Thesis (M.Sc.(Agric.)(Food Science))-University of Pretoria, 2004. / Includes bibliographical references. Available on the Internet via the World Wide Web.

Sorghum is a gluten free cereal and forms the staple diet of a majority of the populations living in the semi-arid tropics dough. It is usually consumed in the form of bread made from the grain flour. Dough made with sorghum flour has poor viscoelastic properties compared to wheat dough and mechanical methods for production of sorghum roti are scarce. This study was conducted to elucidate the rheological and thermal properties of sorghum dough to establish its behavior. The temperature and amount of water used for preparation of the dough and the composition of the flour were varied. Wheat, soya and black gram flours were used to prepare the composite doughs. Sensory characteristics of roti made with these dough samples by the traditional method and mechanical compression were studied. The results are presented and their implications are discussed.

Thesis (Ph. D.)--Kansas State University, 2004. / Includes bibliographical references.

No description available.

In Africa, the grain sorghum (Sorghum bicolor (L.) Moench), is malted to provide the most important ingredient in brewing, malt, which is used primarily for the production of traditional (opaque) sorghum beer. Malting is the germination of cereal grain in moist air under controlled conditions, the primary objective being to promote the development of hydrolytic enzymes which are not present in the ungerminated grain. The malting process can be physically split into three distinct unit operations (viz. steeping, germination and drying). To date, little attention has been given to optimising the conditions of steeping for sorghum. The effects of different steeping variables (time, temperature and aeration) on the quality (in terms of diastatic power (amylase activity), free amino nitrogen and hot water extract) of sorghum malt for brewing were investigated. Malt quality was found to increase with steeping time, over the range 16-40 hours and the optimum steeping temperature was found to be in the range 25 to 30°C. Aeration during steeping appeared to be necessary to maximise the malt quality, particularly when steeping was conducted for long periods at high temperatures. Of particular significance was the observation that final sorghum malt quality was highly significantly correlated (p<0.01) with grain moisture content at steep-out (the end of the imbibition period). When steeping conditions based on these findings were used, a germination temperature of 25-30°C was found to be optimal for sorghum malt quality. As with steep-out moisture, green malt (grain after the specified germination time) moisture content was correlated Significantly (p<0.01) with final sorghum malt quality. The finding that sorghum malt quality is related to steepout moisture content was given further substance when it was shown that the stimulatory effect on sorghum malt quality of steeping sorghum in a dilute solution of alkali, actually increases the amount of water taken up during steeping probably because the alkali disrupted the pericarp cell wall structure of the grain. Barley malting practices have taken advantage of the knowledge that the exogenous application of gibberellic acid can enhance the synthesis of the critically important malt hydrolytic enzyme, a-amylase. To date, literature on the effect of exogenous application of gibberellic acid on sorghum malt quality has been inconclusive; with reports both of no effects, and of positive effects, on amylase activity. To elucidate the possible control mechanisms involved in sorghum germination, a combined HPLC-radioimmunoassay technique was used to determine the levels of selected plant growth regulators from the groups auxin, cytokinins, gibberellins and abscisic acid in sorghum at various stages of germination. Levels of gibberellic acid were low throughout germination. During germination the levels of the other plant growth regulators declined, but a peak in cytokinins followed the first visible signs of root protrusion. The high level of the germination inhibitor and gibberellic acid antagonist, abscisic acid, in the germ (embryo inclusive of scutellum) portion of the mature non-germinated grains was noteworthy. Based on these findings, it was determined that sorghum malt quality could in fact be improved significantly by the application of exogenous gibberellic acid. However, this was effective only if it was administered during the end of steeping or at the beginning of the germination step. By optimising the conditions of steeping and germination and by steeping in dilute NaOH or in gibberellic acid not only should it be possible to enhance the quality of sorghum malt, it should be possible to reduce the time required to obtain the specific quality, thereby offering a saving to the sorghum maltster in terms of operation costs and enhancing the total throughput possible from the malting plant. / Thesis (Ph.D.)-University of Natal, Durban, 1997.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Agric) Food Sience and Technology)--University of Pretoria, 2005. / Food Science / unrestricted

