Antioxidants phenolic type

Catalyst residues, particularly vanadium and aluminum, have to be removed as soluble salts in a water-washing and decanting operation. Vanadium residues in the finished product are kept to a few ppm. If oil-extended EPDM is the product, a metered flow of oil is added at this point. In addition, antioxidant, typically of the hindered phenol type, is added at this point. 

Process 4, conversion of peroxy radicals to hydroperoxides can be interrupted by traditional primary antioxidants (see Fig. 16). The fastest reacting primary antioxidants are the aromatic amines (e.g. Naugard 445). However, these materials yellow upon exposure to UV light which restricts their applieations. More common in adhesives are the hindered phenol types of which numerous types are available, with Irganox 1010 the most common choice for adhesives. 

Sidwell and Zondervan [10] used LC-MS with APCI detection for the identification and quantification of extractable antioxidants from food-contact plastic materials. Identification is based on the presence of the molecular ion (M + FI)+, (M—H) , other key ions or on further ion breakdown (MSn) transitions. The following antioxidant/stabiliser types were examined hindered phenols,... 

Antioxidants act so as to interrupt this chain reaction. Primary antioxidants, such as hindered phenol type antioxidants, function by reacting with free radical sites on the polymer chain. The free radical source is reduced because the reactive chain radical is eliminated and the antioxidant radical produced is stabilised by internal resonance. Secondary antioxidants decompose the hydroperoxide into harmless non-radical products. Where acidic decomposition products can themselves promote degradation, acid scavengers function by deactivating them. 

H. S. Olcott (University of California, Berkeley, Calif.) We have studied the effects of aliphatic amines on the autoxidation of a fish oil and squalene in air at moderate temperatures. There was little protection unless phenolic-type inhibitors were also added, in which case secondary amines were more effective than primary or secondary amines. However, at 70 °C. trioctylamine alone protected the fish oil, whereas at lower temperatures it did not (2). Further study revealed that peroxides react with trioctylamine to yield some dioctylhydroxylamine which has antioxidant properties (1). These and other observations (3) indicate that... 

A typical hindered phenol-type fuel antioxidant... 

When acid chelators are combined with one of the phenolic-type antioxidants, they can act synergistically. This type of synergism has been referred to as acid synergism (S). In this case, the primary role of a chelator is to bind metals, or metalloproteins that promote oxidation and thus, allow the antioxidant to perform its function and capture free radicals. In this manner, acid synergism is different than the BHA/BHT system. 

When the antioxidants were used in the cooked/stored samples, data indicated that they were very effective in inhibiting lipid oxidation and MFD. The chemical and off-flavor indicators were reduced and the on-flavor notes were increased. Thus, phenolic-type primary antioxidants that function as free radical scavengers are very effective tools for preventing lipid oxidation and MFD in ground beef. It should also be noted that the intensity of the desirable flavor notes remained at very high levels, which meant that the patties retained their beefy tastes. Therefore, for an antioxidant to be highly effective, it should not only prevent lipid oxidation, but it should also retain the desirable flavor properties of the food commodity. 

Synunetrically disubstituted molecules of type II are mostly obtained from bifunctional substrates such as bisphenols, cyclic urcids, etc., or bifiinctional amines such as ethylenediamine or piperazine. Accordingly, the amino group replacement of mono-functional Mannich bases by bifunctional nucleophiles such as nitroalkanes or bisamides gives derivatives of type II, as represented by the heat stabilizer for polymers 496, bearing two antioxidant phenolic moieties per molecule. 

The antioxidants studied can be classified into two broad types phenolic antioxidants and non-phenolic antioxidants. Phenolic antioxidants have been found to be more promising as they are obtained from dietary sources.Vitamin E (a-tocopherol), the first known chainbreaking antioxidant, is also an o-methoxy phenol. Pulse radiolysis studies of vitamin E and its water-soluble analogue, trolox C, have been reported several years ago. a-tocopherol reacts with almost all the oxidizing free radicals, and the phenoxyl radicals produced during oxidation reactions absorb at -460 nm (Fig. 1). The regeneration reaction of a-tocopherol phenoxyl radicals back to a-tocopherol by water-soluble antioxidant ascorbic acid was also first reported by pulse radiolysis method. The one-electron reduction potential of vitamin E is -0.48 V vs. NHE. Both a-tocopherol and trolox C are used as standards for evaluating the antioxidant ability of new compounds. 

Yellowing after heat treatment of elastane can also be done to antioxidants in the fibre, especially of the sterically hindered phenol type. 

Definition of the total phenol type antioxidant content and activity of compounds with respect to oxygen and its radicals in various alcohol drinks by two electrochemical methods. 

The total content of phenol type antioxidants (AO) and their activity with respect to oxygen and its radicals are measured by two operative electrochemical methods ammetric and voltammetric in samples more than 100 various alcohol drinks. Results of measurements show good (80-90%) correlation of these methods for dry red and white wines. Use of indicated methods allows revealing forged alcoholic production. 

Table 2 shows results of measurements of the total phenol type antioxidant content in units of GA concentration (C, mg/1 GA), obtained by ammetric, and kinetic criterion (K, pmol/lxmin), characterizing the total antioxidant activity with respect to oxygen and its radicals, for more than 100 samples of alcoholic drinks. 

TABLE 2 Results of measurements of the total phenol type antioxidant content (C, mg/1 GA), and kinetic criterion (K, mmol/lxmin). 

Amine and phenolic type antioxidants, acting as free-radical scavengers, are illustrated below, where general structures for hindered phenol and p-phenylenediamine types are shown. (AH is the antioxidant, and RH is the ruhher molecule.) The relative rates of free-radical quenching and free-radical-chain propagation are indicated hy Jfcg and kp. 

Examples of amine and phenolic-type antioxidants are given in Table 4.10. 

In the first published works, synthetic antioxidants like BHT, BHA, PEG, etc. were studied. Nevertheless, their presence in food is questionable due to potential risks and they require strict legislative control. An alternative that is being studied widely is the use of phenolic type natural antioxidants from plant species, including both integral extraets obtained by diverse methods and their purified components (such as catechin, quercetin, caffeic acid, etc.) obtained by chemical synthesis. 

Methylene-bis-(6-tert-butyl-4-methyl phenol) n. A phenolic-type antioxidant for polyolefins and acrylonitrile-butadiene-styrene resins. 

---