1 Introduction

Agricultural waste is frequently disposed of through burning or landfill dumping, posing a significant threat to ecosystems. This threat primarily stems from the emission of greenhouse gases released by untreated agricultural residues [1, 2]. Consequently, it is imperative to explore sustainable energy strategies for the efficient valorisation of agri-food waste [3, 4]. Such initiatives are closely aligned with the United Nations Sustainable Development Goals (SDGs) for 2030 [5]. Notably, household waste constitutes approximately 42% of total food waste, followed by the food industry which contributes 39% [6]. The economic impact of this waste is estimated at $750 billion (INR 47 trillion) [7]. This pressing issue underscores the necessity of developing a circular bioeconomy framework to valorise agri-food waste by producing high-value bioactive compounds [8].

Agri-food waste is rich in bioactive compounds, which are secondary metabolites such as polyphenols, alkaloids, tocopherols, triterpenes, terpenoids, saponins, and polysaccharides. These compounds exhibit anti-inflammatory, anticarcinogenic, antioxidant, and antimicrobial properties that are essential for human health [9,10,11,12]. Extraction techniques for these compounds are broadly classified into conventional and non-conventional methods. Conventional methods include maceration, decoction, infusion, soxhlet extraction, and hydrodistillation, whereas non-conventional methods comprise microwave-assisted extraction (MAE), pulsed electric field-assisted extraction (PAE), pressurised liquid extraction (PLE), enzyme-assisted extraction (EAE), and supercritical fluid extraction (SFE) [13,14,15]. For instance, a previous study utilised hot water, ethanol, and methanol to extract phenols and flavonoids from Citrus japonica peels [16]. More recently, bioactive compounds have been extracted from saffron petals using ultrasound techniques with acidified ethanol as the solvent [17].

However, the stability of extracted bioactive compounds is often compromised by factors, environmental variations in pH, temperature, oxygen, and light exposure, reducing their shelf life regardless of the extraction method. Encapsulation techniques help address these challenges by protecting delicate bioactive compounds, thereby enhancing their stability and absorption in the human body [18,19,20]. Additionally, encapsulation can mask undesirable odours and tastes associated with certain bioactive compounds [21,22,23]. Bioactive compounds may be encapsulated as nano (< 0.2 μm), micro- (0.2–5000 μm), or macro- (> 5000 μm) capsules [24, 25]. While macroencapsulation is a well-established process, micro- and nanoencapsulation techniques offer superior homogeneity and facilitate the sustained release of bioactive compounds at targeted sites within the body [26]. These approaches also improve the functional, nutritional, and commercial value of the compounds [27].

Although numerous review articles provide broad overviews of extraction techniques, few offer detailed comparative analyses of these methods, particularly with respect to the incorporation of emerging solvent systems. In addition, limited attention has been devoted to systematically comparing nanoencapsulation techniques and their associated carrier systems. Furthermore, critical issues such as in vivo validation, safety profiling, and regulatory assessment of nanoencapsulated bioactive compounds derived from agri-food waste remain insufficiently addressed in the existing literature.

This article seeks to address these gaps by presenting a comprehensive comparative evaluation of various extraction techniques, with a particular focus on the use of novel solvents. It further aims to systematically assess nanoencapsulation methods and their respective carrier systems. Additionally, the study critically examines the current status of in vivo validation, safety considerations, and regulatory frameworks related to the application of nanoencapsulation technologies. Through these analyses, the article intends to provide actionable insights for researchers and stakeholders, ultimately facilitating the advancement of nanoencapsulation strategies toward industrial-scale implementation. This review provides an overview of the various extraction processes used for bioactive compounds, examines their encapsulation methods, and discusses the key challenges associated with industrial scale-up and regulatory considerations of the encapsulated products.

2 Extraction process of bioactive compounds from Agri-food wastes

Extraction is one of the most critical procedures for determining and enhancing the bioaccessibility and availability of bioactive compounds from agri-food waste. These compounds are subsequently extracted and converted into valuable products used in cosmetics, nutraceuticals, food additives, and pharmaceuticals. Since ancient times, numerous extraction techniques have been developed and refined to accommodate the physicochemical properties of the target compounds, as well as the characteristics of the matrices from which they are extracted [28]. Various techniques for extracting bioactive compounds from different waste sources, along with their respective yields are presented in Table 1.

Table 1 Extraction techniques for recovering bioactive compounds from agri-food wastes
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As shown in Table 1, certain extraction techniques are particularly well-suited for recovering specific bioactive compounds from various waste sources. Accordingly, a comparative analysis of different extraction methods for the recovery of these compounds is warranted.

