Antioxidants against oxidative deterioration

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. 

K. Taguchi, K. Iwami, M. Kawabata, and F. Ibuki, Antioxidant effects of wheat gliadin and hen s egg white in powder model systems protection against oxidative deterioration of safflower oil and sardine oil, Agric. Biol. Chem., 1988, 52, 539-545. 

Antioxidants are frequently added to unsaturated fats and oils in order to protect these against oxidative deterioration. For this reason, they are also added to a variety of food products containing unsaturated lipids. Antioxidants frequently applied are esters of gallic acid, butylated hydroxyanisole (BHA), butylated hydroxytoluene... 

Hydroxycinnamates as well as their conjugates may act as powerful antioxidants. In edible plants they have received much attention as protecting agents against oxidative deterioration of food. Antioxidant mechanism studies on ferulic acid and its coupling products with linoleate on the molecular level have been conducted recently. A radical scavenging reaction occurred at the 3 -position of the ferulate radical with four types of peroxyl radicals of ethyl linoleate. The produced peroxides subsequently underwent intramolecular rearrangement to afford stable tricyclic peroxides (Masuda et al. 2006). 

Antioxidants such as a-tocopherol, ascorbic acid and tea catechin can effectively inhibit the oxidation of vegetable oils and development of rancidity in food lipids. However, it has been difficult to protect fish oils containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) against oxidative deterioration and an effective antioxidant method for fish oils is required. As shown in Figure 5, oxidation of ethyl DHA was completely inhibited in the cathodic solution, although it was more easily oxidized in distilled water or in the NaCl solution, therefore, the cathodic solution may be useful as an effective antioxidant for fish oils. 

Plastics are commonly protected against such deterioration (l-k) by the addition of antioxidants against thermal oxidation, and of ultraviolet stabilizers which can absorb the damaging radiation and re-emit it in a harmless form or function by trapping radicals or decomposing hydroperoxides. 

The following sections focus on the antioxidant potential of several natural vitamins, such as carotenoids (provitamin-A), tocophaols (vitamin-E), and ascorbic acid (vitamin-C) against the oxidative deterioration of oil based systems. For each specific compound, the mechanisms of action... 

Even if the adhesive Joints are very strong initially, they are exposed to the environment and may suffer deterioration. For Instance, the simultaneous effect of moisture and stress can lead to failure. Apparently, silane coupling agents minimize this deterioration. For a detailed discussion of environmental effects and its mechanism see ref. Here again stabilization against oxidation is similar to that of bulk oxidation i.e. similar antioxidants have to be used provided they are of low volatility. 

Anti-foaming agent Antioxidant Substance which prevents or reduces foaming Substance which prolongs the shelf life of foodstuffs by protecting them against deterioration caused by oxidation, such as fat rancidity and colour changes... 

From the legal point of view, antioxidants are substances which prolong the shelf-life of foodstuffs by protecting them against deterioration caused by oxidation, such as fat rancidity, colour changes and loss of nutrient value. Hundreds of compounds, both natural and synthesised, have been reported to possess antioxidant properties. Their use in food, however, is limited by certain obvious requirements, not the least of which is adequate proof of safety. 

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