Since ancient times, medicinal plants and herbal teas have been used in everyday human life as traditional medicines due to their healing and therapeutic properties (1, 2). Medicinal plants are the source of many phytochemicals which are secondary metabolites responsible for herbs’ beneficial properties (3). Plant secondary metabolism could be bio-synthetic source of several compounds which are attractive to utilize in the food industry and the pharmaceutical, chemical, cosmetic, and agronomic industries. The fundamental aim of plants is to create secondary metabolites as a defense mechanism against microorganisms, insects, and consumers such as herbivores (4). These secondary metabolites include many biologically active substances, for example, alkaloids, essential oils, flavonoids, bitters, coumarins, tannins, glycosides, and saponins. Figure 1 shows the locations of target phenolic compounds in different parts of a plant. Many studies have discussed biologically active compounds as they have antioxidant, antibacterial, antifungal, anti-inflammatory, and anti-tumor effects (8–10). In recent years, plants and their extracts containing high content of bioactive or aromatic compounds have found use in numerous applications in the food industry as flavors, colorings, antioxidants and antimicrobial agents (preservatives), nutrient enhancers, enzymes, and packaging additives (2, 11).

Plants should be appropriately identified, and a health risk assessment should be undertaken before food application (12); for example, the elimination factor for plants could be if they contain heavy metals, mycotoxins, or residues from chemical treatment or fertilization (13, 14). Chemical compounds’ concentration in plants depends on the soil, climate, agricultural practices, irrigation water quality, plant treatment, harvest season, and environmental pollution (10, 13). As a result, to reduce consumer risks, it is important to avoid harvesting plants in areas of high industrial and traffic activities due to the possibility of contamination of heavy metals (14, 15). Moreover, good agricultural practices should be implemented while applying chemical fertilizers or pesticides. Plant material before the extraction process usually requires pre-treatment, which includes washing, drying, enzymatic processes, fermentation, and grinding. Due to the washing treatment, the loading of plant samples with heavy metal contaminants such as aluminum and lead might be slightly reduced (14).

Plant material pre-treatment prevents bioactive compounds’ degradation and the development of undesirable microorganisms, allowing the plant’s shelf life to be extended (16). Drying is one of the most popular plant material preservation methods because water is necessary for microorganisms and plant enzymes to function correctly (16, 17). Dehydration inhibits certain metabolic processes, such as enzymatic degradation, that might break down the bioactive compounds and change sensory and nutritional properties (16–18). Choosing the correct drying treatment is important since it might significantly lose heat-labile molecules, volatile compounds, flavonoid components, and attractive color pigments in plants (16, 19–21). High drying temperatures, on the other hand, may inhibit enzymes in plants that break down the bioactive compounds (16). The freeze-drying technique has the potential to stabilize, enrich, and prolong the life of plants containing bioactive temperature-sensitive molecules without destroying their chemical structure (16). According to a few authors, it is more appropriate to use freeze-drying than air drying at room temperature in the dark or in the microwave to maintain the maximum amount of carotenoids and chlorophylls in herbs (3, 22). However, high drying temperatures might inhibit enzymes in plants that can break down the bioactive ingredients (16).

Dried plants might be milled into a powder before extraction because increasing the contact surface area between the plant matrix and the solvent might increase the extract’s yield and concentration of bioactive molecules through better segregation (23). On the other hand, the fragmentation method used for homogenizing herbs can reduce the yield of volatile molecules such as essential oils since they are released during the technological process, during which the secretory structure is destroyed (24). For example, the concentration of essential oil in peppermint granules (0.8–2.0 mm) was reduced by around 71% compared to the uncrushed plant (24, 25).

Isolation of some bioactive molecules from plant matrices using only solvents during extraction might be challenging due to their bounds with components of cell walls (16, 26). Enzymatic treatment is an effective strategy that might improve the efficiency of extraction target bioactive compounds by better releasing these substances by degrading cell walls and membranes (16, 26). In addition, this pre-treatment offers the possibility of greener chemistry due to the shorter extraction duration, lower solvent usage, and milder conditions (16, 27). Enzyme-assisted extraction can improve phenolic and flavonoid recovery, hence increasing the antioxidant activity of the extracts (28–31). For example, Chew et al. used enzyme pre-treatment of the mulberry leaves with pectinase before ultrasound-assisted water extraction and fortifying cottage cheese with enhanced mulberry extract (28).

