The importance of antioxidants and place in today’s scientific and technological studies

Abstract

Antioxidants have become scientifically interesting compounds due to their many benefits such as anti-aging and anti-inflammatory. Today, it is still used in many areas. In food technology, antioxidants are added to many foodstuffs in order to enrich the foods and eliminate the problems. Therefore, studies to determine the antioxidant activities of natural foods and their components are also continuing rapidly. Antioxidants have also been replaced in the encapsulation studies used for the preservation and stabilization of food components. Of course, preservation of foods is as important as their production. The latest packaging techniques for food preservation are edible films and coatings. The protective function of edible films and coatings can be improved by the addition of antioxidants. Unlike these, studies on plants and animals have been investigated in vivo in terms of how the antioxidant activity changes as a result of metabolic activities. The role of antioxidant enzymes in these studies is quite large. Many results have been found for the elimination of diseases by either in vivo or in vitro studies regarding antioxidants. Thus, the importance of antioxidants increased with the use in pharmacology, cosmetics and medicine. In this study, we tried to bring a current perspective to antioxidants played an active role in many fields by combining the technological applications and scientific studies of antioxidants. In order to further customize the issue, we have done this especially for the food and health field and we have tried to emphasize the importance of antioxidants in this way.

Introductıon

Antioxidants

Antioxidants are groups of compounds that neutralize free radicals and reactive oxygen species (ROS) in the cell (Abuajah et al. 2015). Antioxidant activity in food and beverages has become one of the most interesting features in the science community. These antioxidants provide protection against damage caused by free radicals played important roles in the devolopment of many chronic disease including cardiovasculer diseases, aging, heart disease, anaemie, cancer, inflammation (Vaibhav et al. 2011) (Table 1).

Table 1 Use of natural antioxidant compounds in foods and their effects on health

Antioxidants can be classified into two basic groups as synthetic and natural. In addition, the antioxidants can be classified as endogenous and exogenous according to their sources or as enzymatic or non-enzymatic according to their effects or water-soluble or lipid soluble to their solubility (Gulcin 2012; Nimse and Pal 2015). This classification is given in the tables below with their samples (Tables 2, 3).

Table 2 Classification of antioxidants based on their origin

Table 3 Classification of antioxidants based on their solubility

Natural antioxidants are substances that exist in foods and prevent their reactions such as disruption, sourness and color change. Natural antioxidants are generally derived from plant sources and their activity varies depending on plant species, diversity, extraction and/or processing methods and growing conditions. They are found in microorganisms, in some animal tissues and in almost all plants. Natural antioxidants, especially red, orange and purple-colored fruits and vegetables, have a high antioxidant activity. Oranges, lemons, blueberries, strawberries, plums, prunes, red beans, broccoli flowers, and more have been proven to contain a high amount of antioxidants and have been incorporated into many dietary menus. As the most important natural antioxidant groups, we can list tocopherols and tocotrienols, ascorbic acid, flavonoids, carotenoids and phenolic acids (Can et al. 2005; Shebis et al. 2013) (Fig. 1).

Fig. 1

Chemical structures of flavonoids (a), ascorbic acid (b), benzoic acid (c), tocopherols (d), carotenoids (α-carotene, β-carotene, lycopene, lutein)(E)

Human antioxidant defense systemis is equipped with enzymatic scavengers such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase; hydrophilic scavengers such as urate, ascorbate, glutathione (GSH) and flavonoids and lipophilic radical scavengers such as tocopherols, carotenoids and ubiquinol. Non-enzymatic antioxidants contains subgroups, the main ones are vitamins, enzyme cofactors, minerals, peptides, phenolic acids, and nitrogen compounds (Carocho and Ferreira 2013; Ratnam et al. 2006).

E and C vitamins are the the most important among vitamins as natural antioxidants. Vitamin C, which contains ascorbic acid and its oxidation product dehydroascorbic acid, has many biological activities in the human body. More than 85% of vitamin C in the human diet is provided from fruits and vegetables. Ascorbic acid can remove superoxide and hydroxyl radicals and may also regenerate α tocopherol (Podsedek 2007). It is important for the biosynthesis of collagen, carnitine and neurotransmitters. Vitamin E is a lipid-soluble vitamin that protects lipids against peroxidative damage with high antioxidant potential. Vitamin E is a chiral compound containing eight stereoisomers (α, β, γ, δ tocopherol and α, β, γ, δ tocotrienol). Only α-tocopherol is the most bioactive in humans (Pham-Huy et al. 2008). Vitamin E is widely regarded as one of the most potent antioxidants. The antioxidant property is associated with the hydroxyl group in the aromatic ring, which gives hydrogen to neutralize free radicals or ROS (Peh et al. 2016). Most of the tocopherols are a chemical class with vitamin E activity. Of these, α-tocopherol is the main peroxyl radical remover in biological lipid phases, such as membranes or low density lipoproteins (Fuchs-Tarlovsky 2013).

