Selective elution of tea catechins and caffeine from polyvinylpolypyrrolidone

Desorption of catechins and caffeine from polyvinylpolypyrrolidone (PVPP) was comprehensively investigated. The result showed that caffeine could easily be desorbed from PVPP by the tested solvents except n‐hexane, while catechins could only be thoroughly done by dimethyl sulphoxide (DMSO) and N, N‐dimethylformamide (DMF). Excellent desorption efficiency of DMSO and DMF might be attributed to their high dipole moments and H‐bond potentials. Addition of ethanol was recommended considering the elution efficiency and fluidity, but ethanol volume should be <40% (v/v) for DMSO or 20% (v/v) for DMF. Desorption would get to equilibrium within 1 h and followed the pseudo‐second‐order model. Caffeine and catechins could be separately desorbed through two‐stage elution procedure, that is, water or 20% aqueous ethanol for desorbing caffeine and part of nongalloylated catechins and DMSO/ethanol (8/2, v/v) for eluting the remaining catechins. Highly purified catechins (~95%) with high level (~70%) galloylated catechins would be achieved when the desorption procedure was applied in column chromatograph.     

The effect of pectin concentration and degree of methyl-esterification on the in vitro bioaccessibility of β-carotene-enriched emulsions

Soluble fibers, like pectin, are known to influence the physicochemical processes during the digestion of dietary fat and may therefore affect the absorption of lipophilic micronutrients such as carotenoids. The objective of the current work was to investigate whether the pectin concentration and degree of methyl-esterification (DM) influence the bioaccessibility of carotenoids loaded in the oil phase of oil-in-water emulsions. The in vitro β-carotene bioaccessibility was determined for different oil-in-water emulsions in which 1 or 2% citrus pectin with a DM of 99%, 66% and 14% was present. Results show that pectin concentration and DM influence the initial emulsion properties. The most stable emulsions with the smallest oil droplets (D(v,0.9) of 15–16 μm) were obtained when medium or high methyl-esterified pectin was present in a 2% concentration while gel-like pectin structures (D(v,0.9) of 114 μm), entrapping oil droplets, were observed in the case where low methyl-esterified pectin was present in the aqueous emulsion phase. During in vitro stomach digestion, these gel-like structures, entrapping β-carotene loaded oil droplets, significantly enlarged (D(v,0.9) of 738 μm), whereas the emulsion structure could be preserved when the medium or high methyl-esterified pectin was present. Initial emulsion viscosity differences, due to pectin concentration and especially due to pectin DM, largely disappeared during in vitro digestion, but were still significant after the stomach digestion phase. The observed differences in emulsion structure before and during in vitro digestion only resulted in a significant difference between emulsions containing low methyl-esterified pectin (β-carotene bioaccessibility of 33–37%) and medium/high methyl-esterified pectin (β-carotene bioaccessibility of 56–62%).     

Preparation of anthocyanin-loaded liposomes using an improved supercritical carbon dioxide method

Anthocyanin-loaded liposomes were prepared via a single step supercritical carbon dioxide (SC-CO₂) process. Phospholipid/anthocyanin suspension equilibrated with CO₂ was depressurized at a constant pressure and rate. The effects of pressure, depressurization rate and temperature on the characteristics of liposomes were investigated. Liposomes obtained had a mean diameter of 160 ± 2 nm, polydispersity index of 0.26 ± 0.01, encapsulation efficiency of 52.2 ± 2.1% and zeta potential of − 44.3 ± 2.9 mV. Elevated pressure and depressurization rate generated smaller particles with higher uniformity while high temperature led to reduced sphericity. The SC-CO₂ method produced liposomes with enhanced intactness, sphericity and uniformity compared to the thin film hydration method. This method offers the possibility to utilize dense phase CO₂ to process the phospholipid aggregates into nano/micro particles and control their characteristics via tuning of processing parameters. SC-CO₂ method shows promise in scalable production of liposomes loaded with a variety of bioactives, targeting food applications.Industrial relevanceHigh quality anthocyanin-loaded liposomes were prepared using SC-CO₂. In this process, heterogenous phospholipid aggregates suspended in an aqueous medium are transformed into unilamellar and spherical liposomes with a narrow size distribution and other characteristics that can be regulated via tuning of the processing parameters (pressure, depressurization rate and temperature). The SC-CO₂ method resulted in superior particle characteristics over those prepared via the traditional thin film hydration method and also overcame some drawbacks like organic solvent residue and vesicle leakage associated with the traditional method. Anthocyanin encapsulated into liposomes can be protected from adverse external conditions with potential benefits in food and nutraceutical formulations for improved efficacy and health benefits. This improved SC–CO₂ process shows great promise for potential scale up of liposome production in the industry to encapsulate a variety of bioactives, targeting food and nutraceutical applications.     

A novel optical technique for observation of global particle distribution in toughened composites

One promising approach to improving fracture toughness is interleaved toughening. Past observations of toughened particles have typically been conducted using the optical microscope; however, such an approach may not be able to provide a 3-D, birds-eye view of how the toughened particles are distributed on a composite interlaminar surface. In this paper, we developed a simple yet novel optical technique for observing global particle distribution on a composite laminate surface. IM7/8551-7, a material used for the fan blades of the GE90, the world’s most powerful commercial aircraft jet engine, was used to demonstrate the strength of our optical technique, which produces high-quality morphological information. High-G_IC laminate had more uniform and denser particle distribution with a smaller particle size, whereas low-G_IC laminate had larger, but far less toughened particles. The same optical technique can also be used on other particle-toughened composite systems.     

