Abstract
The increasing prevalence of malnutrition and diet-related non-communicable diseases in developing countries has intensified the need for innovative nutrient-dense and functional food products from indigenous crops. This study aimed to develop nutritious instant porridge and 3D-printed biscuits from conventional and novel-processed finger millet-Bambara groundnut (FM-BGN) and Moringa oleifera leaf powder (MOLP) blends. Conventional food processing techniques adopted to improve the nutritional and functional quality were fermentation and malting, while the novel food processing technique used was ultrasonication. The first objective of the study was to investigate the impact of conventional and novel food processing techniques on the metabolites of FM, BGN, and MOLP using gas chromatography mass spectrometry (GC-MS). The findings showed various metabolite classes, including amino acids, alcohol, aldehyde, organic acid, ester, fatty acids, glycoside, and sugar, present in FM-BGN flours and MOLP. Among the metabolites identified in the flours were important health-promoting compounds (oleic acid, linoelaidic acid, and linoleic acid), which were identified at their highest levels in fermented FM and BGN flour. In MOLP, health-promoting compounds (L-lysine, valine, threonine, and linolenic acid) were identified at their highest levels in ultrasonicated MOLP (UMOLP). The second phase of the study examined the impact of fermentation, malting, and ultrasonication on the thermo-pasting, microstructural, nutritional, and antioxidant properties of FM-BGN flour and MOLP. Fermentation, malting, and ultrasonication were applied to both FM and BGN, while the latter was also applied to MOLP. Fermentation, malting, and ultrasonication enhanced the water/oil absorption capacity (WAC/OAC) of FM, while in the BGN samples, malting decreased the WAC and OAC. An increase in protein and fibre content was observed in all processed samples. The ash content increased in fermented/malted FM flour (FFM/MFM) and fermented BGN flour (FBGN), while a decrease was observed in ultrasonicated FM/BGN flour (UFM/UBGN) and malted BGN flour (MBGN). For MOLP, ultrasonication facilitated the release of crude protein, fat, and fibre, resulting in the enhanced bioavailability of these constituents. In terms of antioxidant activity, higher ferric reducing antioxidant power (FRAP) values were observed in FFM (22.69 mol TE/g), FBGN (37.40 mol TE/g), and UBGN (49.90 mol TE/g) compared to their respective control samples, RFM (19.77 mol TE/g) and RBGN (18.67 mol TE/g). It also significantly enhanced the extraction of total phenolic content (16.61–18.30 mg GAE/g), total flavonoid content (27.12–35.87 mg QE/g), ferric reducing antioxidant power (FRAP) (130.86–152.01 mM TE/g), and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) %inhibition (7.47–83.22%) of MOLP. Structural analyses revealed modifications in the functional groups, the morphology of the protein body, and other components in FM, BGN, and MOLP.
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The third phase of the study evaluated the influence of ultrasonicated Moringa oleifera leaf powder (UMOLP) incorporation on the various food properties of FFM-FBGN flour. Two groups (A and B) of composite flour were developed, with each group containing its own base flour serving as a control. The A-group composite flour consisted of 70% FFM and 24-30% FBGN, which was substituted with UMOLP at 0%, 2%,4%, and 6% levels of substitution, with 100% FFM serving as a control. The B-group composite flour consisted of 70% FBGN and 24-30% FFM, which was substituted by UMOLP at 0%, 2%,4%, and 6% levels of substitution, with 100% FBGN serving as a control. The protein, fiber, and ash contents after the addition of UMOLP to the A-group composite flour ranged from 8.81 to 11.40%, 3.08 to 3.80%, and 2.13 to 2.75%, respectively; while in the B-group composite flour, they ranged from 13.60 to 16.46%, 5.40 to 6.30%, and 2.73 to 3.64%, respectively. The phytochemicals and antioxidant activity increased significantly as the levels of UMOLP increased in both groups of composite flours. This is the final phase of the study, which focused on the development of instant and 3D-printed food products from FFM, FBGN, and UMOLP. The combination of fermentation and ultrasonication considerably improved the nutritional and antioxidant qualities of the food products. The protein, ash, fibre, RS, and SDS content for instant porridge increased from 18.80 to 20.60%, 2.18 to 3.14%, 2.88 to 3.26%, 7.17 to 9.62 g/100g, and 11.47 to 13.98 g/100g, respectively, while for 3D-printed biscuits increased from 15.40 to 16.50%, 1.82 to 2.14%, 1.67 to 1.77%, 10.56 to 12.50 g/100g, and 5.27 to 7.78 g/100g, respectively. The TPC and TFC content for instant porridge exhibited a significant (p ≤ 0.05) increase from 7.18 to 8.48 GAE mg/g and 24.16 to 37.54 QE mg/g, while for 3D-printed biscuits increased from 3.64 to 8.06 GAE mg/g and 21.73 to 34.69 QE mg/g, respectively. Integrating fermentation and ultrasonication also improved flavonoid compounds like quercetin and luteolin, and phenolic acids like sinapic acid, gallic acid, P-coumaric acid, apigenin, and trans ferulic acid. In terms of overall acceptability of the food products, instant porridge and 3D-printed biscuits made from processed flours were moderately accepted compared to those made from unprocessed flours. However, the improvements in terms of nutritional and antioxidant properties of instant porridge and 3D-printed biscuits made from processed flour blends have the potential to address both noncommunicable diseases and malnutrition. They also highlight the importance of combining indigenous crops with cutting-edge technologies to develop convenient, health-promoting, and customizable foods. This work has the potential to improve the livelihoods of local people because value-added food products (instant porridge and 3D-printed biscuits) were developed from locally available food sources such as FM, BGN, and MOLP. By increasing demand for these crops, the study can help small-scale farmers earn an income.