Edible nanofiber incorporating olive oil for use on food products

Abstract

The invention relates to nanofibers obtained by electrospinning using edible, biocompatible polymer materials (polyvinyl alcohol and chitosan) and the addition of cold-pressed olive oil, which has antimicrobial properties, as well as to the production of these nanofibers.

Description

[0001] EDIBLE NANOFIBER INCORPORATING OLIVE OIL FOR USE ON FOOD PRODUCTS

[0002] TECHNICAL FIELD

[0003] The invention relates to nanofibers produced by electrospinning using edible, biocompatible polymer materials (polyvinyl alcohol and chitosan) in combination, with the addition of cold-pressed olive oil possessing antimicrobial properties. The invention further concerns the production of these nanofibers and their application to food products.

[0004] BACKGROUND

[0005] Edible film coatings applied to food product surfaces using various techniques can be derived from both plant- and animal-based sources. The properties of edible films include reduced moisture loss, biodegradability, aesthetic appearance, barrier performance against oxygen and physical stress, and economic and toxicological safety.

[0006] Because they are produced from natural, biologically renewable materials, they do not contribute to environmental pollution and are recognized as materials that support environmental protection. They also serve as carriers for antimicrobial and antioxidant agents used in food applications. Thus, the use of edible films — particularly in frozen, fresh, and processed foods — is increasingly being modified and expanded to extend shelf life, prevent spoilage, and preserve sensory attributes.

[0007] Edible nanofibers possess semi-permeability to gases and moisture between the food and its surrounding environment. They inhibit bacterial contamination, extend food shelf life, and protect against mechanical damage and light exposure. Being biodegradable, they enhance the properties of packaged foods, reduce moisture loss, and improve nutritional value.

[0008] They serve as carrier systems for antimicrobial and antioxidant substances and can be applied to food surfaces to control the diffusion rate of protective agents into internal layers.

[0009] By regulating the transfer of oxygen, carbon dioxide, and lipids, edible films and coatings improve the mechanical properties of food systems, reduce the loss of flavor and aroma compounds, and enhance food quality and shelf stability by retaining antioxidants, antimicrobial agents, and pigments within the product. Edible films and coatings, which form a non-sticky, non-greasy surface on foods, also provide mechanical protection by reducing crushing and breakage, thereby supporting the food's structural integrity.

[0010] The earliest known use of edible films in food products dates back to the 12th century in China, where a wax-based coating was applied to citrus fruits. Early applications of such coatings in the food industry include candied apples, chocolate- coated confections, and kashar cheeses (a pale yellow cheese made from sheep's milk) coated with edible wax. These applications later expanded, and edible collagen casings began to be used as alternatives to animal intestines in particular meat products.

[0011] In meat and meat products, edible film coatings help reduce moisture loss during storage of fresh or frozen meats, retain purge in fresh red meat or poultry sold in plastic containers, reduce rancidity caused by lipid oxidation, inhibit the penetration of pathogenic microorganisms from the surface into the interior of the meat, and prevent the formation of undesirable off-flavors and odors.

[0012] Edible films are of significant importance for minimizing quality loss in foods and preventing spoilage reactions. They can act as barriers to the diffusion of moisture, oxygen, carbon dioxide, and aroma-active compounds. They also enhance the desirable properties of food components, such as antioxidants and antimicrobial agents. Additionally, they may improve the sensory characteristics and nutritional value of foods.

[0013] Olive oil differs from other oils due to its high content of monounsaturated fatty acids, such as oleic acid, and polyunsaturated fatty acids, such as linoleic acid. The presence of phenolic organic compounds in olive oil imparts anti-inflammatory, antiproliferative, antioxidant, and antimicrobial properties.

[0014] Hydroxytyrosol and oleuropein, found in olive oil, are known for their high antioxidant capacity, as well as their metal-chelating and free-radical-scavenging activities.