Carotenoids (carotenes and xanthophylls) are yellow, orange and red pigments found in many fruits and vegetables and are non-enzymatic natural antioxidants (Podsedek 2007). The antioxidant effects of carotenoids are based on their singlet oxygen quenching properties and their ability to capture peroxyl radicals. For example, lycopene, which is one of them, is known to be very protective especially for prostate cancer. Lycopene’s main diet source is tomato, cooked tomato juice and tomato sauce, which are more bioavailable than raw tomatoes (Pham-Huy et al. 2008).

Phenolic compounds are secondary metabolites of the plant, but are also an important part of plant nutrients. Polyphenol-rich foods are widely studied due to their potential positive effects. Polyphenols have shown various positive bioactivities such as anticarcinogenic properties. A large number of compounds belong to the phenolic group. The most important ones in plants are flavonoids, phenolic acids and stilbenes Chemical structures can vary from very simple molecules to very complex molecules (Jakobek 2015). Phenolic acids form about one-third of dietary phenols that can be found in free and bound forms in plants and are known as potent antioxidants. Relieve almost all oxidant molecules, such as free radicals, by hydroxyl groups (Ignat et al. 2011; Sevgi et al. 2015).

Flavonoids are a large group of low molecular weight polyphenolic substances, and consist of benzo-γ-pyrrole derivatives (Leopoldini et al. 2011). Flavonoids play an important role in various biological processes. They interact with a number of cellular targets in critical cell signaling pathways in the body to exhibit a variety of properties useful for human health. Flavonoids are a class of secondary metabolites that cover more than 10,000 structures (Agati et al. 2012; Singh et al. 2014). Flavonoids are important antioxidants, especially because of their high redox potential; this allows them to act as reducing agents, hydrogen donors and singlet oxygen quenchers. They also have the potential to chelate metal. Flavonoids are generally the most common phytochemicals in which these chemicals help protect the plant against UV light, fungal parasites, herbivores, pathogens and oxidative cell damage. It has been associated with a decrease in the incidence of diseases such as cancer and heart disease with flavonoids when regularly consumed by humans (Ignat et al. 2011).

Both natural and synthetic antioxidants are very important in the food industry. Bad formations (taste, odor, etc.) caused by autoxidation chain reactions in foods cause the quality of the food to be low. For this reason, preservative substances which are used as additives in the food industry for about 60 years in order to prevent or minimize lipid oxidation in food products, are widely used (Shahidi and Zhong 2010). These preservative include natural antioxidants such as ascorbic acid and tocopherols, as well as synthetic antioxidants such as propyl gallate (PG), tertiary butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) (Koksal et al. 2011; Vaibhav et al. 2011). Several in vivo studies carried out in the 80s and the 90s reported some health risks associated with the consumption of synthetic antioxidants. Salud et al. evaluating the studies on this subject; A study conducted in 1993 indicated that the toxic effects produced by BHA and BHT only occur in high doses in long-term treatments, but in another study, it was demonstrated that the normal intake of BHA and BHT in low doses was not associated with gastric cancer. More recently, the European Food Safety Authority studied in depth all the contradictory published data and established that the acceptable daily intakes of 0.25 mg/kg/day for BHA and 1.0 mg/kg/day for BHT are safe for adults and children (Carocho and Ferreira 2013; Mut-Salud et al. 2016).

Nowadays, this issue is still conflicting. Findings in recent years have shown that synthetic antioxidants may exhibit toxic effects, require high cost, and show less efficacy than natural antioxidants. For these reasons, especially in developed countries, because they are more economical, have more antioxidant activity and because of their effects on longevity, interest in natural antioxidant consumption has increased remarkably (Diaz-Garcia et al. 2013; Muanda et al. 2011). As it is understood here, antioxidants have been the focus of many studies for many years and have been used in many areas for many purposes and continue to be used.

In our study, the substances having antioxidant activity, different areas of use and their intended use are tried to be explained. Also there will be many methods in determining the antioxidant activity in the studies given in our manuscript, generally used antioxidant determination methods are given in Table 4.

Table 4 Antioxidant activity methods

The use of antıoxıdant sources ın dıfferent fıelds for dıfferent purposes ın studıes

