF exhibiting the highest level and NIX-MF the lowest. Similarly, zinc levels ranged from 1.45 to 1.92 mg/g, with GSM-MF showing the highest content and GNSM-MF the lowest. These differences highlight the impact of processing methods on the mineral composition of maize flour, which may influence its nutritional value and application.

3.4. Pasting Properties

The influence of processing methods on the pasting properties of maize flour is detailed in

Table 4. Pasting properties of processed maize flour.

Sample	Peak Viscosity (RVU)2	Trough (RVU)	Breakdown (RVU)	Final Viscosity (RVU)	Setback (RVU)	Peak Time (min)	Pasting Temp (°C)
GNSM-MF	980.25 c ± 0.35	887.5 b ± 0.71	91 c ± 1.41	1210 b ± 14.14	331.5 c ± 2.12	4.72 c ± 0.07	84.08 a ± 0.04
GSM-MF	2904.15 a ± 0.21	1755 a ± 1.41	1147 a ± 1.41	2672 a ± 2.83	919 a ± 1.41	5.57 a ± 0.05	73.38 c ± 0.04
NIX-MF	1059 b ± 1.41	410.5 c ± 1.85	639 b ± 1.41	778 c ± 4.24	363.5 b ± 2.12	4.9 b ± 0.05	76.59 b ± 0.01

Values are means of three replicates ± standard deviation. Values in columns with the same alphabet in superscript are not significantly different from each other (p < 0.05). GNSM-MF: grain non-soaking method processed maize flour; GSM-MF: grain soaking method processed maize flour; NIX-MF: nixtamalized maize flour

. Peak viscosity values ranged from 980.25 to 2904.15 RVU, with GNSM-MF exhibiting the lowest and GSM-MF the highest. These differences were statistically significant (p < 0.05). Trough viscosity ranged from 410.5 to 1755 RVU, with NIX-MF showing the lowest value and GSM-MF the highest. Breakdown viscosity values also varied significantly (p < 0.05), ranging from 91 to 1147 RVU. Final viscosity values were between 778 and 1210 RVU, while setback viscosities ranged from 331.5 to 919 RVU. Both parameters differed significantly (p < 0.05) across the samples. Peak time ranged from 4.9 to 5.57 min, with GSM-MF having the shortest and NIX-MF the longest peak time. Pasting temperatures showed significant variation (p < 0.05), ranging from 73.38 °C (GSM-MF) to 84.08 °C (GNSM-MF).

3.5. Functional Properties

The functional properties of processed maize flour samples are shown in

Table 5. Functional properties of processed maize flour.

Sample	WHC (g/g)	EC (g/cm3)	OAC (g/g)
GNSM-MF	80.84 b ± 0.88	42.18 a ± 3.46	186.13 a ± 1.08
GSM-MF	78.93 b ± 1.24	27.33 b ± 3.53	166.57 b ± 1.17
NIX-MF	111.95 a ± 0.14	4.97 c ± 0.01	160.27 c ± 0.24

Values are means of three replicates ± standard deviation. Values in columns with the same alphabet in superscript are not significantly different from each other (p < 0.05). GNSM-MF grain non-soaking method processed maize flour; GSM-MF, grain soaking method processed maize flour; NIX-MF, nixtamalized maize flour; WHC, water-holding capacity; EC, emulsion capacity; OAC, oil absorption capacity.

. Water-holding capacity (WHC) ranged from 78.93% to 111.95%, with NIX-MF showing the highest value and GSM-MF the lowest. Emulsion capacity (EC) and oil absorption capacity (OAC) ranged from 4.97% to 42.18% and 160.27% to 186.13%, respectively, with significant differences (p < 0.05) observed among all samples. GNSM significantly (p < 0.05) increased EC compared to the other processing methods, while nixtamalization (NIX) significantly (p < 0.05) reduced the EC of the maize flour. OAC values also varied significantly (p < 0.05) across samples.

3.6. Pearson Correlation Between Functional Properties and Colour Characteristics of Processed Maize Flour

Table 6. Pearson correlation between functional properties and colour characteristics of processed maize flour.

