Publications by authors named "John R N Taylor"

27 Publications

  • Page 1 of 1

Potential of moringa leaf and baobab fruit food-to-food fortification of wholegrain maize porridge to improve iron and zinc bioaccessibility.

Int J Food Sci Nutr 2021 Apr 15:1-13. Epub 2021 Apr 15.

Department of Consumer and Food Sciences and Institute for Food, Nutrition and Well-being, University of Pretoria, Pretoria, South Africa.

Food-to-food fortification (FtFF) with moringa leaf (iron source) and/or baobab fruit (citric acid and ascorbic acid source) (each 13-15 g/100 g porridge dry basis (db)) was studied to improve iron and zinc nutritive quality in African-type wholegrain maize-based porridges using dialysability assay. Moringa FtFF decreased percentage and total bioaccessible iron and zinc, by up to 84% and 45%, respectively. Moringa was very high in calcium, approximately 3% db and calcium-iron-phytate complexes inhibit iron bioavailability. Baobab FtFF increased percentage and total bioaccessible iron and zinc, especially in porridges containing carrot + mango (β-carotene source) and conventionally fortified with FeSO, by up to 111% and 60%, respectively. The effects were similar to those when ascorbic and citric acids were added as mineral absorption enhancers. While moringa FtFF could be inhibitory to iron and zinc bioavailability in cereal-based porridges, baobab fruit FtFF could improve their bioavailability, especially in combination with conventional iron fortification.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/09637486.2021.1911962DOI Listing
April 2021

Modification of the functional properties of hard-to-cook cowpea seed flours and cooked prepared pastes by γ-irradiation.

J Food Sci Technol 2021 Jan 10;58(1):22-33. Epub 2020 May 10.

Department of Consumer and Food Sciences and Institute for Food, Nutrition and Well-being, University of Pretoria, Private Bag X20, Hatfield, Pretoria, 0028 South Africa.

Cowpeas are an inexpensive source of quality protein but their utilisation is limited by long seed cooking time. This is exacerbated by development of the hard-to-cook (HTC) defect, which also adversely affects starch and protein functionality. Gamma-irradiation can eliminate cowpea seed insect infestation and affects seed functional properties, including reducing cooking time. Hence, the potential of γ-irradiation to modify the starch- and protein-related functionalities of HTC cowpeas was investigated. Gamma-irradiation at approximately 11 kGy was applied to the seeds of two cowpea varieties, differing in HTC susceptibility, where HTC had been induced by high-temperature, high-humidity (HTHH) storage. HTHH storage increased flour pasting peak viscosity by up to 40% in the less susceptible variety and by more than 100% in the more susceptible variety. Gamma-irradiation at least completely reversed this effect, due to starch depolymerisation and debranching. Gamma-irradiation also positively impacted on some protein-related properties adversely affected by HTC; partially reversing the reduction in flour and cooked paste nitrogen solubility index of the HTC-susceptible cowpea, as a result of protein depolymerisation. The multiple benefits of γ-irradiation: disinfection, cooking time reduction and reversing some adverse effects of HTC on functional properties could make it a viable process for improving HTC cowpea quality.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s13197-020-04509-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7813910PMC
January 2021

What is food-to-food fortification? A working definition and framework for evaluation of efficiency and implementation of best practices.

Compr Rev Food Sci Food Saf 2020 11 15;19(6):3618-3658. Epub 2020 Sep 15.

Plants for Human Health Institute, North Carolina State University, Kannapolis, North Carolina.

Food-to-food fortification (FtFF) is an emerging food-based strategy that can complement current strategies in the ongoing fight against micronutrient deficiencies, but it has not been defined or characterized. This review has proposed a working definition of FtFF. Comparison with other main food-based strategies clearly differentiates FtFF as an emerging strategy with the potential to address multiple micronutrient deficiencies simultaneously, with little dietary change required by consumers. A review of literature revealed that despite the limited number of studies (in vitro and in vivo), the diversity of food-based fortificants investigated and some contradictory data, there are promising fortificants, which have the potential to improve the amount of bioavailable iron, zinc, and provitamin A from starchy staple foods. These fortificants are typically fruits and vegetables, with high mineral as well as ascorbic acid and β-carotene contents. However, as the observed improvements in micronutrient bioavailability and status are relatively small, measuring the positive outcomes is more likely to be impactful only if the FtFF products are consumed as regular staples. Considering best practices in implementation of FtFF, raw material authentication and ingredient documentation are critical, especially as the contents of target micronutrients and bioavailability modulators as well as the microbiological quality of the plant-based fortificants can vary substantially. Also, as there are only few developed supply chains for plant-based fortificants, procurement of consistent materials may be problematic. This, however, provides the opportunity for value chain development, which can contribute towards the economic growth of communities, or hybrid approaches that leverage traditional premixes to standardize product micronutrient content.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/1541-4337.12624DOI Listing
November 2020

Influence of Waxy (High Amylopectin) and High Protein Digestibility Traits in Sorghum on Injera Sourdough-Type Flatbread Sensory Characteristics.