Studies for enrichment of food and eliminating negativity

Functional foods, as known, are foods that have a positive contribution to health, in addition to the nutritional value of food. There are components of these foods that are naturally found in the structure of natural, which are health promoting effects and have pharmacological activity (Galland 2013). These substances are nowadays added to the food in accordance with consumer preferences and legal regulations. Antioxidants are additives that do not threaten natural and consumer health and can even contribute to health. For these reasons, the use of these functional components has been important. These substances can be used as coloring agents, antioxidants, preservatives and additives in medicines. It is also called functional components or bioactive components (Munin and Edwards-Lévy 2011). Fibroin is a good example of it. Silk protein fibroin; It is a natural protein obtained from natural silk noils (fibers, fibroin), a biopolymer that is edible, lowers cholesterol, strengthens the immune system, regulates blood pressure, and is important for muscle, brain and nervous systems. Polyphenols found in olive leaf like Oleuropein and routine, attract attention with their high antioxidant capacities. These items are; delays or neutralizes the effects of free radicals causing many other diseases as heart disease, cancer, cholesterol, diabetes. Baycın et al. (2007) conducted a study to adsorb olive leaf polyphenols such as oleuropein and routine on edible silk protein. The maximum adsorption capacities were calculated as 108 mg of oleuropein/g of and 21 mg of rutin/g of silk fibroin. The adsorption of olive leaf antioxidants on silk fibroin was confirmed by FTIR. After adsorption of olive leaf antioxidants, silk fibroin’s antioxidative property increased from 1.93 to 3.61 mmol of TEAC/g and gained antimicrobial activity. In 70% aqueous ethanol solution 81% of rutin and 85% of oleuropein were removed from the adsorbent surface ın a desorption process. As a result, after adsorption of olive, silk fibroin was found to be a promising biomaterial for the production of functional food or dietary supplements.

One of the biggest problems that occur in food is degradation. Antioxidants are used to prevent oxidation which is a chemical degradation. In one study; green tea extracts containing natural antioxidant substances were added (0%,10%, 20% and 30% powder green tea) to the sponge cake due to the toxicogenic, mutagenic, carcinogenic effects of synthetic antioxidants and the effects of green tea extracts on the quality and antioxidant properties of the sponge cake were investigated. Because of the caffeine and nutrient fiber content in green tea, it was found that the bioactive properties of the cake samples with 20% green tea extract instead of wheat flour were better. At the end of sensory analysis, it has been reported that sponge cakes have a pleasant taste and that the green tea extracts can be used functionally in cakes due to their antioxidant properties (Lu et al. 2010). Also aqua products enter high-risk food groups due to their pH, weakness in connective tissue, nutrient composition, water content and their habitat. Deterioration in seafood can be by microbiological and chemical means. In the case of chemical degradation, quality losses due to oxidation and enzymatic activities reduce the fish consumption (Diler and Genc 2013). In this context, The use of essential oils (such as thyme, rosemary, cinnamon, laurel, grape seed, flax and lemon) alone or with modified methods such as modified atmosphere packaging (MAP), salting and radiation has an important place to improve the shelf life of aquaculture (Erkan and Bilen 2010). To investigate the effect of rosemary extract on vacuum packed sardines in different levels, fish were filleted and divided into three groups. First group was used as the control without rosemary extract, second group was treated with 1% rosemary extracts (10 g/L) for 2 min (R1), and the third was treated with 2% rosemary extracts (20 g/L) for 2 min (R2). Then all groups were vacuum-packed, they were stored in the refrigerator condition (4 ± 1 °C) over the storage period of 20 days. TBA values did not significantly increase in the groups R1 and R2. The control group had an increase in TBA values with storage time. 2% of rosemary extract were found to be most effective (p < 0.05) in controlling the rate of lipid oxidation.

Seaweeds or marine macro algae in the seafood group are also potential sources that can be renewed in the marine environment. There are scientific studies proving that algae are potential protective against oxidative stress in target tissues and lipid oxidation in foods (Duan et al. 2006). In recent years, the results of the studies have revealed seaweeds are rich sources of antioxidant compounds due to they rich sources of vitamin C, vitamin B-complex, e.g., folic acid and B12, and vitamin A precursors, such as β-carotene (Rajamani et al. 2011). In two studies for seeweeds; the shelf-life of breads by using Ulva rigida were determined as unacceptable on day 5 at room temperature whereas on day 10 at 4 °C. Breads prepared with Ulva rigida extended the shelf-life of breads for 2 days in two different storage period when compared with control groups. The shelf-life of breads with Lemna minor were extended the acceptable limit on day 8 at room temperature whereas on day 12 at 4 °C. But control group extended this acceptable limit on day 3 at room temperature, on day 8 at 4 °C. Both Ulva rigida and Lemna minör extended the shelf-life of breads (Tekeogul et al. 2011; Turan et al. 2011).

There are also different studies on the antioxidant effects of essential oils and their use in food. One of these foods is meat and meat products. These products are very sensitive, deteriorating and shelf-life products due to their physical and chemical properties as well as microbial and biochemical changes in the storage process (Karagoz and Candogan 2007). Oxidative reactions, which are one of the most important biochemical changes, are important factors that limit the quality and acceptability of the product that occurs during the processing, storage and cooking of meat and meat products (Tomaino et al. 2005). Fresh beef minced meat is very sensitive to oxidative deterioration due to the high fat content of about 20–30%. Lipid oxidation and in parallel, the oxidation of myoglobin, the color pigment, to the metmioglobin, causing the sensory-perceived rancidity and poor color formation in the final product. Thus, the product is rejected by the consumer (Johnston et al. 2005). A study on he subject, the preservative effect, chemical composition, antioxidant and antimicrobial activities of tyme (T. capatita) essential oil against Listeria monocytogenes inoculated in minced beef meat were evaluated (El-Abed et al. 2014). Nineteen components were identified, of which carvacrol represented (88.89%) of the oil. Probably due to the carvacrol component it contains, the findings showed that the essential oil exhibited high antioxidant activity, which was comparable to the reference standards (BHT and ascorbic acid) with IC₅₀ values of 44.16 and 0.463 μg/mL determined by the free-radical scavenging DPPH and ABTS assays, respectively. The application of 0.25 or 1% (v/w) essential oil of T. capitata to minced beef significantly reduced the L. monocytogenes population when compared to those of control samples. So, this essential oil can be used for the preservation of meats and increased shelf life against L. monocytogenes.