A proper extraction method is required to provide a higher yield with a considerable concentration of bioactive components. The various structure of bioactive components might complicate the extraction process because of differences in polarity and solubility (32). Furthermore, the extraction method and various processing parameters strongly influence the extract’s yield, composition, and antioxidant activity; consequently, it is necessary to optimize this process (23, 33). In the last decade, attention has been focused on extraction techniques to limit the use of hazardous substances such as toxic solvents for human health and the environment while minimizing energy requirements and using renewable material as part of a green chemistry strategy (34, 35). Moreover, non-toxic and easy-to-handle solvents for plant extraction are preferred in the food industry (23); for example, water is the safest and least expensive green solvent (36). Water is efficient solvent in extracting polar molecules while in the case of less polar compounds, greater efficiency could be achieved by using organic solvents or binary solvents (36–38). For example, bioactive components such as polyphenols might be poorly soluble in water but have better solubility in organic solvents (39). Water might enhance the efficiency of the extraction process by helping the diffusion of extractable components like polyphenols through plant tissues (40, 41). Furthermore, a low-viscosity solvent may be preferred for preparing plant extract due to the possibility of accelerating mass transfer (42). For example, acidified water or organic solvent (e.g., ethanol or methanol) are effectively used to prepare plant extract rich in anthocyanins (43). Tannins are phenolic compounds with high molecular weights that form colloids when dissolved in water (44, 45). Furthermore, the solubility of tannins is variable, and depending on the target molecules, solvents with different polarities like water, ethanol, methanol, and acetone, as well as their aqueous solutions, might be used for extraction (7, 44, 45). Flavonoid glycosides are more water soluble than aglycones; additionally, both groups may be extracted with binary mixtures of water-alcohol and pure alcohols (46, 47). Furthermore, flavonoids’ hydroxyl groups and sugar moieties influence solubility in water (46). In contrast, less polar flavonoids such as flavanones, flavanols, isoflavones, and methylated flavones might be extracted with ethyl acetate, diethyl ether, chloroform, and dichloromethane (47). Alkaloids are often found in plants as salts of organic acids that are water-soluble under acidic circumstances (48, 49). Moreover, solubility in water increases due to the replacement of organic acid in alkaloid salts by inorganic acid salt (49).

Binary solvent mixtures (e.g., water and organic solvent) are preferred over their neat counterparts because all bioactive molecules in plant material cannot be extracted using only a single solvent (36). In addition, binary solvent like aqueous acetone is better for the extraction of flavanols with higher molecular weight (50). A proper concentration of aqueous and organic solvents could efficiently extract active compounds (50); for example, ethanol is miscible in water, and the relative polarity of binary ethanol-water solvents (80:20, cl/L) is 0.710, which is closer to the value for methanol than ethanol (38). Additionally, the mixture of water and alcohol (ethanol) could be more successful solvent mixture than single solvent in the extraction of polyphenols (41, 51). An organic solvent like methanol might effectively extract moderately polar and polar phenolic molecules (e.g., flavonoid glycosides and phenolic acids), especially those with lower molecular weight (42, 52). This hazardous alcohol might be a concern for food safety. The maximum limit for methanol residues in extracted food components and food is 10 mg/kg; however, the methanol residues should be below 1.5 mg per kg of foodstuff with applied extracts from aromatic plants used as flavorings (23, 53).

Solvents used in producing plant extracts might be removed at the end of the processing step (e.g., by evaporation on a rotary evaporator); however, some residual solvents might remain unintentionally (54). Their level is limited due to quality and safety concerns (53, 55); moreover, their maximum limitations are shown in Table 1 below.

The technology extraction factors influencing the composition of water or ethanol-water plant extracts include the solvent (ethanol concentration, mineral composition of water), the extraction time and temperature, the plant-to-solvent ratio, the size and part of plants, the used container, the addition of other ingredients such as acids, sugar or milk, and others (57–60). Acidification of the solvent can enhance the extraction; for example, hydrochloric acid, acetic acid, or other acids might be used (34, 60, 61). Moreover, Lajoie et al. (62) summarized and compared the most relevant approaches to enhance the water solvent potential for extracting of natural products.