Foods 2020 Nov 26;9(12). Epub 2020 Nov 26.

Department of Consumer and Food Sciences, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa.

Injera, an East African leavened sourdough fermented pancake has remarkable textural properties despite being made from non-wheat flours. However, teff flour, which produces the best quality injera, is expensive and limited in availability. The effects of waxy (high amylopectin) and high protein digestibility (HD) traits in sorghum on injera quality were studied. Eight white tan-plant sorghum lines expressing these traits in various combinations and three normal sorghum types were studied, with teff flour as reference. Descriptive sensory profiling of fresh and stored injera revealed that injera from waxy sorghums were softer, spongier, more flexible and rollable compared to injera from normal sorghum and much closer in these important textural attributes to teff injera. Instrumental texture analysis of injera similarly showed that waxy sorghum injera had lower stress and higher strain than injera from normal sorghum. The improved injera textural quality was probably due to the slower retrogradation and better water-holding of amylopectin starch. The HD trait, however, did not clearly affect injera quality, probably because the lines had only moderately higher protein digestibility. In conclusion, waxy sorghum flour has considerable potential for the production of gluten-free sourdough fermented flatbread-type products with good textural functionality.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/foods9121749DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7759920PMC
November 2020

Solid-State Fermentation of Cassava Roots Using Cellulolytic-Type Alkaliphilic Bacillus spp. Cultures to Modify the Cell Walls and Assist Starch Release.

Appl Biochem Biotechnol 2020 Aug 27;191(4):1395-1410. Epub 2020 Feb 27.

Institute for Food, Nutrition and Well-being and Department of Consumer and Food Sciences, University of Pretoria, Private Bag X 20, Hatfield, Pretoria, 0028, South Africa.

To improve cassava starch extraction by wet milling, solid-state fermentation of ground roots using cellulolytic-type alkaliphilic Bacilli spp., Bacillus akibai, B. cellulosilyticus and B. hemicellulosilyticus was investigated. Enzyme assay and scanning electron microscopy indicated that Bacillus spp. production of extracellular cellulase and polygalacturonase caused the formation of micropores through the root parenchyma cell walls and exposed the embedded cellulosic network. Gas chromatography data of the cell wall constituent sugars remaining after fermentation and Fourier transform infrared data indicated that the Bacillus treatments reduced the levels of pectin and, hemicellulose and to lesser extent cellulose. Wide-angle X-ray scattering data indicated that the Bacillus spp. cell wall degrading enzymes had partially hydrolysed the amorphous fractions of the cell wall polysaccharides. All the Bacillus spp. treatments improved starch extraction by 17-23% compared to fermentation with endogenous microflora. B. cellulosilyticus was most effective in disintegration of large root particles and as result, released marginally the most starch, probably due to it having the highest cellulase activity. Solid-state fermentation using cellulolytic-type Bacillus spp. is, therefore, promising to technology to improve the efficiency of cassava wet milling cell wall disintegration and consequent starch yield without use of commercial cell wall degrading enzymes or polluting chemicals.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12010-020-03286-xDOI Listing
August 2020

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).

J Food Sci Technol 2019 Apr 20;56(4):2244-2256. Epub 2019 Mar 20.

1Department of Consumer and Food Sciences and Institute of Food Nutrition and Well-being, University of Pretoria, Private Bag X20, Hatfield, Pretoria, 0028 South Africa.

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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s13197-019-03711-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6443743PMC
April 2019

Comparison of formation of visco-elastic masses and their properties between zeins and kafirins.

Food Chem 2018 Apr 16;245:178-188. Epub 2017 Oct 16.

