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Characterisation of gluten-free dough mixes from traditional food crops with reduced starch digestibility for baking applications
(2025) Govender, Samantha; Amonsou, Eric
Gluten-free (GF) baking is challenging because gluten, which is absent, gives wheat-based doughs their elasticity, structure, and ability to retain gas. Developing gluten-free dough mixes requires a strategic selection of substitute ingredients that can mimic gluten's functional properties. This calls for the use of various starches, flours, hydrocolloids, and proteins to achieve desirable dough rheology and final product characteristics. The challenge lies in optimizing the interactions between these ingredients to create a cohesive and elastic dough structure that can withstand processing and deliver acceptable sensory attributes. The choice of suitable ingredients and their proportions is crucial for achieving a balance between dough stability, gas retention, and crumb structure. Therefore, food scientists and technologists find it challenging to create baked foods that are gluten-free. For glutenfree products to be more widely accepted by consumers, these ingredients must ensure that they resemble typical bakery goods as much as possible. Amadumbe, millet, and psyllium offer unique properties that can be harnessed to create gluten-free dough mixes. Amadumbe, a starchy root crop rich in resistant starch, can reduce the glycemic load of baked goods. Millet is a gluten-free grain with high nutritional value, providing vital amino acids, minerals, and antioxidants. Psyllium, a soluble fibre, has been shown to improve dough handling, increase viscosity, and improve the textural properties of gluten-free baked goods. The combination of these ingredients can address the textural and nutritional deficiencies often associated with gluten free products. The focus of this research was the characterization of gluten-free dough mixes with reduced starch digestibility for baking applications. This was done by A; investigating the effect of hydrothermal treatments: annealing (ANN) and heat-moisture treatment (HMT) combined with 3% psyllium husk fibre (PHF), on the structural, rheological, pasting, and digestibility properties of maize starch with varying amylose content. B; evaluation of the functional and digestibility profiles of a gluten-free (GF) premix blend made from amadumbe and millet, supplemented with psyllium fibre, and C; the optimized gluten-free flour blend was tested for its dough-forming ability and baking quality. Hydrothermal treatments: annealing (ANN) and heat-moisture treatment (HMT), combined with 3% psyllium fibre supplementation, significantly (p < 0.05) enhanced the rheological, pasting, and starch digestibility profiles. However, hydrothermal treatment alone caused minimal to no change in these functional properties. The results demonstrated that fibre supplementation of both HMT- and ANNtreated starches increased peak viscosity, trough viscosity, final viscosity, and setback viscosity, with ANN exhibiting significantly higher values. ANN fibre-supplemented normal maize starch showed the largest increase in storage modulus (G'), according to rheological analysis. Profiling of starch digestibility revealed that fibre-supplemented high amylose maize starch produced the greatest levels of resistant starch (RS). These findings highlight the importance of developing healthier starches that promote well-being by reducing digestibility and increasing resistance to enzymatic breakdown. This will support the creation of low-glycemic, fibre-rich products. The results of the investigation proved useful in establishing the criteria for the amadumbe-millet and psyllium flours used to produce glutenfree composite blends. The evaluation of processed gluten-free (GF) flour blends made from amadumbe, millet, and psyllium flours revealed that the inclusion of psyllium fibre significantly improved the pasting properties (PV, FV, BV) two-fold. The rheological properties showed enhanced viscoelasticity of the dough, as indicated by the storage modulus (G') consistently being greater than the loss modulus (G") across the frequency range. Starch structural analysis using X-ray diffraction (XRD) indicated that all blends exhibited a typical A-type crystalline structure. The analysis of starch digestibility showed a significant increase in resistant starch (RS) and a decrease in rapidly digestible starch (RDS) due to the presence of psyllium fibre. Results obtained from this study suggest that fibre-supplemented gluten-free flours have great potential for baking, owing to their improved functional properties and reduced digestibility profile. The optimized gluten-free blend of amadumbe, millet, and psyllium (in a ratio of 70-30-3) was further evaluated for its dough-forming properties by examining water absorption capacity (WAC), oil absorption capacity (OAC), rheological properties, and textural properties. All the tests performed showed improvement with the inclusion of fibre. To assess the baking quality of the bread, textural analysis and sensory evaluation were conducted. Sensory evaluation assessed the amadumbe-milletpsyllium bread (AMP1) with a commercially available gluten-free bread. The results for overall acceptance indicated comparable findings (6.62±1.86) for AMP1 bread and (6.91±1.63) for the commercial gluten-free bread. However, starch digestibility results showed a reduction in resistant starch (RS) content, which was attributed to the increased baking temperature and time. This research contributes to the advancement of gluten-free bread with enhanced nutrition, texture and shelf life, meeting the growing demands of health-conscious consumers and gluten-intolerant individuals. Therefore, this study furnishes valuable insights for food scientists, bakers, and ingredient manufacturers, guiding the preparation of novel gluten-free products with enhanced nutritional and sensory attributes.