Different techniques can be used to extract bioactive compounds from the plants and are classified as conventional and nonconventional approaches. These conventional extraction methods are simple, easily available, and low-cost, but their use is limited by the diffusion of solvents into the plant’s cell walls (63). These methods are decoction, leaching, maceration, hydro and steam distillation, percolation, digestion, soxhlet extraction, heat, reflux extraction, and others (63, 64). However, their disadvantages include lower extraction selectivity, a longer time of extraction, and thermal destruction of heat liable chemical compounds at higher temperatures (34, 63). Moreover, these conventional methods might require the use of pure and expensive solvents, which might be toxic. Increasing the temperature enhances the solubility and diffusion coefficient of the phenolic compounds, which speeds up the extraction process (65). However, some compounds may degrade at higher temperatures; for example, rutin begins to degrade at 75°C, and its concentration decreases with increasing temperature until it is no longer quantifiable (90°C) (58, 66). Moreover, the concentration of volatile compounds in the final extract could increase as a function of the temperature, implying that if the water is not hot enough, the aroma from herbs would not be released optimally (67).

On the other hand, non-conventional approaches include ultrasound, subcritical and supercritical fluid, microwave, enzyme, pulsed electric fields, instant controlled pressure drop, extrusion, and other assisted extractions (34, 68). These innovative and promising extraction techniques are used to recover plants’ bioactive molecules while reducing extraction time, energy, and solvent consumption to reduce waste production (68). The advantages of supercritical fluid extraction are that it is suitable for heat-sensitive compounds and prevents their oxidation, ecology without toxic solvents, shorter extraction time, and low viscosity and higher diffusion coefficient (69). That method might extract compounds like flavonoids, carotenoids, essential oils, and fatty acids from natural plant materials; moreover, it might employ several permitted extraction solvents; for example, non-polar hydrocarbons such as propane and butane, carbon dioxide, butane, nitrous oxide, ethanol, etc. (54, 69, 70). On the other hand, supercritical fluid extraction is unsuitable for extracting polar compounds (69). Extraction by the pulsed electric field is ideal for a high number of samples for a short extraction time; moreover, this technique facilitates purified extract, minimizes the degradation of the thermolabile compounds, and increases the extraction yield (69, 71). However, process parameters must be carefully monitored since they depend on various factors such as specific energy input, pulse number, field strength, and temperature (69, 71). Ultrasonic-assisted extraction is a process that extracts target molecules from a mixture of solvents by using ultrasound energy. Furthermore, the benefits of this technology include a higher yield with a shorter processing time and a lower quantity of chemicals and energy (69, 71).

Polyphenols’ structural variety and wide distribution affects their extraction from the complex plant matrix; for example, insoluble polyphenols and flavonoids are located in the cell wall (72, 73). In contrast, soluble phenolic compounds like anthocyanins are found inside the cell vacuoles (72, 74). The high temperature of the solvent may promote the distribution of cell wall polysaccharides into the solvent and weaken the integrity of the cell wall, allowing phenolic compounds to pass into the infusion easily (75, 76). Their extractability could also be influenced by the chemical properties of phenolic substances, such as their molecular structure, polarity, concentration, number of aromatic rings, and hydroxyl groups. Complete extraction of some polyphenols may not be possible due to the formation of complexes with other metabolites, such as proteins and carbohydrates (77–79). Additionally, the extract’s concentration, purification, and fractionation are important methods for phenolic compounds analysis and the subsequent application of the plant extracts in food and beverages (73).

Moreover, it is important to consider that the overall activity of plant extracts may be caused by combinations of constituents with synergistic, additive, or antagonistic effects. For example, high thiamine concentrations (0.1 and 0.8 mg/100 g) reduced the antioxidant activity (AA) of ethanolic tea extracts (80), or Murakami et al. (81) observed a synergistic effect between some phenolic compounds and α-tocopherol.

The current review focuses on using plant extracts to fortify food or beverages, extend their shelf life, control microbiological activity, or increase these products’ sensory and nutritional properties. This study evaluates the potential of aqueous or ethanolic plant extracts rich in bioactive compounds as a natural food additive. In addition, the present paper aims to collect and provide some of the most recent literature on water-ethanol plant extracts and their food applications to present well-arranged data using tables. The application of active plant extracts in oil, beverages, pastry, meat, and dairy products was also studied in detail.

