Interactive effects of casein micelle size and calcium and citrate content on rennet‐induced coagulation in bovine milk

Interactive effects of casein micelle size and milk calcium and citrate content on rennet‐induced coagulation were investigated. Milk samples containing small (SM) and large (LM) micelles, obtained from individual Holstein cows, were modified by addition of calcium and/or citrate and milk coagulation properties were evaluated in a full factorial design. The results showed that LM milk had a higher relative proportion of casein, coagulated faster, and resulted in a stronger gel than SM milk. Addition of calcium slightly decreased casein micelle size, while addition of citrate slightly increased micelle size. Calcium addition resulted in a shorter coagulation time and the strongest gels, while citrate addition increased the coagulation time and resulted in the weakest gels. Addition of calcium and citrate in combination resulted in intermediate coagulation properties. The interactive effect of micelle size and citrate was significant for gel strength. Microstructural differences between the milk gels were consistent with the rheological properties, for example, the micrographs revealed that a more homogeneous network was formed when calcium was added, resulting in a stronger gel. A more inhomogeneous network structure was formed when citrate was added, resulting in a weaker gel. Thus, variations in casein micelle size and in calcium and citrate content influence rennet‐induced coagulation in bovine milk. The calcium and citrate contents in Swedish milk have changed over time, whereby calcium content has increased and citrate content has decreased. In practical cheese making, calcium is added to cheese milk, most likely altering the role of inherent citrate and possibly influencing casein micelle size. The observed interaction effect between casein micelle size and citrate in this study, suggests that larger micelles with moderate citrate level will result in firmer gels, whereas a higher citrate content reduced gel strength more in case of large than SM. Since firmer gels are likely to retain more protein and fat than less firmer gels, this interaction effect could have implications in practical cheese production.     

WASTE SALT DISPOSAL AT THE SAVANNAH RIVER PLANT†

Waste salt solution, produced during processing of high-level nuclear waste, will be incorporated in a cement matrix for emplacement in an engineered disposal facility. Wasteform characteristics and disposal facility details will be presented along with results of a field test of wasteform contaminant release and of modeling studies to predict releases.     

Survival of poliovirus on soft fruit and salad vegetables

A series of studies were performed, using poliovirus, to ascertain the potential for enteric pathogenic viruses to survive on various foodstuffs. The extraction protocols, which could be performed in just a few hours, were developed for use with quantities of food that would normally constitute a portion for consumption. The protocols were based on elution of viruses from food surfaces, followed by differential centrifugation to remove food debris and concentrate viruses. The studies were mostly performed using fresh produce stored at refrigeration temperature for 2 weeks or so, which was considered to represent the maximum time elapsing between purchase and consumption. Each food sample was inoculated with a viral suspension, and samples were analyzed immediately and at intervals throughout the experiment. Statistical analyses were performed on the results, and the decimal reduction times (D-values), or number of days after which the initial virus numbers had declined by 90%, were calculated. In summary, the resulting D-values were as follows: lettuce, 11.6 days; green onion, no decline; white cabbage, 14.2 days; fresh raspberries, no decline; and frozen strawberries, 8.4 days. The results showed that enteric viruses may persist on fresh fruit and vegetables for several days under conditions commonly used for storage in households. Therefore, if contamination has occurred before purchase, there will always be a risk of infection from consumption of the food.     

Influence of waveguide material on light emission in luminescent solar concentrators

Five different substrates were tested for their suitability for use as waveguides for luminescent solar concentrators for solar energy applications. The function of such a waveguide is to collect light and to transport it towards a solar cell. In this study the influence of the material of the waveguide on the light emission of the system was investigated. It was determined that the material chosen for the waveguide was not as important as the presence or absence of additives in the waveguide itself. This indicates that economic factors (material cost) and secondary properties such as refractive index, outdoor lifetime and weight are at least as important in the waveguide selection as the nature of the materials used.     

Incorporation of magnetic nanoparticles into lamellar polystyrene-b-poly(n-butyl methacrylate) diblock copolymer films: Influence of the chain end-groups on nanostructuration

In this article, we present new samples of lamellar magnetic nanocomposites based on the self-assembly of a polystyrene-b-poly(n-butyl methacrylate) diblock copolymer synthesized by atom transfer radical polymerization. The polymer films were loaded with magnetic iron oxide nanoparticles covered with polystyrene chains grown by surface initiated-ATRP. The nanostructuration of the pure and magnetically loaded copolymer films on silicon was studied by atomic force microscopy, ellipsometry, neutron reflectivity and contact angle measurement. The present study highlights the strong influence of the copolymer extremity - driven itself by the choice of the ATRP chemical route - on the order of the repetition sequences of the blocks in the multi-lamellar films. In addition, a narrower distribution of the nanoparticles’ sizes was examined as a control parameter of the SI-ATRP reaction.     

Viscosity Behaviour of the Mucilage Extracted from Ruredzo (Dicerocaryum zanguebarium)

The concentration of metal ions in the mucilage that is extracted from Ruredzo (Dicerocaryum zanguebarium) was determined by atomic absorption spectroscopy. Calcium, magnesium, potassium, iron, copper, lead and zinc were found to occur in concentrations ranging from 0.01 ppm for lead to 15 ppm for calcium. Cations were removed from solutions of the mucilage using Dowex 50W-X12 resin and the viscosity of the decationized mucilage studied. Addition of CaCl₂, NaCl and sucrose decreased the viscosity of the decationized mucilage but addition of sucrose resulted in an increase in viscosity. The effect of incubating the mucilage at various temperatures for up to 30 min before measuring the viscosity at 25°C was investigated. No change in viscosity was observed for samples incubated at 40°C and 60°C. 80°C incubation resulted in reduced viscosity. Solutions of the decationized mucilage exhibited maximum viscosity at pH 5.     

Zur Konstitution des Reaktionsproduktes aus Phenacylthioglykolsäure und Thioglykolsäure

On the Structure of the Reaction Product from Thioglycolic Acid and Phenacyl Thioglycolic Acid The reaction product obtained from phenacyl thioglycolic acid and thioglycolic acid is shown to represent 1,1,2-tris-(carboxymethylthio)-2-phenylethane 4 , and not 1,1,2-tris-(carboxymethylthio)-1-phenylethane 3 as suggested earlier in the literature. Analogously, phenacyl benzyl sulfide 2 and benzyl mercaptan yield 1, 1, 2-tris-(benzylthio)-2-phenylethane 5 . The reaction mechanisms are discussed on the basis of synthetic and n.m.r. spectroscopic studies.