Effect of Emulsion Droplet Size on Foaming Properties of Milk Fat Emulsions

Foamability and foam stability of dairy-based emulsions, as a function of emulsion droplet size ranging from micron- to nanometre-scale, were investigated. Fat phase (10 % w/w of anhydrous milk fat, stearin or olein fraction) was mixed with 2 % w/w protein solution (sodium caseinate or whey protein concentrate) and homogenised at 3, 10 and 35 MPa to obtain emulsions having particle sizes of about 1.20, 0.60 and 0.20 μm, respectively. The emulsions were cooled down and aged at 4 °C for 48 h to promote crystallisation. No fat coalescence was observed in any of the emulsions, as particle size distribution remained the same upon aging and whipping. It was shown that the smaller the particle size, the higher was the apparent viscosity and the lower was the solid fat content. Higher solid fat content tended to yield better foamability and foam stability. Destabilisation of air cells happened fastest with nanosized fat particles, resulting in shorter half-life of foam.     

Rapid Quantification of Low-Viscosity Acetyl-Triacylglycerols Using Electrospray Ionization Mass Spectrometry

Acetyl‐triacylglycerols (acetyl‐TAG) possess an sn‐3 acetate group, which confers useful chemical and physical properties to these unusual triacylglycerols (TAG). Current methods for quantification of acetyl‐TAG are time consuming and do not provide any information on the molecular species profile. Electrospray ionization mass spectrometry (ESI–MS)‐based methods can overcome these drawbacks. However, the ESI–MS signal intensity for TAG depends on the aliphatic chain length and unsaturation index of the molecule. Therefore response factors for different molecular species need to be determined before any quantification. The effects of the chain length and the number of double‐bonds of the sn‐1/2 acyl groups on the signal intensity for the neutral loss of short chain length sn‐3 groups were quantified using a series of synthesized sn‐3 specific structured TAG. The signal intensity for the neutral loss of the sn‐3 acyl group was found to negatively correlated with the aliphatic chain length and unsaturation index of the sn‐1/2 acyl groups. The signal intensity of the neutral loss of the sn‐3 acyl group was also negatively correlated with the size of that chain. Further, the position of the group undergoing neutral loss was also important, with the signal from an sn‐2 acyl group much lower than that from one located at sn‐3. Response factors obtained from these analyses were used to develop a method for the absolute quantification of acetyl‐TAG. The increased sensitivity of this ESI–MS‐based approach allowed successful quantification of acetyl‐TAG in various biological settings, including the products of in vitro enzyme activity assays.     

Studies on chemical resistance of polyesters

Chlorendic anhydride based polyester ( I ,) tetrachlorophthalic anhydride based polyester ( II ), dibromoneopentyl glycol based polyester ( III ,) general purpose polyester ( IV ,) blend of dibromoneopentyl glycol based polyester with general purpose polyester ( V ,) chlorendic anhydride and dibromoneopentyl glycol based polyester ( VI ), and a blend of chlorendic anhydride based polyester and dibromoneopentyl glycol based polyester ( VII ) were prepared and their chemical resistance and moisture absorption studied in various reagents, acid, alkali, and water, at 25 and 65°C. It is found that the polyester ( III ) is the least affected in the presence of the acids. In 20% NaOH, there was a decrease in weight for all polyesters at both the temperatures compared to the control except the polyester ( VII ). Increase in weight of all the polyesters was observed during the absorption of moisture both at 25 and 65°C. The increase was higher at higher temperature. Polyester ( III ) thus shows the least absorption of moisture.     

Creating gold nanoprisms directly on quartz crystal microbalance electrodes for mercury vapor sensing

A novel electrochemical route is used to form highly {111}-oriented and size-controlled Au nanoprisms directly onto the electrodes of quartz crystal microbalances (QCMs) which are subsequently used as mercury vapor sensors. The Au nanoprism loaded QCM sensors exhibited excellent response-concentration linearity with a response enhancement of up to ～ 800% over a non-modified sensor at an operating temperature of 28?°C. The increased surface area and atomic-scale features (step/defect sites) introduced during the growth of nanoprisms are thought to play a significant role in enhancing the sensing properties of the Au nanoprisms toward Hg vapor. The sensors are shown to have excellent Hg sensing capabilities in the concentration range of 0.123-1.27 ppm(v) (1.02-10.55 mg m(-3)), with a detection limit of 2.4 ppb(v) (0.02 mg m(-3)) toward Hg vapor when operating at 28?°C, and 17 ppb(v) (0.15 mg m(-3)) at 89?°C, making them potentially useful for air monitoring applications or for monitoring the efficiency of Hg emission control systems in industries such as mining and waste incineration. The developed sensors exhibited excellent reversible behavior (sensor recovery) within 1 h periods, and crucially were also observed to have high selectivity toward Hg vapor in the presence of ethanol, ammonia and humidity, and excellent long-term stability over a 33 day operating period.     

Surface characteristics and surface behaviour of polymer carbons—II: Adsorption of water vapor

The water adsorption isotherms of polymer carbons obtained on carbonizing different precursor materials (viz. polyfurfuryl alcohol (PF), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), urea formaldehyde resin (UF) and Saran), and having different porosities and associated with varying amounts of oxygenindicate that the adsorption at lower relative vapor pressures (< 0.5) is largely governed by the amount of oxygen associated with different functional groups attached to individual carbon atoms forming the walls of the micropores. The amount of water vapor adsorbed increases with increase in the amount of associated oxygen and vice-versa. In the region of medium relative vapor pressure the steep rise in the adsorption isotherm is not due to the coalescence of discrete islands of adsorbed water but to the filling up of pores by capillary condensation at least in those samples which are porous in nature. In the case of PF, PVDC and Saran chars because of the presence of sufficiently wide pores, capillary condensation plays a significant role. The shape of the isotherms in the case of PVC and UF chars indicates that they are less porous and have pores which are too narrow for capillary condensation to occur.     

Alternating current chronopotentiometry—III. Electroreduction of silver(I), cadmium(II), and thallium(I) in calcium nitrate tetrahydrate melt

The electroreduction of silver(I) on a platinum electrode and of cadmium(II) and thallium(I) on a mercury electrode has been studied by alternating current chronopotentiometry. Expected relations for the diffusion controlled, one-electron deposition of an insoluble substance are obeyed for silver(I); but reduction of cadmium(II) on mercury is more complex. Nucleation of metallic thallium is the rate controlling process during the early stages of the reduction of thallium(I).     

Performance of plate heat exchangers during calcium sulphate fouling — investigation with an in-line filter

The uncertainty about the fouling behaviour is one of the main reasons why plate and frame heat exchangers are not more widely installed in the chemical process industry and in power generating facilities. In the present investigation, the deposition of calcium sulphate in two different plate heat exchanger geometries was investigated. The deposition process was deliberately focused on crystallisation fouling through the installation of an in-line filter and the mode of preparation of the test solution. The investigated operating parameters were solution concentration, flow velocity, and bulk and surface temperatures. The heat exchangers were opened after each experiment to record the appearance and distribution of the deposits. The key result of this investigation is the strong correlation between the plate design and the tendency for deposit formation.