1. A nanocomposite sheet comprising leaf extract of specific plants and zinc nanoparticles.

2. The nanocomposite sheet as claimed in claim 1, wherein said specific plants is selected from Cassia fistula, Bryophyllum pinnatum, Aegle marmelos, Murraya koenigii.

3. The nanocomposite sheet as claimed in claim 1, wherein said nanocomposite sheet further comprises one or more additives.

4. The nanocomposite sheet as claimed in claim 3, wherein said one or more additive is plasticizer.

5. The nanocomposite sheet as claimed in claim 4, wherein said plasticizer is selected from Glycerol, Sorbitol, Mannitol, Xylitol, Ethylene glycol (EG), Diethylene glycol (DEG), Triethylene glycol (TEG), Tetraethylene glycol, Polyethylene glycol (PEG), Propylene glycol (PG), Fatty acids, Vegetable oils, Surfactants, Waxes, Amino acids, Water.

6. A process of preparing a nanocomposite sheet of claim 1, wherein said process comprises - preparing leaf extract of specific plants, - boiling the leaf extract with zinc salt at specific conditions to obtain zinc oxide nanoparticles (ZnO NPs), - preparing aqueous solution of ZnO NPs, - adding a pre-determined solvent and one or more additive to the aqueous solution of ZnO NPs and stirring the solution, - casting the solution on petri dish or teflon coated plate and allowing to dry to obtain nanocomposite film, - peeling off the nanocomposite film from the petri dish or teflon coated plate.

7. The process as claimed in claim 6, wherein said zinc salt is selected from Zn(NO3)2.6H2O and zinc acetate.

8. The process as claimed in claim 6, wherein said specific plants is selected from Cassia fistula, Bryophyllum pinnatum, Aegle marmelos, Murraya koenigii.

9. The process as claimed in claim 6, wherein said at specific conditions to obtain zinc oxide nanoparticles are temperature in a range of 60°C to 80°C for 30 min.

10. The process as claimed in claim 6, wherein said pre-determined solvent is selected from solvent is selected from starches (wheat, potatoes, maize), lignocellulosic products (wood, straws), and others (pectins, chitosan/chitin, gums), agar, gelatin.

11. The process as claimed in claim 6, wherein said one or more plasticizer is selected from glycerol, Sorbitol, Mannitol, Xylitol, Ethylene glycol (EG), Diethylene glycol (DEG), Triethylene glycol (TEG), Tetraethylene glycol, Polyethylene glycol (PEG), Propylene glycol (PG), Fatty acids, Vegetable oils, Surfactants, Waxes, Amino acids, Water.

12. The process as claimed in claim 10, wherein said pre-determined solvent is a solution of 4% gelatin in distilled water.

13. The process as claimed in claim 10, wherein said pre-determined solvent is mixture of chitosan and acetic acid in distilled water.

14. The process as claimed in claim 11, wherein said plasticizer is 30% glycerol.

15. The process as claimed in claim 11, wherein size of the nanoparticles is in the range of 78.1 nm to 90.87 nm.

16. The nanocomposite sheet as claimed in claim 1, wherein said nanocomposite sheet is for use in packaging of food products such as energy bar, cereal bar, protein bar, fruit bar, fruit leather, nachos and croissant to extend the shelf life by two to three times.

DESC:FIELD OF THE INVENTION
The present invention relates to the field of food nano-packaging. The present invention relates to green nano packaging to enhance the shelf life of the food products. More particularly, the present invention relates to a plant based nano packaging material and process of preparing the same.

BACKGROUND OF THE INVENTION
India is a biodiversity rich country and full of traditional knowledge and practices about usage of plants. Medicinal usage of plants is well documented and commercialized to cure ailments. Recently, the nanotechnology has astonishingly changed its outlook for biomedical applications. Nanotechnology has revolutionized several fields with its admirable capabilities and groundbreaking innovations.

The leaves from a vast variety of plants are used as dining plates, food wraps during steam cooking, grilling and frying of various dishes, and food packing material in India. Plant mediated synthesis of nanoparticles (NPs) is a revolutionary technique that has wide range of applications in agriculture, food industry and medicine. Plants possess rich genetic variability with respect to number of biomolecules and metabolites like proteins, vitamins, coenzymes-based intermediates, phenols, flavonoids and carbohydrates. These plant metabolites react with metal ions and reduce their size into nano range. These molecules also play a pivotal role in the capping of the nanoparticles which is important for stability and biocompatibility. Plant type or source species from which plant extract used for NPs synthesis also affects the size of NPs.

The nanotechnology is one of the most exigent and fastest growing sectors of science and engineering. In nanotechnology, a nanoparticle is defined as a small object that behaves as a whole unit in terms of its transport and properties. The synthesis of nanoparticles with specific morphologies and properties is one of the most important aspects of nanotechnology. Nanotechnology has huge potentiality virtually in every area of science and engineering, principally due to its size and shape dependent intrinsic, optoelectronic, catalytic, biological properties and greater surface area.

Biosynthesis of nanoparticles using plant extracts provides a facile and ‘green’ method of nanoparticle synthesis. ZnO (zinc oxide) nanoparticles have gathered the increasing interest of the scientific and industrial community due to diverse application in solar energy conversion, sensors, catalysis, cosmetics, paints, fibers, drug-delivery antibacterial and luminescence properties.

