High temperature water-gas shift step in the production of clean hydrogen rich synthesis gas from gasified biomass

The possibility of using the water-gas shift (WGS) step for tuning the H₂/CO-ratio in synthesis gas produced from gasified biomass has been investigated in the CHRISGAS (Clean Hydrogen Rich Synthesis Gas) project. The synthesis gas produced will contain contaminants such as H₂S, NH₃ and chloride components. As the most promising candidate FeCr catalyst, prepared in the laboratory, was tested. One part of the work was conducted in a laboratory set up with simulated gases and another part in real gases in the 100 kW Circulating Fluidized Bed (CFB) gasifier at Delft University of Technology. Used catalysts from both tests have been characterized by XRD and N₂ adsoption/desorption at ?196 °C.In the first part of the laboratory investigation a laboratory set up was built. The main gas mixture consisted of CO, CO₂, H₂, H₂O and N₂ with the possibility to add gas or water-soluble contaminants, like H₂S, NH₃ and HCl, in low concentration (0–3 dm³ m^?3). The set up can be operated up to 2 MPa pressure at 200–600 °C and run un-attendant for 100 h or more. For the second part of the work a catalytic probe was developed that allowed exposure of the catalyst by inserting the probe into the flowing gas from gasified biomass.The catalyst deactivates by two different causes. The initial deactivation is caused by the growth of the crystals in the active phase (magnetite) and the higher crystallinity the lower specific surface area. The second deactivation is caused by the presence of catalytic poisons in the gas, such as H₂S, NH₃ and chloride that block the active surface.The catalyst subjected to sulphur poisoning shows decreased but stable activity. The activity shows strong decrease for the ammonia and HCl poisoned catalysts. It seems important to investigate the levels of these compounds before putting a FeCr based shift step in industrial operation. The activity also decreased after the catalysts had been exposed to gas from gasified biomass. The exposed catalysts are not re-activated by time on stream in the laboratory set up, which indicates that the decrease in CO₂-ratio must be attributed to irreversible poisoning from compounds present in the gas from the gasifier.It is most likely that the FeCr catalyst is suitable to be used in a high temperature shift step, for industrial production of synthesis gas from gasified biomass if sulphur is the only poison needed to be taken into account. The ammonia should be decomposed in the previous catalytic reformer step but the levels of volatile chloride in the gas at the shift step position are not known.     

A nickel-complex sensitiser for dye-sensitised solar cells

We report the first example of a Ni(II) complex that demonstrates sensitiser function in a Dye-Sensitised Solar Cell (DSSC). Complexes [Ni(dcbpy)(qdt)] (1), [Ni(decbpy)(qdt)] (2) and [Ni(decbpy)Cl₂] (3) (where dcbpy = 4,4′-dicarboxy-2,2′-bipyridine; decbpy = 4,4′-di(CO₂Et)-2,2′-bipyridine; and qdt = quinoxaline-2,3-dithiolate) have been prepared. Characterisation was carried out using electrochemical, spectroscopic and computational techniques. Intensive visible transitions of 1 and 2 have been assigned predominantly to Ligand-to-Ligand Charge Transfer (LLCT) from the qdt to the diimine ligand, suggesting appropriate charge separation for application in a photoelectrochemical device. TiO₂ sensitised with 2, following charge injection, processes a recombination time significantly long for photovoltaic function. In a DSSC, using redox electrolyte, photocurrents and photovoltages of 0.293 mA and 521 mV were observed, with optimum values requiring TiCl₄ post-treatment of TiO₂ and co-adsorption of Chenodeoxycholic acid (Cheno). Although photovoltaic function was observed, the low photocurrent is attributed to a short-lived excited state lifetime resulting in poor charge injection from the Ni(II) sensitiser.     