2.1 Comparison of the efficacy of various conventional extraction techniques

Among conventional extraction techniques, maceration is the simplest method and is particularly suitable for extracting heat-sensitive bioactive compounds [46]. Similarly, percolation is another traditional method that demonstrates greater efficacy than maceration [47]. Solid–liquid extraction is generally more effective than both maceration and percolation, as it uses minimal solvent, and has shorter extraction duration. Although this method enhances mass transfer and contact efficiency, it is unsuitable for extracting heat-sensitive compounds due to the involvement of elevated temperatures. Among traditional techniques, soxhlet extraction is considered the most efficient and widely used method for isolating bioactive compounds from natural materials and concentrating analytes. Compared to maceration or percolation, soxhlet extraction offers time efficiency, reduced solvent usage, and higher extraction yields. In a comparative study, maceration and soxhlet extraction were evaluated for their effectiveness in extracting phytochemicals and assessing the antioxidant activity of onion peels. The results indicated that the TPC (320 mg GAE/g) and TFC (80 mg QE/g) of the onion peel extract were higher when using soxhlet extraction with 90% ethanol at 60 °C than with maceration [48]. Another study compared the extraction of lycopene from tomato pomace using soxhlet extraction and supercritical carbon dioxide (SC-CO₂) extraction. The findings revealed that the lycopene yield (1016.94 mg per 100 g of extract) was higher with SC-CO₂ extraction than with soxhlet extraction [49]. Therefore, based on previous studies, it can be inferred that the efficiency of an extraction technique is influenced by the target compound’s characteristics, the choice of solvent, and the particular technique employed. As different bioactive compounds such as flavonoids, alkaloids, and terpenoids exhibit varying thermal sensitivities and solubilities, selecting an appropriate extraction technique is essential to maximise recovery. It is also important to consider that prolonged extraction times, elevated temperatures and excessive solvent usage can increase energy consumption and accelerate the degradation of heat-sensitive bioactive compounds. While conventional extraction techniques—such as solvent extraction, steam distillation, and Soxhlet extraction—have long been employed for the recovery of bioactive compounds from agri-food wastes, recent advancements in green and non-thermal technologies, including supercritical fluid extraction and ultrasound-assisted extraction, have emerged as more sustainable and efficient alternatives.

2.2 Non-conventional extraction techniques

Non-conventional extraction techniques require less solvent, operate more rapidly, and offer greater selectivity and efficiency [49,50,51]. For example, advanced technologies such as PAE and UAE have been applied to grapes, resulting in a 23–32% increase in polyphenol content and a 17.6-fold reduction in energy consumption. Although these novel approaches enhance the extraction of bioactive compounds from agri-food waste, their efficiencies vary depending on operational parameters. Extraction time and temperature are particularly important for thermo-sensitive compounds, as prolonged exposure can increase energy consumption and degrade heat-sensitive bioactive compounds [52]. PAE typically requires between 5 and 480 min [52], while SFE ranges from 13 to over 60 min [53], making both comparatively time-consuming reactive to MAE and UAE. The primary drawback of SFE is its longer extraction time [54]. Furthermore, factors such as cultivar, source material, and maturity stage significantly influence extraction efficiency and phenolic content, complicating direct comparisons across techniques [55]. Nevertheless, prior studies indicate that MAE yields the highest TPC, followed by PAE, UAE, and SFE [56]. Even when co-solvents are applied, SFE typically results in the lowest TPC, making it more suitable for extracting essential oils and non-polar compounds [57]. Therefore, the selection of an extraction method should be guided the characteristics of the raw material and the extraction parameters. Extraction efficiency and phenolic compound yield can be further optimised through the integration of multiple non-conventional techniques. Among these, the combination of UAE with other extraction techniques seems to be particularly effective. For instance, UAE integrated with SFE increases antioxidant yields, while UAE combined with PAE significantly reduces extraction times. Such integrative strategies enable the production of a broader range of high-value bioactive compounds from a single source. According to the findings from previous studies, polar phenolic compounds can be recovered simultaneously using pressurized aqueous extraction (PAE) and non-polar compounds using supercritical fluid extraction (SFE) when these two techniques are successfully combined [57,58,59]. Since effective extraction is a crucial initial step in the valorisation of agri-food waste, careful consideration should be provided to the stabilization and delivery of these bioactive compounds, which are accomplished through encapsulation.

3 Encapsulation of bioactive compounds

Encapsulation plays a crucial role in protecting and delivering bioactive compounds extracted from agri-food waste. The choice of encapsulation method depends on factors such as the compound’s physicochemical properties, intended application, and process scalability. Careful method selection ensures stability, functionality, and regulatory compliance of the final product. Encapsulation does not merely involve just forming an outer coating or shell; rather it entails the trapping, embedding, and dispersion of bioactive compounds in various matrices. The concept was originally inspired by cellular models and developed to protect labile functional materials from adverse environmental conditions [60,61,62]. The advantages of encapsulating bioactive compounds are illustrated in Fig. 1 (Fig. 1). In encapsulation systems, the substance that forms the outer layer is known as the shell or carrier material, while the encapsulated substance refers to the core material or active agent [63]. The final encapsulated product is known as microspheres, or core-shell microcapsules. Depending on the size of the capsules, bioactive compounds can be encapsulated at the nano- (< 0.2 μm), micro- (0.2–5000 μm), or macro-scale (> 5000 μm) capsules. While macroencapsulation is a well-established method, micro- and nanoencapsulation methods have garnered increasing interest due to their potential to enhance the stability and bioavailability of bioactive compounds [64]. The primary distinction between microencapsulation and nanoencapsulation lies in their particle size and the duration of their application. Microencapsulation has been used for a longer period and typically involves particle sizes ranging from 1 micrometer (µm) and 1 mm (mm) [65]. Additional differences between the two techniques are presented in Table 2.

