Research and Market Application of Antioxidants

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For a long time, synthetic antioxidants such as BHT, BHAT, BHQ, and PG have been used to preserve freshness and prevent oxidation. In recent years, extensive research has been conducted on the safety issues of these synthetic antioxidants. Research conducted by the World Health Organization (FAO/WHO), the European Community’s Child Protection Organization (HACSG), the British Biotechnology Industry Association (BIBRA), as well as organizations in Japan and the United States, has shown that synthetic antioxidants have numerous side effects; they can have adverse effects on the liver, spleen, and lungs, and may also induce malignant tumors. Therefore, the U.S. Food and Drug Administration (FDA) recommends removing BHT from substances that are generally considered safe; Japanese health authorities have concluded, after conducting studies, that the use of BHA should be prohibited; as for TBHQ, although a few countries such as the United States have approved its use in certain oils, the European Union, Japan, and other countries consider the toxicological data on it to be insufficient and have not approved its use yet. In short, there is concern regarding artificially synthesized antioxidants. It has also been proven that in foods consumed over the long term, the toxicity of natural antioxidant components is much lower than that of synthetically produced antioxidants. Therefore, in recent years, research on seeking natural antioxidants from nature has attracted great attention from scientists around the world. Currently, many natural antioxidant products have been developed around the world and are widely popular among people. The sources of its natural antioxidant components include: certain herbs, spices, tea, oilseeds, fruits and vegetables, enzymes, and protein hydrolysates. Most natural antioxidants have chemical structures similar to those of chemically synthesized antioxidants, such as containing aromatic ring structures and at least one hydroxyl group; some of them also possess reducing properties or the ability to chelate metal ions. Antioxidants can be classified according to their mechanism of action as follows: 1) Radical scavengers, most of which are compounds containing phenolic structures in their molecules, such as BHAB, HTBQ, TBHQ, and naturally occurring tocopherols; 2) Reducants, such as ascorbic acid and its salts, sulfites and their salts, riboflavin, etc.; 3) Chelating agents, such as EDTA, citric acid, phytic acid, etc.; 4) Monoserial oxygen inhibitors, such as carotenes. I. Several important types of natural antioxidants Currently, the natural antioxidants that have been developed or are under investigation include the following categories: (1) Spice extracts. Spices refer to a class of natural plant products with characteristic aromatic and pungent flavors, or certain essential oils extracted from plants (such as flowers, leaves, stems, roots, fruits, or whole plants). In addition to endowing foods with distinctive sensory flavors and health benefits, spices also have antibacterial and preservative effects, as well as antioxidant and deodorizing properties. Such spices include star anise, adzuki bean A, ginger, galangal, celery, cinnamon, cloves, bay leaves, coriander, marjoram, perilla, rosemary, plantain leaf, sage, thyme, oregano, etc., as well as their ethanol extracts. Among them, those with the best antioxidant properties are rosmarinic acid and salicylic acid extracted from rosemary and sage, respectively; their antioxidant capacity is higher than that of synthetic antioxidants such as BHT and BHA. Researchers found that at a concentration of 300 ppm, the antioxidant activity of rosemary extract is equivalent to that of 200 ppm BHA and exceeds that of 100 ppm tocopherol. Adding 1000 ppm of the petroleum ether extracts of rosemary and sage to fish oil can exhibit antioxidant effects. The antioxidant components extracted from rosemary are mainly salicyl alcohol, salicylic acid, and rosmarinic acid, all of which possess the active components of diphenol fungicides. Rosemary extract also contains various phenols such as rosmarinic acid and rosmanol, which work together to exert an overall antioxidant effect. It can be used in biscuits, cakes, sausages, cream, ketchup, snack foods, etc., with usage levels generally ranging from 200 to 1000 ppm (based on the lipid content). Rosemary extract can be used in liquid form or in microcapsules, and it can also be added to products using various mixing techniques. Given the high-temperature resistance of extracts from rosemary and olives, they can be added to