Institute for Food, Nutrition and Well-being and Department of Food Science, University of Pretoria, Private Bag X 20, Hatfield 0028, South Africa. Electronic address:

Zeins of differing sub-class composition much more readily formed visco-elastic masses in water or acetic acid solutions than equivalent kafirin preparations. Visco-elastic masses could be formed from both zein and kafirin preparations by coacervation from glacial acetic acid. Dissolving the prolamins in glacial acetic acid apparently enabled protonation and complete solvation. Stress-relaxation analysis of coacervated zein and kafirin visco-elastic masses showed they were initially soft. With storage, they became much firmer. Zein masses exhibited predominantly viscous flow properties, whereas kafirin masses were more elastic. The γ-sub-class is apparently necessary for the retention of visco-elastic mass softness with kafirin and zein, and for elastic recovery of kafirin. Generally, regardless of water or acetic acid treatment, all the zein preparations had similar FTIR spectra, with greater α-helical conformation, than the kafirin preparations which were also similar to each other. Kafirin visco-elastic masses have a much higher elastic character than zein masses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.foodchem.2017.10.082DOI Listing
April 2018

Formation and properties of viscoelastic masses made from kafirin by a process of simple coacervation from solution in glacial acetic acid using water.

Food Chem 2018 Jan 22;239:333-342. Epub 2017 Jun 22.

Institute for Food, Nutrition and Well-being and Department of Food Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa. Electronic address:

Stable viscoelastic masses have been formed from kafirin in a mainly aqueous system. Kafirin was dissolved in glacial acetic acid (GAA) and simple coacervation was performed by rapid addition of 15°C water under low shear. Kafirin precipitated out as a network of hydrated fibrils which could be hand-kneaded into a viscoelastic mass. These could be formed from a very wide range of kafirins, including those where β- or γ-subclass expression was suppressed. Kafirin composition influenced the appearance of the masses but did not fundamentally affect stress-relaxation behaviour. Fresh kafirin masses exhibited similar elasticity and viscous flow balance to gluten. They maintained functionality when stored for several days at 10°C but their elastic component increased. FTIR showed that when kafirin was dissolved in GAA its α-helical conformation increased substantially. Dissociation of the kafirin molecules in GAA, assuming a α-helical conformation may have enhanced water binding, enabling viscoelastic mass formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.foodchem.2017.06.114DOI Listing
January 2018

Mechanism of cassava tuber cell wall weakening by dilute sodium hydroxide steeping.

Food Chem 2017 Aug 3;228:338-347. Epub 2017 Feb 3.

Institute for Food, Nutrition and Well-being and Department of Food Science, University of Pretoria, Private Bag X 20, Hatfield 0028, South Africa. Electronic address:

Steeping of cassava root pieces in 0.75% NaOH in combination with wet milling was investigated to determine whether and how dilute NaOH modifies cassava cell walls. Gas chromatography data of cell wall constituent sugar composition and Fourier transform infrared (FTIR) data showed that NaOH steeping reduced the level of pectin in cassava cell walls. FTIR and wide-angle X-ray scattering spectroscopy also indicated that NaOH steeping combined with fine milling slightly reduced cellulose crystallinity. Scanning electron microscopy showed that NaOH steeping produced micropores in the cell walls and light microscopy revealed that NaOH steeping increased disaggregation of parenchyma cells. Steeping of ground cassava in NaOH resulted in a 12% decrease in large residue particles and approx. 4% greater starch yield with wet milling. Therefore dilute NaOH steeping can improve the effectiveness of wet milling in disintegrating cell walls through solubilisation of pectin, thereby reduced cell wall strength.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.foodchem.2017.02.006DOI Listing
August 2017

Emerging Early Actions to Bend the Curve in Sub-Saharan Africa's Nutrition Transition.

Food Nutr Bull 2016 06 1;37(2):219-41. Epub 2016 Apr 1.

University of Pretoria, Pretoria, South Africa.

Background: Sub-Saharan Africa is the last region to undergo a nutrition transition and can still avoid its adverse health outcomes.

Objective: The article explores emerging responses to "bend the curve" in sub-Saharan Africa's nutrition transition to steer public health outcomes onto a healthier trajectory.

Methods: Early responses in 3 countries at different stages of food system transformation are examined: South Africa-advanced, Ghana-intermediate, and Uganda-early. By comparing these with international experience, actions are proposed to influence nutrition and public health trajectories as Africa's food systems undergo rapid structural change.

Results: Arising from rapid urbanization and diet change, major public health problems associated with overweight are taking place, particularly in South Africa and among adult women. However, public health responses are generally tepid in sub-Saharan Africa. Only in South Africa have policy makers instituted extensive actions to combat overweight and associated noncommunicable diseases through regulation, education, and public health programs. Elsewhere, in countries in the early and middle stages of transition, public health systems continue to focus their limited resources primarily on undernutrition. Related pressures on the supply side of Africa's food systems are emerging that also need to be addressed.