Fig. 1
Fig. 1

Advantages of encapsulation of bioactive compounds extracted from various Agri-food wastes

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Table 2 Differences between micro and nanoencapsulation
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Microencapsulation has been applied across nearly all industrial sectors, including agriculture, cosmetics, and household products. Although various traditional techniques exist for microencapsulating food ingredients, no single method is universally effective for all core ingredients or intended applications. As previously noted, the success of microencapsulation depends on several factors, including the physicochemical characteristics of the core and shell phases, the desired particle size, the overall cost, and release mechanisms [68]. Because encapsulated compounds are often in liquid form, drying methods are often employed to convert them into stable powders. Multiple encapsulation methods are available for incorporating active ingredients into food and nutraceutical products [63]. Many bioactive compounds, particularly hydrophobic or poorly water-soluble nutrients, play a crucial role in human nutrition and maintenance of health. However, their poor solubility and limited bioavailability pose challenges for their effective incorporation into the pharmaceutical and food industries [69]. Nanoencapsulation offers a promising solution by protecting sensitive food components from degradation, and masking unpleasant flavours and odours. Furthermore, nanoencapsulation enables controlled release of active ingredients, thereby enhancing their stability, functionality, and consumer acceptability.

3.1 Nanoencapsulation of bioactive compounds

The nanoencapsulation of bioactive compounds is considerably more complex than microencapsulation and can be broadly classified into three primary approaches: top-down, bottom-up, and hybrid methods which combine both [70]. The bottom-up approach typically involves low-energy processes such as microemulsification, conjugation, precipitation, layer-by-layer assembly, and molecular self-assembly at the nanoscale. In contrast, top-down approaches require high- energy consuming techniques such as ultrasonication, high-pressure homogenization, and spray-drying [71]. The range of available physical and chemical nanoencapsulation techniques is illustrated in Fig. 2 (Fig. 2). Several factors such as the rate of release, end application, stability, solubility of the nano-carrier, and production cost influence the choice of a specific nanoencapsulation technique [70, 71]. The following section provides a comparative discussion of various techniques such as supercritical fluid technology, complex coacervation, electrospraying, gelation, spray drying, spray chilling, freeze drying, and emulsification.

Fig. 2
Fig. 2

Physical and chemical methods for nano-encapsulation of bioactive compounds

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3.1.1 Supercritical fluid technology

Supercritical fluid technology is an advanced and environment friendly method for encapsulating bioactive compounds using supercritical CO₂. CO₂ is a non-toxic, food-grade, and non-combustible solvent. Importantly, it has a low critical temperature, enabling the entrapment of bioactive compounds at near-ambient temperature, which helps prevents their degradation [72]. Dunaliella, a photosynthetic microalga rich in carotenoids, has been extracted and encapsulated using this technology. As previously discussed, supercritical CO₂ acts as an inert solvent, facilitating the encapsulation of carotenoids in Pluronic F-68 without the need for toxic solvents or elevated temperatures. This process operates at a temperature of 40–60 °C and a pressure of 10 MPa without the need of organic solvents. Remarkably, the solubility of carotenoids increased by a factor of 650 [73]. Additionally, carotenoid stability was significantly enhanced when stored at 5 °C.

In more advanced application, curcumin was extracted and simultaneously encapsulated in liposomes using a single step using supercritical CO₂ process conducted at temperatures ranging from 50 to 70 °C and pressures between 15 and 25 MPa. Zeta potential measurements confirmed the high stability of the nanoencapsulated product. Moreover, the resulting liposomes were found to be suitable for drug delivery applications. Despite the advantages of using CO₂ as a non-toxic solvent, the high operational costs associated with this technique pose challenges towards large-scale implementation.

3.1.2 Complex coacervation

In complex coacervation, oppositely charged polyelectrolytes interact in an aqueous medium to form encapsulation structures. The bioactive compound is surrounded by a protein or a carbohydrate-based encapsulating agent. Several parameters such as temperature, pH, concentration, molecular weight, and ionic strength, influence this interaction. The process results in the formation of particles in which the bioactive compounds are protected by a layer of the encapsulating agent [74]. Although complex coacervation offers significant advantages for the food and nutraceutical industries, optimising the encapsulation conditions remains a challenge. In one study, response surface methodology was employed to optimise key variables, including pH, polymer concentration, and the ratio of core to coating materials. Under optimised conditions, the encapsulation efficiency reached 86%. The extract powder derived from black carrot was successfully incorporated into skimmed milk, juice, and other beverages at a concentration of 1 g/100 mL. Notably, heat treatment did not adversely affect the stability of the encapsulated product, allowing its use in both hot and cold food applications [75]. Flavonoids such as taxifolin and rutin exhibit significant medicinal benefits but suffer from oxidative degradation, and poor solubility, which limit their incorporation into functional foods. In vitro studies demonstrated a 1.6-fold increase in antioxidant activity when encapsulated flavonoids were compared with their non-encapsulated counterparts. These findings suggest that complex coacervation is an effective method for encapsulating bioactive compounds in nutraceutical formulations [76]. However, further in vivo studies are necessary to fully understand the efficiency and potential applications of this technique.

3.1.3 Electrospraying

Electrospraying is a technique in which an electric field is applied to a polymer solution to produce nano- or microstructures at ambient temperature. Depending on the properties of the solution, two techniques—electrospinning and electrospraying—are used for encapsulation applications [77, 78]. In electrospraying, low intermolecular cohesion allows the solution jet to break into fine droplets under electrostatic forces. Upon solvent evaporation, these droplets solidify into nano- or microparticles.