Another food used of vegetable-derived antioxidants is butter. In Turkey, instability of butter is an important problem. Generally it is not possible to preserve the produced butter even for a few weeks. Therefore, many sensory defects occur. As a remedy, with salting or melting is applied converting to mere oil in order to increase its durability. This situation limits the use of butter for breakfast (Bulca 2014). In a study by Cakmakcı et al. (2014), antioxidant effect was investigated during storage at 4 °C after the addition of donut seed oil at 0.05%, 0.1% and 0.2% concentrations to the butter. At the end of this, antioxidant property donut oil was compared with synthetic preservatives (BHT). As a result, the amount of 0.2% of essential oil had showed strong antioxidant activity, which was almost equal to that of BHT. It was determined that thiobarbituric acid and peroxide values of volatile oil samples decreased as depend on volatile oil concentration as a result of shelf life work.

Bread and bread products, as we know, have an important place in our daily diet. In 2013 Butnariu and Caunii examined the effect of water-soluble antioxidants on oxidative stress in bread enriched with antioxidants. Functional food strategy aims to improve basic nutrition by directly benefiting health in a positive way. The aim of this clinical trial was to test the benefits of a wide variety of functional foods enriched with antioxidant compounds from plant extracts in healthy adult volunteers. Oxidative stress was expressed by total radicalic activity of whole blood determined by the FORMox free oxygen radicals test (FORT), a colorimetric method based on Fenton’s reaction, approved for clinical studies. For the FORT test, conventional units called FORT units (UFORT) was used. As a result of the study, it was observed that oxidative stress decreased in the subjects fed with functional food compared to the control group. Successive to the diet enriched with multicomponent antioxidant foods, total hydrosoluble antioxidants in serum determined by photochemoluminometry significantly increased from 220.61 ± 27.92 to 313.56 ± 37.09 μg/L compared to control. This increase was associated with a significant decrease in oxidative stress, from 308.66 ± 108.32 to 244 ± 89.46 UFORT (p < 0.05), attaining normal range in all subjects and proving the antioxidant benefit of this multicomponent diet. Accordingly, the response of chronic disease prevention to functional food strategy is dependent on how the body absorbed and used food, and an antioxidant diet containing natural bioactive components may become an interesting solution for degenerative disorders in which oxidative stress increases. Another interesting study about bread; Alvarez-Jubete et al. (2010) examined the polyphenol composition and antioxidant properties of methanolic extracts obtained from amarant, quinoa, buckwheat and wheat. They evaluated how these properties are affected after two processes such as sprouting and the cooking. As a result, total phenol content in seed extracts was found to be significantly higher in black buckwheat (323.4 mgGAE/100 g). The total phenolic content decreased in the order given: buckwheat > quinoa > wheat > amarant. It was stated that total phenol content and antioxidant activity increased in general with sprouting and then there was some decrease in bread production. It was also observed that antioxidant capacities and total phenol contents of gluten-free bread containing amarant, quinoa, buckwheat and wheat were significantly higher than those without gluten-free control. In general, quinoa and buckwheat seeds and sprout have been reported to be potentially rich sources of polyphenols to enhance the nutritional properties of foods such as gluten-free bread.

Since fermentation improves the antioxidative activity of flavonoids by increasing the release of nutrients from plant origin, it is a useful method to increase the contribution of natural antioxidants. Recent research has shown that antioxidative activity of protein hydrolyzate and peptides can be produced by microbial proteases during fermentation (Ricci et al. 2010). In a study by He et al. (2012), they reported, rapeseed peptides (RPs) were prepared by solid state fermentation with Bacillus subtilis. They also stated that these amino acids and peptides would effect as antioxidants. Glutamic acid (19.5%), lysine (7.6%) and proline (7.3%) were the most dominant amino acids present in the RPs but serine (1.5%), tryptophan (1.3%) and cysteine (0.5%) were present in least amounts. Concentration-dependent effect on antioxidant activities was present in RPs, which showed high activities of scavenging free radical, reducing power, and inhibition of lipid peroxidation, but low ferrous ion-chelating activity. The cleavage of peptide bonds by hydrolysis increases the levels of free amino and carboxyl groups and leads to an increase in solubility. This increased solubility may increase the antioxidant activity of the peptide (Sarmadi and Ismail 2010).