Conclusions: Three types of intervention appear most feasible: maternal and child health programs to simultaneously address short-term undernutrition problems while at the same time helping to reduce future tendencies toward overweigh; regulatory and fiscal actions to limit access to unhealthy foods; and modernization of Africa's agrifood food system through job skills training, marketing reforms, and food industry entrepreneurship.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/0379572116637723DOI Listing
June 2016

Inactivation of tannins in milled sorghum grain through steeping in dilute NaOH solution.

Food Chem 2015 May 23;175:225-32. Epub 2014 Nov 23.

Institute for Food, Nutrition and Well-being and Department of Food Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa. Electronic address:

Steeping milled sorghum in up to 0.4% NaOH was investigated as a method of tannin inactivation. NaOH steeping substantially reduced assayable total phenols and tannins in both Type III and Type II sorghums and with Type III sorghum caused a 60-80% reduction in α-amylase inhibition compared to a 20% reduction by water steeping. NaOH treatment also reduced starch liquefaction time and increased free amino nitrogen. Type II tannin sorghum did not inhibit α-amylase and consequently the NaOH treatment had no effect. HPLC and LC-MS of the tannin extracts indicated a general trend of increasing proanthocyanidin/procyanidin size with increasing NaOH concentration and steeping time, coupled with a reduction in total area of peaks resolved. These show that the NaOH treatment forms highly polymerised tannin compounds, too large to assay and to interact with the α-amylase. NaOH pre-treatment of Type III sorghums could enable their utilisation in bioethanol production.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.foodchem.2014.11.102DOI Listing
May 2015

Biocompatibility and biodegradation of protein microparticle and film scaffolds made from kafirin (sorghum prolamin protein) subcutaneously implanted in rodent models.

J Biomed Mater Res A 2015 Aug 29;103(8):2582-90. Epub 2014 Dec 29.

Institute for Food, Nutrition and Well-Being and Department of Food Science, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa.

Kafirin, the sorghum prolamin protein, like its maize homologue zein, can be made into microparticles and films and potentially used as a biomaterial. Zein has good bio- and cyto-compatibility. Kafirin could be advantageous as it is more hydrophobic, more crosslinked, more slowly digested by mammalian proteases than zein and is non-allergenic. The safety and biocompatibility of kafirin implants in two forms was determined in rodent models. One week post subcutaneous injection of kafirin microparticles (size 5-µm diameter) in mice, chronic inflammation, abnormal red blood cells, and gross fibrin formation were observed. This chronic inflammatory response was possibly caused by the release of hydrolysis products such as glutamate during the degradation of the kafirin microparticles. In contrast, films made from kafirin microparticles (50-µm thick, folded into 1 cm(3) ) implanted in rats showed no abnormal inflammatory reactions and were only partially degraded by day 28. The slower degradation of the kafirin films was probably due to their far smaller surface area when compared to kafirin microparticles. Thus, kafirin films appear to have potential as a biomaterial. This study also raises awareness that the form of prolamin based biomaterials, (kafirin and zein) should be considered when assessing the safety of such materials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jbm.a.35394DOI Listing
August 2015

Effect of sorghum type and malting on production of free amino nitrogen in conjunction with exogenous protease enzymes.

J Sci Food Agric 2015 Jan 9;95(2):417-22. Epub 2014 Jun 9.

Department of Food Science, University of Pretoria, Hatfield, South Africa.

Background: Sorghum types suitable for brewing and bioethanol production are required. The effect of sorghum type (white non-tannin versus white type II tannin) on free amino nitrogen (FAN) production from sorghum grain and malt using exogenous protease enzymes was investigated over extended incubation at moderate temperature (45 °C).

Results: With grain in the absence of exogenous proteases, white non-tannin sorghum produced substantially higher levels of FAN than white type II tannin sorghum, due to the tannins in the latter. Incubating sorghum grain with neutral proteinase and amino-peptidase in combination improved FAN production. The two sorghum types produced similar FAN levels when malted and incubated in the absence of the exogenous proteases. When both sorghums were malted and incubated with neutral proteinase alone substantially more FAN yield (124-126 mg 100 g(-1)) occurred than with grains (61-84 mg 100 g(-1)). The combination of amino-peptidase and proteinase did not improve FAN further. Neither, did malting influence wort free amino acid profile. Group B amino acids constituted the highest percentage (42-47%).

Conclusion: With grain, white non-tannin sorghum plus proteinase and amino-peptidase yields the highest FAN, with malt both white non-tannin and white type II tannin sorghums plus proteinase yield the highest FAN.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jsfa.6739DOI Listing
January 2015

Effects of processing sorghum and millets on their phenolic phytochemicals and the implications of this to the health-enhancing properties of sorghum and millet food and beverage products.

