Microbiological attack, changing

The chemistry and performance of annatto extract is essentially that of bixia, a brownish red crystalline material that melts at 198°C. It is moderately stable toward light and has good stabiUty toward oxidation, change ia pH, and microbiological attack. Bixia is very stable toward heat up to 100°C, fairly stable at 100—125°C, and unstable above 125°C, where it tends to form 13-carbomethoxy-4,8-dimethyltridecahexanoic acid. 

Titanium Dioxide. The specifications of titanium dioxide have been given previously. Titanium dioxide exists ia nature ia three crystalline forms anatase, brookite, and mtile, with anatase as the commonly available form. Anatase has a high refractive iadex (2.52) and excellent stabiUty toward light, oxidation, changes ia pH, and microbiological attack. Titanium dioxide is virtually iasoluble ia all common solvents. 

Titanium dioxide is a very stable compound with excellent stability towards light, oxidation, pH changes, and microbiological attack. It is virtually insoluble in all common solvents. It is available in oil-dispersible and water-dispersible forms with a wide variety of carriers. Titanium dioxide is a very effective whitener for confectionery, baked goods, cheeses, icings, toppings, and numerous pharmaceuticals and cosmetics. 

Attack by microorganisms can generally be stopped by changing environmental conditions so that they are unfavorable to the microorganisms. Most microbiological attack can be suppressed by controlling the moisture content of the wood, but there are situations in which this control may not... 

Chlorine is the oldest and most widespread method of water disinfection. In reverse osmosis systems, chlorine may be added to feedwater for control of micro-organisms and, in addition, to prevent membrane fouling by microbiological growth. According to Vos et al. [i,2], chlorine will attack cellulose diacetate membranes at concentrations above 50 ppm. Membranes were found to show a sharp increase in salt permeability and a decrease in strength after one week of continuous exposure. Under milder conditions (10 ppm chlorine for 15 days) no detectable change in performance was observed. Spatz and Friedlander [3] have also found cellulose acetate membranes to be resistant to chlorine when exposed to 1.5 ppm for three weeks. 

It is probable that caries initiation is the result of a combined attack by all the acid-forming plaque organisms but there is no doubt that 5. mutans is one of the more virulent bacteria in this respect. A simple microbiological technique which relies on changes in a pH indicator... 

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