Reduction of Campylobacter jejuni by natural antimicrobials in chicken meat-related conditions

Nowadays it is essential to test new preservation and decontamination procedures using naturally occurring chemicals against important pathogenic bacteria in meat. We tested the antimicrobial effect of rosemary extracts and the bacteriocin nisin against Campylobacter jejuni at a low storage temperature (8 °C) with or without short-term pre-freezing. The antimicrobial effect of rosemary extract was four times greater in laboratory media than in chicken meat juice. Furthermore, low temperature storage conditions prolonged the survival of C. jejuni in chicken meat juice. Nisin, with an approximately 1.0 log reduction was neither effective alone nor in combination with the extract. Pre-freezing with plant extract addition proved to be effective treatment by more than 3.0 log reduction in 48 h. The results in chicken meat food model again showed the synergistic effect of freezing and plant extract antimicrobial activity. As the combination of pre-freezing and plant extract treatment reduced the cell number by more than 2.0 log reduction, studies should be conducted to further evaluate this promising treatment for Campylobacter reduction in the poultry meat supply.     

Effect of green mate in overweight volunteers: A randomized placebo-controlled human study

Overweight and obesity have become a global epidemic and they may impair health. Traditional use and growing evidence indicate that mate (Ilex paraguariensis A. St.-Hil.) may be helpful in losing excessive weight and fat. The present randomized, double-blind, placebo-controlled study evaluated efficacy and safety of an extract from green mate in 60 overweight subjects aged 20–39 years during 6-weeks. Body composition was measured by Dual-Energy X-ray Absorptiometry (DEXA) at baseline and after 6 weeks. Body weight, body mass index (BMI), waist circumference (WC) and various safety parameters were monitored. After 6 weeks, subjects taking mate experienced a significantly greater reduction of percent of body fat (?0.3% vs. +0.6%, p = 0.04) and fat mass (?0.5 kg vs. +0.2 kg, p = 0.04) than placebo. No significant differences were observed in other measurements. No adverse events occurred and all safety parameters were within normal ranges during the study in both groups. Thus, taking green mate extract reduced body fat after 6 weeks, while the treatment was safe and well tolerated.     

The choice of homogenisation equipment affects lipid oxidation in emulsions

Milk proteins are often used by the food industry because of their good emulsifying properties. In addition, they can also provide oxidative stability to foods. However, different milk proteins or protein components have been shown to differ in their antioxidative properties, and their localisation in emulsions has been shown to be affected by the emulsification conditions. The objective of this study was to investigate the influence of homogenisation equipment (microfluidizer vs. two-stage valve homogeniser) on lipid oxidation in 10% fish oil-in-water emulsions prepared with two different milk proteins. Emulsions were prepared at pH 7 with similar droplet sizes. Results showed that the oxidative stability of emulsions prepared with sodium caseinate was not influenced by the type of homogeniser used. In contrast, the type of homogenisation equipment significantly influenced lipid oxidation when whey protein was used as emulsifier, with the microfluidizer resulting in lower levels of oxidation.     

Iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions: effect of emulsifier type and pH

The objective of this study was to investigate the protective effect of five different emulsifiers on iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions. The emulsifiers were either based on protein (whey protein isolate and sodium caseinate) or based on phospholipid (soy lecithin and two milk phospholipids with different phospholipid contents, MPL20 and MPL75). Lipid oxidation was studied at pH 4.5 and 7.0, and results were compared to lipid oxidation in neat fish oil. Results showed that all emulsions oxidised more than neat oil. Furthermore, emulsions prepared with proteins oxidised more at low pH than at high pH, and casein emulsions oxidised the least (Peroxide value (PV) at day 7 was 0.5–0.7 meq kg^?1). Among emulsions prepared with phospholipids, emulsions with MPL75 were the most oxidised followed by emulsions prepared with lecithin and MPL20. Thus, PV in MPL75 emulsions was 5.0–5.5 meq kg^?1 at day 7 compared with 0.9–1.9 meq kg^?1 in MPL20 emulsions.     