In vitro studies on natural foods

Nowadays, the beneficial effects of many foodstuffs and beverages for human health are thought to be due to their antioxidant activities. For this purpose, in vitro studies about antioxidant and antiradical capacities of many natural and industrial products that we consume as food and the compounds they contain and the methods developed for these studies have been continuing from the past to the present. As a result of investigations, it has been found that many fruits and vegetables contain flavonoids, phenolic acids and carotenoids. It is suggested that a diet rich in antioxidants will be beneficial for human health and therefore focuses on determining the antioxidant capacity of natural products (Alarcon and Deicona 2013; Gulcin 2012).

Due to the antioxidant activity of fruits and vegetables, antioxidants can be used in many fields such as food industry, packaging technology, pharmacology and cosmetics. Khanam et al. in their study published (2012), of eight leafy vegetables to be Komatsuna, Mizuna, Pok choi, Mitsuba, Salad spinach, lettuce, red amaranth and green amaranth investigated the antioxidant activity. The phenolic compounds were characterized as hydroxybenzoic acids, hydroxycinnamic acids and flavonoids. Isoquercetin and rutin, the most common flavonoids, ranged from 3.70 to 19.26 and 1.60 to 7.89 μg/g ffw, respectively. As a result of their studies, the antioxidant capacities of the vegetables were listed as Pokchoi > Komatsuna > Mizuna > Mitsuba > Redamaranth > Lettuce > Green amaranth > Salad. The antioxidant activities also vary according to the harvest, growth and development times of fruits and vegetables to. For example, Ghasemnezhad et al. (2011) investigated the antioxidant activity of various peppery fruits in the maturity stages of bioactive compounds and their importance as dietary antioxidants. As a result of the researches, it was observed that there were differences between antioxidant capacities of pepper varieties in different maturity periods. Concentration of antioxidant components and taste-related properties varied among the pepper cultivars at both the mature and whole coloured ripened stages. When advanced maturation, total antioxidant activity increased, but the amount of total phenols decreased such as ascorbic acid. Reddy et al. (2010) in their study published investigated the anitoxidant properties of fourteen commonly consumed fresh fruits and ten dry fruits were studied because of the possibility of reducing the risk of chronic degenerative disease. ABTS activity of fresh fruits ranged from 22 to 496 mg TE/100 g, with high activity being found in guava, Indian plum, mango, custard apple and pomegranate, while low activity was observed in banana, papaya, pineapple, sweet lime and watermelon. Similarly the FRAP activity of dry fruits also showed a wide range, with values ranging from 1174 to 32.416 mg/100 g, the highest activity being in walnuts (32.416 mg/100 g) and the lowest in cashew nuts (1174 mg/100 g). Thus the ABTS in fresh fruits and FRAP in dry fruits showed that both had reasonably good antioxidant activity. Probably due to their low moisture content, dry fruits had higher activity than fresh fruits. As a result, most of the fruits examined were rich in phenolic antioxidants and stated that they had radical cleaning activity.

In another study, different parts of faba bean plant were examined in various stages. For the raw immature faba bean, seed coat showed the highest total fenolic compound (TPC) (68.54 mg/g) followed by pod coat, whole pod, whole seed, and cotyledon (12.31 mg/g). For the raw mature faba bean, seed coat also showed the highest TPC (41.46 mg/g) followed by pod coat, whole seed, and cotyledon (4 mg/g). Similar to their studies, they stated that Gujral et al. (2013) recorded higher total phenolic amounts in seed coat fraction of some legumes including red kidney bean and chickpea than in whole seeds (Chaieb et al. 2011). Dogmus and Durucasu (2013) conducted a study on the antioxidant activities of different flax seeds (yellow 85 and mcgregor) in their study. The DPPH radical scavenging activity of BHT is almost the same as that of the Yellow-85 flax seed and Yelllow-85 is higher than the BHA and Mcgregor flax seed varieties (Yellow-85 > BHT > BHA > Mcgregor). Yellow-85 (5.4279 μg/mL GAE) had a higher phenolic content than Mcgregor (0.1407 μg/mL GAE). Beevi et al. (2010) conducted research to determine the antioxidant activity of Raphanus sativus plants on leaves and roots, which are usually discarded. Methanolic and acetone extracts of R. sativus leaves had total polyphenolic content of 86.16 and 78.77 mg/g dry extract, which were comparable to the traditional rich sources such as green tea and black tea. Methanolic extract of leaves and stem showed potent reductive capacity, significantly inhibited linoleic acid peroxidation and displayed metal chelating activity. IC₅₀ values were found for leaf and root; 31, 42 for DPPH radical, 23, 52 for superoxide radical, 67, 197 for hydrogen peroxide, and 56, 62 μg/mL for nitric oxide respectively.

There are numerous studies examining the antioxidant capacity of vegetables and fruits such as these. The above-mentioned are just a few of these. As a result of above studies, it has been concluded that these natural products used in the studies can be used as an alternative to the food industry instead of synthetic antioxidants (Table 5).