The current trend is a healthy lifestyle and diet; therefore, consumers worldwide demand the development of food with a reduced level of synthetic ingredients like colorings, flavors, stabilizers, preservatives, and other food additives (82, 83). These requirements respond to concerns about the potentially harmful effects of long-term consumption of artificial additives on human health (84). However, only a small percentage of food producers develop products without food additives due to goods’ short shelf life and their susceptibility to microbial contamination. Consequently, there is an effort to find alternative natural food additives with appropriate organoleptic, antioxidant, or antibacterial properties that will extend the shelf life of food products and be attractive to consumers (33, 82, 83, 85).

Lipids are the food ingredients most susceptible to oxidation, which limits the shelf life of products or changes their quality and nutritional value. The most prevalent cause of rancidity is lipid autooxidation, a free radical chain reaction. Heat, light, oxidants, ionizing radiation, metalloproteins, transition metals, enzymes, and compounds susceptible to homolytic cleavage might initiate lipid oxidation. Oxidative changes can result in rancidity, change in flavor and odor, color loss, nutritional value, or toxic compounds that can be harmful to consumer health (hydroperoxides, endoperoxides, and epoxides of fatty acids and cholesterol, alkoxy and hydroxy radicals, aldehydes such as malondialdehyde) (86–88). Consumers notice odors formed from molecules such as hexanal, heptanal, and other volatile compounds produced by lipids’ oxidation, and these substances reduce the shelf life of a food product (89).

Antioxidants can delay the oxidation of lipids in food, which helps in food preservation by slowing the development of rancidity and color change. Natural antioxidants are a heterogeneous group of compounds with various chemical properties. This category includes phenolic compounds such as flavonoids, and the antioxidant activity (AA) is affected by their chemical structure and interaction with biomembranes. Many compounds have AA and might inhibit oxidation, but only some of them can be used in food. According to some studies, plant extracts can contribute to consumers’ health while they might have a more potent antioxidant capacity than synthetic antioxidants (90, 91). On the other hand, several natural antioxidants showed lower antioxidant activities than their synthetic counterparts, suggesting that they should be applied to food in larger amounts (92).

Although the traditional usage of plants supports their safety, and they are generally recognized as safe (GRAS) food additives, many of them have not been studied in scientific research, and their efficacy and safety have not been thoroughly established (93). Assessing their safety and toxicity is important because plants’ extracts are usually concentrated and contain a higher amount of bioactive and toxic compounds. The biological effect of plant extract might be therapeutic, functional, or poisonous and depend on the quantity and quality of the components (94). For example, their application may cause phytotoxicity and allergies in excessive concentrations (85, 94); moreover, some extracted polyphenols in higher doses might contribute to the development and progression of cancer (42). Safety and toxicity studies are important for validating plants’ ongoing use and help establish the dosage of extracts for further application (95, 96).

If plant extract (e.g., herbal infusion) already has a significant history of consumption in food in the EU before 15 May 1997, it implies that this extract does not fall within the scope of the Novel Food Regulation (EC) No. 258/97 and can be considered safe. Also, the type of solvent should be considered because an aqueous extract may be classified entirely differently from a plant extract prepared with other solvents (97). According to López-Rodríguez et al., a total of 18 plant extracts have been approved as novel food or ingredients until 2022 (98). The examples of leaves extract in this group are rosemary extracts (Rosmarinus officinalis L., ethanolic extracts or extracts prepared by supercritical CO₂ extraction) (99), aqueous extracts of Ilex guayusa (98), and a purified extract of green tea [Camellia sinensis (L.)] Kuntze, containing at least of 90% (−)-epigallocatechin-3-gallate (100). Roots are another part of plants that could be used for the preparation of extracts; for example, the powder of three herbal roots (Angelica gigas Nakai, Phlomis umbrosa Turcz., and Cynanchum wilfordii Hemsley) obtained by aqueous extraction, evaporation, and finally, spray drying (101). Moreover, this powder might be used as a food supplement, and its maximum level is 175 mg daily for adults (101). Other roots used to prepare aqueous-ethanolic extract with maltodextrin are Panax notoginseng and Astragalus membranaceus (Fisch.) Bunge; in addition, the maximum level of consumption for adults except pregnant women is 35 mg/day (102). Furthermore, cranberry extract powder is obtained by ethanolic extraction of concentrated juice from Vaccinium macrocarpon fruit, and the maximum level is 350 mg/day for adults (103).