Thesis (Ph.D.(Microbiology)) -- University of Limpopo, 2022 / Traditional sorghum juice is produced in many African countries for human consumption. The juice is very rich in calories, B-group vitamins including thiamine, folic acid, riboflavin, nicotinic acid, and essential amino acids such as lysine. Low earning income women at village level produce sorghum juice for home consumption and sale. The short shelf life (2 to 3 days) of sorghum juice is a major problem for both the brewers and consumers of this drink. The aim of the study was to use 12 Combretum plants to improve the microbiological quality and shelf life of sorghum juice. Fresh stems and leaves of C. caffrum, C. vendae, C. erythrophyllum, C. elaegnoides, C. apiculatum, C. imberbe, C. adenogdium, C. padoides, C. bracteosum, C. kraussii, C. mkuzense and C. zeyherii were collected at Nelspruit, National Botanical Gardens, Mpumalanga, South Africa. Voucher specimens and tree labels were used to verify the identity of the plants. The stems and bark collected were cut into pieces and air dried for 30 days. When dried, the plant material was ground to a fine powder and stored in paper bags at room temperature. The wood was burnt in an open fire; fuel was not used to minimise contamination. The qualitative phytochemical composition of both the leaves and stems of Combretum plants analysed in this study revealed the presence of saponins, tannins, terpenoids, steroids, cardiac glycosides and flavonoids. The following phytoconstituents were lost in the ashes; tannins with the exception of C. mkuzense and C. padoides; cardiac glycosides and flavonoids. The quantitative phytochemical analyses revealed that both the leaves, stems and some ashes such as C. apiculatum and C. vendae contained appreciable levels of phenolic compounds, tannins and flavonoids. Quantitative analysis of antioxidant activity, the 2, 2, diphenyl-1-picrylhydrazyl (DPPH) assay was used as a screen test for the radical scavenging ability of the compounds present in the different 36 70% acetone extracts. DPPH screening method indicated great scavenging activity with the 70% acetone leaf extracts of C. kraussii, C. zeyherii and C. mkuzense. The leaf and stem extracts showed substantial great antioxidant activity in a concentration-dependent manner. There was a significant decrease in the antioxidant activity in the ashes (p=001), when compared to both the leaves and the stems. The proximate and nutritional analysis of the 70% acetone extracts were performed by AOAC and ICPE protocols, respectively. The results indicated that all the extracts had substantial amounts of ash, moisture, protein and energy. Mineral content of the plant parts was analysed as well, calcium had the highest concentration, while zinc was lowest in concentration. The mineral content decreased significantly in the stems (p ≤ 0.05) when compared to the leaves. There was a further decrease in mineral content with regard to the ashes with the exception of calcium. Based on these findings, the leaves and ashes of C. adenogonium and C. apiculatum could provide a good source of calcium in the diet, while C. adenogonium, C. bracteosum and C. apiculatum had high levels of sodium. A serial micro-dilution assay was used to determine the minimum inhibitory concentration (MIC) values for 70% plant extracts using tetrazolium violet reduction as an indicator of growth. Two Gram-positive (Stapylococcus aureus ATCC 29213 and Enterobacter faecalis ATCC 29212) and two Gram-negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) bacterial strains were used in this study. The leaves had good antibacterial properties with the lowest MIC value being 0.04 mg/ml against E. coli and S. aureus. E. faecalis was found to be resistant against all the leaves with the exception of C. imberbe. The stem extracts of Combretum spp. tested in the study showed antimicrobial properties with the lowest MIC value being 0.04 mg/ml against E. coli shown by C. bracteosum. However, E. faecalis was resistant against all the 12 plants tested. All the test microorganisms showed resistance to the ashes, with the exception of S. aureus, which was found to be susceptible to 75% of the test ash extracts with the lowest MIC value of 0.16 mg/ml. Cytotoxicity and anticancer activity of the acetone extracts of the 12 Combretum plants were evaluated using tetrazolium-based colorimetric assay (MTT assay) on A549 lung carcinoma cells. The assays revealed that 50% of the leaf extracts of tested plants showed cytotoxicity and cell proliferation inhibition in A549 lung carcinoma cells in a concentration-dependent manner. The A549 cells were more sensitive to the following plants: C. elaegnoides, C. erythrophyllum C. imberbe, C. kraussii and C. mkuzense. The following stems extract, C. adenogdium and C. caffrum did not have any anticancer activity, whereas C. apiculatum and C. bracteosum were only able to reduce cell viability to less than 60%. C. mkuzense, C. padoides, C. vendae and C. zeyherii acted in a concentration-depended manner with the greatest activity seen at the highest concentration (1000 µg/ml). The plants had activity at concentrations between 31.25 and 1000 µg/ml allowing only 20% and 50%, respectively, of the cells to remain viable. Ashes from C. mkuzense showed good anti-cancer activity at the highest concentration (1000 µg/ml) reducing cell viability to around 10%. Enterobacteriaceae, total coliform, S. aureus, B. cereus, E. coli and lactic acid bacteria viability were studied during the four weeks storage period of prepared sorghum juices. Juice samples were collected after preparation; the samples were serially diluted using peptone water. Tempo instrument (Biomereiux) was used to enumerate total coliform, total aerobic count, E. coli, S. aureus, lactic acid bacteria, enteric bacteria, yeast and mould using the most probable number following the manufacturers instruction. C. mkuzense and C. padoides plants were able to inhibit the growth of B. cereus, lactic acid bacteria and S. aureus during the first three weeks of storage. E. coli was not present throughout the four weeks storage time. Vitek 2 Compact (Biomereiux) was used for the characterisation and identification of the dominant bacterial isolates using biochemical reactions. The isolates were characterised by morphological differences. Sixty five percent of the isolates were the Enterobacter genus that are commonly found in soil, water, and sewage. The nutritional composition and sensory properties of the prepared sorghum juices treated with Combretum plants were investigated. All the juices had appreciable amounts of protein, ash and energy. Sorghum juice treated with ashes of C. caffrum, C. erythrophyllum and C. kraussii had the highest levels of proteins when compared with other treated sorghum juices. The sorghum juices prepared in the study had varying levels of trace element or minerals with potassium -(3, 55 – 104 mg/l) and calcium (3.2-148 mg/l). Similarly, cobalt (-1.22), coppr (-0.99), iron(-0.962), magnesium (0.004), sodium (-0.145), nickel (-2.7)) and zinc (-1.2)are present in very low amounts. The juices treated with ashes had relatively higher levels of calcium, potassium, magnesium and sodium. Sorghum juices treated with the ashes had better sensory and organoleptic properties when compared with those treated with the leaves. The juices treated with the ashes of C. caffrum and C. bracteseum were more accepted by most of the panellist when compared with other treated juices. Overall, this study presents valuable information on the phytochemical composition, nutritional composition and antioxidant properties of some Combretum species in South Africa. It recommended its use as food and in pharmaceutical preparations for the local industries. In addition, Combretum plants showing the effects tested in this study may be explored further for development into drugs. functional food as food preservatives and nutraceutical applications, beside their traditional use / University of Limpopo and Foodbev SETA

