Organic Food Systems Meeting the Needs of Southern Africa
Organic agriculture world-wide allows farmers to produce healthy food with low levels of external inputs, and often shortens the value chains, giving farmers a higher share of the consumer dollar.
This book reports on long-term comparative organic farming systems research trials carried out over the last four years in South Africa’s Southern Cape, as well as research on the organic sector and the technical tools it requires in South Africa, Zambia, Uganda and Tanzania.
The trials show how the yield gap between organic and conventional crops was closed over 3 years. Water use efficiency was also greater in the organic farming system, and pests and diseases were effectively controlled using biological products. Farmer training approaches, soil carbon analysis, participatory guarantee systems, the Zambian organic farming sector (agronomy) and Ugandan organic farmer training support, and a sector plan for southern African organic farming are examined.
Foaming properties of total zein, total kafirin and pre-gelatinized maize starch blends at alkaline pH
The effect of 0.1 M NaOH as a solvent and blending with pre-gelatinized maize starch on the foaming properties of laboratory extracted total zein and total kafirin were determined. Both total zein and total kafirin in 0.1 M NaOH were found to have higher foaming capacity (up to 118% foam volume increase) compared to their non-foaming (0% foam volume increase) properties in water. Blending with pre-gelatinized maize starch reduced the foam volume but increased the foam stability to more than 24 h. Total zein and total zein-pre-gelatinized starch blends had relatively higher foaming capacity than total kafirin and total kafirin-pre-gelatinized starch blends probably because zein was more surface active (more negative zeta potential value) than kafirin. However, total zein and total zein-pre-gelatinized starch blend foams were less stable with time than total kafirin and total kafirin-pre-gelatinized starch blend foams. This is possible because total kafirin, having higher amount of cysteine, can have higher degree of cross linking than total zein to form stronger lamellae. The foam microstructure, bubble size and foam film thickness are related to the foaming capacity and foam stability. Larger bubble size corresponded with higher foaming capacity but smaller bubbles and thicker film lamellae corresponded with lower foaming capacity and improved stability. The improved foam formation of total zein and total kafirin in 0.1 M NaOH solution compared to water could be due to the higher degree of deamidation in 0.1 M NaOH, which in turn would make them more surface-active and could increase their solubility/dispersibility.
Food fermentation and mycotoxin detoxification: An African perspective
Mycotoxins are toxigenic fungal secondary metabolites and known carcinogens that pose a significant threat to economies, trade, health and compromises food safety. Favourable environmental conditions on the African continent encourage the proliferation of fungal species, increasing the possibility of attendant mycotoxins to be present in foods, a situation that aggravates challenges to address them. Due to the susceptibility of common food crops to these toxins and the general inability of some conventional food processes to eliminate them, they are found in derived/processed foods. Detoxification and reduction of mycotoxins in the food chain still remains a significant topic necessitating a sustainable, affordable and effective strategy for mycotoxin control. Fermentation of food confers desirable properties and improves food quality. This food processing technique is also a notable inexpensive mycotoxin decontamination strategy that can be explored not only to improve the constituents in food, but equally reduce and at best eliminate mycotoxins. In the absence of sophisticated monitoring and prevention mechanisms in Africa, exploiting fermentation would be vital in improving nutrition and ensuring food safety. While this processing technique generally favours mycotoxin reduction, preventing the occurrence of these toxins in crops, effective handling and storage practices before fermentation may ensure complete prevention of the heinous effect of these toxins on human health.