barbecue oil in combination with 0.02% citric acid; sometimes tocopherol is used as an antioxidant enhancer. Thyme oil or oregano oil, added to cream at a concentration of 200 ppm, can prevent rancidity in cream stored at room temperature, and it exhibits a better preservative effect than BHT at the same concentration. The main antioxidant component in ginger is curcuminoids, while the antioxidant component in chili peppers is capsaicin; both of them exhibit good efficacy in preventing the oxidation of unsaturated fatty acids. (2) Tea polyphenols: Teas are rich in a class of polyhydroxyphenolic substances known as tea polyphenols. These are polyphenols primarily composed of catechins; in addition, they also contain flavanols, flavanones, phenolic acids, and anthocyanins. The antioxidant capacity of tea polyphenols is 10-20 times higher than that of vitamin E. Researchers have found that catechins have a significant inhibitory effect on the oxidation of fish oil containing 27% DHA (docosahexaenoic acid). Spraying an alcoholic solution of tea polyphenols on the surface of ham and cured meats can extend their shelf life. Adding a certain amount of tea polyphenols in ppm amounts to instant noodles can provide antioxidant effects. In salad oils as well, the antioxidant capacity of tea polyphenols is higher than that of dl-a-tocopherol and BHA. It was also found that the addition of catechins together with tocopherols, ascorbic acid, and other organic acids (such as citric acid) has a synergistic effect. (3) Natural xanthoid compounds mainly refer to those with 2-phenylchroman as their core structure, and one or more amino groups can be attached to the three rings. Such compounds are extremely widespread in nature, existing in the form of free flavonols or flavonoids bound to sugars, such as luteolin, rutin, quercetin, mulberry pigment, hesperidin, and soy isoflavones. Since the 1960s, extensive research has been conducted on the antioxidant properties of flavonoid compounds, particularly their antioxidant effects in edible oils. Early studies have reported that the para hydrogens adjacent to the 3’4’ position of Huangtong’s B ring confer antioxidant activity, whereas an additional para hydrogen at the 5’ position enhances its antioxidant effects. It was later shown that the 3-OH5-OH4-muciquinone structure, along with the presence of hydroxyl groups at the 3’4’ positions of the B ring, is most effective in inhibiting the auto-oxidation of fats. Luteolin is a 5,7,3’,4’-tetrahydroflavone with excellent antioxidant properties; it can be obtained in pure form by using peanut shells as a raw material, extracting them with 70% ethanol, and then performing column chromatography. This is an ideal antioxidant for oily foods. Rutin can be prepared from Sophora flower buds; it is hydrolyzed with 2% dilute H2SO4 for 1 hour, and after cooling the precipitate is filtered out, washed with water and dried. The crude product is recrystallized from ethanol to obtain high-purity rutin. Mixing other flavonoid compounds such as quercetin with alpha-tocopherol or catechins can exhibit a synergistic effect. Isoflavones extracted from soybeans are also ideal natural antioxidants. (4) Vitamins: Vitamins ACE and their derivatives are both food nutrients and can function as antioxidants. Tocopherol is available. , p,, 8 – 4 types of foreign substances, whose antioxidant activity follows the sequence a -> (3 -> -y -> 8). Tocopherol is oil-soluble due to its long side chain. Natural tocopherols can be isolated from the unsaponifiables obtained during oil processing using molecular distillation. Tocopherol A has antioxidant properties at a concentration of 250 ppm, while tocopheryl acetate exhibits such properties at 50 ppm; however, above these concentrations, they instead have an oxidizing effect. Vitamin C is a water-soluble vitamin; to make it oil-soluble, it can be converted into ascorbyl palmitate. Encapsulating vitamin C in microcapsules can improve its stability and broaden its range of applications. The combined use of 25% Vc, brown vinegar acid, 5% alpha-tocopherol, and 7% lecithin can **improve its antioxidant effects. This antioxidant combination works well when used in creams, salad dressings, chocolate, and crackers. VC and vE exhibit a significant synergistic antioxidant effect, and the addition of chelating agents can also enhance the antioxidant capacity of tocopherols. (5) Proteins and enzymes such as superoxide dismutase (SOD) can exert antioxidant effects by scavenging superoxide radicals; SOD prevents these superoxide radicals from participating in metal-catalyzed oxidative chain reactions. Glutenin also has antioxidant effects. Glutenin is