Research is being conducted globally to development green technology for packaging of food products. Packaging is strongly associated with food, allowing, amongst other functions, containment, protection, stability and transportation of contents, and thus can be seen as an integral part of food systems. A safe, nontoxic and biodegradable packaging shows positive effects on the total environmental sustainability, reduced food losses and food waste or increased transport efficiency.

T.Kaviyarasi et al.; International Journal of ChemTech Research , CODEN (USA): IJCRGG: Vol.10 No.15, pp 344-348, 2017 teaches biomaterial-based nanostructures from Aegle marmelos in the form of nanoparticles, nanocomposites, nanofibers, hydrogels, and bio-inspired sponges, in biomedical applications for wound healing, tissue engineering and drug delivery. It discusses the synthesis and characterization of
zinc Nanoparticles by green synthesis method by using zinc acetate and leaf extract of Aegle marmelos. Aegle marmelos leaf (50 g) were thoroughly washed, dried and then boiled in 50 ml of deionised water for half an hour. The resulting extract was cooled and used as the extract solutions. 0.25 g of zinc acetate was dissolved in 50 ml water. 4 ml of the extract of Aegle marmelos was added dropwise and the resulting mixture was stirred for 10 minutes using a magnetic stirrer. pH is adjusted to 12 using NaOH. A white crystalline precipitate of zinc oxide was obtained, which is washed repeatedly with water, filtered and dried in an oven at 60°C to obtain the ZnO nanoparticles.
Minha Naseer et al.; Scientific Reports (2020) 10:9055 discloses synthesis of nanoparticles (NPs) using leaf extracts of two medicinal plants Cassia fistula and Melia azedarach. 0.01M zinc acetate dihydrate was used as a precursor in leaf extracts of respective plants for NPs synthesis. The C. fistula and M. azedarach mediated ZnO NPs showed strong antimicrobial activity against clinical pathogens compared to standard drugs, suggesting that plant-based synthesis of NPs can be an excellent strategy to develop versatile and eco-friendly biomedical products. Fresh leaves of C. fistula and M. azedarach were thoroughly washed with tap water followed by distilled water (d.H2O) to remove any contamination. The leaves were air dried for a week at room temperature (~37°C). About 5 g of leaves from each of C. fistula and M. azedarach were ground to fine powder with the help of pestle and mortar. This powder was mixed in 500mL of d.H2O and then heated at 70°C for 30 minutes. The mixture was filtered first by muslin cloth and then using Whatman filter paper No.1. As a result, pale yellow and red colored solutions were obtained as leaf extracts of C. fistula and M. azedarach respectively which were stored at 4 °C. 0.01M zinc acetate dihydrate (Zn (C2H3O2)2.2H2O) solution was prepared in d.H2O. For synthesis of ZnO nanoparticles, 95mL of 0.01M zinc acetate dihydrate (Zn (C2H3O2)2.2H2O) solution was mixed separately with 5mL plant extract of each of C. fistula and M. azedarach in individual 250mL flasks. These mixtures were incubated at 70°C for 1 hour with continuous shaking at 150 rpm. This led to the settlement of bio-reduced salt at the bottom of the flask which appeared as white precipitate. The supernatant was decanted and powdery precipitate was transferred to 1.5mL centrifuge tubes. Both the samples were subjected to washing with d.H2O by centrifugation at 3000 rpm for 30minutes. Washing step was repeated thrice to ensure removal of impurities. The morphological measurements of the ZnO NPs samples were recorded with field emission scanning electron microscope in the range of 0.1 nm to 10,000nm.
K. Elumalai et al.; Materials Science in Semiconductor Processing 34 (2015) 365-372 teaches bio-fabrication of zinc oxide nanoparticles using leaf extract of curry leaf (Murraya koenigii) and its antimicrobial activities. The X-ray diffraction (XRD) analysis showed the crystalline structure, and atomic force microscopy (AFM) showed the morphology of the ZnO NPs to be spherical with an average size of 12 nm. The collected leaves were washed thoroughly 2–3 times with running tap water and sterilized with double-distilled water. The leaves sample was allowed to dry in room temperature (32°C) and 20 g was taken for synthesis purpose. 20 g weighed leaves were boiled with 100 mL of double distilled water for 20 min at 60°C. During the procedure of boiling, a light-yellow colored solution was formed and it was cool at room temperature. After that, the yellow-colored extract was filtered with filter paper (Whatman No.1) and stored in refrigerator until further use. Further, 20 mL of M. koenigii aqueous extract was taken from the stock solution (stored at refrigerator) and boiled at 60–80 °C. When the temperature of the solution reached at 60 °C, 2 g of zinc nitrate hexahydrate crystals (Zn(NO3)2.6H2O) was added. The mixture was boiled until the formation of deep yellow colored paste. The paste was transferred to a ceramic crucible cup and heated in muffle furnace which was maintained at 400 °C for 2 h. The
obtained light yellow colored powder was used for structural, antibacterial and antifungal activities.

J. Fowsiya et al.; Green Process Synth 2019; 8: 488–495 synthesizes the ZnO NPs by slight modification in the conventional method. 10 mg of extract was mixed with 1 mM of zinc acetate and heated over the water-bath for 30 min. The UV-Vis spectrophotometer utilized to screen the preparation of ZnO NPs at 5 min interval. The green synthesized ZnO NPs showed antibacterial and antifungal properties.