Seasonal consumption and contribution of indigenous leafy vegetables to household food security and daily recommended intakes in a rural community in Ndwedwe, KwaZulu-Natal
(2025) Hlekwane, Ayanda; Grobbelaar, Heleen; Napier, Carin E.
Food insecurity remains a significant challenge in sub-Saharan Africa. Improving food security in rural South Africa can be achieved by assisting smallholder farmers, offering agricultural loans, providing competent agricultural services, and promoting the consumption of indigenous leafy vegetables (ILVs). Studies indicate that ILVs can alleviate food and nutrition insecurity while enhancing dietary diversity, particularly among rural families. However, ILVs are still underutilised. This study investigated the seasonal patterns of ILV consumption and their role in household food security and daily nutrient intake recommendations in Mangangeni village, Ndwedwe, KwaZulu-Natal. A group of 118 participants (aged 18 and older) was selected through snowball sampling. Various questionnaires were employed, including those for demographic information, food frequency, 24-hour food recall, and food coping strategies. The data were analysed using the Statistical Package for the Social Sciences (SPSS) version 27, utilising descriptive statistics and one-way ANOVA for comparative analysis. The findings revealed that women (62.7%) primarily handled food preparation. Many participants were unemployed and relied on family members for essential needs. ILVs such as Bidens pilosa, blackjack, black nightshade, and amaranth were mainly foraged from the wild, household gardens, or farms. Households regularly consumed approximately six ILVs, with most participants eating them at least once or twice a week. All participants perceived ILVs as healthy, cheaper than other vegetables, tasty, beneficial for preventing and regulating illnesses, high in nutrients, quick to cook, and energy-giving. Seasonal shifts in ILV consumption were noted, with higher levels in summer and spring and a decrease in autumn and winter due to limited availability. Nutrient intake assessments revealed high carbohydrate consumption and imbalances in micronutrients. The most common strategy for coping with food insecurity involved choosing less expensive foods, while the least common strategy was consuming seed stocks intended for planting. While ILV consumption is influenced by seasonal availability, the results indicate that ILVs are crucial for mitigating food insecurity in rural South Africa. Enhancing access to ILVs year-round and promoting a balanced diet could improve dietary intake and diversity.
A smartphone-based application for the colorimetric detection of lead in wastewater using gold nanoparticles
(2025) Kubheka, Penuel Nkanyezi; Mokhothu, Thabang Hendrica; Shange, Sindisiwe Fortunate; Mdluli, Phumlani Selby
This study was conducted to develop and validate a straightforward, selective, and efficient colorimetric optical sensor that relies on gold nanoparticles for the detection and quantification of Pb(II) in wastewater systems. Gold nanoparticles were synthesized by chemical reduction of gold(III) chloride trihydrate, with trisodium citrate as a stabilizing agent to prevent aggregation. The synthesized AuNPs were characterized by ultraviolet-visible (UV-Vis) spectroscopy and transmission electron microscopy (TEM), confirming a spherical morphology with an average diameter of approximately 20 nm and a characteristic surface plasmon resonance (SPR) peak at 520 nm. The detection mechanism was based on Pb(II)-induced nanoparticle aggregation, resulting in a visible color change from red to blue. Quantitative analysis was conducted using both UVVis spectroscopy and digital image processing in ImageJ. The method was further validated using spiked river and tap water samples across a concentration range of 0.1–20 mg/L. Selectivity was assessed in the presence of potential interfering ions, while colorimetric response was analysed using the CIE Lab* color space. The presence of Pb(II) resulted in a red shift in the UV-Vis spectra, with the identification of two distinct SPR peaks at 520 nm and 680 nm, confirming nanoparticle aggregation. The colorimetric sensor demonstrated a strong linear response over the concentration range of 0.0520.0 mg/L (R² = 0.9901), with a detection limit of 0.01 mg/L. The recovery studies yielded values of 93%-99% for the ImageJ method and 88%-98% for the UV-Vis method. The Analysis of wastewater samples revealed Pb(II) concentrations ranging from 0.0 to 0.0379 mg/L. Then, minimal interference from other metal ions (Cr, Cu, Fe, Ni, Zn, Mn) was observed, indicating high selectivity. Colour analysis showed a systematic transition from red to green in the CIE Lab* space, with increasing Pb(II) concentration strongly correlating with measurable colour variation. The colorimetric sensor based on AuNPs developed provides a swift, cost-efficient, and exceptionally selective means for detecting Pb(II) in wastewater. The robust alignment between ImageJ and UV-Vis results indicates that smartphone image analysis can serve as a reliable alternative to standard spectrophotometric techniques. This strategy holds significant potential for on-site environmental assessments and in settings with limited resources.
