Nanoencapsulation of vegetable phytonutrients: Health Implications, delivery techniques, and future prospects

Introduction

Science, engineering, and technology carried out at the nanoscale roughly 1 to 100 nanometers is known as nanotechnology. Richard Feyman, a physicist and 1965 Nobel winner, is considered the father of nanotechnology. Norio Taniguchi of Tokyo Science University first used the word "nanotechnology" in 1974. The development of the fundamental ideas of nanotechnology took place over a longer period of time, despite the technology itself being a comparatively recent breakthrough in scientific study. The combination of experimental developments, including the development of the scanning tunnelling microscope in 1981 and the discovery of fullerenes in 1985, led to the rise of nanotechnology in the 1980s. Due to its numerous uses in a variety of fields, including health, pharmaceuticals, materials, energy, and catalysis, nanotechnology has attracted a lot of interest recently. These nanoparticles, which range in size from 1 to 100 nm, have a variety of possible uses. Both industrialised and developing nations are eager to spend more in nanotechnology since it has brought about a new economic revolution (Qureshi et al., 2012) [14] . As a result, nanotechnology presents several chances for the creation and use of systems, materials, or structures with novel characteristics in a variety of fields, including food, medicine, and agriculture.

Researchers are being driven to investigate ways to improve food quality without minimising the product's nutritional content due to growing customer concerns about food quality and health advantages. The food sector has seen a rise in demand for materials based on nanoparticles since many of them are non-toxic and include vital ingredients (Roselli et al., 2003) [16] . Additionally, it has been discovered that they remain stable at high pressure and temperature. From food production and processing to packaging, nanotechnology provides comprehensive food solutions. With the promise of better flavour, texture, and consistency, nanostructured food ingredients are being produced (Cientifica Report, 2006) [2] . Nanotechnology helps reduce the amount of food waste caused by microbial infestation and extends the shelf life of various food items. These days, food additives are transported in food items using nanocarriers as delivery mechanisms without changing their fundamental shape. It has been observed that in some cell lines, only submicron nanoparticles can be successfully absorbed, whereas bigger size micro-particles cannot (Ezhilarasi et al., 2013) [6] . This suggests that particle size may have a direct impact on the distribution of any bioactive molecule to different places inside the body. In addition to masking smells or tastes, nanoencapsulations regulate how active ingredients interact with the food matrix, regulate the release of the active agents, guarantee availability at a predetermined time and rate, and shield them from moisture, heat, chemical, or biological deterioration during processing, storage, and use. They also show compatibility with other compounds in the system. Furthermore, because of their tiny size, these delivery methods can effectively distribute active substances to specific locations throughout the body by penetrating deeper into tissues. Many industries, including agriculture and the food sector, have hailed nanotechnology as the next big thing. From production to processing, storage, and the creation of novel materials, goods, and uses, it has been transforming the whole food system. Numerous reviews have looked at nanoencapsulation techniques in food systems, but there isn't yet a comprehensive synthesis that focusses mainly on phytonutrients, their stability problems, encapsulation effectiveness, increased bioavailability, and food-grade safety concerns. Therefore, this study critically evaluates recent developments in phytonutrient nanoencapsulation techniques, contrasts various methods, draws attention to safety and regulatory issues, and suggests future directions for functional food applications research.

Phytonutrients Phyto -Greek word for plant

Nutrient -A substance that is needed to keep a living thing alive and to help it grow.

Definition: Nutrients that protect the plant from harmful oxidation, viruses, bacteria, parasites and insects are called as phytonutrients. These are the plant-derived bioactive compounds associated with positive health effects. They are also known as phytochemicals.

Phytonutrients come in many forms:

 Natural pigments that give colors-For example in Tomato, Lycopene is the pigment that is responsible for its characteristic deep-red color and in Turmeric, Curcumin is responsible for its bright yellow color.  Some phytonutrients are responsible for strong odors and flavors-For example, in Onion, Allyl propyl disulfide is responsible for its strong flavour.