Tahir Iqbal et al. Applied Nanoscience; 30 November 2021 teaches plant-mediated green synthesis of zinc oxide nanoparticles for novel application to enhance the shelf life of tomatoes. Zinc oxide nanoparticles (ZnO NPs) have been synthesized successfully by simple single-step Green’s method using leaf extract of cheese weed mallow plant and to spray these NPs on fresh tomatoes in order to enhance their shelf life. To confirm these biogenic NPs, various analytical techniques have been involved including SEM, EDX, XRD and UV–vis. To calculate the effect of ZnO NPs on the shelf time of tomatoes was investigated by various parameters including physiological weight loss, physical appearance and overall appropriateness under room temperature.
Malva Parviflora plant, commonly known as Cheese weed mallow, was collected from the garden of the university. Then these fresh leaves were washed with deionized water
and have been cut into tiny pieces, 10 g of cut leaves has been soaked in 200 mL of deionized water. The solution has been heated for 20 min on a magnetic stirrer. The leaf extract has been cooled to room temperature. Then, the leaf extract has been filtered into a flask by using a Whatman number-1 filter paper and stored for synthesis purposes. 0.02M zinc acetate [Zn(CH3CO2)2·2H2O] was added and dissolved into 50 mL of deionized water and stirred for half an hour at normal room temperature. Then, leaf extract was added drop by drop into the solution until a light-yellow color of solution appeared. The concentration of leaf extract used here was 4 mL. The solution was kept on stirring for 3 h by using a magnetic stirrer. 0.04 M NaOH was added and dissolved into 50 mL of distilled water and stirred for 20 min. Then, solution of NaOH was added drop by drop in solution of Zinc acetate and leaf extract until pH of the solution reached to 12. Then, the solution was kept on stirring for one hour. After that, the white precipitates are formed in the bottom of beaker. The solution has been washed by using distilled water over and over again and pH was continuously checked until it reached 7. Then, the precipitates of ZnO NPs were collected and dried at 80 °C for 6 consecutive hours in an oven. Then dried precipitates were crushed and were grinded into dust form. The white colored ZnO NPs were obtained and preserved in an airtight container. Same procedure was repeated twice by replacing 0.04 M NaOH with 0.05 M and 0.1 M NaOH in 50 mL distilled water, respectively. In both processes, the leaf extract was half concentrated because, instead of 10 g of leaves, 5 g of leaves was added into 200 mL of distilled water. In second attempt, 10 mL of leaf extract was used while in the third attempt, 12 mL of leaf extract was used. So, three samples of ZnO NPs were prepared and named sample 1, sample 2 and sample 3, respectively. The concentration of leaf extract used in synthesis processes was lowest in case of sample 1 and highest in case of sample 3. The precipitates of ZnO NPs of sample 3 were obtained quicker as compared to other two samples on the base of beaker because of lesser dilute solution of NaOH.

The synthesis process involves two steps. First step is the bioreduction of zinc acetate dehydrate to zinc hydroxide and second step is production of ZnO NPs precipitates in the presence of aqueous solution of pH stabilizing agent NaOH. The flavonoids present in plant extract are responsible for bioreduction of zinc acetate and they behave as ligands stabilizing the ions to the nano scale.

Betty Jarma Arroyo et al. (2019) aimed to develop different formulations of alginate and chitosan-based coatings added with nanoZnO. The coatings produced were applied to guava Psidium guajava to determine their effectiveness in delaying maturation, preserving quality, and extending the shelf life of guavas.
Khoa Hai Le; Progress in Organic Coatings 158 (2021) 10633 teaches a novel antimicrobial ZnO nanoparticles-added polysaccharide edible coating for the preservation of postharvest avocado under ambient conditions. The precursors Zn(CH3COO)2.2H2O and hexamethylene tetramine were dissolved in distilled water. The ammoniac solution was used to adjust the pH to 8. The solution was then subjected
to a hydrothermal process in an autoclave at a temperature of 150 ?C for 24 h. The precipitates were vacuum-filtered, washed, and completely dried. The dried powder was calcined in a N2 atmosphere at 400 ?C for 4 h to form ZnO nanoparticles.

Santosh Kumar et al.; Foods 2020, 9, 1143 teaches biodegradable hybrid nanocomposite of chitosan/gelatin and green synthesized zinc oxide nanoparticles for food packaging using fruit of Cassia fistula.

Gayathri.K et al., International Journal of Novel Research and Development; Volume 7, Issue 8 August 2022 discloses green synthesis and characterization of zinc oxide nanoparticals using Murraya koenigii leaf extracts. Freshly collected Murraya koenigii leaf was washed with deionized water before the extraction. Then the leaf was dried at a room temperature about 4-5 days. The dried leaf was powdered into a fine granules. About 5 grams of powdered leaf were boiled in 500ml of distilled water for 3 hours [51]. The resulting green colour extract were cooled and it can be double filtered to get the pure extract of Murraya koenigii leaf. Then it was collected and stored in refrigerated for further use. 0.1M of zinc acetate solution was added with leaf extract in a beaker. The solution was kept under the condition of constant stirring under the atmospheric pressure for 3 hours. During the stirring process the colour of the content changes from green to brown colour. And the final step the precipitate can be obtained. So that it indicated the zinc oxide nano particles can be formed. The particle size of the ZnO nanoparticles from the particle size analyser was found to be 65.8nm.