Metagenomic fingerprinting of waterborne enteric viruses and their inhibition using phyto-nanomaterials
(2025) Lanrewaju, Adedayo Ayodeji; Swalaha, Feroz Mahomed; Folami, Abimbola Motunrayo; Sabiu, Saheed
Waterborne enteric viruses are major causes of diseases including gastroenteritis, hepatitis, encephalitis, meningitis, conjunctivitis, and respiratory disorders. Transmission occurs primarily through the faecal-oral channel via contaminated water or food, constituting significant public health risks. These viruses have been reported in South Africa following exposure to contaminated surface waters, dams, and wastewater. Nevertheless, limited data exist on their prevalence, diversity and abundance, especially in wastewater treatment plants (WWTPs) in eThekwini Municipality, Durban, KwaZulu-Natal, South Africa, necessitating metagenomic surveillance. In addition, the development of resistance to conventional drugs and high treatment costs necessitates the development of novel approaches to identify inexpensive and efficient antiviral medications. Interestingly, Spondias mombin and Macaranga barteri extracts have exhibited antiviral activity against several enteric viruses while Dicerocaryum eriocarpum with reported antibacterial activity remain unexplored as a reservoir of antiviral drug candidates. Accordingly, for the first time, this study profile the prevalence and diversity of viral families, including human and plant pathogenic viruses at the selected WWTPs and receiving rivers in eThekwini, Durban, Kwazulu-Natal, South Africa, using metagenomics next-generation sequencing (mNGS) approach and evaluates metabolites from S. mombin, M. barteri and D. eriocarpum against severe acute respiratory syndromecoronavirus-2 (SARS-CoV-2) and rotavirus A (RVA) using in silico techniques. The mNGS viral surveillance investigation identified viral families with a wide range of hosts including vertebrates (19.46%), plant (6.89%), insect (1.90%), fungal (0.13%), unclassified (7.25%) and phages (64.37%). Altogether, 30 viral families encompassing 26 different human pathogenic viral species were identified including enteroviruses, hepatovirus A, rotavirus A, norovirus, and astrovirus A. Conversely, plant viruses accounted for eight families dominated by the Virgaviridae. Most phytopathogenic reads belonged to the Tobamovirus genus, with additional representation from the family Bromoviridae detected across all sampling sites except RIVER4. These findings highlight the significance of wastewater surveillance in tracking known infections and unveiling possible emerging viral threats. RVA, one of the commonest waterborne enteric viruses detected in this study and SARS-CoV-2, although not detected in this study, probably due to low circulation within the communities at the time of sampling, were selected due to their clinical relevance and therapeutic limitations for in silico drug discovery from selected antiviral plants (S. mombin, M. barteri and D. eriocarpum). Molecular docking identified top-ranked compounds with higher negative docking scores against SARS-CoV-2 and RVA targets from the 77 pooled metabolites identified from the three selected medicinal plants against each of the investigated targets [main protease and RNAdependent RNA polymerase (RdRp)] of SARS-CoV-2 and RVA [capsid protein (VP7A, VP7C, VP7D), RdRp (VP1), spike protein (VP5*, VP8*)]. A minimum of three top-ranked compounds were subsequently identified owing to their physicochemical, pharmacokinetic and toxicological profiles suitable for drug development. The profiled top ranked compounds against the selected druggable targets of SARS-CoV-2 and RVA were subsequently subjected to 120-ns molecular dynamics (MD) simulations using the in-house HEAL1361 program with the Amber 18 package of the Centre for High Performance Computing (CHPC), South Africa. At least three of the top-ranked compounds exhibited higher negative binding free energy across the evaluated targets, suggesting structural and thermodynamic compatibility of the ligands at the binding domain of the targets and their suitability for drug development thereby validating the antiviral potential of the selected medicinal plants. However, against SCMP, only quercetin 3-O-rhamnoside had a higher negative