Vitamins and minerals are the essential nutrients that our body needs to work properly, but unlike vitamins & minerals, phytonutrients are not essential to life but boost overall health and prevent chronic diseases.

Types of phytonutrients 2.1. 1Polyphenols

It includes antho-and beta-cyanins, flavonoids, isoflavones, lignans, and lignins. Blue, blue-red and violet colorations seen in berries, grapes and purple eggplant are due to their phenolic content. Blueberries, for example, are high in phenolic anthocyanidins giving them their reddish hue.

Alkaloids

Phytochemicals in this group are small to large complex carbon compounds which include esters and lactones. It acts as an antioxidant, cancer preventives, liver protectors, and inflammatory mediators.

Organosulfur group

It includes majorly glucosinolates, indoles, isothiocyanates and Allylic Sulfur Compounds. It provides the source of sulfur vital for phase-2 enzymes activity in cancer protection. Cruciferous vegetables were the first to be promoted by the American cancer society as cancer preventive.

Terpenoids

These are the group of unsaturated hydrocarbons, found in essential oils and oleoresins of plants used in organic syntheses. Terpenoids are classified into carotenoids and non-carotenoids. Carotenoids include lycopene, xanthophylls (lutein and zeaxanthin), alpha and betacarotene while non-carotenoids include phytosterols, terpenes, saponin, limonene, chlorophyll. Tumor fighting, protects cell damage, support arteries, bones and circulation Onion, Garlic, Cauliflower (Dias, 2012) [3]

General functions of phytonutrients

Encapsulation

It is a process of enclosing the substances within an inert material (i.e., the material which doesn't undergoes any physical, chemical or biological transformations and it doesn't affects the other matter with which it comes into contact) which protects it from adverse environment as well as controls the release of bioactive compounds.

Nanoencapsulation Definition:

Nanoencapsulation is defined as a technology to encapsulate substances in miniature and refers to bioactive packing at the nanoscale range (Lopez et al., 2006) [10] .  This technique is based on enclosing a bioactive compound (BAC) within a matrix or inert material for preserving the coated substance (food or flavor molecules/ingredients). The suitable size of nano capsule is about 10-1000 nm, for the encapsulation of phytonutrients.  Nano capsules of size, less than 10 nm are subjected to clearance by kidney excretion. Conventionally when we talk about nanomaterials, they only fall into the range of 1-100 nm, but its only in the food application, that this definition has been extended to 1000 nm.  Polymeric nanoparticles are categories into nano capsules and nanospheres. Nano capsules are vesicular systems in which bioactive compound is confined to a cavity surrounded by a polymer membrane. Whereas nanospheres are matrix systems in which the bioactive compound is physically and uniformly dispersed.

(Orive et al., 2009) [13]  Phytonutrients have poor body absorption in their original form, thus nanoencapsulation increases the reactivity and bioavailability of phytonutrients.

Shell and core materials in nanoencapsulation

The material that is being encapsulated is known as core material, while the encapsulating material is known as shell material. The various shell and core materials used in the preparation of nano capsules are:

Techniques of nanoencapsulation

The major nanoencapsulation techniques are summarized in table 3. Emulsification, coacervation, inclusion complexation, emulsification-solvent evaporation, nanoprecipitation and supercritical fluid technique are considered as nanoencapsulation techniques since they can produce capsules in the nanometer range (10-1,000 nm). Both top-down and bottom-up methods are used in nanoencapsulation procedures to create nanomaterials Table 2. Using precise techniques that enable size reduction and structural sculpting for the intended use of the nanomaterials being created is part of a top-down strategy. According to Augustin and Sanguansri (2009), the bottom-up technique builds materials by the self-assembly and self-organization of molecules, which are impacted by a variety of variables such as pH, temperature, and ionic strength. The top-down technique makes use of methods like emulsification and emulsification-solvent evaporation. Conversely, the bottom-up strategy makes use of inclusion complexation, coacervation, supercritical fluid technology, and nanoprecipitation. Numerous hydrophilic and lipophilic bioactive substances can be encapsulated using these nanoencapsulation processes. Both hydrophilic and lipophilic molecules are encapsulated via emulsification, coacervation, and supercritical fluid techniques (Leong et al., 2009) [9] . However, lipophilic chemicals are primarily treated via inclusion complexation, emulsification-solvent evaporation, and nanoprecipitation methods (Reis et al., 2006) [15] .