Analysis of one-dimensional consolidation of soft soils with non-Darcian flow caused by non-Newtonian liquid

Based on non-Darcian flow caused by non-Newtonian liquid, the theory of one-dimensional (1D) consolidation was modified to consider variation in the total vertical stress with depth and time. The finite difference method (FDM) was adopted to obtain numerical solutions for excess pore water pressure and average degree of consolidation. When non-Darcian flow is degenerated into Darcian flow, a comparison between numerical solutions and analytical solutions was made to verify reliability of finite difference solutions. Finally, taking into account the ramp time-dependent loading, consolidation behaviors with non-Darcian flow under various parameters were analyzed. Thus, a comprehensive analysis of 1D consolidation combined with non-Darcian flow caused by non-Newtonian liquid was conducted in this paper.     

Diversity of Bacillus cereus strains in extended shelf life

Characterisation of 49 Bacillus cereus strains obtained from extended shelf life (ESL) milk and filler nozzles was done using (GTG)₅ rep PCR fingerprinting, determining the presence of the virulence genes cytK, nheA, cer and hblA, and discrimination of psychrotrophic and mesophilic strains with 16S rDNA. Fourteen isolates were selected for 16S partial sequencing. Fingerprinting and sequencing showed evidence of filler nozzles contaminating ESL milk despite high heterogeneity existing between the isolates. While there is high prevalence of cer, hblA and nheA; cytK was not widely distributed. There was 100% and 8% prevalence of mesophilic and psychrotrophic signatures, respectively. Despite the large diversity of the B. cereus strains in this study, there is evidence that filler nozzles and raw milk are a source of contamination of B. cereus in ESL milk.     

Prevalence and antimicrobial susceptibility of Vibrio species related to food safety isolated from shrimp cultured at inland ponds in Thailand

Inland farming of marine shrimp species is a relatively recent development, in response to increasing demand for the products. This study aimed to investigate the prevalence and antimicrobial resistance of potentially pathogenic Vibrio species in shrimps cultured at inland ponds with low salinity in Thailand. Of 16 shrimp samples (white-leg shrimps and black-tiger shrimps) from ponds with water temperatures from 29 to 32 °C, and salinities from 1 to 5 parts per trillion, 15 contained Vibrio cholerae (densities: 62–252,000 MPN/g). Vibrio parahaemolyticus was present in six samples (370–6,300,000 MPN/g), and Vibrio vulnificus was present in two samples (16–1300 MPN/g). V. parahaemolyticus has higher affinity for non-native white-leg shrimp than for native black-tiger shrimp. The minimum inhibitory concentrations were then measured for 12 common antimicrobial agents. Resistance to ampicillin and oxytetracycline (8% and 2% of the isolates) was documented in V. cholerae isolates, resistance to ampicillin and oxytetracycline (72% and 3%) was found in V. parahaemolyticus isolates, and resistance to nalidixic acid (20%) was detected in V. vulnificus isolates. β-lactamase and tetracycline resistance genes were detected in the resistant Vibrio isolates. The oxytetracycline-resistance phenotype was eliminated by plasmid curing, suggesting that the resistance was related to R-plasmids. Our results show that shrimps cultured even in low salinity ponds are potentially contaminated with pathogenic Vibrio species, and that shrimp are a vehicle for transfer of species with antimicrobial resistance genes to the public.     

Enhanced alkali resistance of CeO2/SO42 −–ZrO2 catalyst in selective catalytic reduction of NOx by ammonia

Ceria catalysts supported on sulfated zirconia showed a remarkable resistance towards alkali metal poisoning in selective catalytic reduction of NO by NH₃. TPD results revealed sulfation treatment of supports produced massive acid sites on the surface of catalysts. Adequate acidity was of importance for the enhanced resistance to alkali metal ions. The introduction of potassium did not affect the crystalline phases and morphology of catalysts, but it could lead to higher surface areas of samples.     

Buckling of cylindrical open-topped steel tanks under wind load

Vertical cylindrical welded steel tanks are typical thin-walled structures which are very susceptible to buckling under wind load. This paper investigates the buckling behavior of open-topped steel tanks under wind load by finite element simulation. The analyses cover six common practical tanks with volumes of 2×10³ m³ to 100×10³ m³ and height-to-diameter ratios H/D<1. The linear elastic bifurcation analyses are first carried out to examine the general buckling behavior of tanks under wind load, together with comparison to that of tanks under uniform pressure and windward positive pressure (only loaded by positive wind pressure in the windward region). The results show that for larger tanks in practical engineering, the stability carrying capacity of wind load is relatively lower. It is also indicated that the buckling behavior of tanks under wind load is governed by the windward positive pressure while wind pressure in other region of tank essentially has no influence on the buckling performance. The geometrically nonlinear analyses are then conducted to investigate the more realistic buckling behavior of tanks under wind load. It is found that the buckling behaviors of perfect tanks and imperfect tanks are much different. The weld induced imperfection only has little influence on the wind buckling behavior while the classical buckling mode imperfection has significant influence, leading to a considerable reduction of wind buckling resistance. The influences of thickness reduction of cylindrical wall, liquid stored in the tank and wind girder on the buckling behavior are also examined. It shows that the thickness reduction of cylindrical wall considerably reduces the wind buckling resistance while sufficient liquid stored in the tank and wind girder significantly increase the wind buckling resistance.