Variables	L*	a*	b*	∆C	∆E	H*	%W	FCI	YI	BI
WHC	0.888	0.838	0.998 b	0.998 b	0.962 a	−0.954 a	−0.987 b	−0.999 b	0.999 a	0.998 b
EC	−0.999 b	0.504	−0.919	−0.921	−0.982 a	−0.728	0.889	0.875	−0.917	−0.918
OAC	−0.948	0.176	−0.726	−0.731	−0.858	−0.449	0.676	0.654	−0.722	−0.724

^a: Significant correlation at the 1% level. ^b: Significant correlation at the 5% level; L*, Lightness; a*, redness; b*, yellowness; ∆C, deltachroma; ∆E, colour intensity; H*, hue angle; %W, % whiteness; FCI, flour colour index; YI, yellowness index; BI, brownness index; WHC, water-holding capacity; EC, emulsion capacity; OAC, oil absorption capacity.

shows the correlation of water-holding capacity (WHC) and emulsion capacity (EC) with various colour and functional parameters. WHC exhibited significant correlations (p < 0.05) with b* (0.998), ∆C (0.998), %W (−0.987), and BI (0.998). Additionally, WHC showed highly significant correlations (p < 0.01) with ∆E (0.962), H* (−0.954), and YI (0.999). Emulsion capacity (EC) was significantly correlated (p < 0.05) with L* (−0.999) and highly significantly correlated (p < 0.01) with ∆E (−0.982).

4. Discussion

4.1. Proximate Composition

The increase in protein content observed for NIX-MF in this study may be attributed to the removal of soluble starch during processing. This phenomenon results in the solubilization of corn pericarp hemicelluloses, which are subsequently lost in the nejayote. However, only trace amounts of protein (less than 5%) are lost during this process compared to other constituents [13]. Additionally, the aleurone structure of maize, which remains attached to the endosperm during nixtamalization, plays a critical role in minimizing protein loss, as demonstrated in multiple studies [14,15,16,17].

The methods of processing significantly influenced the moisture content of the maize flour samples. Contrary to the findings of [18] (2015), which associated the soaking of whole grains with increased moisture content, the GNSM showed a significant (p < 0.05) increase in moisture content. This discrepancy may arise from the high intrinsic moisture content of the whole maize grain used in this study. Furthermore, the moisture content of NIX-MF was notably higher compared to that of maize processed using the GSM, likely due to the increased water absorption rate during the initial stages of steeping and cooking. Steeping for approximately three hours followed by cooking has been shown to lead to about a 36% increase in moisture content, which stabilizes or progresses slowly [14]. The hydration process during NIX is influenced by the physical properties of the grain, nixtamalization variables, and the permeability of the pericarp. Maize pericarp, which typically acts as a barrier to water entry, enhances hydration when hydrolyzed [19].

The findings of this study align with [20] (2013), which compared dietary crude fibre between nixtamalized and steeped millet dough, revealing reduced crude fibre content in the former. Fibre loss during NIX may be linked to pericarp removal during processing [21,22]. Additionally, reduced ion interactions (OH⁻ and Ca²⁺) within the maize grain constituents and the cooking medium may hinder the formation of indigestible products, further contributing to lower crude fibre content. However, the authors of [23] (2010) reported contrasting results, where millet cooked in lime exhibited the highest crude fibre content. These variations are likely due to differences in the raw materials used, particularly their physical properties.

None of the processing methods significantly (p > 0.05) influenced crude fat and carbohydrate contents. Nevertheless, maize flour produced via the GSM exhibited the highest crude fat values, whereas NIX increased carbohydrate content. The GNSM and NIX, in contrast, reduced both parameters. The high temperature achieved during NIX may facilitate fat degradation and oxidation, similar to findings reported by [20] (2013) for nixtamalized millet. Consequently, NIX-MF might be less prone to rancidity during storage compared to maize flour processed using GNSM and GSM methods. This is advantageous for maintaining preferred aroma and flavour during storage [23]. The carbohydrate content of the maize flour samples ranged higher than values documented by [18] (2015), [24] (2012), and [25] (2012) for quality protein maize and maize-based products.

4.2. Colour Properties

The significant (p < 0.05) increase in yellowness observed in NIX-MF can be attributed to the yellowing of the pericarp during processing, which is linked to the presence of o-glycoside flavonoid-type pigments in the pericarp. These pigments are typically colourless in acidic and neutral media; however, the alkaline environment characteristic of nixtamalization facilitates substitution of hydroxyl groups on the benzopyrone rings. This reaction results in the formation of flavonol structures, leading to the distinct yellow coloration [20]. This transformation during nixtamalization presents a potential advantage in industries such as bakery, snack production, and complementary flour manufacturing, where enhanced yellowness may be desirable. Lower yellowness values recorded for GNSM-MF and GSM-MF align with findings by [6] (2020) for whole maize meal. Hue angles, which are classified as follows: 0° for red, 90° for yellow, and 180° for green hues, further reinforce the results. NIX-MF, with its highest hue angle and corresponding yellowness (b* = 25.00), exhibits a vibrant yellow hue. This is complemented by its highest saturation level (chroma = 24.03), confirming the distinctive colour characteristics of NIX-MF [26].