J Sci Food Agric 2015 Jan 27;95(2):225-37. Epub 2014 May 27.

Institute for Food, Nutrition and Well-being and Department of Food Science, University of Pretoria, Hatfield, 0028, South Africa.

Sorghum and millet grains are generally rich in phytochemicals, particularly various types of phenolics. However, the types and amounts vary greatly between and within species. The food-processing operations applied to these grains, i.e. dehulling and decortication, malting, fermentation and thermal processing, dramatically affect the quantity of phenolics present, most generally reducing them. Thus the levels of phytochemicals in sorghum and millet foods and beverages are usually considerably lower than in the grains. Notwithstanding this, there is considerable evidence that sorghum and millet foods and beverages have important functional and health-promoting effects, specifically antidiabetic, cardiovascular disease and cancer prevention, due to the actions of these phytochemicals. Also their lactic acid bacteria-fermented products may have probiotic effects related to their unique microflora. However, direct proof of these health-enhancing effects is lacking as most studies have been carried out on the grains or grain extracts and not the food and beverage products themselves, and also most research work has been in vitro or ex vivo and not in vivo. To provide the required evidence, better designed studies are needed. The sorghum and millet products should be fully characterised, especially their phytochemical composition. Most importantly, well-controlled human clinical studies and intervention trials are required.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jsfa.6713DOI Listing
January 2015

Effects of aqueous soaking on the phytate and mineral contents and phytate:mineral ratios of wholegrain normal sorghum and maize and low phytate sorghum.

Int J Food Sci Nutr 2014 Aug 13;65(5):539-46. Epub 2014 Feb 13.

Department of Food Science and.

Soaking of cereal grains has been suggested as a method to reduce their phytate content and hence increase their mineral availability. Whole and milled wholegrain, normal and low phytate sorghum and normal maize were studied. Soaking of unmilled sorghum and maize did not result in substantial reductions in phytate or mineral contents. With milled grains, phytate solubilisation was somewhat greater in maize than in sorghum after a short (1 h) soaking period but not after 6-12 h of soaking when practically all phytate had been solubilised. Also, with milled, low phyate sorghums, phytate solubilisation was not substantially higher than in their null controls. Soaking milled grain substantially reduced mineral contents and Ca × phytate:zinc molar ratios. However, the loss in soluble minerals could have a greater negative effect on mineral availability, compared to the positive effect of the phytate reduction. Thus, soaking does not seem to be a viable household method to improve sorghum and maize mineral availability.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3109/09637486.2014.886182DOI Listing
August 2014

Co-suppression of synthesis of major α-kafirin sub-class together with γ-kafirin-1 and γ-kafirin-2 required for substantially improved protein digestibility in transgenic sorghum.

Plant Cell Rep 2014 Mar 19;33(3):521-37. Epub 2014 Jan 19.

CSIR/BioSciences, Meiring Naude Road, Brummeria, Pretoria, 0001, South Africa.

Key Message: Co-suppressing major kafirin sub-classes is fundamental to improved protein digestibility and nutritional value of sorghum. The improvement is linked to an irregularly invaginated phenotype of protein bodies.

Abstract: The combined suppression of only two genes, γ kafirin-1 (25 kDa) and γ-kafirin-2 (50 kDa), significantly increases sorghum kafirin in vitro digestibility. Co-suppression of a third gene, α-kafirin A1 (25 kDa), in addition to the two genes increases the digestibility further. The high-digestibility trait has previously only been obtained either through the co-suppression of six kafirin genes (α-A1, 25 kDa; α-B1, 19 kDa; α-B2, 22 kDa; γ-kaf1, 27 kDa; γ-kaf 2, 50 kDa; and δ-kaf 2, 18 kDa) or through random chemical-induced mutations (for example, the high protein digestibility mutant). We present further evidence that suppressing just three of these genes alters kafirin protein cross-linking and protein body microstructure to an irregularly invaginated phenotype. The irregular invaginations are consistent with high pepsin enzyme accessibility and hence high digestibility. The approach we adopted towards increasing sorghum protein digestibility appears to be an effective tool in improving the status of sorghum as a principal supplier of energy and protein in poor communities residing in marginal agro-ecological zones of Africa.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00299-013-1556-5DOI Listing
March 2014

Role of γ-kafirin in the formation and organization of kafirin microstructures.

J Agric Food Chem 2013 Nov 4;61(45):10757-65. Epub 2013 Nov 4.

Institute for Food, Nutrition and Well-being and Department of Food Science, University of Pretoria , Private Bag X20, Hatfield 0028, South Africa.