Table 5 Antioxidants, their components and applications

Studies in encapsulation

The encapsulation; It is a relatively new technology used for the preservation, stabilization and slow release of food components. Encapsulation is applied for many purposes such as increasing shelf life, increasing nutritional value, providing digestibility and shortening the ripening time. In recent years, it has provided many benefits such as increasing the variety of foods and ensuring its naturalness (Gokmen et al. 2012).

In 2014 Naufalin and Rukmini stated that Kecombrang fruit has a bioactive compound as antioxidant in their studies. They added that the extract of the kecombrang fruit is volatile, and its stability decreases with the effect of light and oxygen. They aimed to produce practical nano-encapsulant antioxidants which are stable and applicable to food products. The results showed that the formulas based nanoencapsulant kecombrang fruit extract with fillers maltodextryn and soy protein and tween 20 had potential as a natural antioxidant, with the total phenolic content of 289.86 mg/100 g and antioxidant activity of 32.165%.

As it is known, it should be required that the body is adequately getting in order to see the positive effects of functional components. The low stability of these components negatively affects their bioavailability during food processing and consumption. These components are protected by the encapsulation technique which has been used in food industry for many years and their bioavailability can be increased (Heidebach et al. 2012). The fact that phenolic compounds have low stability against environmental influences and process conditions, storage and even consumption stages has brought along technological difficulties. Studies have been carried out to protect these compounds from the factors affecting their stability. In particular, studies have been carried out to protect from light, generally from environments with pH greater than 7, from temperatures as high as 60–80 °C, from the presence of oxygen, from the enzymes in the environment and from the presence of substances such as ascorbic acid, sulfides, kopigments and metallic ions (Cavalcanti et al. 2011).

Encapsulation technology has been found to be successful in increasing the stability and biologically accessibility of various phenolic substances. The use of anthocyanins, one of the these phenolic substances especially in processed food products is very limited because they are sensitive to various factors such as heat, light, metal ions, pH, sugar and ascorbic acid in anthocyanins. Furthermore, the biologically benefits and accessibility of phenolic compounds are very low due to their low absorption and rapid metabolism in the body. Most of the anthocyanins are metabolised in the stomach shortly after ingestion, while the portion reaching the small intestine is degraded in high pH conditions (McGhie and Walton 2007). Coruhli (2013) in his thesis work; because it contains anthocyanins which have positive effects in terms of health and used as natural colorants, it has worked on the fruit of the berry which has the potential to be used in the food and beverage industry. They studied to encapsulate mulberry anthocyanins into chitosan-coated calcium-alginate particles and to optimize some of the factors used in encapsulation using the response surface method. Total phenolic content was measured 462.85 ± 35.35 GAE/100 g fresh sample for black mulberry and 3224.30 ± 745.67 mg GAE/100 g extract for anthocyanin extract, total flavonoid content was found 1349.26 ± 34.3 mg QUE/100 g fresh mulberry sample and 10,421.30 ± 396.8 mg QUE/100 g anthocyanin extract, antioxidant capacity was measured as 1393.14 ± 40.6 mg trolox/100 g fresh sample for mulberry and 15,165.23 ± 117.99 mg trolox/100 g sample for anthocyanin extract and finally total anthocyanin content was measured as 462.85 ± 35.35 mg Cy-3-gly/100 g mulberry sample and 3224.30 ± 745.67 mg Cy-3-gly/100 g extract. Response surface methodology results show that aspect ratio is between 1.043 and 1.118, sphericity factor is between 0.021 and 0.070, encapsulation efficiency is between ~ 54 and 70% and release in gastric medium is between 10 and 27%. When the theoretical and experimental data obtained by encapsulation as 2% extract, 0.1% chitosan and 23 min were compared, it was found as 65.16% and 64.32% for the encapsulation efficiency, respectively. In the results of working; if the amount of chitosan in the extract is high, chitosan will be insufficient to protect the active substance and cause the release in the stomach environment and this will not be desired to obtain stable capsules resistant to acidic hard conditions such as stomach.

Fucoxanthine is an important xanthophyll found in some brown algae. Xanthophylls are compounds with significant antioxidant activity. Fucoxantin is known to have anticancer activity. Unfortunately, the low solubility of this carotenoid in water prevents it from becoming a drug candidate. Fucoxanthine is also a pigment sensitive to temperature and light. One possible way to reduce the effect of light and temperature is to microencapsulate it. Noviendri (2014) microencapsulated fucoxanthin using a suitable technique to remove these disadvantages. He used poly (D,L-lactic-co-glycolic acid) (PLGA) microsphere tecnique for preparation of fucoxanthin-loaded microsphere (F-LM). The F-LM fabricated from PLGA (50/50) as coating needed 2 months for their degradation. The F-LMs were totally collapsed and disintegrated into irregular particles. As a result, no solid sphere was observed with electron microscopy (FE-SEM). In a study conducted Pahlevi et al. (2008) tried to obtain good quality carotene microcapsules for food industry and health purposes. As a result of these investigations, they suggested that the microcapsule with encapsulating sodium caseinate and 30% carotene extract had the highest microencapsulation activity and total carotene and carotene retention values. In another study carried out, it was aimed to increase the functional properties of food with these components by obtaining the valuable components of the apple’s waste shells. In addition, in order to examine the effectiveness of these components in foods, it was aimed to determine the effectiveness of the encapsulation technique and to determine whether the encapsulation method increases the bioavailability. As a result, they claimed that the phenolic components extracted from the apple peel can be coated with liposome-chitosan-maltodextrin to increase their stability during consumption and to increase their bioavailability (Demircan 2016).