Lallan Ram et al.; J. Biol. Chem. Research Volume 30 (2) 2013 Pages No. 381-386 showed effect of ZnO nano particle containing packaging on shelf life of fresh Nagpur Mandarin (Citrus reticulata Blanco) Segments.

Thus, the innovations for applications of nanotechnology in food packaging are being increased by every passing day. In recent few years, nanotechnology have many promising applications in food sector such as development of nano packaging materials and active packaging of food. However, there is no successful packaging available for cereal and confectionary products. It is necessary to improve morphology of NPs such as ZnO NPs in such a way that they can be used to prolong the shelf life while maintaining the nutritive value of the packaged food item.

OBJECTS OF THE INVENTION
To obviate the drawbacks in the existing state of the art, the main object of the present invention to provide nano packaging to enhance the shelf life of the food products.

Another object of the present invention to provide nano packaging material to enhance the shelf life of the food products, wherein the nano packaging material is plant based.

Yet another object of the present invention to provide nano packaging sheet made up of nano material to enhance the shelf life of the food products.

Yet another object of the present invention to provide a green process for the preparation of nano packaging material to enhance the shelf life of the food products.

Yet another object of the present invention is to provide a process of making nano packaging sheet made up of nano material to enhance the shelf life of the food products.

SUMMARY OF THE INVENTION
Accordingly, the present invention provides a green nano packaging material and nano packaging film to enhance the shelf life of the food products. The nano packaging material is plant based. The nano packaging is prepared by reacting zinc salt with the extract of plant parts of specific plants at pre-determined reaction conditions. The specific plants are selected from Murraya koenigii, Aegle marmelos, Cassia fistula, Bryophyllum pinnatum.

The invention provides zinc oxide nanoparticles possessing antimicrobial activity. The zinc oxide nanoparticles are characterized for particle size and morphology. Chitosan and acetic acid are reacted under pre-determined reaction conditions to obtain chitosan solution. The chitosan solution is blended with gelatin solution.

Specific quantity of zinc oxide nanoparticles is mixed in the blend of chitosan and gelatin to obtain nanocomposite film solution. The nanocomposite film solution is kept still in petri dish to obtain nanocomposite sheet. The nanocomposite sheet is characterized for thickness, mechanical properties, microstructural characteristics, and antimicrobial activity.

Thus, the present invention is a green synthesis of nanoparticles and nanocomposite sheet. The nanoparticles obtained have good stability and produces non-toxic by-products. The nanocomposite sheet of the present invention is environment-friendly and cost effective. The nano packaging of present invention preserves and enhances the shelf life of the food products. The process of the present invention is user friendly and industrially scalable. The nanocomposite sheet of the present invention is capable of being used for packaging of food products such as, but not limiting to, jam, candies, chutney, berries, energy bars, fruit bars, donuts, nachos, croissant and increases shelf life of the preserved food products.

Additional features of the invention will be or will become apparent to one with skill in the art. It is intended that all such additional features and advantages be included within this disclosure, be within the scope of the invention.

The subject matter of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Indeed, many modifications and other embodiments of the subject matter of the present invention set forth herein will come to mind to one skilled in the art to which the subject matter of the present invention relates. Therefore, it is to be understood that the subject matter of the present invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the present disclosure.

As a preliminary matter, it will readily be understood by one having ordinary skill in the relevant art that the present disclosure has broad utility and application. As should be understood, any embodiment may incorporate only one or a plurality of the above-disclosed aspects of the disclosure and may further incorporate only one or a plurality of the above-disclosed features. Furthermore, any embodiment discussed and identified as being “preferred” is considered to be part of a best mode contemplated for carrying out the embodiments of the present disclosure. Other embodiments also may be discussed for additional illustrative purposes in providing a full and enabling disclosure. Moreover, many embodiments, such as adaptations, variations, modifications, and equivalent arrangements, will be implicitly disclosed by the embodiments described herein and fall within the scope of the present disclosure.

Accordingly, while embodiments are described herein in detail in relation to one or more embodiments, it is to be understood that this disclosure is illustrative and example of the present disclosure are made merely for the purposes of providing a full and enabling disclosure.

Any sequence(s) and/or temporal order of steps of various processes or methods that are described herein are illustrative and not restrictive. Accordingly, it should be understood that, although steps of various processes or methods may be shown and described as being in a sequence or temporal order, the steps of any such processes or methods are not limited to being carried out in any particular sequence or order, absent an indication otherwise. Indeed, the steps in such processes or methods generally may be carried out in various different sequences and orders while still falling within the scope of the present invention.
Additionally, it is important to note that each term used herein refers to that which an ordinary artisan would understand such term to mean based on the contextual use of such term herein. To the extent that the meaning of a term used herein - as understood by the ordinary artisan based on the contextual use of such term - differs in any way from any particular dictionary definition of such term, it is intended that the meaning of the term as understood by the ordinary artisan should prevail.