The possible importance of the cysteine-rich γ-prolamin in kafirin and zein functionality has been neglected. The role of γ-kafirin in organized microstructures was investigated in microparticles. Residual kafirin (total kafirin minus γ-kafirin) "microparticles" were non-discrete (amorphous mass of material), as viewed by electron microscopy and atomic force microscopy. Adding 15% γ-kafirin to residual kafirin resulted in the formation of a mixture of non-discrete material and nanosize discrete spherical structures. Adding 30% γ-kafirin to the residual kafirin resulted in discrete spherical nanosize particles. Fourier transform infrared spectroscopy indicated that γ-kafirin had a mixture of random-coil and β-sheet conformations, in contrast to total kafirin, which is mainly α-helical conformation. γ-Kafirin also had a very high glass transition temperature (Tg) (≈270 °C). The conformation and high Tg of γ-kafirin probably confer structural stability to kafirin microstructures. Because of its ability to form disulfide cross-links, γ-kafirin appears to be essential to form and stabilize organized microstructures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf403571eDOI Listing
November 2013

Effect of phytate reduction of sorghum, through genetic modification, on iron and zinc availability as assessed by an in vitro dialysability bioaccessibility assay, Caco-2 cell uptake assay, and suckling rat pup absorption model.

Food Chem 2013 Nov 13;141(2):1019-25. Epub 2013 Feb 13.

Centre for Nutrition and Institute for Food, Nutrition and Well-being, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.

Improved iron and zinc availability from sorghum, a commonly consumed staple, will benefit many malnourished communities in rural Africa burdened with high prevalence of iron and zinc deficiency. This research compared the effect of genetic phytate reduction in sorghum on iron and zinc bioaccessibility and uptake measured by in vitro dialysability and Caco-2 cell uptake assays to that of iron and zinc absorption measured by a suckling rat pup model. The phytate reduction (80-86%) in these sorghums significantly increased zinc availability. The Caco-2 cell method, but not the dialysability assay, proved useful in estimating zinc absorption. The measured increase in iron availability differed between the methods, possibly due to the effect of varying mineral (Ca, Fe, Zn, P) contents of the sorghums. This effect was most prominent in the iron uptake results. More research is needed to determine the effect of naturally occurring variations in mineral contents of sorghum on the iron uptake by Caco-2 cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.foodchem.2013.01.105DOI Listing
November 2013

Highly viscous dough-forming properties of marama protein.

Food Chem 2012 Oct 28;134(3):1519-26. Epub 2012 Mar 28.

Department of Food Science, University of Pretoria, Private Bay X 20, Hatfield 0028, South Africa.

Marama bean is an indigenous southern African oilseed legume with an unusual protein composition. Hence, its rheological properties were studied. Marama protein formed a highly viscous and extensible dough when compared to soya and gluten. With a dough of 38% moisture, marama protein extensibility was very high (304% of its original length), twice that of gluten and soya, and this increased considerably (>3-fold) when the moisture content was increased to 45%. With added peroxidase, the storage modulus (G') of marama protein dough increased with time, suggesting the formation of new and strong protein networks. Dityrosine crosslinks were detected in the doughs. Marama protein showed a single transition with a denaturation temperature higher than soya glycinin. Marama protein was more hydrophobic and contained more β-sheet structure than did soya. Thus, the highly viscous and extensible rheological behaviour of marama protein is probably related to its high β-sheet conformation, hydrophobic interactions and tyrosine crosslinks.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.foodchem.2012.03.066DOI Listing
October 2012

Physicochemical modification of kafirin microparticles and their ability to bind bone morphogenetic protein-2 (BMP-2), for application as a biomaterial.

J Agric Food Chem 2012 Aug 17;60(34):8419-26. Epub 2012 Aug 17.

Institute for Food, Nutrition and Well-being and Department of Food Science, University of Pretoria , Private Bag X20, Hatfield 0028, South Africa.

Vacuolated spherical kafirin microparticles with a mean diameter of 5 μm can be formed from an acidic solution with water addition. Three-dimensional scaffolds for hard tissue repair require large structures with a high degree of interconnected porosity. Cross-linking the formed kafirin microparticles using wet heat or glutaraldehyde treatment resulted in larger structures (approximately 20 μm), which, while similar in size and external morphology, were apparently formed by further assisted assembly by two significantly different mechanisms. Heat treatment, which increased the vacuole size, involved kafirin polymerization by disulfide bonding with the microparticles being formed from round, coalesced nanostructures, as shown by atomic force microscopy (AFM). Kafirin polymerization of glutaraldehyde-treated microparticles was not by disulfide bonding, and the nanostructures, as revealed by AFM, were spindle shaped. Both treatments enhanced BMP-2 binding to the microparticles, probably due to their increased size. Thus, these modified kafirin microparticles have potential as natural, nonanimal protein bioactive scaffolds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf302533eDOI Listing
August 2012

Improvement in water stability and other related functional properties of thin cast kafirin protein films.