[0015] Olive oil has been reported to exhibit antioxidant, anti-inflammatory, and antibacterial effects. Moreover, due to its content of vitamins A, E, and K, essential minerals (calcium, potassium, iron, etc.), amino acids, unsaturated fatty acids, and trace nutrients, it is recommended as a regular component of daily diets. Studies on animal models have shown that squalenes in olive oil may reduce colon, lung, and skin tumors.

[0016] The time between production and consumption is critical for food products, and spoilage must be prevented during this period. Therefore, selecting appropriate packaging materials that protect food from oxygen, water vapor, harmful ultraviolet (UV) radiation, microorganisms, and chemically reactive compounds is essential. Biodegradable films and coating materials are preferred over plastics due to their lower environmental impact. Environment-friendly packaging materials include polymeric structures such as polysaccharides, proteins, and lipids. These materials are non-toxic, non-allergenic, biodegradable, and highly biocompatible.

[0017] Given the state of the art, no study has been found that incorporates a binary polymer blend with olive oil in an edible food-packaging material as proposed in the present invention. The most significant component of the invention is olive oil, which provides pronounced antimicrobial properties.

[0018] AIM OF THE INVENTION

[0019] The primary objective of the present invention is to directly incorporate olive oil into the polymer blend, thereby eliminating the extraction step. This approach provides a significant cost advantage by removing the need for prior extraction.

[0020] Medically, oleic acid — widely consumed in the Mediterranean region — is known to have beneficial effects on coronary artery disease. Furthermore, olive oil improves the lipid profile by reducing the LDL / HDL cholesterol ratio, thereby lowering cardiovascular risk. Olive oil positively influences several physiological parameters, including insulin resistance, lipid levels, DNA oxidation, thrombotic factors, and blood pressure. In this invention, olive oil produced from olives grown in the Aydmcik district of Mersin is used as the third component in the production of nanofibers, and its composition is known to consist of fatty acids and phenolic compounds. Although the general composition of olive oil is well documented, the fatty acid ratios and types were further clarified for verification using a Gas Chromatography-Flame Ionization Detector (GC-FID) system.

[0021] When compared with the methods used in the state of the art, the originality of the present study becomes evident, and its antimicrobial results demonstrate activity against a wide range of microorganisms. A comparative evaluation of the data obtained relative to existing techniques is presented in the table below. Antimicrobial

[0022] Distance Flow

[0023] Study Name Voltage (kV) activity (zone Reference

[0024] (cm) Rate diameter)

[0025] S. Aureus, E. Coll

[0026] Chitosan / PEO / yarrow 0,1- Kharat et

[0027] 18-20 15 22.0 ± 0.4 (mm),

[0028] (2%) 0,3mL al., 2021 20.9 ± 1.1 (mm)

[0029] S.Aureus /

[0030] B.Cereus / E.Coli

[0031] Chitosan / gelatin / St. John's / S.Tyhpi Yildinm &

[0032] Electrospinning Type: Non-spun (Casting Method) wort (1 %, 5%) (Inhibition zone Kuguk, 2020 diameters 21-14 mm)

[0033] PVA / CS (0.5-1 ; 6-7) Nur KUTLU,

[0034] 13-16 16-20 0,2-0, 6

[0035] Enzyme study 2017

[0036] Doganci et

[0037] 10% PVA / 5% ozone oil 30 15 5 mL al., 2022 Erdem &

[0038] PolyamideS / chitosan 34 15 0,5 Sancak, 2013

[0039] Zarghami et al., 2015

[0040] B. subtilis, S. aureus,

[0041] PVA / CS / olive oil (1 %, E.faecalis, E. coll, Our

[0042] 20-25 18 0,5

[0043] 2%) K.pneumoniae, invention

[0044] P. aeruginosa, C. albicans, A. niger,

[0045] LIST OF FIGURES Figure 1. SEM image of the nanofibers of the present invention

[0046] Figure 2. Infrared spectrum graph of the nanofibers of the present invention

[0047] DETAILED DESCRIPTION OF THE INVENTION

[0048] The present invention relates to an edible film with a nanofibrous structure, obtained by mixing PVA / CS / olive oil in predetermined ratios and processing the mixture via electrospinning.