Furthermore, it is important to note that, as used herein, “a” and “an” each generally denotes “at least one”, but does not exclude a plurality unless the contextual use dictates otherwise. When used herein to join a list of items, “or” denotes “at least one of the items”, but does not exclude a plurality of items of the list. Finally, when used herein to join a list of items, “and” denotes “all of the items of the list”.

BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a flowchart for the synthesis of Zinc Oxide Nanoparticles from Murraya koenigii (MK) and Aegle marmelos (AM) leaves, according to an example of the present disclosure.
Fig. 2 is a flowchart for the preparation of Nano Packaging Film by using ZnO NPs, according to an example of the present disclosure..
Fig. 3 is a flowchart for the synthesis of Zinc Oxide Nanoparticles from Cassia fistula (CF) leaves, according to an example of the present disclosure..
Fig. 4 is a flowchart for the preparation of Nano Packaging Film by using ZnO NPs, according to an example of the present disclosure..

DETAILED DISCLOSUTE OF THE INVENTION WITH NON-LIMITING EMBODIMENTS AND EXAMPLES
In the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be obvious to a person skilled in the art that the invention may be practiced with or without these specific details. In other instances, well known methods, procedures and components have not been described in details so as not to unnecessarily obscure aspects of the invention.

Furthermore, it will be clear that the invention is not limited to these alternatives only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art, without parting from the scope of the invention.

The terms nanocomposite sheet, nanopackaging sheet, nanopackaging film, nanocomposite film are interchangeably used in the disclosure.

The plant parts used in the present invention are obtained from Banasthali Vidyapith, Banasthali, Rajasthan, India.

In an embodiment of the present disclosure, there is provided a nanocomposite sheet for use in packaging of food products to enhance the shelf life of food products.

In an embodiment of the present disclosure, there is provided a nanocomposite sheet comprising leaf extract of plants selected from Cassia fistula, Bryophyllum pinnatum, Aegle marmelos, Murraya koenigii and zinc nanoparticles.

In an embodiment of the present disclosure, there is provided a nanocomposite sheet comprising leaf extract of plants selected from Cassia fistula, Bryophyllum pinnatum, Aegle marmelos, Murraya koenigii and zinc nanoparticles and one or more additives.

In an embodiment of the present disclosure, said one or more additive is plasticizer.

In an embodiment of the present disclosure, said plasticizer is selected from gelatin and glycerol.

In an embodiment, there is provided a process of preparing nanocomposite sheet. The process comprises preparing leaf extract of pre-determined plants, boiling the leaf extract with zinc salt at specific conditions to obtain zinc oxide nanoparticles (ZnO NPs), preparing aqueous solution of ZnO NPs, adding a pre-determined solvent in the aqueous solution of ZnO NPs, adding pre-determined additive, casting the solution on petri dish or teflon coated plate and allow to dry to obtain nanocomposite film, and peeling off the nanocomposite film from the petri dish or teflon coated plate.

In an embodiment, the zinc salt is selected from Zn(NO3)2.6H2O and zinc acetate.

Preparing leaf extract
In an embodiment, the 20 g leaves of the plants are dried and mixed in 100 ml double distilled water in a beaker. The contents of the beaker are then boiled using a thermostatic water bath for 60 min. or until the colour changes from pale yellow to brown colour. The brown coloured solution is then filtered using Whatman No.1 filter paper to obtain leaf extract. The leaf extract is then stored in a refrigerator.
In an embodiment, the dried leaves are grounded to make leaf powder. 5 gm of the leaf powder is mixed in 500 ml water and heated at 70°C for 30 min. The resultant heated solution is then filtered using Whatman No.1 filter paper to obtain leaf extract. The Leaf extract is then stored in a refrigerator.

Preparing Zinc Oxide Nanoparticles (ZnO NPs)
20 ml of leaf extract is boiled in a water bath at temperature between 60 °C to 80 °C. When the temperature reaches 60 °C, add the zinc salt and boil until solution is converted into a thick golden-brown paste. The paste is then ignited in a muffle furnace at 400 °C for 2 hours to obtain white coloured powder of ZnO NPs.

Preparing Nanocomposite sheet:
ZnO NPs solution is prepared by adding 0.20 g of ZnO NPs in a 70 ml of distilled water. The ZnO NPs solution is then heated for 1 hour at 90 °C with stirring by using magnetic stirrer. Plasticizer and solvent are mixed with the ZnO NPs. Resultant mixture is stirred at 300 rpm to 500 rpm for a period between 15 mins to 40 mins to obtain nanocomposite film solution. The nanocomposite sheet solution is casted on teflon coated glass plate or petri dish to allow the nanocomposite film solution to dry to obtain nanocomposite film. The nanocomposite sheet is then peeled off.

In an embodiment of the present disclosure, the solvent is selected from starches (wheat, potatoes, maize), lignocellulosic products (wood, straws), and others (pectins, chitosan/chitin, gums), agar, gelatin.

In an embodiment of the present disclosure, the plasticizer is selected from Glycerol, Sorbitol, Mannitol, Xylitol, Ethylene glycol (EG), Diethylene glycol (DEG), Triethylene glycol (TEG), Tetraethylene glycol, Polyethylene glycol (PEG), Propylene glycol (PG), Fatty acids, Vegetable oils, Surfactants, Waxes, Amino acids, Water.

In an embodiment, the solvent is a solution of 4% gelatin in distilled water.