J Agric Food Chem 2011 Dec 15;59(23):12674-82. Epub 2011 Nov 15.

Department of Food Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.

Improvement in the water stability and other related functional properties of thin (<50 μm) kafirin protein films was investigated. Thin conventional kafirin films and kafirin microparticle films were prepared by casting in acetic acid solution. Thin kafirin films cast from microparticles were more stable in water than conventional cast kafirin films. Treatment of kafirin microparticles with heat and transglutaminase resulted in slightly thicker films with reduced tensile strength. In contrast, glutaraldehyde treatment resulted in up to a 43% increase in film tensile strength. The films prepared from microparticles treated with glutaraldehyde were quite stable in ambient temperature water, despite the loss of plasticizer. This was probably due to the formation of covalent cross-linking between free amino groups of the kafirin polypeptides and carbonyl groups of the aldehyde. Thus, such thin glutaraldehyde-treated kafirin microparticle films appear to have good potential for use as biomaterials in aqueous applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf203273yDOI Listing
December 2011

Transgenic sorghum with altered kafirin synthesis: kafirin solubility, polymerization, and protein digestion.

J Agric Food Chem 2011 Sep 16;59(17):9265-70. Epub 2011 Aug 16.

Department of Food Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.

Transgenic sorghum (TG) lines with altered kafirin synthesis, particularly suppression of γ-kafirin synthesis, and improved protein quality have been developed. The proportion of kafirin extracted with 60% tert-butyl alcohol alone was greatly increased in the TG lines. However, the total amount of kafirin remained unchanged. Further, in the TG lines, the kafirin was much less polymerized by disulfide bonding. There was also evidence of compensatory synthesis of other kafirin proteins. Cooked protein digestibility was increased in the TG form, even after removal of interfering starch. The TG protein bodies were intermediate in appearance between the normal type and the invaginated high digestibility mutants. Hence, the increased protein digestibility of these TG lines is probably related to their lower levels of disulfide-bonded kafirin polymerization, allowing better access of proteases. This work appears to confirm that disulfide bond formation in kafirin is responsible for the reduced protein digestibility of cooked sorghum.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf201878pDOI Listing
September 2011

Rat bioassay of the protein nutritional quality of soy-fortified sorghum biscuits for supplementary feeding of school-age children.

J Sci Food Agric 2011 Aug 29;91(10):1814-21. Epub 2011 Mar 29.

Department of Food Science, University of Pretoria, Hatfield, South Africa.

Background: Protein-energy malnutrition (PEM) remains a major deficiency disease among children in developing countries. The protein nutritional quality of soy-fortified sorghum biscuits was evaluated with respect to their potential as a protein-rich supplementary food. Three isonitrogenous diets based on 50:50 ratio decorticated sorghum:defatted soy flour biscuits, 100% sorghum biscuits, casein, and a protein-free diet were fed to male Sprague Dawley weanling rats.

Results: Protein efficiency ratio (PER) for the sorghum-soy biscuit diet was equivalent to the reference casein diet, and zero for the 100% sorghum diet. Faecal bulk for 100% sorghum diet was 1.5 times higher than sorghum-soy and casein diets. True protein digestibility of the three diets was high-88-95%-agreeing with previous rat studies with sorghum. Biological value and net protein utilization of the sorghum-soy biscuit diet were similar to the casein diet, but lower than the 100% sorghum biscuit diet

Conclusion: Notwithstanding limitations of rat bioassay for assessing sorghum food protein quality, the high PER of defatted soy flour-fortified sorghum biscuits (sorghum:soy 50:50 ratio) indicates they have considerable potential as a supplementary food to young children to alleviate PEM.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jsfa.4389DOI Listing
August 2011

Protein biofortified sorghum: effect of processing into traditional african foods on their protein quality.

J Agric Food Chem 2011 Mar 21;59(6):2386-92. Epub 2011 Feb 21.

Department of Food Science, University of Pretoria, Pretoria 0002, South Africa.