In contrast, electrospinning involves higher molecular cohesion, which leads to the formation of ultrafine fibres as the solvent evaporates. Among the two, electrospraying is more suitable for food applications, as the resulting particulate structures are readily dispersible in food products, unlike fibres produced via electrospinning. The encapsulation of betalains—a class of plant-derived pigments—using electrospraying has been investigated in a previous study. Coaxial electrospraying with gelatin as the encapsulated agent effectively protected betalains from environmental stressors and enhanced their shelf life. Notably, the antioxidant capacity of the encapsulated betalains remained intact and, in fact, improved. Increased stability was attributed to molecular interactions between the functional groups of betalains and gelatin, as confirmed by FTIR analysis. Thermogravimetric analysis further revealed the interactions between the carboxyl groups of gelatin interacted and the amino group of betalains, which modified protein side chains and prevented thermal degradation [79]. A similar coaxial electrospraying strategy was used to encapsulate rosemary oil with gelatin, yielding improved stability [80]. Although electrospraying is a relatively simple, single-step process, it requires precise control and optimisation of parameters, particularly when scaling up for industrial applications.

3.1.4 Spray chilling/spray drying

Spray chilling/spray drying is encapsulation methodologies where nano- or microstructures are formed by the addition or removal of energy, respectively. In spray drying, hot air is used to evaporate the solvent, forming capsules. Conversely, in spray chilling, cold air or liquid nitrogen is applied to remove the energy, leading to capsule formation. Both processes use similar apparatus, with minor modifications [81]. Response surface methodology (RSM) was used to optimize parameters such as yield, antioxidant capacity, encapsulation efficiency, phenolic content, and flavonoid concentration. An in vitro release study observed a maximum value of 9.86 mg gallic acid equivalent/g after 12 h [82].

3.1.5 Emulsification

Emulsification is a widely employed encapsulation technique that utilises lipid-based systems to form nanocarriers. This method involves mixing two immiscible liquids, typically water and oil, followed by the addition of emulsifiers to act as stabilizing agents [83]. In one of the previous studies, resveratrol and curcumin were encapsulated using emulsification. Resveratrol (0.01% wt) was entrapped in nanoemulsions based on peanut oil, stabilized by emulsifiers such as sugar esters and soy lecithin [84]. Additionally, curcumin was encapsulated in a solid fat nanoemulsion using stearic acid (0.1% wt). While encapsulation increased the antioxidant activity of curcumin, its activity in the emulsion-based compound was lower when compared to that of its non-encapsulated counterpart. Nevertheless, the encapsulated compounds exhibited significantly improved stability [85]. In contrast, another study encapsulated food-grade vitamin E using mustard oil, resulting in a nanoemulsion with notable stability and enhanced antioxidant activity. This finding suggests that such emulsions could be effective for extending the shelf life of fruit juices. However, concerns regarding the potential toxicity of certain synthetic emulsifiers have underscored the need for safer alternatives, particularly those derived from plants and algae [86]. Although such plant-based emulsifiers show promise, further in vivo studies are required to validate the emulsifying efficiency, bioavailability, and stability.

3.1.6 Other encapsulation techniques

Gelation is an effective encapsulation method that employs bioactive compounds using coating materials such as alginic acid, cellulose, gelatin, chitosan, dextran, and protein. Among gelation methods, ionic gelation is a simple and inexpensive process that does not require high temperatures or solvents, making it ideal for heat-sensitive compounds. In this technique, a polymeric solution is dripped into an ionic solution under constant agitation, resulting in the formation of gelled particles. The release behaviour of the encapsulated compound depends on factors, such as the particle size and the physical and chemical properties of the coating material [87]. Martinović et al. (2023) applied ionic gelation to encapsulate grape pomace powder using sodium alginate alone or in combination with chitosan or gelatin. While the combination of coatings improved encapsulation efficiency, the absorption of certain phenolic compounds in the intestinal tract was limited, possibly due to incomplete release from the encapsulated beads or degradation within the digestive environment [88]. Therefore, further studies are required to confirm the efficiency of ionic gelation, despite its advantages, such as low cost, simplicity, and high encapsulation efficiency.

Freeze drying is another widely used technique, especially for thermolabile compounds. It involves freezing the material followed by drying under extremely low pressure, leading to the sublimation of ice crystals [89]. In a comparative study involving ciriguela peel extracts encapsulated with gum arabic and maltodextrin, spray drying demonstrated higher encapsulation efficiency (98.83%) than freeze drying [90]. A similar trend was observed in another study involving acerola pulp and residue extracts, where spray drying preserved higher concentrations of bioactive compounds. However, freeze-dried samples exhibited greater hygroscopicity, making them more suitable for long-term storage [91]. Interestingly, freeze drying achieved higher encapsulation efficiency in a study involving Haritaki (Terminalia chebula Retzius) using zein and starch as the coating materials. However, the study did not investigate the thermal, pH, and storage stabilities of the encapsulated compound [92]. This underscores the importance of evaluating multiple parameters when assessing the suitability of encapsulation methods. Among the critical parameters influencing method selection, the nature of the carrier material plays a decisive role. Thus, a comparative analysis of different carrier systems is essential for optimising encapsulation outcomes.

Among the diverse encapsulation techniques, supercritical fluid technology stands out for its solvent-free and thermally gentle conditions, though its scalability is limited by high operational costs. Complex coacervation and electrospraying offer good encapsulation efficiency and bioactivity retention, yet require precise control of formulation parameters. In contrast, spray drying and emulsification are more industrially viable but may compromise compound stability under heat or surfactant exposure. Ultimately, the choice of technique must balance bioactive sensitivity, application purpose, material compatibility, and scale-up feasibility.

