Oxidation deterioration from

Many antioxidants ia these classes are volatile to some extent at elevated temperatures and almost all antioxidants are readily extracted from their vulcanizates by the proper solvent. These disadvantages have become more pronounced as performance requirements for mbber products have been iacreased. Higher operating temperatures and the need for improved oxidation resistance under conditions of repeated extraction have accelerated the search for new techniques for polymer stabilization. Carpet backiag, seals, gaskets, and hose are some examples where high temperatures and/or solvent extraction can combine to deplete a mbber product of its antioxidant and thus lead to its oxidative deterioration faster (38,40). 

Corrosion is described as hot corrosion and sulfidation processes. Hot corrosion is an accelerated oxidation of alloys caused by the deposition of Na2S04. Oxidation results from the ingestion of salts in the engine and sulfur from the combustion of fuel. Sulfidation corrosion is considered a form of hot corrosion in which the residue that contains alkaline sulfates. Corrosion causes deterioration of blade materials and reduces component life. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Later, it was realized that while amyl alcohol reacts with nitrogen oxides liberated from deteriorating propellant to form amyl nitrate or nitrite, these in turn were not very stable in the presence of acidic decomposition products and would decomp with the liberation of oxides of nitrogen which would further accelerate the decomposition of the propellant. Since any aliphatic alcohol could be expected to behave similarly, subsequent stabilizers were made from aromatic compds or derivatives which formed stable NOa compounds with oxides of nitrogen... 

Several methods have been introduced which express the degree of oxidation deterioration in terms of hydroperoxides per unit weight of fat. The modified Stamm method (Hamm et at 1965), the most sensitive of the peroxide determinations, is based on the reaction of oxidized fat and 1,5-diphenyl-carbohydrazide to yield a red color. The Lea method (American Oil Chemists Society 1971) depends on the liberation of iodine from potassium iodide, wherein the amount of iodine liberated by the hydroperoxides is used as the measure of the extent of oxidative deterioration. The colorimetric ferric thiocyanate procedure adapted to dairy products by Loftus Hills and Thiel (1946), with modifications by various workers (Pont 1955 Stine et at 1954), involves conversion of the ferrous ion to the ferric state in the presence of ammonium thiocyanate, presumably by the hydroperoxides present, to yield the red pigment ferric thiocyanate. Newstead and Headifen (1981), who reexamined this method, recommend that the extraction of the fat from whole milk powder be carried out in complete darkness to avoid elevated peroxide values. Hamm and Hammond (1967) have shown that the results of these three methods can be interrelated by the use of the proper correction factors. However, those methods based on the direct or indirect determination of hydroperoxides which do not consider previous dismutations of these primary reaction products are not necessarily indicative of the extent of the reaction, nor do they correlate well with the degree of off-flavors in the product (Kliman et at. 1962). 

With the advent of noncorrodible dairy equipment, oxidative deterioration in fluid milk as a result of copper contamination has decreased significantly, although it has not been completely eliminated (Rogers and Pont 1965). However, the incidence of spontaneous oxidation remains a major problem of the dairy industry. For example, Bruhn and Franke (1971) have shown that 38% of samples produced in the Los Angeles milkshed are susceptible to spontaneous oxidation Potter and Hankinson (1960) have reported that 23.1% of almost 3000 samples tasted were criticized for oxidized flavor after 24 to 48 hr of storage. Significantly, certain animals consistently produce milk which develops oxidized flavor spontaneously, others occasionally, and still others not at all (Parks et al. 1963). Differences have been observed in milk from the different quarters of the same animal (Lea et al. 1943). 

However, its presence is not the only determinant of whether or not oxidative deterioration occurs. Olson and Brown (1942) showed that washed cream (free of ascorbic acid) from susceptible milk did not develop an oxidized flavor when contaminated with copper and stored for three days. Subsequently, the addition of ascorbic acid to washed cream, even in the absence of added copper, was observed to promote the development of an oxidized flavor (Pont 1952). Krukovsky and Guthrie (1945) and Krukovsky (1961) reported that 0.1 ppm added copper did not promote oxidative flavors in milk or butter depleted of their Vitamin C content by quick and complete oxidation of ascorbic acid to dehydroascorbic acid. Krukovsky (1955) and Krukovsky and Guthrie (1945) further showed that the oxidative reaction in ascorbic acid-free milk could be initiated by the addition of ascorbic acid to such milk. Accordingly, these workers and others have concluded that ascorbic acid is an essential link in a chain of reactions resulting in the development of an oxidized flavor in fluid milk. 

Josephson (1943) reported that butterfat prepared from butter heated to 149°, 177°, and 204.5°C was extremely stable to oxidation, while that heated to 121 °C oxidized readily when stored at 60°C. When butter oil itself was heated from 121 to 204.5 °C, it also oxidized rapidly. However, the addition of 1% skim milk powder to butter oil prior to heating at 204.5°C for 10 min also resulted in a significant antioxidative effect, which Josephson concluded was the result of a protein-lactose reaction (carmelization). Wyatt and Day (1965) reported that the addition of 0.5% nonfat milk solids to butter oil followed by heating at 200 °C and 15 mm Hg for 15 min caused the formation of antioxidants which protected the butter oil against oxidative deterioration for 1 year, surpassing the effectiveness of many synthetic antioxidants tested. 

Oil from expeUer is filtered, packaged under nitrogen or other neutral gas into bottles protecting from light exposure, and ready for distribution. Flax oil is very susceptible to oxidative deterioration, and treatment to eliminate oxygen needs to be applied. On the North American continent, flax oil is considered as a health food oil. 

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