Protein biofortification into crops is a means to combat childhood protein-energy malnutrition (PEM) in developing countries, by increasing the bioavailability of protein in staple plant foods and ensuring sustainability of the crop. Protein biofortification of sorghum has been achieved by both chemically induced mutation and genetic engineering. For this biofortification to be effective, the improved protein quality in the grain must be retained when it is processed into staple African foods. Suppression of kafirin synthesis by genetic engineering appeared to be superior to improved protein digestibility by chemical mutagenesis, because both the lysine content and protein digestibility were substantially improved and maintained in a range of African foods. For the genetically engineered sorghums, the protein digestibility corrected amino acid score was almost twice that of their null controls and considerably higher than the high protein digestibility sorghum type. Such protein biofortified sorghum has considerable potential to alleviate PEM.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf104006vDOI Listing
March 2011

Kafirin microparticle encapsulation of catechin and sorghum condensed tannins.

J Agric Food Chem 2009 Aug;57(16):7523-8

Department of Food Science, University of Pretoria, Pretoria, South Africa.

To exploit the porous nature of previously developed kafirin microparticles, encapsulation of the bioactive polyphenols, catechin and sorghum condensed tannins, was investigated. The antioxidant release profiles of the encapsulated substances were studied under simulated gastric conditions. Kafirin microparticles encapsulating catechin or sorghum condensed tannins were similar in size to control kafirin microparticles (5-6 mum). TEM showed that kafirin microparticles encapsulating catechin had a rough porous surface. Microparticles encapsulating sorghum condensed tannins were irregular in shape, some apparently joined together, with a mixture of rough and smooth surfaces. Over a period of 4 h, catechin and sorghum condensed tannin encapsulated kafirin microparticles showed virtually no protein digestion but released approximately 70 and 50%, respectively, of total antioxidant activity. Thus, the use of kafirin microparticles to encapsulate catechin and sorghum condensed tannins has potential as an effective method of controlled release of dietary antioxidants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf901592qDOI Listing
August 2009

Preparation of free-standing films from kafirin protein microparticles: mechanism of formation and functional properties.

J Agric Food Chem 2009 Aug;57(15):6729-35

Department of Food Science, University of Pretoria, Pretoria 0002, South Africa.

A method of preparing free-standing films using kafirin microparticles made by phase separation from acetic acid is described. Film preparation involved the suspension of the microparticles in acetic acid solution containing plasticizer. On evaporation of the acetic acid, a complete, smooth, flexible, transparent film was formed. A minimum concentration of acid was required to form a cohesive film relative to the concentration of kafirin. This was approximately 10.8:1, percent acetic acid to percent kafirin. Film formation appears to be by controlled aggregation of kafirin microparticles, followed by dissolution of the microparticles in acetic acid and drying into a cohesive film. The functional properties of microparticle films were generally superior to films cast directly from a solution of kafirin, at the same protein content. Kafirin microparticle films were very thin (<15 microm), relatively strong but not very extensible, with better water barrier properties and lower protein digestibility than conventionally cast kafirin films.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf900957sDOI Listing
August 2009

Properties of heat-treated sorghum and maize meal and their prolamin proteins.

J Agric Food Chem 2009 Feb;57(3):1045-50

Department of Food Science, University of Pretoria, Pretoria, Republic of South Africa.

The digestibility of sorghum protein is reduced when wet cooked. Size exclusion chromatography (SEC) together with other protein analytical techniques was applied to further elucidate the effects of cooking on the sorghum and maize and their prolamin proteins. Sorghum and maize meal and their respective tertiary butanol extracted kafirin and zein were wet heat treated by boiling or pressure cooking. As expected, the in vitro pepsin protein digestibility of sorghum meal and kafirin reduced with boiling and pressure cooking, whereas the decrease in maize meal and zein protein digestibility was much less. SDS-PAGE showed that the boiled and pressure-cooked kafirin was more polymerized than the corresponding zein preparations. SEC of kafirin also revealed a substantially increased high molecular weight peak with boiling and pressure cooking. In contrast, the high molecular weight peak was very small for control and wet heated treated zein. The highly polymerized kafirin occurs as a result of extensive disulfide bonding of kafirin monomers during cooking. Cooking sorghum meal and kafirin also resulted in a relative change in secondary structure from alpha-helical to beta-sheet, as determined by Fourier transform infrared spectroscopy. The pepsin indigestible kafirin residues were mainly in beta-sheet conformation. In contrast, the conformational changes were very small for cooked maize meal and zein. Disulfide bonds formed during heating cause polymeric kafirin formation and also promote realignment of kafirin into beta-sheet structures. These conformational changes apparently cause the lower proteolysis susceptibility of kafirin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf802672eDOI Listing
February 2009