Quillaia extract (E 999, bark and wood) is probably safe when used in amounts found in food; moreover, an acceptable daily intake of 0–1 mg/kg body weight per day has been determined. Additionally, the presence of saponins in quillaia extract was responsible for the adverse effects on human health (104). In addition, betanin extracted from beetroot was accepted as food additive E162; this natural colorant provides a red-violet color when applied to food (105). The majority of approved application of beetroot extract has no maximum numerical level for a food additive, and only the necessary amount of extract is utilized (quantum satis) (106). However, the application of colors is forbidden in any food products for infants and young children (106).

Green tea is rich in catechins, of which (−)-epigallocatechin-3-gallate (EGCG) is the most relevant and abundant polyphenol (107, 108). However, according to the European Food Safety Authority, green tea extract consumed as a food supplement at higher concentrations of EGCG exceeding 800 mg/day increases the likelihood of liver damage (108). As a result, food with green tea extract must include less than 800 mg of EGCG, and producers must specify on the label that the total daily dose of 800 mg must not be exceeded (100). However, a safe dose could not be established (107). Because EGCG is a polar molecule soluble in water and ethanol-water mixtures (108), adverse effects related to the consumption of green tea were observed on both aqueous and hydroalcoholic extracts (94).

Functional food fortified with plant extracts appear across food categories, as shown in Figure 2. Herbal extracts have the potential to be used in different food products containing fats and oils, including biscuits, fresh meat, meat preparations, cheeses, yogurts, margarine, mayonnaise or salad dressings, and other products (81, 83, 86, 109).

Before food application of extract, it is necessary to consider the type of food matrix to which it will be added because the nature of some natural antioxidants might limit their solubility depending on whether they are hydrophilic or hydrophobic (110). For example, the lipophilic nature of carotenoids might limit their solubility in aqueous-based products (111). In contrast, hydrophilic molecules like phenolic acids cannot be easily incorporated into high-fatty food products such as oils and fats (111, 112). Moreover, adding plant extracts into the food matrix can be challenging since the bioactive compounds are exposed to different processing conditions, affecting their stability (113). For example, phenolic compounds’ molecular size and structural conformation influence their sensitivity during food processing (113). In addition, various degradation mechanisms of bioactive molecules, like oxidation, hydrolysis, condensation, enzymatic deterioration, polymerization, and others, can occur due to the heterogeneous composition of the extract (111, 113).

Incorporating plant extracts as a food ingredient could negatively impact the product’s quality due to their distinctive aroma and color (114). Because plant extracts are usually potent antioxidants, rich in phenolic compounds, they are likely to contribute to the bitter taste, astringency, and darkening of manufactured food and beverages (23, 104, 115, 116). Because of changes in the organoleptic properties of food products, consumers may reject food or beverages containing plant antioxidants, especially those with essential oils (92). Furthermore, these volatile essential oils give a strong flavor, and polyphenols may have an unpleasant taste; therefore, encapsulation methods might mask these compounds before they are added to food (92, 118). For example, liposomes, nanoemulsions, nanoparticles, phytosomes, and ethosomes might be used to protect and improve the stability of plant bioactive molecules (111). On the other hand, another potential strategy for overcoming natural extracts limits is investigating the synergistic and additive interactions between antioxidants, which might result in more effective multi-antioxidant systems with less of each component (110, 118).

Consumers’ dietary preferences are changing, and more consumers prefer naturally processed and safe products without synthetic food additives. In addition, plant extracts are becoming more popular in the food industry because of their low-cost, functional characteristics, and in some cases, renewable source of biologically active components (227). Moreover, extracts have a concentrated taste and flavor and a longer shelf life than fresh plants, making them ideal as ingredients for food products. Natural antioxidants found in these extracts have the potential to fortify food, and extend its shelf life, improve nutritional and sensory properties. Herbal extracts could inhibit or slow the oxidation of lipids, but they can also affect the qualitative properties of food products in both positive and negative ways. As a result, only relevant toxicologically tested extracts should be used to develop novel fortified products, followed by sensory analysis. The human senses are used to evaluate product attributes, and consumer perceptions and reactions to product attributes are studied. Some herbal extracts can give a distinctive food taste that may be unacceptable to consumers; hence, sensory quality is one of the important aspects of successful marketing (86, 228). From a commercial perspective, the overall acceptability of a product is often more important than evaluating the enriched product in terms of antimicrobial activity and slowing or inhibiting lipid oxidation. Additionally, the traditional application of natural extract directly on the food surface, such as spraying, pulverization, and dipping, might be replaced by incorporating extract and its active antimicrobial compounds into active packaging material. These novel active packaging could help extend food shelf life and prevent changes in taste caused by excessive amounts of bioactive compounds (11, 156, 229, 230). This allows the packaging film to become a dynamic and interactive element of the preservation procedure of food products (231).

