Effect of malted millet blends with defatted soybean and cinnamon flours on physiochemical and bioactive properties

Millet, cinnamon and soybean were purchased from Ondo central market and identified at the Herbarium Unit, Department of Botany, Obafemi Awolowo University, Ile-Ife, Nigeria. Malted millet was processed following the method described by Ogunjemilusi et al. (2022) and Sighn et al. (2012). Malted millet flour was obtained by cleaning whole millet flour to remove extraneous materials. It was soaked and spread in a soaked bag for sprouting before kilning and eventually dry milled, sieved and packaged as shown in the preparation of malted millet flour as reported by Alka et al. (2012) and Ogungemilusi et al. (2022). The process of kilning at 40°C was to arrest the enzymes in action during sprouting and prevent further actions.

Defatted soybeans flour was processed following the method described in flow diagram on def-fated soybean flour as described by Kang et al. (2017) and Ogunjemilusi et al. (2020). The soybeans was cleaned from dirt by sorting out contaminants such as sands and any other evident impurities, crack, dehulled, milled and extracted with solvent through FDS (flash desolventising system) technology, then the cake was dry milled and sieved into fine flour, by passing them through 2 mm mesh sieve as shown flow diagram on def-fated soybean flour. The heating and milling process was to orient the molecular protein to enhance functional properties. Table 1 shows blend proportion used for the formulation from defatted soybean flour.

The Cinnamon barks was cleaned from dirt by sorting out contaminants such as sands and any other evident impurities then washed and oven dried. The barks were dried and milled using attrition mill (SK-30-SS, Munson Mach Co, Utica, NY, USA) and sieved into fine flour, by passing them through a 0.35 mm mesh sieve as shown in the preparation of cinnamon flour before packaging. Table 1 shows blending proportions used for the formulation from cinnamon flour.

The water absorption, oil absorption, and swelling capacity of the flour blends [MDSCB1, millet flour (75%) + defatted soybeans flour (20%) + cinamon flours (5%); MDSCB2, millet flour (65%) + defatted soybeans flour (30%) + cinamon flours (5%); MDSCB3, millet flour (55%) + defatted soybeans flour (40%) + cinamon flours (5%)] as shown in Table 1 were determined at room temperature following the AACC (2005) method. The method described by Okezi and Bello (1988) were used to determine the packed and loosed bulk densities of the flour.

Following the procedure described by AOAC (2005), the proximate composition of the flour blends as shown in Table 1 was determined.

DPPH radical scavanging ability was determined according to the method described by Pownall et al. (2010). The method described by Benzie and strain (1999) was applied to calculate the FRAP of flour blends in Table 1. The approach outlined by Singh and Kumar (2022) was employed for the metal chelating ability assay.

The α-glucosidase inhibition was accomplished by the use of a slightly modified version of the approach outlined by McCue et al. (2005). A technique described by Giancarlo et al. (2006) was used to determine the α-amylase inhibition of the flour blends in Table 1.

A nine-point hedonic scale was used as described by Iwe and Onuh (2009) with an approved Reference code wesy-023 on the 2nd of September, 2022 by the Sensory Department Wesley University Ondo. The panelists for the sensory test were students and lecturers at the Department of Fod Science and Technology, Wesley University Ondo. Nigeria. Trained panelists were asked to rate each sensory characteristic of the coded porridge of defatted soybean and malted millet mixture with added cinnamon powder on a scale from extremely liking (9) to extremely disliking (1).

All values are mean±SD (n=3) from three readings. Data were analyzed statistically using analysis of variance (SPSS version 2.0) technique. Values with level of significance within mean was separated using the Duncan’s multiple range test (Steel and Torrie, 1980).

Table 2 shows the proximate composition of the blends. The values of moisture content for the flours used for producing the composite flour in this study are 7.86% in malted millet flour, 8.27% in soy flour, and 6.15% in cinnamon flour. The moisture contents of combined mixture of malted millet, defatted soy, and cinnamon flour were 8.74-9.00% with the highest value in sample 55% (malted millet flour + 40% defatted soybean flour + 5% cinnamon flour) MDSCB3 (9.00%). Moisture content obtained from this study was higher than the range of moisture (3.34-4.06%) reported by Ikuomola et al. (2017) but lower than those obtained by (Ndife et al., 2014), which ranged from 7.24-9.80% for wheat and full fat soybeans cookies. The crude protein content of the flours that make up the composite flour are 9.45% for malted mullet flour, 9.13% for defatted soy flour and 2.61% for cinnamon flour. The crude protein values in Table 2 showed a significant (p<0.05) decrease with millet malting maybe due to heat effect on protein natures. Protein content also ranged between 10.08-12.18% for samples having malted millet flour as its main flour MDSCB1, 3 with MDSCB3 having the highest values. The crude fiber ranged was 1.56-2.25% in 75% malted Millet flour+20% defatted soybean flour+5% cinnamon flour MDSCB1 samples. The inclusion of rootlets and shoots during milling of germinated grains also appears to increase the fiber content of the malted millet flour (Muyanja et al., 2003). The increase agrees with the research work done by Ogbonna et al. (2012) which showed increase in crude fiber in sorghum grist after malting. Low quantities of ash obtained in MDSCB1 samples is an indication of its low mineral contents as the ash content decreased from 3.56-2.02% which was caused by uptake during malting. An increase in the ash contents with an increase in defatted soybeans flour is an indication of nutrient enhancement by defatted soybeans and cinnamon flours. This agreed with the findings of Jakhetia et al. (2010). Also, the fat content value for the MDSCB1 samples ranged between 3.00-5.75%. MDSCB3 had the highest value due to increased inclusion of defatted soybeans flour.