[0049] In the production of the invention, the aqueous solution of polyvinyl alcohol (PVA) was first homogeneously prepared and subsequently mixed with a 1.5% chitosan solution. The PVA / chitosan ratio in the solution was maintained at 70:30 (w / w). Olive oil was then added to the prepared mixture at concentrations of 1% and

[0050] 2%, after which electrospinning was performed on the resulting solutions. Preparation of PVA / CS Solution Containing 1 % Olive Oil

[0051] The PVA / CS ratio was kept constant at 70:30 (w / w), and 1 % olive oil was incorporated. To prepare the 1 % olive oil solution, 24.75 g of the PVA / CS (70:30) mixture was heated to 45°C on a magnetic stirrer hot plate for 30 minutes to increase the solution temperature and facilitate dissolution of the olive oil. Subsequently, 0.25 g of olive oil (1 %) was added to the PVA / CS solution at 45°C, and the mixture was stirred for 3 hours to ensure complete dissolution. Once the mixture had achieved a homogeneous appearance, it was stirred at room temperature for an additional 20 hours. After mixing, the PVA / CS / olive oil solution was allowed to rest.

[0052] Preparation of PVA / CS Solution Containing 2% Olive Oil

[0053] The PVA / CS ratio was again maintained at 70:30 (w / w), and 2% olive oil was incorporated. To prepare the 2% olive oil solution, 19.6 g of the PVA / CS (70:30) mixture was heated to 45°C on a magnetic stirrer hot plate for 30 minutes to increase the solution temperature and facilitate dissolution of the olive oil. Then, 0.4 g of olive oil (2%) was added to the PVA / CS solution at 45°C, and the mixture was stirred for 3 hours until complete dissolution was achieved. Once homogeneous, the solution was stirred at room temperature for 20 hours. After mixing, the PVA / CS / olive oil solution was left to rest.

[0054] The nanofibers were prepared by optimizing the parameters listed below.

[0055] Solution Mixture Distance(cm) Tension / Potentail(kV) Pump

[0056] Speed (mL / sa)

[0057] PVA 14 16 0.5

[0058] PVA / CS (70:70) 14 17 0.5

[0059] PVA / CS / % one olive oil 18 25 0.5

[0060] PVA / CS / % two olive oil 18 25 0.5

[0061] Chromatographic (GC-FID) Analysis of Olive Oil Components

[0062] The olive oil used in nanofiber production contains fatty acids and various organic compounds. The combination of fatty acids present in olive oil is determined using chromatographic instruments — primarily the Gas Chromatography (GC-FID) system equipped with a Flame Ionization Detector. In this analysis, the fatty acids in olive oil are converted to methyl esters using KOH in an alcoholic medium.

[0063] Oleic Acid Methyl Ester is the most abundant component in olive oil (63.581 %). Following oleic acid methyl ester, Palmitic Acid Methyl Ester (16.433%) and Linoleic Acid Methyl Ester (12.692%) are present.

[0064] When the SEM image of the obtained nanofibers, magnified 20,000 times (Figure 1 ), is examined, it is observed that the addition of olive oil slightly darkened the nanofiber color. The nanofibers are smooth and homogeneous. Their diameters are approximately 200 nm, as shown in Figure 1.

[0065] Due to the increase in phenolic organic compounds after adding olive oil, and the presence of hydroxyl (O-H) groups in its structure, the intensity of the peaks in the infrared spectrum increased (Figure 2). At the same time, the O-H band appeared broader and more diffuse.

[0066] The antibacterial and antifungal activities of the nanofibers were evaluated using the Minimum Inhibitory Concentration (MIC) method in 96-well microplates, following the broth microdilution procedure described by the National Committee for Clinical Laboratory Standards.