Studies in edible films and active packaging

It is important to protect as much as the production of foods. Various packaging materials can be used for food preservation. Some of these materials can cause environmental pollution. Therefore, in recent years, alternative packaging materials that will not contribute to environmental pollution and contribute to the physical, chemical and sensory properties of foodstuffs have been started to be investigated. One of these materials is edible films and coatings. The most important advantages of edible films are that they are reliable in terms of health, require simple technology, have low production costs and have no polluting effect on the environment. Protective function of edible films and coatings can be improved by adding antioxidant and antimicrobial agents to film and coating (Janes et al. 2002; Quintavalla and Vicini 2002). Antioxidants are widely used in food to improve the oxidation stability of the food and prolong the shelf life (Biji et al. 2015).

This new alternative packaging technology is based on the inclusion of antioxidant agents in the packaging as a means of improving the stability of oxidation-sensitive food products. When the developments in this technology are examined and compared, it has been stated that these developments can be designed and optimized for each specific product and in short, ready for implementation by the food industry (Gomez-Estaca et al. 2014).

In food industry, lipid oxidation is the main cause of deterioration in the variety of foods such as nuts, fish, meat, whole milk powder, sauce and oil. Various strategies have been implemented to reduce lipid oxidation, such as the direct addition of antioxidants to foods or the design of appropriate packaging technology. Ou et al. (2005) in their study, they used different concentrations of ferulic acid in the preparation of soy protein based edible film. They have determined that an optimal concentration of ferulic acid increases the stretching and elongation ability of the film and also increases the antioxidant activity of the film to protect fresh pork fats. The optimal concentration for ferulic acid in film forming solution is 100 mg/100 g. Moreover, the properties of the film were further improved when ferulic acid was oxidized by hydrogen peroxide.

In another study, two types of antioxidant (Oregano-and garden type thyme) were added to produce soy protein based edible films and investigated the effects of fresh beef ground meat on oxidative and color stability during cold storage (4 °C) (Kodal 2008). Oregano and thyme essential oils used in the study showed high antioxidative activity. The IC₅₀ values of oregano and thyme essential oils were 6.64 and 7.62 respectively. TBA values of control and soy protein film groups were higher than oregano (OR), garden thyme (TH) and OR:TH (1/1) groups; however, no significant differences were found between samples. When the results obtained from the study are evaluated, it has been determined that the application of thyme essential oils with significant antioxidant activity in the model system by formulating with edible film shows the same high activity on oxidative stability. However, it is stated that meat and especially ground meat was a very complex system. In addition, the antioxidant activity obtained in the product was observed not to be remissible when considering the factors such as the level of antioxidant transition from the edible film to the product.

Akcan (2013) prepared an edible film with the addition of laurel and sage extract from the whey protein. This edible film was applied to meatballs. For this purpose, the edible films made by whey protein, that includes two different concentrations of laurel or sage extract (2% or 4%) were rolled onto the meatballs and oven-cooked until the central temperature reached to 72 °C. During the storage period, the primary and secondary oxidation products were determined at 1st, 4th and 7th days in cold storage and every 15 days at frozen storage. It has been investigated how edible films affect the oxidation stability of meat products such as meatballs. It was determined that the meatballs with laurel extract containing edible films have higher antiradical activity compared with the meatballs with sage extract containing edible films and control groups.

In vivo studies in plants and animals and their importance in eliminating diseases

There are many studies on plants and animals related to antioxidants. These studies indicate how antioxidant activity changes as a result of actions in metabolism. In order to determine this, the change of antioxidant enzymes in living organisms was investigated (Table 6).

Table 6 Health effects of antioxidants and their compounds

Salt stress is one of the important stress factors that limit the product efficiency by affecting the development of plants especially in arid and semi-arid regions. In plants exposed to salinity, various metabolic events, especially photosynthetic activity, may decrease the chance of survival of plants. There are physiological and biochemical responses that provide tolerance mechanisms in the plant against salinity. One of them are antioxidant systems. Gao et al. (2008) investigated the effects of increased NaCl concentration in Jatropha curcas L. seedlings on antioxidant enzymes such as SOD, peroxidase (POD) and CAT. Seedlings were divided into 5 groups and one of them was used as control group. The other 4 groups were exposed to increased NaCl concentration of 50–200 mmol. As a result, significant differences were observed between the antioxidant defense enzymes and the reactions of different plant organs of plants exposed to different NaCl concentrations. Antioxidant activities of enzymes such as POD, SOD and CAT increased with increasing stress and Jatropha curcas L. seedlings were able to tolerate NaCl up to 150 mmol.