4 Carrier systems for nanoencapsulation of bioactive compounds

4.1 Natural polymer-based nanocarriers

4.1.1 Polymer-based nanocarriers

Polymer-based nanosystems consist of solid colloidal polymeric nanostructures and are primarily derived from natural, artificial, or semi-artificial sources. Natural sources include starch, chitosan, casein, and albumin. Chitosan has been extensively used as a wall material. For example, the marine carotenoid fucoxanthin was encapsulated using chitosan, and it was observed that the anticancer activity of the compound improved significantly. Beyond pharmaceutical applications, bioactive compounds extracted from grape pomace were encapsulated using alginate and chitosan, which not only enhanced their bioactivity but also inhibited the hydrolysis of compounds in the gastrointestinal tract [88].

4.1.2 Protein-based nanocarriers

Protein-based nano carriers are widely recognized for their nutritional value and are considered safe materials with emulsifying properties for encapsulation. Additionally, protein-based nanoencapsulation exhibits superior entrapment efficiency than other materials [93, 94]. Protein-based carriers are formed through either hydrophobic or hydrophilic interactions between bioactive compounds or the encapsulating materials [95, 96]. Common protein sources are caseins and proteins present in soy, cereals, pulses, potatoes, and gelatin [97].

Propolis, a resin-like material produced by bees from the buds of certain trees, displays significant medicinal properties due to its bioactive compounds [98]. Despite its significant health benefits, propolis has restricted use because of its strong aroma, low stability, and limited bioavailability [99]. In response to these challenges, Shakoury et al. (2022) conducted a study to encapsulate propolis extract in whey protein nanoparticles (WPN). This encapsulation technique not only masked the odour and aroma, but also provided properties that improved stability in the digestive system. The study reported sustained release at pH 3.2, and 7.5 for 4% propolis extract, indicating enhanced protection under digestive conditions [100]. Another notable study by Ji et al. (2021) investigated the co-encapsulation of hydrophilic (L-ascorbic acid) and hydrophobic (quercetin) substances using gelatin and sodium carboxymethyl cellulose as emulsifiers. Due to the compounds’ differing solubility, the process involved double emulsions followed by complex coacervation. The results indicated that quercetin had better encapsulation efficiency (88.21%) than L-ascorbic acid (69.91%). Similarly, resveratrol and quercetin was co-encapsulated in zein/carboxymethyl cellulose nanoparticles, resulting in synergistic antioxidant properties and therapeutic potential for tumour angiogenesis and spinal cord injuries [101].

These findings suggest that protein-based nano carriers play a significant role in co-encapsulation due to their amphipathic properties, which facilitate interactions between their hydrophobic groups and the active compounds, thus enhancing the solubility of bioactive compounds [102]. However, the encapsulation technique for different bioactive compounds may not be universally applicable. For instance, phytosterols, which are hydrophobic, cannot be co-encapsulated with Lactobacillus a hydrophilic bacterium, as their combined effect negatively impacts the lipid profile [103]. Therefore, it can be concluded that encapsulation is successful and beneficial when it is feasible to deliver multiple drugs with antioxidant, antimicrobial, and anti-inflammatory properties in a single encapsulated unit. Although the application of protein-based carriers in the agricultural sector is still in nascent stage, they are widely used in the food, and pharmaceutical industries due to their biocompatibility, biodegradability, and GRAS status.

4.2 Synthetic polymer-based nanocarriers

In another study, naturally and artificially synthesized polymeric nanoparticles were compared for their encapsulation efficiency. Poly(lactic-co-glycolic acid) (PLGA) and zein nanoparticles (a biopolymer synthesized from corn) were used to encapsulate rutin, a plant- derived flavonoid. The results indicated that PLGA nanoparticles exhibited a slower release profile, with only 25% of rutin released after 60 h, compared to faster release observed with zein-based carriers [104]. Although zein nanoparticles are natural biopolymers, they are also categorised as protein-based nanocarriers. Other similar protein-based nanocarriers are discussed in the following section. While the application of polymeric nanoparticles in agricultural sector is still emerging, it is well established in the food and pharmaceutical sectors particularly due to the availability of novel, biodegradable, and Generally Recognized as Safe (GRAS) polymers.

4.3 Nanocarriers based on lipids

Lipid-based nanocarriers, also referred as vesicular carriers, consist of a core material composed of solid and liquid lipids [105]. These carriers are formed when surfactant molecules interact with an aqueous solution, resulting in the formation of a lipid bilayer membrane that encloses a spherical vesicle. When solid and liquid lipids are combined, nanostructured lipid carriers (NLCs) are produced. Within these systems, solid lipid nanoparticles (SLNs) form a stable internal matrix that immobilises encapsulated compounds and prevents their premature diffusion or degradation [106, 107]. Common examples of lipid-based nano-carriers include niosomes, nano-liposomes, and particulate carriers. In one study, the efficacy of nanocapsules containing the drug eplerenone was evaluated in rabbits and showed significantly greater efficiency compared to conventional formulations [108].

