N. Queiroz

Phenolic profile, antioxidant activity and palynological analysis of stingless bee honey from Amazonas, Northern Brazil

In this study honey samples produced by Melipona (Michmelia) seminigra merrillae, collected in seven counties distributed in the central and southern region of Amazonas state in Brazil, were analysed for their botanical origin, content and profile of phenolic compounds, and antioxidant and antimicrobial activities. Twenty-two pollen types were identified. The total phenolic content ranged from 17 to 66 mg GAE/g of extract; the highest contents were found in honeys produced from pollen types such as Clidemia and Myrcia. The antioxidant activity was higher in the samples that contained higher quantities of phenolic compounds. In relation to the antibacterial activity, samples CAD3, CAD4 and SAD3 presented the best results. Fourteen phenolic compounds were determined. Among them, we identified the flavonoid taxifolin, which has not previously been described in honeys from stingless bees, and we report the identification of catechol in Brazilian honey samples for the first time.

Antioxidant activity of co-products from guava, mango and barbados cherry produced in the Brazilian northeast.

Co-products from the juice processing of guava (CG), mango (CM) and barbados cherry (CB) were investigated with a view to their exploitation as a potential source of natural antioxidants. The ethanolic extracts were analyzed for total extractable phenolic content (TEP), DPPH radical scavenging activity (RSA-DPPH), ferric reducing antioxidant power (FRAP) and antioxidant activity in relation to the β-carotene/linoleic acid system. The TEP levels in the CG, CM and CB extracts were (24.15 ± 1.59), (44.18 ± 1.73) and (49.21 ± 3.70) mg GAE/g extract, respectively. The CM extract showed higher DPPH, FRAP and antioxidant activity in the β-carotene/linoleic acid system. The data revealed a positive linear correlation between TEP, RSA-DPPH and FRAP (r2 = 0.85 − 0.98); however, the β-carotene/linoleic acid system (r2 = 0.01 − 0.26) shows low correlation with the TEP levels and other assessment systems. The results suggest that co-products generated from the juice processing of the studied fruit have promising use as a natural source of antioxidants.

Evaluating the emissions from the gasification processing of municipal solid waste followed by combustion

In this study, we evaluated the emissions of pollutants generated from the combustion of syngas in the gasification of Municipal Solid Waste (MSW) in Brazil using a mobile grille gasifier fed with domestic waste without any previous separation or grinding. The basic syngas composition (H2, CH4 and CO) was analyzed by gas chromatography and the Lower Calorific Value was calculated, which ranged from 1.9 to 10.2 MJ/kg. In the monitoring of combustion gases (CO2, CO, NO, NO2, SO2 and Total Hydrocarbon Content), values were found for these pollutants that were lower than the values established by the Brazilian legislation, except for SO2. Regarding the determination of the emission of metals, values lower than those permissible in the legislation were found for the most toxic metals grouped as class I (Cd, Hg, Tl). Therefore, it was evident that gasification followed by the combustion of syngas from MSW without prior segregation at source has the advantages of having fewer process steps, allowing the low emission of pollutants into the environment and it avoids that the residues are deposited in landfills, which are generators of leachate and greenhouse gas (methane).

Flow properties of biodiesel: correlation between TMDSC and dynamic viscosity

Sustainable and renewable energy has become more attractive due to its environmental benefits. Among these alternative sources, biodegradable and low emission biodiesels have been gaining attention as compared to diesel. However, their performance at low temperatures affects their commercial viability, because of engine performance problems, and when starting. Cold Filter Plugging Point, Pour Point, and Cloud Point are employed to predict the limits of operability for biodiesel. However, dynamic viscosity and TM-DSC methods are also useful to assess these properties and can be correlated. Viscosity curves were obtained, and TM-DSC revealed that the start temperature (transition liquid–solid) exhibits an increase in flow resistance for soybean, colza, sunflower, corn, and babassu oil biodiesels. The nucleation processes which occur during cooling are unique for each type of biodiesel due to the presence of different ester compositions and the values for viscosity and flow at low temperatures varied accordingly.