isolated by extracting gluten using a 70% ethanol solution, and then produced through freeze-drying. Ovalbumin and its complexes with polysaccharides also possess antioxidant activity. Muscle extract is a dipeptide formed from the amino acids alanine and histidine; it originates from skeletal muscle and prevents muscles from being oxidized by iron ions. For raw beef stored at 4°C with 2% salt, adding 1.5% muscle extract yields better results than adding 0.5% sodium tripolyphosphate. The effects of tocopherol and 200 ppm BHT are even better. (6) Phytic acid, also known as inositol hexaphosphate, is a phosphorus-containing organic acid isolated from the residues of grains such as rice bran and wheat bran, as well as from oilseeds. It is a natural antioxidant with high safety. Adding 0.01% phytic acid to vegetable oils can increase the antioxidant capacity of soybean oil by 4 times, that of cottonseed oil by 2 times, and that of peanut oil by 40 times. After 28 days, the odor of the phytate-treated chicken pieces remained acceptable. In Japan, phytic acid is widely used in soybean oil, meat products, fish paste, and other applications. (7) Chinese herbal extracts: In recent years, several research studies in China have shown that components found in Chinese herbs such as red ginseng, angelica, rehmannia, spiny jujube seed, and asafoetida all possess anti-lipid peroxidation properties and can inhibit the formation of malondialdehyde. Ferulic acid, found in plants such as asafoetida, Sichuan peony root, and others, is an antioxidant. The hydroxyl group on its benzene ring is the active component responsible for antioxidant effects; it can eliminate free radicals and inhibit oxidative and free-radical reactions. Ferulic acid can also inhibit OH-induced lipid peroxidation, thereby protecting the structure and function of biological membranes. Ginsenoside Rg2, a natural compound extracted from plants such as ginseng stems and roots as well as Panax notoginseng roots, possesses a significant anti-lipid peroxidation effect; it can not only inhibit free radical reactions but also eliminate free radicals through indirect mechanisms. In addition, scholars from Taiwan, Japan, South Korea, and other countries in my country have also conducted numerous studies on the antioxidant effects of extracts from traditional Chinese herbs, achieving a great deal of research results. Taiwanese scholars such as Su in our country used ethanol to extract 195 Chinese herbal medicines, and studies showed that 22 of them had a stronger antioxidant capacity than an equal weight of tocopherol. Among them, the methanol extracts of Gardenia jasminoides, pomegranate peel, and Verbena officinalis, as well as the ethyl acetate extracts of Gardenia jasminoides, Gorgon fruit, and Uncaria rhynchophylla, all exhibited stronger antioxidant activity than BHA. II. Current Status and Prospects of Natural Antioxidants Application At present, natural antioxidants are widely used in the following areas: (1) as food additives, whose main function is to prevent or slow down oxidation in foods, thereby improving their stability and extending their shelf life. (2) Used in health foods, its main function is to eliminate free radicals or inhibit their activity, thereby helping to prevent aging, suppress the development of tumors, prevent cardiovascular and cerebrovascular diseases, and enhance immune function. (3) Used in cosmetics, it helps prevent skin aging and promotes beauty. (4) Used in new drugs for the treatment of cardiovascular and cerebrovascular diseases, cancer, etc. In the past, due to the high production costs of natural antioxidants and the competition from cheaper synthetic antioxidants, they were never commercialized. With the progress of time, people have become aware of the contamination of food by chemical synthetics, leading to an increasing desire for natural products. Over the past decade or so, in-depth research has been conducted on extraction methods for tea polyphenols, rosemary ethers, etc., resulting in the development of natural products with greater antioxidant activity than synthetic antioxidants. Natural antioxidants that can currently be produced on an industrial scale include natural VE, rosemary extract, tea polyphenols, licorice antioxidants, and phospholipids. In the 21st century, which emphasizes sustainability and a return to nature, with the rapid development of industry and an increasing awareness of safety among people, the use of natural antioxidants will become increasingly common. As the variety of natural antioxidants increases and production costs further decrease, natural antioxidants will gradually replace synthetic antioxidants.