Problems and Safety Issues on Nanoencapsulation

Protection, regulated distribution, and improved bioavailability of bioactive compounds are made possible by the development of the nanoencapsulation method. In addition to its progress, it has brought up a variety of safety, environmental, ethical, and regulatory concerns that result from our ignorance of how nano-sized materials affect the environment and human health (EFSA 2009). The biotransformation of nanoparticles following oral delivery was a crucial aspect of nanoencapsulation that received little attention. Less was known about even the excretion of nanoparticles (FAO 2009). Particle size, mass, chemical composition, surface characteristics, and the aggregation of individual nanoparticles all generally affect how harmful nanoparticles are to the body. According to a European Food Safety Authority report (EFSA 2009), in order to address the dangers associated with nanotechnologies, current risk assessment approaches for micro/nanoscale compounds need to be changed. The usage of nanoparticles as authorised food ingredients or additions in food or materials that come into contact with food is unclear. They should be considered unique items that need to be evaluated and approved, and the authorities in charge of regulation must make explicit declarations concerning their usage. An internal FDA nanotechnology task group was established in 2006 to decide on regulatory strategies for nanomaterials (FDA 2006). Furthermore, precise inclusion or exclusion criteria for nano-specific risk assessment are not provided by the existing level of knowledge about the special characteristics of manufactured nanomaterials. As a result, taking into account a variety of possible characteristics, such as distinctive biological or physical behaviour and their toxicological evaluation, may be helpful in the risk assessment (FAO 2009). There will be a protracted debate over the advantages and disadvantages of using nanotechnology in the food sector. Furthermore, there is currently no solid evidence about the negative health effects of nanotechnology in the food chain. As a result, it is prudent to implement regulatory controls as a proactive way to safeguarding the public from the possible negative consequences of nanotechnology until proven otherwise. Furthermore, current scientific knowledge of nanotoxicity must be closely linked to newly developed nano goods in order to produce updated nanofood laws that minimise the potential health effects of nanotechnology (Chau et al., 2007) [1] . [12,17] . The creation of smart and stimuli-responsive nanocarriers offers a viable option for future research. Such systems, which can release phytonutrients in response to pH changes, enzymatic activity, or redox conditions, have the potential to dramatically improve targeted delivery and bioavailability while reducing dosage requirements (McClement, 2018) [12] . Furthermore, combining nanoencapsulation with upcoming technologies like spray-freeze drying, electrospinning, and green supercritical fluid techniques should improve encapsulation efficiency and product stability (López-Rubio et al., 2022) [11] . Future research must link technology innovation with safety evaluation and honest risk communication in order to be regulatory and consumer-friendly. Harmonisation of international laws, the creation of nano-specific risk assessment frameworks, and the generation of strong toxicological data are critical for ensuring consumer trust and regulatory approval (EFSA, 2021). Interdisciplinary collaboration among food scientists, toxicologists, regulatory agencies, and industry stakeholders will be critical for developing nanoencapsulation technologies for safe, sustainable, and commercially successful functional food applications.

Conclusion

Nanoencapsulation-based technologies are unique and modern, and their application opens up new business potential. Their use is the development of nanostructured food additives that improve the solubility, stability, flavour, colour, and texture of foods during processing and storage. It has a larger potential for increasing the efficacy of bioactive ingredient delivery to benefit human health. It is a viable solution for masking undesirable flavours or odours while simultaneously increasing the bioavailability and regulated release of several nutrients in meals. The potential risks of nanoparticles on human health are unclear and must be investigated and examined. Nanotechnology's success in the food and bioprocessing industries is dependent on customer perception and societal acceptability.

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