Recent advancements have led to the development of lipid-polymer hybrid nanoparticles (LPHNPs), used for the targeted delivery of drugs. For example, nanocapsules containing gallic acid and quercetin were encapsulated using LPHNPs, with soy lecithin serving as a coating for PLGA nanoparticles. The encapsulation efficiency was found to be 90% for gallic acid and 70% for quercetin. This system achieved sustained release kinetics [109]. Although LPHNPs are considered highly effective for targeted delivery, other lipid-based nanocarriers have demonstrated even higher encapsulation efficiency. A separate study reported over 85% efficiency for the encapsulation of piperine and quercetin using surfactant-based carriers such as Span 80, and Tween 80 [110]. These systems also facilitated controlled release of the bioactive components, suggesting that the efficiency and release kinetics of nano carriers largely depend on the properties of the carrier material, the nature of the bioactive compounds, and the encapsulation method employed. While each nanoencapsulation strategy has its respective advantages and limitations, the selection of an appropriate method depends primarily on the intended application, the nature of the carrier material, and the bioactive compound. For example, lipid-based carriers such as liposomes and nanostructured lipid carriers are suitable for lipophilic compounds such as essential oils and carotenoids, providing controlled release and enhanced solubility. In contrast, encapsulation methods such as freeze drying, spray drying, coacervation, and nanoemulsion are applied in food sector to improve stability and shelf-life. Edible films incorporating nanoencapsulated agents also provide additional benefits in preserving product freshness through antimicrobial and antioxidant mechanisms. Biopolymer-based systems such as those using chitosan and alginate offer advantages in shielding compounds from degradation during processing and gastrointestinal transit. Liposomal encapsulation technology is efficient as it can encapsulate both hydrophilic and hydrophobic compounds and has a broader spectrum of application (food, pharmaceutical, and personal care products) [70, 111].

4.4 Hybrid nanocarriers

Hybrid nanocarriers are advanced delivery systems composed of an internal polymeric/ or metallic network surrounded by an external lipid layers. The internal network typically consists of metals or polymers, while the outer network may be a single- or multi-layered lipid unit. This external layer not only protects bioactive compounds from degradation, but also enhances targeted drug delivery and prevents the entry of water [112]. Hybrid nanocarrier systems are primarily used for the targeted release of bioactive compounds at specific sites in cancer treatment [80, 113]. For instance, in the treatment of glioblastoma, a hybrid nanosystem was developed in which liposome-encapsulated gold nanoparticles were conjugated with oligonucleotide miRNA inhibitors. To improve targeting, apolipoprotein E (ApoE) or rabies virus glycoprotein was connected to the liposomes. In vivo studies conducted using mice with glioblastoma revealed that the expression of miRNA-92b was successfully inhibited, demonstrating targeted delivery at the tumour site [114]. Although the aforementioned example is relevant to the pharmaceutical sector, the hybrid nanocarriers domain is also applicable in the food, and agriculture fields. Its synergistic structural configuration overcomes the limitations of individual carrier systems, offering improved stability, controlled release, and enhanced functional performance across diverse application areas. Furthermore, advanced tools such as RSM, artificial intelligence (AI) and machine learning (ML) can further optimize encapsulation processes by identifying critical parameters, thereby improving the selection and performance of encapsulation techniques. The following table (Table 3) presents different encapsulation techniques, carrier materials, and their advantages. Different types of carrier systems, along with their advantages, limitations, and applications, are presented in Table 4.

Table 3 Encapsulation of bioactive compounds and their pharmaceutical properties
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Table 4 Advantages, disadvantages, and applications of nanocarrier system
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5 Applications of encapsulated bioactive compounds

5.1 Food industry

Nutraceuticals, bioactive compounds derived from food sources, offer health benefits that extend beyond basic nutrition, including anti-inflammatory, cardiovascular protectives, and antioxidants properties [12]. These compounds, often found in various plant-based residues, hold significant health and environmental benefits. For instance, resveratrol-rich grape skins, a by-product of wine production, exhibit antioxidant and anti-inflammatory effects that support liver detoxification and cellular protection. Mango peels, which are high in phenolic compounds and vitamins, have been associated with reduced risks of cancer, cataracts, Alzheimer’s disease, and Parkinson’s disease [129]. The extraction of caffeine from spent tea leaves provides a sustainable approach to repurposing tea waste as a valuable source [19].

Other bioactive compounds recovered from food waste, such as algal polysaccharides, demonstrate immunomodulatory and anti-allergic properties, while monosaccharides exhibit antithrombotic, antiviral, and antioxidant activities [130]. Banana extracts, for instance demonstrate anti-leishmanial effects, suggesting potential applications in treating protozoan infection treatments. The utilisation of diverse bioactive compounds from agri-food waste not only promotes human health but also supports environmental sustainability, and minimizes environmental impacts [12]. By-products such as overripe berries, fruits peel, pomace, and seeds offer innovative applications as natural antioxidants in foods [131]. For example, apple peel extract prevents oxidation in chilled minced rainbow fish [132] and inhibit enzymatic browning, thereby enhancing the appearance and appeal of fresh foods [133].

Natural colourants such as carotenoids and anthocyanins provide a sustainable alternative to synthetic colourants. Anthocyanins derived from berries, sweet potatoes, crimson kale, black carrots, and distillery by-products function both as natural colourants and nutraceuticals [134]. Similarly, carotenoids extracted from citrus peels have been shown to extend the shelf life by preventing spoilage and off-flavour [135]. Additionally, citrus peel, rich in pectin, serves as a gelling instrument in various food products such as confections, meat, and baked goods [136]. Avocado byproducts, including the seed and peel, are rich in high quality protein and exhibit enhanced water and oil absorption, as well as free-radical scavenging capability. Avocado seed starch also shows potential as a thickener or carrier for bioactive compounds delivery [137]. These examples underscore how agri-food waste can be effectively repurposed for innovative applications within the food industry.