4.3. Mineral Content

Nixtamalization (NIX) significantly (p < 0.05) increased the calcium content of maize flour compared to other processing methods. This increase may be attributed to the inherent calcium content of the reagent used, which facilitates calcium diffusion into the endosperm through percolation. As steeping time and temperature increase during NIX, the solubilization and hydrolysis of the pericarp intensify, creating micro holes that promote calcium diffusion into the endosperm [27,28]. These findings are consistent with those of [29] (2002) for ground nixtamalized maize, [30] (2005) for corn tortillas, and [31] (2010) for eleven maize varieties. In contrast, the significant (p < 0.05) reduction in calcium content observed in GNSM-MF may result from the absence of soaking, which prevents the hydrolysis and solubilization of the maize pericarp required for calcium release into the endosperm. However, the lack of steeping in GNSM-MF favoured a significant (p < 0.05) increase in iron content compared to other processing methods. This aligns with the findings of [18] (2015), which documented reductions in iron content following soaking in the production of complementary foods using quality protein maize (QPM).

The grain soaking method (GSM) significantly (p < 0.05) increased the zinc content of maize flour compared to GNSM-MF, which exhibited significantly (p < 0.05) lower zinc levels. However, some studies have reported contrary findings, noting that soaking decreased the zinc content of complementary flours from finger millet and chickpea [32,33], likely due to leaching. These discrepancies may arise from differences in the raw materials used or the prolonged steeping times adopted. Supporting the current study, the authors of [34] (2009) and [35] (2010) observed that soaking enhanced zinc content in sorghum flour.

It is evident that the effects of processing methods on mineral content vary across agricultural raw materials. This variability can present both challenges and opportunities for flour processors and end users. While GSM alone may not be the optimal method for enhancing mineral bioavailability, optimizing soaking conditions and combining it with other techniques, such as NIX, could prove beneficial. Thus, integrating GSM and NIX into traditional maize processing practices holds promise for improving mineral delivery, particularly calcium, in Nigeria and other developing countries.

4.4. Pasting Parameters

The pasting profile of flour is strongly influenced by factors such as the amylopectin-to-amylose ratio, starch content, protein amylase, and lipids [36]. In this study, the steeping involved in the GSM appeared to enhance the swelling index of the maize flour samples, consistent with findings from [37] (2005), [38] (2009), and [39] (2019), which reported increased pasting profiles in pre-treated maize flour.

The cooking stage of NIX likely facilitated the formation of partially gelatinized starch granules, which may have lowered the peak viscosity. This observation aligns with reports by [40] (2008) and [41] (2014). Annealing, which strengthens intragranular forces and enhances starch granule crystallinity, also likely contributed to these changes [16,20,42]. However, a decrease in peak viscosity for NIX-MF is plausible when the rate of gelatinization surpasses the annealing effect [43].

The significantly (p < 0.05) lower breakdown viscosity observed in maize flour processed via the GNSM suggests strong paste stability, making it better able to withstand shear-thinning during further processing [44]. Setback viscosity, an indicator of retrogradation and associated syneresis, was lower in flours processed using GNSM, suggesting minimal retrogradation tendencies [45]. Conversely, maize flour processed via the GSM demonstrated a higher retrogradation tendency when cooked, potentially due to differences in starch structure.

The significant increase in pasting temperature observed in GNSM-MF indicates higher resistance to swelling and starch granule rupture. On the other hand, the soaking and cooking stages involved in GSM and NIX appear to have modified the starch granules’ swelling behaviour, enhancing their hydration potential. These results align with those of [46] (2017), where similar findings were reported. The gelatinization temperature, which occurs due to molecular order disruption inside starch granules, typically ranges between 60 and 70 °C for ideal corn starch, but it is influenced by the adopted processing method [47]. The presence of partially pregelatinized starch granules in NIX-MF (resulting from the high cooking temperatures) may have resisted further gelatinization, elevating the pasting temperature.

The lower pasting temperature observed in GSM-MF suggests that it is likely to gelatinize more quickly than those from the other processing methods. This may be attributed to enzyme stimulation during soaking, which breaks down the starch matrix and facilitates swelling and gelatinization [48]. The reduction in peak time for GNSM-MF and NIX-MF samples indicates a potential reduction in energy and time required for processing in food formulations. However, this contrasts with the findings of [6] (2020), where maize fractions with lower peak times achieved peak viscosity faster. In the current study, GSM-MF exhibited the highest mean peak viscosity but required longer times to attain this, likely due to the use of whole maize rather than its fractions.