As shown in the previous tables, several researchers extracted many beneficial active compounds from food waste, and then they applied extracts to new products (135, 140, 153, 184). There is currently a global trend of utilizing co-product or waste, which arose in a considerable amount during food production, and extracting functional compounds from it can help reduce the environmental burden of waste while also adding value to the developed functional food product (232).

According to Lourenç et al. (92), plant extracts that inhibit oxidation should also be non-toxic and suitable for human consumption; furthermore, the application of plant extracts should be effective already at low concentrations, between 0.001 and 0.01%, because organoleptic properties such as flavor, odor, color, and stability of the food matrix will probably not be affected negatively. Finally, the extract’s economic aspect and stability during its processing, storage, and as part of food are also important. The stability of polyphenols is affected by the pH value; for example, an aqueous solution with tea catechins was more stable at a highly acidic pH below 4 than at a slightly acidic higher than pH 6 (233). Furthermore, acid pretreatment may improve anthocyanins’ stability by creating a more favorable extraction environment and inactivating enzymes capable of destroying anthocyanins (234). In an acidic aqueous environment, anthocyanins exist in equilibrium, while their degradation occurs as the pH increases above 6 (233).

The supercritical fluid extraction (SFE) approach is utilized on an industrial scale, particularly for essential oil extraction; however, following a potential modification, this technique might be used to extract non-polar compounds (235). SFE is an efficient method that might be used for extracting phenolic molecules and flavonoids (69).

Bioactive compounds such as flavonoids, phenolic acids, essential oils, tannins, carotenoids, organosulfur compounds, phytosterols, and tocopherols are used in the food industry in the processing of vegetable oils, meat and seafood products, pastries, dairy products, beverages, etc. (236). Additionally, plant extracts may contain up to thousands of different molecules and determine the constituents responsible for a specific biological effect can be challenging since mixtures’ behavior cannot always be characterized by the presence of only a few identified compounds (237). In addition, herbal extract as a whole or several herbs in complex formulations could show better efficacies than equivalent doses of individual bioactive molecules or single herb (238).

It is important to remember that medical herbs and their mixtures can pose a health risk due to non-essential and toxic metals, such as lead, cadmium, aluminum, mercury, or chromium, which can accumulate in plants (239). These toxic metals can be extracted into the infusion during its preparation and can be hazardous to consumers’ health. The maximum values for these metals in food supplements are defined by Commission Regulation (EC) No 629/2008, as amended, notably lead (3.0 mg·kg⁻¹), cadmium (1.0 mg·kg⁻¹), and mercury (0.10 mg·kg⁻¹) (240). Their overall concentration mostly determines the release of metals into the herb infusion, the metal’s affinity for the herb matrix, the metal’s solubility in solution, and the extractability of the components at high temperatures (77, 241). Some toxic metals, such as arsenic and lead, could be organically bound by biomacromolecules - polyphenols, with which they form ligands, and therefore are not biologically available in plant infusions. As a result, infusions could be less hazardous (241, 242). For example, Arpadjan et al. (242) observed that lead might not enter the infusions made from lead-contaminated plants since it is often weakly soluble in water and has a very low extraction factor. On the other hand, ethyl alcohol as a solvent showed a higher extraction power than water because ethanol could dissociate organic matrices and release bounded lead (243).

The techniques used to produce fortified food should be developed to avoid protein denaturation or nutritional loss. Furthermore, it is necessary to choose the appropriate application of plant extracts to food because a good approach can improve the efficiency of the extracts even at a lower dose. For example, lyophilization or extract encapsulation techniques appear acceptable for preparing extract to fortify food. Freeze drying was one of the most popular methods for preserving bioactive compounds in plant extracts used as food ingredients in analyzed studies.

