Thesis (M.Inst.Agrar.)(Food production and processing)--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

Whole grain and bran samples of two Malawian sorghums, Phatafuli, (a brown-coloured condensed tannin variety) and Shabalala, (a white-coloured condensed tannin-free variety) were analysed for their content of total phenols, condensed tannins and antioxidant activities. The effect of oxidizing conditions during extraction, and the storage stability of a freeze-dried crude phenolic extract (CPE) from the condensed tannin sorghum bran as influenced by packaging, storage temperature and length of storage, in relation to its content of total phenols, condensed tannins and antioxidant activity was also investigated. Antioxidant activity of the CPE, in comparison with tertiary butyl hydroquinone (TBHQ), was then evaluated in sunflower oil at concentrations of 1000, 1500 and 2000 ppm in the absence or presence of ferric ions at 2.2 and 4.4 ppm in the dark at 65oC.Progression of oxidation was monitored by measurement of peroxide values (PV) and anisidine values (AV) during a 14-day storage period. Phatafuli contained higher content of total phenols and antioxidant activity than Shabalala both in the whole grain and the bran, probably due to the presence of condensed tannins in Phatafuli sorghum, which were not detected in Shabalala sorghum. For both sorghum varieties, the bran contained higher levels of total phenols and antioxidant activity than the whole grain, confirming that phenolic compounds in sorghum are largely concentrated in the bran. Antioxidant activities of the sorghum varieties correlated highly with their total phenol and condensed tannin contents, suggesting that the phenolic compounds were largely responsible for the antioxidant activities of the sorghum grains. Bubbling of oxygen into the liquid crude phenolic extract did not have any significant effect on the parameters tested. Similarly, vacuum-packed samples did not differ significantly in the parameters tested from the samples that were not vacuum-packed. CPE samples stored at –20oC had significantly higher levels of total phenols, condensed tannins and antioxidant activity than those stored at 25oC during some days of storage. Storage time was however the major factor influencing the levels of total phenols, condensed tannins and antioxidant activity of the CPE from Phatafuli sorghum during storage, which suggested that CPE from condensed tannin sorghum bran might need to be used shortly after extraction to ensure optimum antioxidant activity. There was an insignificant correlation between the antioxidant activities of the CPE and their phenolic contents during storage, which could have been due to the formation of new compounds with a lower antioxidant capacity. The CPE inhibited oxidation of sunflower oil as shown by lower peroxide values and anisidine values compared to control samples. The CPE was however less effective in reducing peroxide values compared to TBHQ, but was similar to TBHQ in reducing anisidine values. In the presence of ferric ions, the CPE appeared to be less effective in reducing peroxide values compared to TBHQ, but appeared to be more effective than TBHQ in reducing anisidine values. The results showed that the tannin sorghum bran CPE appeared to act as both lipid radical scavengers and metal chelators. The CPE however imparted colour to the sunflower oil, which could limit its application as a natural antioxidant in edible oils. / Dissertation (MSc(Agric) Food Science and Technology)--University of Pretoria, 2008. / Food Science / unrestricted

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / The industrialisation of the twenty-first century and the worldwide population growth led to the high demand for energy. Fossil fuels are the leading contributor to the global energy, and subsequently, there is a high demand of fuels. The decrease of global fossil fuels and the environmental air pollution caused by these fuels are concerning. Therefore, eco-friendly and renewable fuel such as biodiesel is one the leading alternative. Chromatography and Spectroscopy are the most used analytical methods and proven reliable but are time-consuming, requires qualified personal, extensive samples preparation, costly and do not provide in-situ real-time monitoring. Fourier Transform Infrared (FTIR) has mainly been used for qualitative analysis of biodiesel, but not much work has been reported in real-time monitoring. This study focused on the modelling of in-situ real-time monitoring of the biodiesel production from sunflower oil using FTIR (Fourier Transform Infrared). The first part of the study investigated the effect of catalyst ratio and methanol to oil ratio on biodiesel production by using central composite design (CCD). Biodiesel was produced by transesterification using Sodium Hydroxide as a homogeneous catalyst. A laboratory-scale reactor consisting of; flat bottom flask mounted with a reflux condenser, a hot plate as heating element equipped with temperature, timer and stirring rate regulator was used. Key parameters including, time, temperature and mixing rate, were kept constant at 60 minutes, 60 oC and 600 RPM, respectively. From the results obtained, it was observed that the biodiesel yield depends on catalyst ratio and methanol to oil ratio. The highest yield of 50.65 % was obtained at a catalyst ratio of 0.5 wt% and methanol to oil mole ratio 10.5. The analysis of variances of biodiesel yield showed the R2 value of 0.8387. A quadratic mathematical model was developed to predict the biodiesel yield in the specified parameters range. The same set-up was used to produce waste margarine biodiesel using a homogeneous catalyst, potassium hydroxide (KOH). The effects of four reaction parameters were studied, these were: methanol to oil ratio (3:1 to 15:1), catalyst ratio (0.3 to 1.5 wt. %), temperature (30 to 70 oC), time (20 to 80 minutes). The highest yield of 91.13 % was obtained at 60°C reaction temperature, 9:1 methanol to oil molar ratio, 0.9 wt. % catalyst ratio and 60 minutes. The important biodiesel fuel properties were found to be within specifications of the American Standard Test Method specifications (ASTM). It was concluded that waste margarine can be used to produce biodiesel as a low-cost feedstock. The core of the study was performed using EasyMax Mettler Toledo reactor equipped with a DiComp (Diamond) probe. The quantitative monitoring of the biodiesel production was performed by building a quantitative model with multivariate calibration using iC Quant module from iC IR 7.0 software. Fourteen samples of known concentrations were used for the modelling which were taken in duplicate for model calibration and cross-validation, data were pre-processed using mean centring and variance scale, spectrum math square root and solvent subtraction. These pre-processing methods improved the performance indexes from 7.98 to 0.0096, 11.2 to 3.41, 6.32 to 2.72, 0.9416 to 0.9999, RMSEC, RMSECV, RMSEP and R2Cum, respectively. The R2 values of 1 (training), 0.9918 (test), 0.9946 (cross-validation) indicated the fitness of the model built. The model was tested against the univariate model; small discrepancies were observed at low concentration due to unmodelled intermediates but were quite close at concentrations above 18%. The software eliminated the complexity of the Partial Least Square (PLS) chemometrics. It was concluded that the model obtained could be used to monitor transesterification of sunflower oil at industrial and lab scale. The model thus obtained, a batch reactor setup, EasyMax Mettler Toledodo reactor was used, the experiments were designed and monitored using iControl software. The results were recorded and quantified using iC IR software based on the biodiesel calibrated monitoring model built. The optimisation of the biodiesel was performed using three key parameters (methanol to oil ratio, catalyst ratio and temperature) while keeping time at 60 minutes and mixing rate at 150RPM. The highest yield of 97.85 % was obtained at 60 oC, 0.85 wt % catalyst ratio and 10.5 methanol to oil mole ratio. The analysis of variances of biodiesel production showed the values of 0.9847, 0.9674 and 0.8749, for R-squared, adjusted R-squared and predicted R-squared, respectively. A quadratic mathematical model was developed to predict the biodiesel conversion in the specified parameters ranges. Using the Arrhenius equation, activation energy (Ea) and frequency factor were found to be 41.279 kJ.mole-1 and 1.08 x10-4 M-1. s-1, respectively. The proposed kinetics model was a pseudo-first-order reaction. It was concluded that the model obtained can be used for industrial and laboratory-scale biodiesel production monitoring.