Alpha-tocopherol concentration and stereoisomer composition in plasma and milk from dairy cows fed natural or synthetic vitamin E around calving

The aim of this study was to compare the effects of supplementing dairy cows with 1000 IU/day of all-rac-alpha-tocopheryl acetate (SynAc), RRR-alpha-tocopheryl acetate (NatAc), or RRR-alpha-tocopherol (NatAlc), from approximately 3 weeks before estimated calving until 2 weeks after calving, on the concentration of alpha-tocopherol and its stereoisomers (RRR-, RSS-, RRS-, RSR- and the four 2S-forms of alpha-tocopherol) in blood and milk. An unsupplemented group was included as control. Blood samples were collected at 3, 2 and 1 weeks before estimated calving, at calving, and 3, 7 and 14 days after calving, while milk samples were taken twice within 24 h after calving and at 7 and 14 days in milk. Overall, time and treatment had significant effects on plasma alpha-tocopherol with higher concentrations in NatAc than in the other groups. In addition, SynAc had higher concentrations than Control, and NatAlc tended to be higher than Control. The lowest plasma concentrations were observed at calving and 3 days after calving. Independent of treatment, the concentration was higher in colostrum than in milk day 7 and 14 after calving. Analyses of the stereoisomer distribution in plasma and milk showed that, irrespective of dietary treatment, RRR-alpha-tocopherol was the most predominant form, constituting more than 86%, whereas the remaining part of alpha-tocopherol was made up by the three synthetic 2R isomers, while the 2S isomers only contributed less than 1% of the total alpha-tocopherol. In control cows and cows supplemented with natural vitamin E, the proportion of RRR-alpha-tocopherol in plasma and milk constituted more than 98% of the total alpha-tocopherol. In conclusion, the results indicate that daily oral supplementation of dairy cows with RRR-alpha-tocopheryl acetate gives the highest blood concentrations of alpha-tocopherol in the periparturient period. Analyses of the distribution of the individual stereoisomers of alpha-tocopherol further indicate that the bioavailability of RRR-alpha-tocopherol relative to synthetic stereoisomers in cattle is considerably higher than officially accepted until now.     

Antimicrobial enzymes: Applications and future potential in the food industry

Antimicrobial enzymes are ubiquitous in nature, playing a significant role in the defense mechanisms of living organisms against infection by bacteria and fungi. Hydrolytic antimicrobial enzymes function by degrading key structural components of the cell walls of bacteria and/or fungi, whereas antimicrobial oxidoreductases exert their effects by the generation in situ of reactive molecules. The potential of these enzymes in food preservation is still far from realized at present.     

Dietary differences among commercially important fishes in Lake Tanganyika assessed using stable isotope analysis

The pelagic fishery of Lake Tanganyika, which is largely made up of the three species Lates stappersii, Limnothrissa miodon, and Stolothrissa tanganicae, has been in decline, and there is no clear understanding of the primary underlying causes. It has been suggested that climate change has altered the primary productivity of the system, but detailed knowledge of the system's food web is required to elucidate the effect on higher trophic levels. The aim of this study is to determine the diet of the three commercially important fish species. Muscle tissue samples for stable isotope analysis were taken from February through April 2017, supplemented with stomach samples from L. stappersii for use in stomach content analysis. The stomach analysis showed an ontogenetic change in the diet composition of L. stappersii, shifting from copepods to fish larvae, supplemented with shrimp, to whole fish prey as the fish grew larger. Stable carbon and nitrogen isotope values from fish muscle were consistent with this observation, and also seemed to indicate that fish of similar sizes had similar diets, irrespective of species. This suggests that the diet of the pelagic fish species might be better explained by size, rather than species. The isotope data revealed a short range of δ¹⁵N values from primary consumers to fish, which may help explain the high fisheries productivity of Lake Tanganyika, and the strong impact of primary productivity changes on fisheries yield.