[0067] MIC values of the tested nanofibers were determined against three Grampositive bacteria, three Gram-negative bacteria, and two fungal species. According to the results, the PVA / CS / olive oil 2% nanofiber exhibited higher antimicrobial activity against all Gram-positive, Gram-negative, and fungal species compared to the PVA / CS / olive oil 1% nanofiber. While both nanofibers (1% and 2% olive oil) showed lower activity than the antibiotic amoxicillin against the Gram-positive bacterium Bacillus subtilis, they exhibited higher activity than amoxicillin against the Gramnegative bacterium Pseudomonas aeruginosa. Both the 1 % and 2% olive oil nanofibers showed lower activity than the antibiotic tetracycline against Gram-positive bacteria (B. subtilis, S. aureus, E. faecalis) and Gram-negative bacteria (E. coli, K. pneumoniae). The 2% olive oil nanofiber demonstrated higher activity than tetracycline against P. aeruginosa. Additionally, the 2% olive oil nanofiber exhibited lower activity against the fungus Aspergillus niger compared to the antifungal drug ketoconazole. MIC values of the tested nanofibers ( g / mL)

[0068] Nanofibers and standards A B C D E F G H

[0069] Nanofiber 1 2048 2048 2048 2048 2048 128 -

[0070] Nanofiber 2 1024 1024 1024 1024 1024 32 1024

[0071] Amoxicillin <2 >1024 >1024 >1024 >1024 >1024 -

[0072] Tetracycline <2 64 64 <2 64 64 -

[0073] Ketoconazole 1 2

[0074] A: Bacillus subtilis ATCC 6623;

[0075] B: Staphylococcus aureus ATCC 25923;

[0076] C: Enterococcus faecalis ATCC 29212;

[0077] D: Escherichia coli ATCC 25922;

[0078] E: Klebsiella pneumoniae ATCC 70060;

[0079] F: Pseudomonas aeruginosa ATCC 27853;

[0080] G: Candida albicans ATCC 10231 ;

[0081] H: Aspergillus niger ATCC 16404.

[0082] The mechanical properties of the obtained nanofibers were examined through texture analysis. Characteristics such as hardness, adhesiveness, viscosity, and elasticity are essential to producers because they directly influence the shelf life of food products. Since the nanofibers produced from PVA / CS / olive-oil polymer solutions are food-grade materials intended for packaging and co-consumption with food, their elastic structure is critical. Texture analysis results demonstrated that the nanofiber containing 2% olive oil possesses a much more elastic and robust structure.

[0083] The peroxide value of the 1 % oil sample was higher than that of the 2% sample, attributed to the oil's higher active oxygen content. Due to this active oxygen, the elevated peroxide value indicates that the nanofiber produced with 1% olive oil undergoes a higher degree of degradation compared to the nanofiber containing 2% olive oil. Considering peroxide levels in food packaging applications, the 2% oil nanofiber is the more suitable option.

[0084] According to the "Communique on Oils Named After the Plant" specified in the Turkish Food Codex, refined oils may contain a maximum of 10 meq / kg active oxygen. In contrast, cold-pressed oils may contain up to 15 milliequivalents of active oxygen per kilogram.

[0085] PVA / CS / zy (%1) Peroxide Value 0,266 - meq / kg

[0086] PVA / CS / zy (%2) Peroxide Value 0,191 - meq / kg

Claims

CLAIMS1 . An edible nanofiber characterized by the inclusion of olive oil.

2. An edible nanofiber characterized by the inclusion of PVA (polyvinyl alcohol), chitosan, and olive oil.

3. The nanofiber according to any of the preceding claims, characterized by the olive oil content being 1%.

4. The nanofiber according to claim 1 or claim 2, characterized by the olive oil content being 2%.

5. A method for producing an edible nanofiber, characterized by the steps of:- Preparing an aqueous solution of polyvinyl alcohol (PVA) as the supporting polymer in a homogeneous manner,- Subsequently, mixing it with a 1.5% chitosan solution while maintaining a PVA / chitosan weight ratio of 70:30,- Adding olive oil to the prepared solution and electrospinning the resulting mixtures.

6. The added olive oil mentioned in claim 5, characterized by a 1% ratio.

7. The added olive oil mentioned in claim 5, characterized by a 2% ratio.

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