4.5. Functional Properties

Water absorption is the first change that occurs in the endosperm during the steeping and cooking stages of nixtamalization, as starch granules absorb water and swell. The increased water-holding capacity (WHC) observed in this study may be attributed to the enhanced ability of starch granules to absorb water during alkaline cooking, particularly within the initial three hours of steeping. This process is facilitated by the effect of lime on starch gelatinization. Calcium hydroxide (Ca(OH)₂) dissociates into hydroxide (OH⁻) ions, which penetrate starch granules, breaking bonds between the hydroxyl groups of starch chains and water molecules. This mechanism increases water penetration into starch granules, thus enhancing their water absorption capacity [49,50,51]. These findings align with those reported by [23] (2010) for nixtamalized millet flour.

While GNSM exhibited a significantly (p < 0.05) increased effect on emulsion capacity (EC), NIX significantly (p < 0.05) reduced the EC of maize flour samples. This reduction could be attributed to the significantly (p < 0.05) lower crude lipid content of nixtamalized maize flour, as previously noted. A contrasting observation was reported by [23] (2010) for untreated and lime-cooked millets, though the mean EC value for GNSM-MF in the present study exceeded that reported for untreated millet (26%). As a result, maize flour produced via the GNSM is likely to be more easily incorporated into food preparations compared to NIX-MF. To overcome this limitation, NIX-MF may need to be blended with flours possessing higher EC.

The GNSM also significantly (p < 0.05) increased the oil absorption capacity (OAC) of maize flour, whereas NIX significantly (p < 0.05) reduced it. This disparity may be attributed to the higher fat content observed in GNSM-MF compared to the lower fat value recorded for NIX-MF. Similar findings were reported in [5] (2014), who noted that fat loss during nixtamalization was a factor contributing to reduced OAC. Oil binding capacity depends on the surface properties of hydrophobic amino acids [52], which may be more prevalent in untreated whole maize grains, facilitating the exposure of non-polar residues within interior protein molecules. Enhanced OAC in processed flour formulations is particularly important, as fat serves as a major flavour retainer [53], enhancing mouthfeel during food consumption. This suggests that GNSM-MF may have better functional properties in food applications requiring high OAC.

4.6. Pearson Correlation Between Functional Properties and Colour Characteristics of Processed Maize Flour

The strong positive correlation between WHC and b*, ∆C, ∆E, and YI suggests that yellowness and chromatic characteristics of the flour contribute significantly to its water-holding behaviour. Conversely, the strong negative correlation between WHC with variables like H, %W, and FCI, indicates that structural and hydrophobic characteristics of maize flour samples may inversely influence water absorption.

The strong negative correlation between EC and L*, implies that as flour samples become lighter, their ability to form emulsions diminishes. Negative correlations with other variables, including b*, ∆C, ∆E, and YI, further highlight the impact of flour colour and compositional changes on EC.

Negative correlation between OAC and most variables, such as L*, b*, ∆C, and YI indicates that colour properties have less influence on OAC, while other factors, such as the presence of hydrophobic amino acids, likely play a more critical role. Weak positive correlations with %W and FCI suggest slight dependencies on specific structural or physical characteristics of the flour.

These results underscore the importance of colour and structural properties in defining the functional characteristics of maize flour. Enhanced water-holding and oil absorption capacities are particularly critical in food formulations, as they influence the behaviour and quality of the final product [54]. Additionally, the high emulsion capacity observed in grain non-soaking method maize flour makes it a strong option for applications where emulsification is essential. By understanding these relationships, processors can optimize maize flour formulations for specific industrial and dietary uses.

5. Conclusions

The processing methods studied significantly influenced the proximate, colour, functional, and pasting characteristics of maize flour. Nixtamalized maize flour (NIX-MF) demonstrated the highest protein content, calcium content, and water-holding capacity, making it particularly suitable for inclusion in the diets of pregnant women and young children in developing countries, where nutritional enhancement is critical. Conversely, the grain non-soaking method maize flour (GNSM-MF) exhibited the highest oil absorption capacity, while NIX-MF had the lowest.

The grain soaking method maize flour (GSM-MF) with the highest values for pasting properties, including peak viscosity, trough, breakdown viscosity, final viscosity, setback viscosity, and peak time, making it ideal for diverse applications in food formulations, such as snacks, complementary foods, and puddings. Additionally, GNMS-MF displayed the lowest breakdown viscosity, indicative of improved paste stability under processing conditions.

In summary, each processing method presents unique functional advantages that cater to different nutritional and industrial needs. The incorporation of nixtamalization (NIX) and grain soaking methods (GSM) into traditional processing practices could significantly enhance the value and applicability of maize flour in both dietary and industrial contexts.