antioxidants and food microbiology detailed content and Stuff.pptx

antioxidants and food microbiology detailed content and Stuff.pptx

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  Antioxidants
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  • Antioxidants aresubstances that can delay onset, or slow the rate, of oxidation of autoxidizable materials Or • Antioxidants are substances that can prevent or slow damage to cells caused by free radicals, unstable molecules that the body produces as a reaction to environmental and other pressures
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  Enzymatic Antioxidants • PrimaryAntioxidants • Superoxide Dismutase: It removes the superoxide radical and repairs the cells damaged by free radical. SOD catalyzes the reduction of superoxide anions to hydrogen peroxide
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  • Catalase: DecomposesH2O2 into water and oxygen. Catalase along with glucose peroxidase is also used commercially for the preservation of the fruit juices, cream consisting of egg yolk, and salad. Glutathione Peroxidase: GPx (cellular and plasma) catalyzes the reaction of H2O2 by reduced glutathione (GSH); as a result, oxidized glutathione (GSSG) is produced and it is again recycled to its reduced form by glutathione reductase (GR) and reduced nicotinamide adenine dinucleotide phosphate (NADPH).
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  Non-enzymatic antioxidants • VitaminA: Vitamin A is helpful in night vision and in maintenance of epithelial cells in mucus membranes and skin. Because of its antioxidant properties, it assists immune system also and is found in three main forms: retinol, 3,4-didehydroretinol, and 3- hydroxyretinol. The main sources of this include sweet potatoes, carrots, milk, egg yolks, and mozzarella cheese. • Vitamin C: Vitamin C is water soluble and is also called as ascorbic acid. It is found in fruits (mainly citrus), vegetables, cereals, beef, poultry, fish, etc. It is helpful in preventing some of the DNA damage caused by free radicals, which may contribute to the aging process and the development of diseases, such as cancer, heart disease, and arthritis. • Vitamin E: Vitamin E is a lipid-soluble vitamin. This consists of eight different forms such as α-, β-, γ-, and δ-tocopherol and α-, β-, γ-, and δ-tocotrienol. Most abundantly found in almonds, safflower oil, soybean oils, oil of wheat germs, nuts, broccoli, fish oil, etc., α-tocopherol possesses highest bioavailability and is the most important lipid-soluble antioxidant which reacts with the lipid radical and protects the membranes from lipid peroxidation; as a result, oxidized α-tocopheroxyl radicals are produced that can be recycled to the reduced form through reduction by other antioxidants, such as ascorbate and retinol.
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  • Carotenoid: Carotenoidconsists of β-carotene, lycopene, lutein, and zeaxanthin. They are fat-soluble colored compounds found in fruits and vegetables. β- Carotene is found mostly in radish-orange-green color food items including carrots, sweet potatoes, apricots, pumpkin, mangoes, and cantaloupe along with some green and leafy vegetables, including collard greens, spinach, and kale. Tomato is a good source of lycopene and spinach is a good source of zeaxanthin. It has been shown that lycopene is a potent antioxidant and is the most effective compound in removing singlet oxygen found in tomatoes, watermelon, guava, papaya, apricots, pink grapefruit, and other foods.
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  • Polyphenols: Thisis a class of the phytochemicals that possess marked antioxidant activities. These consist of phenolic acids, flavonoids, gingerol, curcumin, etc. Curcumin is an excellent scavenger of ROS, such as superoxide radicals, lipid peroxyl radicals, OH radicals, and nitrogen dioxide radicals, which induced oxidative stress.
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  • Food processingoperations can remove antioxidants or cause oxidative stress that can overcome the endogenous antioxidants systems in the food. Therefore, it is common to incorporate additional antioxidant protection into processed foods. Antioxidant mechanisms of compounds that are used to increase the oxidative stability of foods include control of free radicals, prooxidants, and oxidation intermediates.
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  • Free radicalscavengers (FRSs) or chain- breaking antioxidants can interact with peroxyl (LOO•) and alkoxyl (LO•) radicals by the following reactions
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  Control of Prooxidants •Control of prooxidants is therefore a very effective strategy to increase the oxidative stability of foods. Both endogenous and exogenous antioxidants will impact the activity of transition metals and singlet oxygen. • Control of prooxidant metals: Iron and copper are examples of important prooxidant transition metals that accelerate lipid oxidation by promoting hydroperoxide decomposition. Chelators inhibit the activity of prooxidant metals by one or more of the following mechanisms: prevention of metal redox cycling; occupation of all metal coordination sites; formation of insoluble metal complexes; and/or steric hindrance of interactions between metals and lipids or oxidation intermediates
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  • Control ofsinglet oxygen: Carotenoids chemically quench singlet oxygen when singlet oxygen attacks the double bonds of the carotenoid. This reaction leads to the formation of oxygenated carotenoid breakdown products such as aldehydes, ketones, and endoperoxides.
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