5.2 Packaging industry

Encapsulated bioactive compounds are also increasingly utilised in food packaging, where they help maintain product stability, extend shelf-life, and preserve sensory qualities. This approach supports the development of edible, intelligent, and functional packaging materials [138]. Amylopectin, enzymes, phytochemicals, functional nutrients, dietary fibres, vitamins, and oils are among the valuable bioactive compounds that may be found in underutilised wastes. These bioactive compounds are utilized in the manufacturing of active packaging films [139]. Electrospinning is commonly employed to produce nanofibres, with their properties influenced by the operating environment, including the characteristics of the spinning solution, the polymer composition, and mechanical parameters such as nozzle configuration. These nanofibres, which can range from 1 μm to several nanometres in diameter, are increasingly used as reinforcement materials in food packaging. In order to preserve product freshness, encapsulated bioactive compounds that are high in antimicrobials, and antioxidants such as carotenoids, vitamin C, and vitamin E are added to edible films as active ingredients during the manufacturing process. These active films help prevent oxidative spoilage and microbial contamination while preserving the organoleptic qualities of the packaged food through the inclusion of flavours, colours, and sweeteners. For example, cinnamon essential oil nanofibers encapsulated in polyvinyl alcohol/β-cyclodextrin were applied as a film coating to packaging boxes. The film coating acts as an antibacterial barrier to prevent bacterial and fungal spoilage and prolongs the shelf life of the food sample by 5 days [139]. However, there are certain limitations to encapsulated packaging, as illustrated in Fig. 3 (Fig. 3).

Fig. 3
Fig. 3

Challenges in active packaging using nanoencapsulated bioactive compounds

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5.3 Agriculture industry

Bioactive compounds derived from agri-food waste can be used to produce organic fertilizers, offering an eco-friendly alternative to chemical fertilizers while also serving as a nutritional source for livestock [34]. Due to their great potential to improve nutrient utilization efficiency, nanofertilizers are beneficial for nutrition management. These nano-sized formulations often composed of adsorbents bonded to nutrients either individually or in combination. For example, mushroom cultivation on agri-food waste not only reduces environmental impact but also enhances soil microbial communities and increases agricultural productivity. Additionally, nutrient-rich biogas waste derived from the anaerobic digestion of agri-food wastes serves as a valuable organic fertilizer with high agronomic potential [140]. Chitosan and its encapsulated derivatives have also gained attention as sustainable alternatives in agricultural systems. These materials have been extensively used as soil conditioners, growth promoters, seed treatment agents, biofertilizers, and biopesticides. In plant protection, chitosan has been employed as a co-encapsulating material for curcumin and resveratrol. This strategy has been used to develop nanocomposite films capable of preventing the growth of fungi such as Aspergillus niger, Penicillium chrysogenum, and Aspergillus flavus.

In another study, neem seed oil extract —rich in the insecticidal bioactive compound azadirachtin—was encapsulated using spray drying with maltodextrin and whey protein isolate as encapsulating agents. The findings showed that smaller microcapsules exhibited higher encapsulation efficiency, with values ranging between 60 and 92%. These results demonstrate that encapsulated bioactive compounds play a significant role in enhancing the agricultural productivity while mitigating adverse environmental effects [141, 142]. By enhancing the solubility, stability, and controlled release of bioactive compounds, nanoencapsulated agro-inputs enable dose reduction, minimize application frequency, and mitigate environmental contamination. From an industrial perspective, encapsulation methods such as spray drying and emulsification have potential for integration into current agrochemical production lines due to their scalability. However, regulatory pathways remain in their infancy, and there is minimal international agreement on risk assessment procedures tailored to nanotechnology for agricultural applications. Standardized safety evaluations and environmental impact assessments are essential to foster confidence among stakeholders and facilitate approval for commercial use. Furthermore, incorporating nanoencapsulated bioactives into precision agriculture frameworks may maximize resource efficiency and promote sustainable and climate-resilient farming methods [34].

5.4 Bio-based surfactants and detergents

The global demand for bio-based surfactants, valued at US$30.64 billion, continues to grow due to their sustainability and broad applicability across various industries [12]. Utilisng agri-food waste as a substrate for producing bio-based surfactants such as rhamnolipids and sophorolipids is both economically feasible and environmentally beneficial, as supported by life cycle assessments. Soy molasses and used cooking oil are notable examples of nutrient-rich substrates for the production of these biosurfactants [141, 142]. In another study, red beans and mangos were composed of pectin which was separated and combined with sodium alginate to form a soluble ternary biopolymer system for the encapsulation of microorganisms. The capsules were assessed using a bacterial consortium for hydrocarbon bioremediation and described both thermally and physically. Compared to non-encapsulated controls, bioremediation experiments using the encapsulated demonstrated reduced degradation time by 3 days for diesel and 4 days for hexadecane—and improved hydrocarbon uptake (5% for hexadecane and 10% for diesel). This multidisciplinary approach which integrates inexpensive and underutilised materials for bioencapsulation highlights the potential for broad application across environment, industry, and agricultural sectors [12, 138, 142].

