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Quality, Research and Development Manager at the Cairo Company for Oil Extraction and Refining.
Antioxidants... We often hear this term, what is meant by antioxidants, their benefits, mechanism of action and types.. That's what we'll try to answer in this article.
• At the beginning, it is necessary to understand the term oxidation. Oxidation can be defined as a process that occurs in organic materials, specifically oils and fats, which results in primary oxidation compounds (peroxides and hydroperoxides) and then they break down into secondary oxidation compounds (aldehydes, ketones, free acids, hydrocarbons and polymers) through three stages:
The triggers are usually energy (light, heat, etc.), and the effects of heavy metals that lead to the breakdown of fatty acids into a free radical and a hydrogen radical at the position adjacent to the fatty acid double bond. The free radicals that have formed are highly reactive and react with oxygen dissolved in the oil to form peroxides.
The peroxides formed in turn react with hydrogen in other fatty acids, forming hydroperoxides and a free radical of fatty acid, which in turn reacts with oxygen, forming new peroxides in a chain reaction that does not end until all oxygen in oil, fat or fatty acids is consumed, which is known as self-oxidation of oils and fats.
3. Termination: -
The hydroperoxides formed break down into secondary oxidation compounds, forming unwanted odors. Some free radicals also react with each other to form polymers.
• Autooxidation is the irreversible oxidation process of fats. It is impossible to avoid it completely, but it is possible to delay it by adding antioxidants. This can only be achieved during the first phase of the oxidation process (induction phase), where once the oxidation process reaches the reproduction phase, it is no longer possible to delay or stop the said process. Therefore, the antioxidant is injected directly into the oil coming out of the removal device along with the inert nitrogen gas.
• Free radicals are not limited to oils or fats used in food manufacturing processes as they are found in the human body as a result of vital processes and interaction with the environment. Increased concentration of free radicals in the body is linked to an increased risk of diseases, the most famous of which are heart disease, cancer and arthritis. Therefore, eating foods rich in antioxidants is the body's first line of defense.
• Antioxidants can be defined as compounds that interact with free radical scavenger through their ability to give hydrogen to the free radical without oxidizing a new molecule and beginning the oxidation chain reaction.
• Antioxidants are divided into two types
1. The first type (primary antioxidant) is either natural or artificial as follows: -
A. Natural antioxidants such as: - Tocopherols - Flavonoids found in vegetables and fruits
B. Industrial antioxidants such as: - butylated hydroxyanisole (BHA) - propyl gallate (PG) - butylated hydroxytoluene (BHT) - tertiary butylhydroquinone (TBHQ)
• This type is involved in the synthesis of an aromatic benzene ring and the associated hydroxyl group. This is the so-called phenolic compound, in addition to aliphatic subgroups connected to the benzene ring. This is the essence of its function.
• The -OH group easily gives up hydrogen in favor of free radicals such as ROO• or R• instead of obtaining it from fatty acid, thus stopping the oxidation chain.
• The free radical produced by the antioxidant is relatively stable as the aromatic ring (benzene) allows the unpaired electron in the radical to move within the resonance stabilized ring.
• The role of side groups in protecting the root resulting from any interactions is undeniable as they represent a protective shield for it in addition to promoting Resonance.
• It is necessary to adhere to the globally specified doses of antioxidants as an increase in antioxidant concentration may lead to a reverse effect (Pro-oxidant effect), especially in the presence of stimuli such as minerals, light or heat. Free radicals resulting from the antioxidant itself accumulate, stimulating secondary oxidation reactions.
2. Secondary antioxidant: - Type 2 antioxidants are not directly effective in stopping the oxidation chain, such as type 1. However, they play a vital role in preventing or delaying the onset of the oxidation process by neutralizing oxidation-inducing factors such as: -
a. Metal chelators disable heavy metal ions (such as iron and copper), which accelerate the breakdown of peroxides and generate free radicals by forming compounds with these ions such as Citric acid- EDTA.
B. Singlet oxygen quenchers (Singlet oxygen quenchers) are compounds that absorb or inhibit the energy of single oxygen resulting from photostimulation, such as beta-carotene (β-carotene), turning it into triple oxygen that is less effective in oxidation processes.
• Synergism when two or more antioxidants are used together results in a protective effect that exceeds the total effect of each of them separately. This phenomenon is clearly seen when primary antioxidants (inhibiting free radicals) are combined with secondary antioxidants (such as chelating agents), achieving greater stability in the fatty system.
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• Antioxidants aim to reduce the rate of oxidation rather than prevent it completely during the shelf life, which can be called induction period, in order to maintain product quality, flavor, and color, reduce the formation of harmful compounds resulting from oxidation, and maintain nutritional value by protecting vitamins A, D, E, K
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• Choosing the right antioxidant in the food industry is a decision that depends on several factors, including: the composition of the product (fatty, emulsified), the nature of storage, temperature, exposure to light, and the presence of metal catalysts.
• In oils and ghee used for frying, it is important to use phenolic antioxidants such as BHT and TBHQ with citric acid.
• In biphasic products such as mayonnaise, a dual system is preferred that includes ascorbic acid for the aqueous phase with fatty antioxidants for the fatty phase as the oxidation process can start from the aqueous phase.
• In light-sensitive products such as whole milk powder, photoantioxidants such as β-carotene are used with tocopherols, as well as packaging solutions in opaque packaging to reduce photooxidation and ensure stable quality and nutritional value.