In an embodiment, the solvent is mixture of chitosan and acetic acid in distilled water.

In an embodiment, plasticizer is 30% glycerol.

In an embodiment of the present disclosure, there is provided a zinc oxide nanoparticles (ZnO NPs) synthesized by using pre-determined plant leaf extracts.

In an embodiment of the present disclosure, the pre-determined plant leaf extracts are obtained from plants selected from Murraya koenigii (MK), Aegle marmelos (AM), and Cassia fistula (CF).

Examples:

Example 1:
As shown in Fig. 1, 20 g dried leaves of Murraya koenigii or Aegle marmelos are taken in a beaker. 100 ml double distilled water is added in the beaker. The beaker is boiled for 60 min or until the color of the solution changes from pale yellow-brown by using a thermostatic water bath. The boiled solution is filtered by using Whatman No.1 filter paper to obtain leaf extract. The leaf extract is stored in a refrigerator. Thereafter, 20 ml of leaves extract is boiled in a water bath at 60 C. to 80 °C. When the temperature reaches 60 °C, 2 g of Zn(NO3)2.6H2O is added, and boiled until the solution is converted into a thick golden-brown paste. The paste is ignited in a muffle furnace at 400 °C for 2 hours yielding white-colored powder of ZnO NPs.

As shown in Fig. 2, 0.20 g of ZnO NPs are mixed in 70 ml of distilled water, heated for 1 hour at 90 °C by using magnetic stirrer to prepare ZnO NPs solution. 4 g of gelatin solvent and 1.2 g of glycerol plasticizer is added slowly in the ZnO NPs solution, and resultant solution is stirred constantly at 80 °C for 30 minutes to obtain final solution. The final solution is casted on teflon coated glass plate to allow it to dry and convert in nanocomposite sheet which was then peeled off.

Example 2:
As shown in Fig. 3, fresh leaves of C. fistula are air dried and grounded in powder form in pastel and mortar. 5 g leaf powder is dissolved in 500 ml double distilled water. The solution is heated at 70°C for 30 min or till it turns pale yellow in colour. The heated solution is filtered using Whatman filter paper No.1 5ml leaf extract is mixed with 0.219 g zinc acetate and heated at 70º for 1 hr.

As shown in Fig. 4, Chitosan (6g), acetic acid (2ml) and distilled water (8ml) are mixed to prepare chitosan solution to be used as solvent. 2% chitosan solution and 4% gelatin solution in distilled water are blended for 30 mins. 100 ml of chitosan solution + gelatin solution is mixed with 50 mg ZnO NPs. To this, 30% glycerol is added and resultant solution is stirred on Magnetic stirrer at 500 rpm for 15 min to obtain final solution of nanocomposite sheet. The nanocomposite sheet solution is casted on petri dish to get dry and convert into nanocomposite sheet.

The nano packaging sheet of the present disclosure is used for packaging of food products such as energy bar, cereal bar, protein bar, fruit bar, fruit leather, nachos and croissant to extend the shelf life by 200% to 300% or two to three times.

In one of the non-limiting examples, in case of cereal bar, the shelf life has been increased from 10 days with normal packaging to 6 weeks with the nanocomposite sheet packaging, showing 300% increase or three times increase.

In one of the non-limiting examples, the shelf life of a protein bar in normal packaging was 3 months. The shelf life with the use of nanocomposite sheet has been enhanced for up to 5 months, showing 200% increase or two times increase.

In one of the non-limiting examples, the shelf life of a fruit bar in normal packaging was 4.5 months. The shelf life with the use of nanocomposite sheet has been enhanced for up to 7.5 months, showing 300% increase or three times increase.

In one of the non-limiting examples, the shelf life of nachos in normal packaging was 1.5 months, which was enhanced for up to 3.5 months with the use of nanocomposite sheet showing 200% increase or two times increase in shelf life.

In one of the non-limiting examples, the shelf life of croissant, the shelf life in normal packaging was 2.5 weeks. The shelf life with the use of nanocomposite sheet has been enhanced for up to 4 weeks, showing more than 100% increase or two times.

In one of the non-limiting examples, the shelf life of fruit leather in normal packaging was 4 months and with this nanocomposite sheet, it has been enhanced for up to 6 months.

The synthesized nanoparticles (NPs) of Murraya koenigii and Aegle marmelos leaves were characterized by using (a) Ultraviolet-visible spectroscopy/ Optical spectroscopy, (b) Scanning electron microscopy (SEM), (c) X-ray diffraction (XRD), (d) Particle size, Polydispersity index (PDI), Zeta potential, (e) Fourier transform infrared spectroscopy (FTIR) and (f) Antibacterial activity. The developed nano composite sheet was characterized by thickness measurement, moisture absorption measurement, color measurement, mechanical strength measurement, and antibacterial activity.
Table 1: Shelf-life analysis of Cereal Bar