A food product fortified with microencapsulated extract may have a better sensory evaluation than a free extract due to masking the aroma and taste of plant material (117, 244). Furthermore, the encapsulation method might prevent compounds from being vulnerable to the digestive process and the AA of the extract from being lost during digestion (189). The extract’s encapsulation can potentially preserve its bioactive properties and increase its shelf life, storage stability, bioavailability, and solubility, as well as reduce hygroscopicity and retention of microstructure (245). However, the size of the prepared particles can affect the acceptability of the novel food product fortified with them, as larger particles can cause a gritty-mouth feeling (246).

The stability of polyphenols in extracts is crucial for various food applications because they might be easily influenced by oxygen, temperature, pH, light, enzymes, and other factors (247). Polyphenols are recognized as beneficial phytochemicals for human health; nevertheless, these compounds can interact with proteins, carbohydrates, lipids, and other food matrix components, which might significantly affect the nutritional and nutraceutical potential of fortified products (248–251). For example, tannins might develop tannin–protein complexes, which reduces their antioxidant ability (44, 45). Because of the complexity of polyphenol interactions within the food matrix (252), it is important that each food matrix be assessed individually regarding its interacting phenolic compounds throughout the development of functional food enriched with phenolic-rich plant extract. Interactions of bioactive compounds with other food ingredients could limit their full release during gastrointestinal digestion. Moreover, the polyphenols’ bioavailability is a limiting factor of their efficacy in preventing some diseases because these molecules’ chemical structure and biological activity might be transformed during metabolic processes and interaction with colon microbiota (247, 253).

Furthermore, there are countless studies regarding antioxidants of natural origin in the literature; nevertheless, they have not been completely investigated their toxicity and the amount of biologically active compounds reaching the targeted spot in the human body. Future use of plant extracts as antimicrobial or antioxidant agents to preserve food requires that their efficacy as a food additive be proven and regulatory approved. Food fortified with plant extracts might offer health benefits; in that case, further research on in vitro tests (e.g., simultaneous digestion) and animal trials is needed to assess the health advantages to consumers.

We can find the use of extracts in botanical ingredients, such as plant extract in food and beverages, is growing worldwide. Currently, the most popular applications of plant extract are mainly non-alcoholic and alcoholic beverages. We can also find confectionery, pastries, and dairy products with botanicals, such as cheese and yogurt.

According to KerryDigest’s study, just 11% of European customers believe they completely understand all the benefits of botanicals; consequently, they recommend further education regarding botanical ingredients and how they may enhance human health (254). According to Future Market Insight reports, the global food market is expected to grow from USD 10.9 billion in 2022 to USD 34.5 billion in 2032, exhibiting a compound annual growth rate (CAGR) of 12.2% (255). More specifically, the global market for food botanicals demand is estimated to grow at 3.2% CAGR in these 10 years. The food botanicals market is expected to surpass USD 1.95 billion by the end of 2032. In conclusion, even though the previously mentioned study included just oleoresins, essential oils, and dried herbs from various sources (plants, algae, fungi, or lichens), we anticipate market growth in food and beverages with applied plant extract (256). Moreover, López-Rodríguez et al. (2022) assume that plant-origin extracts will be the most likely examined group in the scientific literature because this type of extracts has been the most approved as novel food in the last 5 years more than algal, fungal, and animal-origin extracts (98).

In conclusion, the use of plant extracts in the food industry has received significant interest in recent years. Plant extracts consist of functional and sensory properties such as nutraceutical, antioxidant (radical scavenger) and antimicrobial activities, and attractive color and flavor, making them suitable for use as a natural additive for food applications. They are also used in food applications since they are non-toxic, affordable, readily available, and environmentally acceptable. Plant extracts with high AA may be commercialized and applied in various food formulations because they might improve the product’s qualities and make it functional food. Moreover, these extracts might be options for replacing synthetic compounds, which could be potentially harmful to human health. On the other hand, it is important to consider that plant extracts used as food ingredients may present various challenges related to their stability, purity levels, compatibility with food matrix, regulatory limitations, and cost-based aspects (extraction and application should be economical).

AP: conceptualization, software, writing—original draft preparation, and visualization. JM: writing—review and editing, supervision, project administration, and funding acquisition. All authors contributed to the article and approved the submitted version.

This research was supported by the internal grant of Tomas Bata University in Zlin, grant number IGA/FT/2023/003.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.