Detailed kinetic study of anisole pyrolysis and oxidation to understand tar formation during biomass combustion and gasification

Anisole was chosen as the simplest surrogate for primary tar from lignin pyrolysis to study the gas-phase chemistry of methoxyphenol conversion. Methoxyphenols are one of the main precursors of PAH and soot in biomass combustion and gasification. These reactions are of paramount importance for the atmospheric environment, to mitigate emissions from wood combustion, and for reducing tar formation during gasification. Anisole pyrolysis and stoichiometric oxidation were studied in a jet-stirred reactor (673–1173 K, residence time 2 s, 800 Torr (106.7 kPa), under dilute conditions) coupled with gas chromatography–flame ionization detector and mass spectrometry. Decomposition of anisole starts at 750 K and a conversion degree of 50% is obtained at about 850 K under both studied conditions. The main products of reaction vary with temperature and are phenol, methane, carbon monoxide, benzene, and hydrogen. A detailed kinetic model (303 species, 1922 reactions) based on a combustion model for light aromatic compounds has been extended to anisole. The model predicts the conversion of anisole and the formation of the main products well. The reaction flux analyses show that anisole decomposes mainly to phenoxy and methyl radicals in both pyrolysis and oxidation conditions. The decomposition of phenoxy radicals is the main source of cyclopentadienyl radicals, which are the main precursor of naphthalene and heavier PAH in these conditions.     

Zinc incorporation capacity of whey protein nanoparticles prepared with desolvation with ethanol

Whey protein isolate (WPI) nanoparticles were prepared using ethanol desolvation, and their capacity to incorporate ZnCl(2) was analysed. Desolvation was carried out at pH 9 and the volume of added ethanol was 0-3 times the volume of protein solution. The desolvated solutions were dispersed in acidified water (pH 3) immediately after desolvation. The size of the WPI nanoparticles increased with the volume ratio of ethanol:water used, as well as with the amount of ZnCl(2). The nanoparticles showed high incorporation efficiencies, and remained stable after 30 days of storage at 22 °C. The amount of zinc incorporated in the WPI particle suspensions was within the range of daily zinc requirements for healthy adults.     

Acidification of grape marc for alcoholic beverage production: effects on indigenous microflora and aroma profile after distillation

Grappa is an Italian alcoholic beverage obtained from distillation of grape marc, the raw material derived from separation of must during the winemaking process. Marc is stored for a period lasting from few days to several weeks, when fermentation of residual sugars occurs mainly by yeast activity. Many distilleries have adopted different solutions to manage this critical phase in order to avoid spoilage microorganisms: marc acidification is the most widely diffused. In this work, Prosecco grape pomace was acidified with sulphuric acid (to pH 2.9) and stored, whereas non-acidified grape marc was used as control (pH 3.9). Samples for microbiological analysis were collected at the beginning of the storage period, after 15 and 43 days. At the beginning of the ensilage (time T0) the indigenous microflora was represented both by yeasts and bacteria at a concentration of about 10⁶ cfu/g. During the first 15 days, when the fermentation generally takes place, yeast population grew considerably (up to 10⁷ cfu/g) in acidified grape marc, where bacterial population was maintained at low levels. Moreover, yeast populations recovered at the three sampling times in both treated and untreated marc were genetically characterised. This analysis showed that the species succession lead to non-Saccharomyces species dominance (in particular Issatchenkia and Pichia genera) in both conditions although acidified marc showed a lower percentage of Saccharomyces at any sampling time analysed, this meaning that non-Saccharomyces species were favoured in this environment. Gas chromatographic analysis showed a remarkable change in the aromatic profile of distilled grape marcs at the end of the storage, thus evidencing that concentration of monitored volatile compounds usually produced by microflora was generally lowered by the acidification treatment.This work demonstrates for the first time the strong effect of a persistent acidification treatment both on the microbiota of grape pomace and on the aromatic profile of the distillate. Indeed, the lowering of the pH caused significant changes in yeast-bacteria populations ratio and in yeast species turnover. These microbiological changes determine an improvement of the aromatic profile of the distillate, due to the reduction of the main volatile products associated with potential off-flavours.     