Storage Time
(Weeks)
pH Titratable Acidity
(%) Peroxide Value
(meq/kg) Total Plate Count (TPC)
(CFU/g)
A B A B A B A B
0 3.3 3.3 0.48 0.48 5.5 5.5 1.4 * 102 1.4 * 102
1 3.8 3.5 0.91 0.52 7.7 6.1 2.5 * 102 1.8 * 102
2 4.6 4.0 1.19 0.64 9.2 7.6 3.7 * 102 2.1 * 102
3 6.4 4.4 1.45 0.79 12.9 8.2 1.2 * 103 2.4 * 102
4 7.9 4.9 1.62 0.99 16.3 9.6 2.4 * 103 2.9 * 102
5 8.4 5.5 1.81 1.02 19.1 11.2 2.2 * 104 3.5 * 102
6 9.1 5.9 2.23 1.10 22.8 14.4 3.4 * 104 2.1 * 103
Packaging material: A – Polyethylene zip lock pouch; B – Nano composite sheet

Table 2: Shelf-life analysis of Protein Bar

Storage Time
(Months)
pH Titratable Acidity
(%) Peroxide Value
(meq/kg) TPC
(CFU/g)
A B A B A B A B
0 3.5 3.5 0.16 0.16 5.7 5.7 Nil Nil
1 3.9 3.7 0.45 0.32 7.0 6.5 1.5 * 102 1.1 * 102
2 4.3 4.0 0.84 0.56 9.3 7.8 1.9 * 102 1.3 * 102
3 4.8 4.4 1.15 0.79 11.5 8.3 2.8 * 102 1.7 * 102
4 6.6 4.9 1.94 0.91 15.4 10.8 2.4 * 103 2.0 * 102
5 8.1 5.1 2.11 1.05 19.9 12.4 2.7 * 104 2.4 * 103
Packaging material: A – Polyethylene zip lock pouch; B – Nano composite sheet

Table 3: Shelf-life analysis of Fruit Bar

Storage Time
(Months)
pH Titratable Acidity
(%) Peroxide Value
(meq/kg) TPC
(CFU/g)
A B A B A B A B
0 3.1 3.1 0.41 0.41 6.2 6.2 Nil Nil
1 3.5 3.2 0.57 0.49 7.8 6.5 1.4 * 102 1.4 * 102
2 3.9 3.6 0.72 0.54 9.2 7.0 1.8 * 102 1.5 * 102
3 4.2 3.8 0.92 0.66 11.7 8.1 2.4 * 102 1.8 * 102
4 5.0 4.0 1.11 0.73 14.1 10.4 2.7 * 102 2.1 * 102
5 6.4 4.3 1.46 0.88 17.3 12.6 1.1 * 103 2.5 * 102
6 7.7 4.7 1.92 0.95 21.6 15.5 2.4 * 103 2.8 * 102
7 8.1 5.3 2.33 1.02 25.3 17.2 3.0 * 104 1.1 * 103
Packaging material: A – Polyethylene zip lock pouch; B – Nano composite sheet

Table 4: Shelf-life analysis of Nachos

Table 5: Shelf-life analysis of Croissant

Storage Time
(Months)
pH Titratable Acidity
(%) Peroxide Value
(meq/kg) TPC
(CFU/g)
A B A B A B A B
0 3.0 3.0 0.64 0.64 4.9 4.9 2.1 * 102 2.1 * 102
1 4.1 3.5 0.95 0.71 7.5 6.1 2.9 * 102 2.5 * 102
2 4.8 4.2 1.11 0.84 10.1 7.4 3.3 * 102 2.9 * 102
3 6.2 4.7 1.21 0.92 14.5 10.2 2.2 * 103 3.6 * 102
3.5 7.1 5.1 1.32 1.08 17.0 12.6 1.6 * 104 2.9 * 103
Packaging material: A – Polyethylene zip lock pouch; B – Nano composite sheet

Storage Time
(Weeks)
pH Titratable Acidity
(%) Peroxide Value
(meq/kg) TPC
(CFU/g)
A B A B A B A B
0 3.2 3.2 0.27 0.27 6.8 6.8 2.2 * 102 2.2 * 102
1 4.9 3.4 0.93 0.43 9.6 8.0 3.0 * 102 2.8 * 102
2 5.5 3.8 1.04 0.64 12.9 10.2 2.7 * 103 3.4 * 102
3 6.2 4.2 1.39 0.88 18.5 13.4 1.1 * 104 3.9 * 102
4 7.4 4.7 1.54 1.10 24.8 17.7 3.2 * 104 1.2 * 103
Packaging material: A – Polyethylene zip lock pouch; B – Nano composite sheet

Table 6: Shelf-life analysis of Leather

Storage Time
(Months) pH Titratable Acidity (%) TPC
(CFU/g)
A B A B A B
0 3.6 3.6 0.12 0.12 Nil Nil
1 4.7 3.8 0.35 0.23 2.1x102 1.6x102
2 5.2 4.2 0.69 0.39 5.7x102 2.6x102
3 5.8 4.6 0.91 0.52 9.1x102 3.9x102
4 6.2 4.9 1.24 0.78 1.2x103 4.5x102
5 7.6 5.0 1.36 0.93 1.5x103 6.2x102
6 8.0 5.2 1.51 1.10 1.8 x103 7.4x102
Packaging material: A – Polyethylene zip lock pouch; B – Nano composite sheet

Thus, the ZnO NPs of the present disclosure are prepared by green synthesis from plant leaves extract for increasing the antibacterial properties. The developed ZnO NPs showed a good spherical shape in SEM and FTIR analysis confirmed that phenolic compounds have the capacity as capping and stabilizing agent in ZnO NPs synthesis. Therefore, this green method is one of the eco-friendly, economical and effective process to synthesis ZnO NPs. The nanoparticles formed have good stability and non-toxic by-products could be easily scaled up for large-scale synthesis. The antibacterial properties of zinc oxide nanomaterials can prevent the formation of molds, bacteria, and other microbes that cause food to deteriorate. This aids in maintaining the food’s safety and quality.