6 Challenges and regulatory policies in commercialising encapsulated materials

The encapsulation of bioactive compounds plays a significant role in delivering nutraceutical and functional products that address current market demands [143]. Although encapsulation techniques show considerable promise, they face several challenges, particularly regarding the stability of encapsulated products during storage and gastrointestinal transit. Some compounds become unstable or undergo morphological changes upon interaction with digestive fluids [144].

Co-encapsulation represents a notable advancement, enabling the simultaneous delivery of multiple pharmaceutical and nutritional compounds within a single encapsulated system [145]. However, this approach presents challenges, such as differences in the physicochemical properties of the encapsulated compounds, potential interactions that may alter release kinetics, and the possible adverse health effects. Another challenge lies in the selection of coating agents and their physicochemical characteristics which must protect the bioactive compound from adverse environmental conditions while masking undesirable odours or appearances [146]. The optimisation of process variables is essential to ensure the desirable properties of the end product. While RSM aids in the selection of wall materials, advanced approaches such as artificial neural networks and ML may further enhance the optimisation of encapsulation processes. The type of encapsulation material and production method significantly influence the safety and toxicity profile of the final product. To mitigate health risks, natural and biodegradable polymers should be prioritised, and encapsulation procedures must be closely monitored. Comprehensive toxicity assessments are essential for evaluating potential hazards associated with each technique [147]. It is crucial to assess the safety profiles of nanoparticles, as their nano-scale size allows them to penetrate cell membranes and interact with biological systems, potentially leading to negative outcomes. Nanoparticles can induce oxidative stress, inflammation, and cell death, making cytotoxicity a critical concern. Therefore, the biocompatibility of nanoparticles must be thoroughly evaluated by conducting both in vitro and in vivo studies. To minimise side effects, risk assessments should focus on cellular responses and the establishment of safe dosage levels [148].

Although extensive research has been conducted on the short-term effects of nanomaterials, recent studies have begun to examine their long-term biological impacts. Prolonged use of nanoparticles may elicit immunological reactions or interfere with intercellular communication. These findings underscore the need for further research and robust regulatory oversight of nanoparticle applications [149]. Toxicity concerns are generally lower in macroencapsulation compared to microencapsulation and nanoencapsulation techniques. Biocompatible polymers such as alginate, gelatin, and starch are non-toxic and are frequently used in the food and pharmaceutical industries. In contrast, certain substances—such as organic solvents or surfactants used in microencapsulation—have the potential to induce cytotoxicity. Therefore, the use of solvent-free techniques or non-toxic solvents is strongly recommended [150]. Additionally, chemical modifications during polymerisation can lead to the formation of harmful by-products, posing further challenges in microencapsulation technologies [151, 152]. Other encapsulation methods, such as liposomal and dual-polymer encapsulation, also raise safety considerations. Liposomal encapsulation employs phospholipid bilayers, which are typically non-toxic and highly compatible with biological tissues. However, liposomes are susceptible to oxidative degradation, potentially leading to the formation of harmful substances [153].

Ultimately, regulatory and safety issues remain significant barriers to the commercialisation and large-scale application of nanoencapsulation technologies, particularly in food and pharmaceutical products. Currently, there is no unified system of standardised testing procedures or harmonised national regulations across countries, making risk assessments and product approval processes more difficult [154]. In the food industry, authorities such as the European Food Safety Authority (EFSA) and the U.S. Food and Drug Administration (FDA) require comprehensive characterisation and safety evaluations of nanomaterials. However, regulatory frameworks for nanoencapsulated bioactive compounds are still evolving (EFSA Scientific Committee, 2021). Therefore, extensive consumer trust and regulatory compliance, extensive toxicological testing and transparent labelling practices must be implemented [155].

7 Conclusion and future prospects

This review suggests that the physicochemical properties of the target bioactive compounds and their intended functional application must be considered when selecting extraction methods, whether they are conventional or innovative. Although sustainable technologies such as supercritical CO₂ extraction have potential for heat-sensitive compounds, their limited scalability and high operating costs prevent widespread adoption, particularly in industrial settings with limited resources. Similarly, although plant-based proteins (like zein, rice bran, and soy) and natural carriers (like chitosan, starch, and alginate) have shown improved absorption and stability through nanoencapsulation, additional encapsulation parameter optimization is needed to ensure consistency, scalability, and product integrity across different food matrices.

There is still a considerable need in the application of small-scale encapsulation techniques, such as co-encapsulation systems and lipid–polymer hybrid nanoparticles (LPHNPs), to industrial settings. Future research should focus on standardization of protocols for process scalability, compatibility testing for multi-component encapsulation, and thorough assessment of compound stability during processing and storage. In vivo studies are still lacking and critically needed to confirm bioavailability, efficacy, and potential toxicological effects, especially when nanoforms of GRAS substances are added to food and pharmaceutical systems. Additionally, there is a lack of uniformity in the regulatory environment across jurisdictions. One of the significant barriers to commercialization and consumer confidence is the absence of uniform international standards for nanoencapsulated ingredients. The establishment of clear, science-based regulatory frameworks that foster innovation while guaranteeing safety must be established through strategic cooperation between researchers, regulatory agencies, and industry stakeholders. Ultimately, this review advances the discourse on sustainable bioprocessing by emphasizing the potential of valourising agri-food waste into high-value, functional ingredients, thereby supporting the objectives of circular economy and reducing environmental impact.