Efficient and adaptive congestion control for heterogeneous delay-tolerant networks

Detecting and dealing with congestion in delay-tolerant networks (DTNs) is an important and challenging problem. Current DTN forwarding algorithms typically direct traffic towards more central nodes in order to maximise delivery ratios and minimise delays, but as traffic demands increase these nodes may become saturated and unusable. We propose CafRep, an adaptive congestion aware protocol that detects and reacts to congested nodes and congested parts of the network by using implicit hybrid contact and resources congestion heuristics. CafRep exploits localised relative utility based approach to offload the traffic from more to less congested parts of the network, and to replicate at adaptively lower rate in different parts of the network with non-uniform congestion levels. We extensively evaluate our work against benchmark and competitive protocols across a range of metrics over three real connectivity and GPS traces such as Sassy [44], San Francisco Cabs [45] and Infocom 2006 [33]. We show that CafRep performs well, independent of network connectivity and mobility patterns, and consistently outperforms the state-of-the-art DTN forwarding algorithms in the face of increasing rates of congestion. CafRep maintains higher availability and success ratios while keeping low delays, packet loss rates and delivery cost. We test CafRep in the presence of two application scenarios, with fixed rate traffic and with real world Facebook application traffic demands, showing that regardless of the type of traffic CafRep aims to deliver, it reduces congestion and improves forwarding performance.     

Interfacial design of protein-stabilized emulsions for optimal delivery of nutrients

Proteins are often used as ingredients in food emulsions, as their amphiphilic structures provide electrostatic and steric stabilization. Significant attention has recently been directed at understanding how the composition and structure of oil-water interfaces change during digestion and how these can be manipulated to enhance the delivery of nutrients contained within the oil droplets. These efforts have necessitated the development of more sophisticated in vitro digestion models of greater physiological relevance and increased efforts in research to identify the role of the various digestive parameters on interfacial dynamics. The changes occurring at the oil-water interface will affect the adsorption of gastro-intestinal lipases and, ultimately, affect lipid digestion. The composition of a protein-stabilized oil droplet changes continuously during digestion, because of proteolysis and the formation of peptides with different affinities for the interface. In addition, natural bio-surfactants such as phospholipids and bile salts, other surface- active molecules present in foods, and the products of lipolysis (i.e. mono and diglycerides, lysophospholipids), all compete for access to the interface, and contribute to the dynamic changes occurring on the surface of the oil droplets. A better understanding of how to tailor the composition of oil droplet surfaces in food emulsions will aid in optimizing lipid digestion and, as a result, delivery of lipophilic nutrients. This review focuses on the physico-chemical changes occurring in protein-stabilized oil-in-water emulsions during gastric and small intestine digestion, and on how interfacial engineering could lead to differences in fatty acid release and the potential bioavailability of lipophilic molecules.     

Antimicrobial effectiveness of lysozyme immobilized on polyvinylalcohol-based film against Alicyclobacillus acidoterrestris

In this study, the effectiveness of an active polyvinylalcohol-based film against Alicyclobacillus acidoterrestris was assessed. The active film was fabricated by immobilizing an active compound on the surface of a polymeric matrix and then tested by putting the film in contact with a medium that had been inoculated with microbial cells. Microbiological tests showed that the film was antimicrobial against both a single strain and a culture cocktail of A. acidoterrestris, at 44 degrees C. By monitoring the viable cell concentration under three different packaging conditions, it was possible to demonstrate that the active film was equally effective against both the single strain and the culture cocktail and that it maintained this efficacy at various medium volumes. The same microbial tests were also conducted on viable spores of the investigated microorganism, inoculated both into a laboratory medium and apple juice. The results indicate that these viable spores were better inhibited than cells by the active film in both investigated media.     

Physicochemical and phytochemical properties of cold and hot water extraction from Hibiscus sabdariffa

Hibiscus cold (25 °C) and hot (90 °C) water extracts were prepared in various time-temperature combinations to determine equivalent extraction conditions regarding their physicochemical and phytochemical properties. Equivalent anthocyanins concentration was obtained at 25 °C for 240 min and 90 °C for 16 min. Total phenolics were better extracted with hot water that also resulted in a higher antioxidant capacity in these extracts. Similar polyphenolic profiles were observed between fresh and dried hibiscus extracts. Hibiscus acid and 2 derivatives were found in all extracts. Hydroxybenzoic acids, caffeoylquinic acids, flavonols, and anthocyanins constituted the polyphenolic compounds identified in hibiscus extracts. Two major anthocyanins were found in both cold and hot extracts: delphynidin-3-sambubioside and cyanidin-3-sambubioside. In general, both cold and hot extractions yielded similar phytochemical properties; however, under cold extraction, color degradation was significantly lower and extraction times were 15-fold longer. PRACTICAL APPLICATION: Hibiscus beverages are prepared from fresh or dried calyces by a hot extraction and pasteurized, which can change organoleptic, nutritional, and color attributes. Nonthermal technologies such as dense phase carbon dioxide may maintain their fresh-like color, flavor, and nutrients. This research compares the physicochemical and phytochemical changes resulting from a cold and hot extraction of fresh and dried hibiscus calyces and adds to the knowledge of work done on color, quality attributes, and antioxidant capacity of unique tropical products. In addition, the research shows how these changes could lead to alternative nonthermal processes for hibiscus.