The defatted soybean flour had its bulk density as 0.66 g/mL and malted millet flour as 0.71 g/mL. The bulk density for MDSCB1 samples ranged from 0.64-0.73 g/mL. The bulk density (BD) improved significantly for pearl millet with increase in the level of soybean and cinnamon flour. The Table 3 results indicated that supplementation of pearl millet with soybean and cinnamon flour improved significantly (p≤0.05) the bulk density of millet composite flour. The values obtained could be slightly compared to the value (0.52-0.68 g/mL) of bulk density for plantain-soybeans-cinnamon blended flour (Adegunwa et al., 2019).

The swelling capacities (SC) of the blends increased with increase in swelling temperature. The water absorption capacity (WAC) of the flour ranged from 167.67-187.67 g/g in MDSCB1 samples while the oil absorption capacity (OAC) of MMF samples ranged from 120-125 g/g. The OAC and WAC values of the MDSCB1 samples increased as the inclusion of cinnamon and defatted soybeans flour increased. The result obtained is close to that obtained by Awolu et al. (2015) for rice, cassava and kersting’s groundnut composite flour, that falls in the range of 1.53-2.23 g/mL obtained by Awolu et al. (2017) for millet flour fortified with soybeans and tiger nut flour. Meanwhile, there was significant difference (p<0.05) between the flour formulations. Awolu et al. (2015) reported OAC ranging from 1.75-2.21 g/mL for rice, cassava and kersting’s groundnut composite flour. Variation in oil absorption capacity might be due to the different proportion of the protein molecules present in each of the samples. The temperatures for swelling capacity are 70, 80, and 90°C. The values of SC obtained in this study were ranged from 297-300% in MDSCB1, 3 samples at 70°C; 397-410% in MDSCB1, 3 samples at 80°C, and 365-441% in MDSCB1, 3 samples at 90°C.

DPPH scavenging activity ranged from 44.68-53.06% for MDSCB1 samples. It was observed that sample MDSCB3 had the highest value 53.05% of DPPH. Hence, exhibit the highest ability to scavenge free radicals. The results obtained in the present study on Table 4 are higher than those reported by Adefegha and Oboh (2013) for wheat–bambara flour blends and cookies made from un malted millet flour, defatted soybean and cinnamon flours blend. The ability to reduce Fe³⁺ to Fe²⁺ by the blended flours decreases with decrease in supplementation with malted millet flour and increase with defatted soybeans flour which may be attributed to the ability of incorporated soy defatted soybean flour to form reductant that could react with the free radicals thereby stabilizing and terminating the radical chain (Moktan et al., 2011). The metal chelating ability of the blends revealed that MDSCB3 exhibit the highest metal chelating ability. This implies that combination of malted millet, defatted soybeans flour at 40% level and cinnamon flour at 5% level is the best in terms of sequestering or chelating metals in the blends. The result suggests that the blends possess an average potency to chelate metal. Following this observation, Sample MDSCB3 reported the highest value, which could be due to the possible high contents of hydrophobic amino acids.

On Table 4, the results depict that percentage inhibition was concentration dependent. MDSCB3 and MDSCB2 at 0.1 concentration had the least inhibitory activity 27.47% and 24.64%, respectively. Percentage α-amylase inhibition increased with increase in supplementation with soybeans and decrease in malt from millet flour. However, MDSCB1 exhibited the highest α-amylase inhibitory activity (32.20%). There were significance differences between the percentage α-amylase and α-glucosidase inhibitory activity of samples. This discovery in this study agreed with previous reports which ascertained that plant phytochemicals and underutilized legumes inhibited salivary and pancreatic α-amylase activities (Ademiluyi and Oboh, 2012; Nickavar and Yousefian, 2009). Sample MDSCB3 had the highest value of α-glycosidase amongst all, hence could inhibit disaccharide breakdown and absorption within the mucosal wall linings.

Addition of defatted soybeans flour and cinnamon to malted millet flour produced a noticeable effect on color, taste, flavor, texture, crispiness and overall acceptability on the blends produced on Table 5. Gruel produced from 55: 40:5 had higher sensory characteristics in the malted millet samples except for aroma. Among the porridge produced, sensory scores increased with an increase in the addition of defatted soybeans flour with MDSCB1 having the least acceptability (See Table 5). However, there was a decrease in the values for aroma scores in MDSCB3 samples. This could be the effect of malting on millet flour used. The sensory scores for taste ranged from 5.20-7.80 for MDSCB1-3 samples, respectively. The increase in the values for each group could be due to the increase in the inclusion of defatted soybeans flour, which added to appearance and the Taste. Flavor scores for the cookies ranged from 5.26-7.53 in MDSCB1-3 samples. The brown color resulting from Maillard reaction and inclusion of defatted soybeans and cinnamon flour were responsible for the chocolate cookies obtained though Maillard reaction is always associated with baked food products. The MDSCB3 blend with 40% replacement with defatted soybean flour had the highest overall acceptability. The result confirmed that taste, color, flavor and crispiness as an important effect on overall acceptability.