Oxygen atmospheric control

It seems that the effect of the induction of phenol-content increment by high oxygen atmospheres is affected also by the exposure time of the product to the given atmosphere (Ayala-Zavala and others 2007). Awad and others found no losses of flavonoids in apples stored under conventional or controlled atmosphere (Awad and others 2000). No changes in the concentration of simple phenols, flavonoids, and anthocyanins were observed for Delicious and Ralls apples held for 4 to 5 months under refrigeration (Ju and others 1996). However, they found a decrease in simple phenols in earlier harvested apples after 3 months of cold storage. However, after 7 days at 20°C storage, phenols and flavonoid content decreased rapidly. 

Zheng YH, Yang ZF and Chen XH. 2008. Effect of high oxygen atmospheres on fruit decay and quality in Chinese bayberries, strawberries and blueberries. Food Control 19(5) 470-474. 

Fig. 3.12 Manufacturing processes for the ferrites (a) atmosphere controlled two step firing (b) usual heat-treatment (in Nj gas). In the hatched regions (1) and (6) in (a), the samples are heated or cooled under flowing N2 gas. In the other regions, Po. has to be controlled to obtain the required oxygen content.

A third factor controlling surface composition is the atmosphere in which the catalyst is used. The surface will be enriched in that component of the alloy that has the highest heat of adsorption of the gas. In an oxygen atmosphere the surface of a nickel-gold catalyst becomes enriched with nickel rather than gold. 57 In the presence of CO the surface of a palladium-silver alloy becomes enriched with palladium while, normally, silver would be the predominant surface component. 58 This enrichment of the surface by palladium should also be observed in a hydrogen atmosphere. 

Oxidation of metallic elements under controlled oxygen atmospheres as described above (e.g., Ru + O2 = RUO2). At the elevated temperatures required for these processes, steam also serves as an excellent oxidizing agent. 

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