Assessment of nutritional and phytochemical quality of Dawadawa (an African fermented condiment) produced from Bambara groundnut (Vigna subterranea)
This study investigated the nutritional composition, antinutrients and phenolic composition of raw, hulled and dehulled Bambara groundnuts (BGN) (Vigna subterranea) and their derived dawadawa products. Phenolic compounds were investigated using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS) system while determination of amino acids and mineral contents were done using high performance liquid chromatography (HPLC) and inductively coupled plasma optical emission spectrometry (ICP-OES), respectively. Oxalate, tannin and phytic acids were quantified while microstructure of the samples was viewed using scanning electron microscopy (SEM). Results showed a decrease in quinic acid, medioresinol and quercetin-3-O-galactoside-7-O-rhamnoside in all dawadawa samples. Likewise, significant (p ≤ 0.05) increases were observed for protein, majority of the amino acids and minerals after fermentation. On the contrary, levels of oxalate, tannin and phytic acids were noted to have decreased in the dawadawa samples, as compared to the BGN. SEM also revealed modifications in the structural morphology of the samples. The higher phenolic compounds in the hulled dawadawa, positions it as an excellent source of health beneficial components, while the dehulled samples could be equally considered from a nutritional perspective.
Dynamic Oral Texture Properties of Selected Indigenous Complementary Porridges Used in African Communities
Child malnutrition remains a major public health problem in low-income African communities, caused by factors including the low nutritional value of indigenous/local complementary porridges (CP) fed to infants and young children. Most African children subsist on locally available starchy foods, whose oral texture is not well-characterized in relation to their sensorimotor readiness. The sensory quality of CP affects oral processing (OP) abilities in infants and young children. Unsuitable oral texture limits nutrient intake, leading to protein-energy malnutrition. The perception of the oral texture of selected African CPs (n = 13, Maize, Sorghum, Cassava, Orange-fleshed sweet potato (OFSP), Cowpea, and Bambara) was investigated by a trained temporal-check-all-that-apply (TCATA) panel (n = 10), alongside selected commercial porridges (n = 19). A simulated OP method (Up-Down mouth movements- munching) and a control method (lateral mouth movements- normal adult-like chewing) were used. TCATA results showed that Maize, Cassava, and Sorghum porridges were initially too thick, sticky, slimy, and pasty, and also at the end not easy to swallow even at low solids content—especially by the Up-Down method. These attributes make CPs difficult to ingest for infants given their limited OP abilities, thus, leading to limited nutrient intake, and this can contribute to malnutrition. Methods to improve the texture properties of indigenous CPs are needed to optimize infant nutrient intake.
Pasting, flow, thermal and molecular properties of maize starch modified with crude phenolic extracts from grape pomace and sorghum bran under alkaline conditions
This study determined the effects of phenolic extracts from grape pomace and sorghum bran, reaction time and washing with aqueous ethanol on the pasting, flow, thermal and molecular properties of maize starch. The starch modification was carried out under alkaline conditions. The phenolic extracts increased the peak viscosity of the starch. Reaction time had no significant effect on starch properties. Washing with aqueous ethanol significantly increased the peak, final, and setback viscosities of the phenolic modified maize starches. DSC of phenolic modified starches showed higher enthalpy (ΔH) before and after washing with aqueous ethanol in comparison with starch without phenolic extract. FTIR spectra suggested the possible formation of hydrogen and ether (covalent) bonds between starch and phenolic compounds. It can be concluded that the pasting, flow and thermal properties of maize starch can be modified with phenolic extract under alkaline conditions to produce “clean label” starch-phenolic complex.
Storage stability of encapsulated ascorbyl palmitate in normal and high amylose maize starches during pasting and spray dryin
This study determines storage stability and release of encapsulated ascorbyl palmitate in normal and high amylose maize starch by pasting and spray drying. The amount of ascorbyl palmitate released was analysed in the stored samples (dark cupboard, and under UV light at a temperature of 40 °C for 12 weeks) and their antioxidant activity determined. Storage of encapsulated ascorbyl palmitate at 40 °C under both dark and UV light conditions did not affect the amount release and the ability to scavenge the free radical (ABTS+). However, the antioxidant activity of free ascorbyl palmitate exponentially decreased at 40 °C under UV light condition. The analysed residues after α-amylase digestion of encapsulated ascorbyl palmitate showed some endothermic peaks, suggesting that amylose-lipids complexes formed were resistant to α-amylase digestion. Encapsulation of ascorbyl palmitate in maize starch may improve its storage stability under light (UV) conditions.