The effect of storage on the qualities of energy bars, nachos, croissant, and fruit leather were analysed by chemical parameters such as pH, titratable acidity, peroxide value, microbial assay (TPC), and sensory characteristics. The food product packed with the nanocomposite sheet of the present disclosure was significantly more stable than the one packed with Polyethylene zip lock pouch (PZLP). The result concluded that in all the developed food products showed gain in analysed parameters and decrement in sensory parameters in all products over the storage period of 6 weeks (in Cereal bar), 5 months (in Protein bar), 7 months (in Fruit bar), 3.5 months (in Nachos), 4 weeks (in Croissants), and 6 months (in Fruit leather). In PZLP, the shelf life of food products 10 days (in Cereal bar), 3 months (in Protein bar), 4.5 months (in Fruit bar), 1.5 months (in Nachos), 2.5 weeks (in Croissants), and 4 months (in Fruit leather).

Therefore, nanocomposite sheet of the present disclosure is a good alternative as the biodegradable, sustainable packaging material instead of synthetic ones in food industries. Nanocomposite sheet enhances the shelf life without using any synthetic preservatives as used in readily available food products in market. In commercial food packaging, energy bars, nachos, croissant, and fruit leather were packed in the presence of inert gases such as argon, helium, nitrogen and carbon dioxide that helps to increase the shelf life of food products.

The process of the present disclosure is rapid, facile, convenient, less time-consuming, and environmentally safe. The process for the synthesis of nanocomposite sheet on large scale using ZnO NPs from the plant leaves extracts has commercial viability and is sustainable.

,CLAIMS:We Claim:
1. A nanocomposite sheet comprising leaf extract of specific plants and zinc nanoparticles.
2. The nanocomposite sheet as claimed in claim 1, wherein said specific plants is selected from Cassia fistula, Bryophyllum pinnatum, Aegle marmelos, Murraya koenigii.
3. The nanocomposite sheet as claimed in claim 1, wherein said nanocomposite sheet further comprises one or more additives.
4. The nanocomposite sheet as claimed in claim 3, wherein said one or more additive is plasticizer.
5. The nanocomposite sheet as claimed in claim 4, wherein said plasticizer is selected from Glycerol, Sorbitol, Mannitol, Xylitol, Ethylene glycol (EG), Diethylene glycol (DEG), Triethylene glycol (TEG), Tetraethylene glycol, Polyethylene glycol (PEG), Propylene glycol (PG), Fatty acids, Vegetable oils, Surfactants, Waxes, Amino acids, Water.
6. A process of preparing a nanocomposite sheet of claim 1, wherein said process comprises
- preparing leaf extract of specific plants,
- boiling the leaf extract with zinc salt at specific conditions to obtain zinc oxide nanoparticles (ZnO NPs),
- preparing aqueous solution of ZnO NPs,
- adding a pre-determined solvent and one or more additive to the aqueous solution of ZnO NPs and stirring the solution,
- casting the solution on petri dish or teflon coated plate and allowing to dry to obtain nanocomposite film,
- peeling off the nanocomposite film from the petri dish or teflon coated plate.
7. The process as claimed in claim 6, wherein said zinc salt is selected from Zn(NO3)2.6H2O and zinc acetate.
8. The process as claimed in claim 6, wherein said specific plants is selected from Cassia fistula, Bryophyllum pinnatum, Aegle marmelos, Murraya koenigii.
9. The process as claimed in claim 6, wherein said at specific conditions to obtain zinc oxide nanoparticles are temperature in a range of 60°C to 80°C for 30 min.
10. The process as claimed in claim 6, wherein said pre-determined solvent is selected from solvent is selected from starches (wheat, potatoes, maize), lignocellulosic products (wood, straws), and others (pectins, chitosan/chitin, gums), agar, gelatin.
11. The process as claimed in claim 6, wherein said one or more plasticizer is selected from glycerol, Sorbitol, Mannitol, Xylitol, Ethylene glycol (EG), Diethylene glycol (DEG), Triethylene glycol (TEG), Tetraethylene glycol, Polyethylene glycol (PEG), Propylene glycol (PG), Fatty acids, Vegetable oils, Surfactants, Waxes, Amino acids, Water.
12. The process as claimed in claim 10, wherein said pre-determined solvent is a solution of 4% gelatin in distilled water.
13. The process as claimed in claim 10, wherein said pre-determined solvent is mixture of chitosan and acetic acid in distilled water.
14. The process as claimed in claim 11, wherein said plasticizer is 30% glycerol.
15. The process as claimed in claim 11, wherein size of the nanoparticles is in the range of 78.1 nm to 90.87 nm.
16. The nanocomposite sheet as claimed in claim 1, wherein said nanocomposite sheet is for use in packaging of food products such as energy bar, cereal bar, protein bar, fruit bar, fruit leather, nachos and croissant to extend the shelf life by two to three times.