binding free energy, suggesting the need for optimization of other metabolites. Notably, chrysoeriol7-glucuronide and spiraeoside demonstrated broad-spectrum affinity for RdRp of SARS-CoV-2 and RVA. Furthermore, (2S)- 6-(gamma,gamma-dimethylallyl)-3’,4’-dimethoxy-6’’,6’’- dimethylpyran[2’’,3’’:7,8]flavanone (2SG) and sericetin had better broad-spectrum affinities for both RVA VP5* and VP8*, while 2SG, apigenin-4 ′-glucoside and gnetin L exhibited better broad-spectrum affinities for RVA VP7A, VP7C and VP7D, suggesting their potential as multitarget antiviral candidates. However, some compounds induce higher thermodynamic entropy within the proteins relative to the standard. For instance, against VP5*, 2SG (-20.98 kcal/mol, 1.88 Å), sericetin (-20.46 kcal/mol, 1.93 Å) and sacranoside (-16.96 kcal/mol, 1.50 Å), though having higher negative binding free energies, exhibited higher RMSD values compared to the standard (1.30 Å) and unbound VP5* (1.45 Å). A partly similar trend was illustrated against VP8*, where sericetin (-18.31 kcal/mol, 1.27 Å) and 2SG (-20.98 kcal/mol, 1.18 Å) exhibited higher negative binding free energies yet had higher RMSD and RMSF values respectively, compared to the standard (1.19 Å, 1.01 Å). This observation highlights the need for optimizing these leads to improve their thermodynamic stability while boosting their affinity for the target proteins. Thus, due to their critical role in viral entry and infection, silver complexation optimization was limited to VP5* and VP8* of RVA to block the first and most vulnerable stage of infection. Accordingly, the silver complexation approach was employed to model possible silver nanoparticle conjugates for each lead compound, treating the compound as the reducing and capping agent. Thereafter, the effect of the complexation was evaluated whether complexation of the lead compound with silver enhances their binding affinity in silico. Improved binding affinity enhances drug activity through silver complexation which help mitigate drug resistance, broaden activity spectrum and enhance potency in vitro and in vivo. Thus, the study adopted silver complexation approach by conjugating silver with identified lead compounds against VP5* and VP8* via in silico modelling to achieve improved activity, reduced toxicity and maintain favorable pharmacokinetic profiles. To comprehend the effect of the complexation, quantum chemical calculations (density functional theory) were used to compare the molecular features of the silver-complexed leads against the lead compounds alongside assessment of drug-likeness and toxicity profiles. Thereafter, 12 and 19 silvercomplexed leads were docked against VP5* and VP8* respectively, followed by comparative interaction analysis between lead and silver-complexed compounds. Notably, the silvercomplexed leads exhibited enhanced molecular properties, suggesting better reactivity than their corresponding lead compounds without significantly altering their pharmacokinetic properties and toxicity profiles; hence, they remain suitable for drug development. Remarkably, higher negative docking scores were observed in all silver-complexed leads docked against VP5* compared to their corresponding lead compounds, except in the sacranoside A series. Conversely, lower negative docking scores were reported in the apigenin-4'-glucoside series, gnetin L A-E, and sericetin B relative to their lead compounds, while the remaining silvercomplexed leads exhibited improved binding affinity. Comparative interaction analysis identified 2SGC (-6.59 kcal/mol) and 2SGA (-6.77 kcal/mol) against VP5* and 2SGC (-8.06 kcal/mol) and SERA (-7.26 kcal/mol) against VP8* as promising candidates. Further computational investigation, including MD simulation, is recommended to elucidate the thermodynamics profile of the resulting protein and silver-complexed leads. Summarily, the observed enhanced binding capability of the silver-complexed leads could be attributed to their higher reactivity and increased interactions with essential amino acids at the binding pocket of the targets investigated. To validate the therapeutic potential of the profiled silver-complexed leads in combating viral infections, complementary in vitro and in vivo studies are strongly recommended.