One of the most detrimental factors in human life is the exposure to many toxic elements in the environment. Especially lead, widely used in industry, is a major environmental health problem in both humans and animals. In a study conducted by Attia et al. (2013) in order to cause damage to the liver of rats; For 50 days, they added 500 mg of lead acetate to the drinking water. Then, a fresh ginger aqueous solution was prepared at the desired concentration (160 mg/kg body weight) and administered to the rats with the injector by mouth for 50 days. Oxidative damage caused by lead in liver was determined by increase in lipid peroxidation levels in control group and decrease in GSH level. As a result, SOD and GPx activities were significantly increased in ginger treated rats. They stated that ginger has protective effect against lead-induced damage in rats due to antioxidant mechanisms and may be appropriate for treatment.

In a studies published, Caple et al. (2010) reported that antioxidant properties in diets rich in fruits and vegetables reduce the risk of cancer. They investigated the effect of supplementation of antioxidant-enriched foods on DNA damage. The supplement provided 100 μg Se, 450 μg vitamin A (300 μg retinol equivalent retinol, 150 μg retinol equivalent β-carotene), 90 mg vitamin C and 30 mg vitamin E per capsule. The subjects were asked to abstain from alcohol for 2 days before blood collection. Of the forty-eight volunteers recruited, eight were randomly allocated to a control group who took no supplement. The remaining subjects were provided with the supplements and instructed to take one capsule daily for 6 weeks while following their normal diet; forty-eight individuals completed the 6-week supplementation period. At baseline and after 6 weeks of supplementation, fasting blood samples (40 mL) were collected in evacuated containers containing EDTA. A second aliquot of lymphocytes was used to prepare an extract for assay of base excision repair (BER). Whole blood was frozen at − 80 °C for DNA extraction. Plasma was frozen at − 80 °C for subsequent antioxidant analysis. As a result, they noted a significant reduction in DNA damage after reinforcement, while having a high level of damage prior to reinforcement. Even among healthy, young and non-smoker adults, there were significant differences in DNA damage, BER rates, and response to an antioxidant supplement in BER. (BER is the main mechanism responsible for the protection of the integrity of the human genome against oxidative damage.) In a study on smoking; Alvarez-Parrilla et al. (2010) published a study that they examined the intake of antioxidant diets rich in fruits and vegetables and inversely proportional to the development of cardiovascular diseases and their effects on humans. In the present study, the effect of the consumption of a pear, an apple and 200 mL orange juice, during 26 days, on total plasma antioxidant capacity (TAC) and lipid profile of chronic smokers and non-smoking healthy adults was analyzed. Fruit consumption increased TAC in non-smokers, but not in smokers. In non-smokers, total cholesterol and low-density lipoprotein-cholesterol increased significantly; while in smokers thet decreased. In non smokers high-density lipoprotein-cholesterol are increased too. Similar to the above study it was observed that there was no effect in smokers, but non-smokers increased total antioxidant capacity.

Ellinger et al. (2011) in their review published suggested that green tea consumption had a protective effect against cardiovascular diseases and different types of cancer. In this review they investigated the effect of green tea consumption on antioxidant effects ex vivo and in vivo. For this purpose, the Medline and Cochrane databases were searched for controlled intervention studies (English) on green tea consumption and antioxidant effects published up to June 2010. As a result, they stated there was limited evidence that regular consumption of green tea (at least 0.6–1.5 L/day) might increase plasma antioxidant capasity and reduce lipid peroxidation (especially oxidation of LDL). The beneficial effects of tea were seen more clearly in participants exposed to oxidative stress.

Bahadoran et al. (2012) reported that dietary antioxidants may have positive effects on the attenuation and prevention of metabolic disorders and therefore examined that dietary total antioxidant capacity (TAC) and metabolic syndrome (MetS) components and the occurrence of the MetS during a 3-year follow-up. In this study; 1983 adults (between 2006–2008 and 2009–2011) aged 19–70 years were studied in the framework of Tehran Lipid and Glucose Study. Dietary TAC was estimated at baseline measuring the usual intakes of participant. The MetS components were assessed at baseline and 3 years later. TAC capacity more than 1080 μmolTE/100 g of food, resulted in a 38% decrease in the risk of central obesity. As a result of this study, higher antioxidant intake had positive effects on metabolic disorders and they suggested that weight gain and abdominal fat gain were prevented.

Result

As a result, all studies on antioxidants show that antioxidants have always maintained their place in scientific studies from past to present, and that the search for natural resources has always continued. Antioxidants have become very popular in addition to enriching foods, stabilization, bad taste and deodorization, in the technological fields such as encapsulation, edible film and packaging, in vivo studies in animals and plants. Thus, antioxidants have always make an indelible impression in areas such as especially food, cosmetics, pharmacology and medicine. As it can be understood from the studies, the daily intake of natural antioxidant sources is very important in the prevention of oxidative stress, since it has many positive effects on our health.