Reduction of Mycotoxins during Fermentation of Whole Grain Sorghum to Whole Grain Ting (a Southern African Food)
Mycotoxins are fungal secondary metabolites that pose health risks to exposed individuals, requiring necessary measures to reduce them. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), mycotoxins were quantified in whole grain sorghum and ting subsequently derived from two sorghum varieties (high and low tannin). The whole grain (WG) ting samples were obtained by fermenting sorghum with Lactobacillus fermentum strains (FUA 3165 and FUA 3321). Naturally (spontaneously) fermented WG-ting under the same conditions were equally analysed. Among the mycotoxins investigated, fumonisin B1 (FB1), B2 (FB2), B3 (FB3), T-2 toxin (T-2), zearalenone (ZEA), alpha-zearalenol (α-ZOL) and beta-zearalenol (β-ZOL) were detected in sorghum. Results obtained showed that mycotoxin concentrations significantly (p ≤ 0.05) reduced after fermentation. In particular, L. fermentum FUA 3321 showed the capability to significantly (p ≤ 0.05) reduce all the mycotoxins by 98% for FB1, 84% for T-2 and up to 82% for α-ZOL, compared to raw low tannin sorghum. Fermenting with the L. fermentum strains showed potential to effectively reduce mycotoxin contamination in whole grain ting. Thus, we recommended L. fermentum FUA 3321 in particular to be used as a potential starter culture in sorghum fermentation.
Improving iron and zinc bioaccessibility through food-to-food fortification of pearl millet with tropical plant foodstuffs (moringa leaf powder, roselle calyces and baobab fruit pulp)
Essential mineral (iron and zinc) deficiencies are still prevalent in the Semi-arid Tropics, where many people consume monotonous, predominantly cereal-based diets. This study aimed to evaluate the potential of including tropical plant foodstuffs high in iron and zinc (moringa leaves and roselle calyces) or mineral availability enhancers (baobab fruit pulp) in a pearl millet-based food containing a plant food-based provitamin A source, with the aim of preventing iron and zinc deficiencies in the Semi-arid Tropics. Mineral bioaccessibility was assessed by dialysability assay. Moringa, roselle and baobab considerably increased iron and zinc bioaccessibility when added at 10 parts:100 parts pearl millet (dry basis). These foodstuffs, increased the contribution to the absolute iron requirements of women of reproductive age by 2.5, 2.1 and 2.3 times for moringa, roselle and baobab, respectively and to their absolute zinc requirements by 2.4, 2.1 and 2.7 times, respectively. Combining these plant foodstuffs could contribute up to 28% and 41% of the women’s absolute iron and zinc requirements, respectively, from a single meal. Moringa, despite having the highest iron content, when added at a very high level (30 parts:100 parts pearl millet) decreased bioaccessible iron and zinc, most probably primarily due to its high calcium content. Food-to-food fortification of staple cereal foods with moringa leaves, roselle calyces or baobab fruit pulp plus a provitamin A source can potentially sustainably improve iron and zinc bioavailability in the diets of at-risk communities in the Semi-arid Tropics.
Pasting properties of hydrothermally treated maize starch with added stearic acid
The effects of stearic acid addition followed by hydrothermal treatment on the functional properties of maize starch were studied. Addition of stearic acid followed by hydrothermal treatment resulted in non-gelling starch. Starch with stearic acid had significantly (P < 0.05) higher viscosity as compared to heat-moisture treated starch. There was no significant difference on the pasting properties of starch with stearic acid alone and in combination with annealing. Stearic acid addition followed by heat-moisture treatment significantly reduced starch susceptibility to acid hydrolysis as compared to stearic acid alone and heat-moisture treatment alone. These changes related well with the increased amylose lipid complexes and relative crystallinity observed by the DSC and XRD, suggesting that heat-moisture treatment promoted amylopectin side chain crosslinking and amylose-stearic acid complex formation. Stearic acid addition followed by hydrothermal treatment produced a ‘clean label’ starch that can potentially substitute chemically cross-linked and non-gelling starch in the food industry.