Thesis (M.Sc. Agriculture (Agricultural Economics) -- University of Limpopo, 2019 / Studies have indicated that sorghum hectares in South Africa have been decreasing over the past decades. This has resulted in a huge importation of the grain sorghum by the country. This study was undertaken due to sorghum production variability in South Africa. The objectives of this study were to estimate elasticity of sorghum production to changes in price and non-price factors, as well as estimating the short-run and long-run sorghum price elasticity. The study used time series data spanning from 1998 to 2016. This data was obtained from the abstracts of agricultural statistics and verified by South African Grain Information Services. Variance Error Correction Model (VECM) was employed to address both objectives. A number of diagnostic tests were performed to ensure that the study does not produce spurious regression results. This study estimated sorghum supply elasticity using two dependent variables being the area and yield response functions as model one and two respectively. The results have shown that area response function was found to be a robust model as most of the variables were significant, responsive and elastic. Maize price as a competing crop of sorghum negatively influenced the area allocation; however, the remaining variables positively influenced the area allocation in the long-run. In this model, all variables were statistically significant at 10% and 1% in the short and long-run respectively. In the yield function, most of the variables were insignificant, not responsive and inelastic, therefore, this model was found not to be robust and hence not adopted. Thus, it was concluded that sorghum output in South Africa is less sensitive to changes in price and nonprice factors. The findings further indicated that error correction term for area was -1.55 and -1.30 for yield response function. This indicated that the two models were able to revert to equilibrium. Therefore, it was concluded that the area response function was more robust, while the yield response function was not. Furthermore, it was concluded that sorghum production was more responsive to area allocation than yield function. Based on the findings, the study recommends that amongst other methods to enhance sorghum output, producers could use improved varieties or hybrids, as this action would result in allocation of more land to sorghum production, following price change.