John J. Mellem

Translocation and accumulation of Cr, Hg, As, Pb, Cu and Ni by Amaranthus dubius (Amaranthaceae) from contaminated sites.

Phytoremediation is an emerging technology where specially selected and engineered metal-accumulating plants are used for bioremediation. This study was undertaken to evaluate the potential of Amaranthus dubius for phytoremediation of chromium (Cr), mercury (Hg), arsenic (As), lead (Pb), copper (Cu) and nickel (Ni). Locally gathered soil and plants of A. dubius were investigated for the metals from a regularly cultivated area, a landfill site and a waste water treatment site. Metals were extracted from the samples using microwave-digestion and analyzed using Inductively Coupled Plasma–Mass Spectroscopy. The mode of phytoremediation, effect of the metals on the plants, ability of the plant to extract metals from soil (Bioconcentration Factor) and the ability of the plants to move the metals to the aerial parts of the plants (Translocation Factor) were evaluated. The survey of the three sites showed that soils were heavily contaminated with Cr, Hg, Cu and Ni. These levels were far above acceptable standards set for soils and above the standards set for the Recommended Dietary Allowance. Specimens of A. dubius from the three sites showed that they could tolerate Hg, sequester it from the soil, and translocate it to the shoots. Cr could only be removed from the soil and stored in the roots, with limited amounts translocated to the aerial parts. Pb, As, Ni, and Cu have some degree of transportability from the soil to the roots but not to aerial parts. The ability of A. dubius to be considered for phytoremediation has to be viewed with caution because translocation of the metals to the aerial parts of the plant is limited.

Effects of amadumbe starch nanocrystals on the physicochemical properties of starch biocomposite films

The influence of amadumbe starch nanocrystals (SNCs) at varying concentrations (2.5, 5 and 10%) on the physicochemical properties of biocomposite films prepared using two starch matrices, amadumbe and potato starches were investigated. Amadumbe SNCs exhibited square-like platelets morphology, typical of SNC derived from A-type starches. In general, the inclusion of SNCs significantly decreased water vapour permeability (WVP) of composite films whilst thermal stability and opacity were increased. Amadumbe starch films showed substantially high tensile strength (TS) compared to potato starch in the presence of SNCs. At 2.5% SNCs, TS of composite amadumbe film (8MPa) was about four times that of composite potato films. However, SNCs≥5% generally decreased TS of both potato and amadumbe films. Amadumbe SNCs can potentially be used as fillers to improve the properties of biodegradable starch films. Amadumbe starch has better film forming properties compared to potato starch.

Microstructure, thermal properties and crystallinity of amadumbe starch nanocrystals

Amadumbe (Colocasia esculenta), commonly known as taro is a tropical tuber that produces starch-rich underground corms. In this study, the physicochemical properties of starch nanocrystals (SNC) prepared by acid hydrolysis of amadumbe starches were investigated. Two varieties of amadumbe corms were used for starch extraction. Amadumbe starches produced substantially high yield (25%) of SNCs. These nanocrystals appeared as aggregated and individual particles and possessed square-like platelet morphology with size: 50-100nm. FTIR revealed high peak intensities corresponding to OH stretch, CH stretch and H2O bending vibrations for SNCs compared to their native starch counterparts. Both the native starch and SNC exhibited the A-type crystalline pattern. However, amadumbe SNCs showed higher degree of crystallinity and slightly reduced melting temperatures than their native starches. Amadumbe SNCs presented similar thermal decomposition property as their native starches. Amadumbe starch nanocrystals may have potential application in biocomposite films due to their square-like platelet morphology.

Effect of simulated gastrointestinal digestion on the phenolic compound content and in vitro antioxidant capacity of processed Cowpea (V. unguiculata) cultivars

ABSTRACT The aim of this study was to analyze the phenolic content and antioxidant activity of five cowpea cultivars after processing and in vitro digestion. Raw cowpea samples showed a significant decrease in total phenolic content (TPC) when compared with the processed samples, however an increase was subsequently observed in digested samples. The antioxidant activity determined using, DPPH, ABTS, ferric reducing antioxidant power (FRAP) assay, and total peroxyl radical-trapping antioxidant parameter showed a similar trend to the phenolic content with a significant decrease in activity upon processing and an increase after digestion. In conclusion, all cowpea cultivars showed a high TPC content as well as an increased antioxidant activity after digestion indicating the potential health benefits which cowpea could provide to consumers. Therefore, this study shows that in vitro digestion improves the digestion and absorption of beneficial components of processed cowpea at the intestinal level.

Improvement of some quality attributes of soymilk through optimization of selected soybean sprouting parameters using response surface methodology

ABSTRACT This study aimed at producing functional soymilk by optimizing the sprouting conditions of soybeans using response surface methodology. Soaking (12–24 h) and germination times (48–96 h) were optimized using central complete randomized design. Responses obtained from experimental runs were fitted into second order polynomial regression model. Significance of model parameters was tested using ANOVA and R2 was evaluated. The optimum sprouting conditions of soybeans were 12 h soaking and 52 h germination using desirability concept. Soymilk made from optimized conditions had 17% increase in total proteins, 50% reduction in phytic acid, 1.7% increase in total phenolics and a color change (∆E) of 4.89 compared with the control. There was a significant reduction in trypsin inhibitor activity (0.03 mg/g TI), with increase in total amino acids and similar rheological properties in optimized soymilk. Optimized conditions obtained are adequate in the production of soymilk with improved nutritional and quality attributes.