Production of mycosporine-like amino acids from Euhalothece sp. for use as a photoprotectant
(2025) Mahmud, Uwais; Rawat, Ismail; Mogany, Trisha; Bux, Faizal
Protecting skin from harmful UV radiation is a well-recognized health imperative. Given that UV exposure is a primary cause of sunburn, premature skin aging, and significantly increases the risk of skin cancers including melanoma, the use of sunscreens has become a vital tool in public health strategies, leading to their widespread use. Whilst effective, there are concerns about the longterm effects of synthetic sunscreen ingredients that are driving the search for natural alternatives. Cyanobacteria are constantly exposed to short-wave ultraviolet (UV) radiation as they require solar energy to perform processes such as photosynthesis and nitrogen fixation. These microorganisms have developed multiple UV defence mechanisms to protect themselves from the higher amounts of UV radiation in the environment. Some of these strategies include mat formation, active repair mechanisms, accumulation of detoxifying enzymes and antioxidants, and synthesis of photo-protectants such as mycosporine-like amino acids (MAAs) (Rastogi et al., 2014). Mycosporine-like amino acids have gained a lot of interest in cosmetics and pharmaceutical industries since they act as natural photoprotectants and have shown to aid in overcoming rashes, pigmentation, aging as well as possess anticancer properties. Mycosporine-like amino acids are secondary metabolites produced by cyanobacteria in response to environmental stress such as salinity, temperature, high light irradiance and UV wavelengths. Cyanobacteria are a good source of MAAs, can be easily cultivated and requires a very short generation time, making them an environmentally friendly source of alternate photoprotectants. This study focuses on elucidating factors affecting MAA production using indigenous halophilic cyanobacteria Euhalothece sp. Light, salinity, and nitrogen concentration were optimised using response surface methodology to maximise MAA production. UV light irradiance was used to further induce expression of the protein. DNA was extracted and purified for gene expression analysis targeting the mys gene cluster. Purified MAAs were tested for their antioxidant activity and their stability under a range of temperatures, pH and UV irradiance to assess their potential for commercial use. Preliminary experiments confirmed the individual influence of abiotic factors, with light and salinity significantly impacting MAA production (p = 0,0395 and p = 0,0009 respectively). Using response surface methodology (RSM), the effects of light irradiance, salinity, nitrogen concentration, and UV exposure were optimized. A significant model (p = 0,0099) was developed, predicting optimal MAA production under 92 hours of UV exposure, nitrogen deficiency, and high salinity (90 or 120 g/L). Using 90 g/L salt was more cost-effective, requiring 28% less salt for a 5,36% reduction in MAA production. Molecular analysis through PCR confirmed the presence of the MAA biosynthetic gene cluster utilizing the OMT and DHQS and demonstrated its upregulation in response to UV exposure through qPCR. The UV-exposed culture showed amplification around cycle 14 while the control showed amplification around cycle 26. Purified MAAs demonstrated antioxidant activity and high stability across varying conditions over 48 hours. This included room temperature and neutral pH (p = 0,02), 4°C (p = 0,046), 40°C (p = 0,041) and UV irradiance (p = 0,04). These compounds showed excellent stability across various conditions, effectively maintaining their protective abilities. While their antioxidant capacity was measured (50,15%), it was clear that the main strength of MAAs lies in their strong UV protecting ability, making them highly suitable as active ingredients. This study demonstrates the potential of MAAs from Euhalothece sp. as a highly stable, effective, naturally derived, and industrially viable product. The optimized culture conditions, validated by molecular techniques, coupled with the high stability and additional beneficial properties of MAAs, position them as a compelling natural resource. Mycosporine-like amino acids can significantly advance photoprotection strategies and offer several other valuable applications in the cosmetic and pharmaceutical industries.